Ln occ health_final

LECTURE NOTES
For Environmental and Occupational Health Students
Occupational Health
and Safety
Takele Tadesse
Mengesha Admassu
University of Gondar
In collaboration with the Ethiopia Public Health Training Initiative, The Carter Center,
the Ethiopia Ministry of Health and, and The Ethiopia Ministry of Education
August 2006

Funded under USAID Cooperative Agreement No. 663-A-00-00-0358-00.
Produced in collaboration with the Ethiopia Public Health Training Initiative, The Carter
Center, the Ethiopia Ministry of Health, and the Ethiopia Ministry of Education.
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©2006 by Takele Tadesse and Mengesha Admassu
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Occupational Health and Safety
1
CHAPTER ONE
OCCUPATIONAL HEATH AND SAFETY
1.1. Learning objectives
At the end of this chapter, the student will be able to:
1. Define occupational health
2. Discuss challenges for the development of occupational
health and safety.
3. Explain the scope of occupational health and safety.
4. Describe the interrelationship between ooccupational health
and development
5. Identify the elements of a work environment.
6. Discuss the three common interactions in the work place.
7. Explain the interrelationships between work and health.
1.2. Introduction
Occupational health and safety is one of the most important aspects
of human concern. It aims an adaptation of working environment to
workers for the promotion and maintenance of the highest degree of
physical, mental and social well being of workers in all occupations.
The question of occupational health and safety, as a global issue, is
now taking a new turn. The main contributory factors towards this
idiocyncracy seem to be due to the rapid industrial and agricultural
development that are taking place in the developing countries, and
the emergence of new products and product processes from these

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places. Many of these countries are moving from manual labour to
service mechanization in the main productive sectors, such as
manufacturing, mining and agriculture, hence the potential
occupational health ramifications should be anticipated. Also the
insatiable desire of these countries for technical advancement has
brought about the importation of sophisticated machinery and pieces
of equipment not only into the industrial production sector, but also
to services and commerce. This invariably has been associated with
a change in the structure of the labour force as a whole including a
rise in the employment of women. As to be expected the health
problems would also change. For example, more emphasis on
ergonomics and occupational psychosocial factors would be needed
in the services industry. This obviously would be a new challenge for
occupational health and safety practice in most of the African
countries because the tool to deal with such a problems and the
expertise is not yet advanced when compared to the developed
countries.
The benefit of occupational health service in developing countries is
seen locally as well as on a national level. The positive impact of
occupational health service locally may be observed in reducing
morbidity and work-related injuries. In addition, this also means
fewer losses to employer and worker as there will be a reduction of
wage losses and decreased compensation costs. The reduction of
absenteeism is of great importance concerning skilled labour,
especially so in countries where there is a shortage of skilled labour.

3
Making working conditions healthy and safe is in the interest of
workers, employers and governments, as well as the public at large.
Although it seems simple and obvious, this idea has not yet gained
meaningful universal recognition. Hundreds of millions of people
throughout the world are employed today in conditions that breed ill
health and/or are unsafe.
Each year, work-related injuries and diseases kill an estimated 2
million people worldwide, which is greater than the global annual
number of deaths from malaria. Annually, an estimated 160 million
new cases of work-related diseases occur worldwide, including
respiratory and cardiovascular diseases, cancer, hearing loss,
musculoskeletal and reproductive disorders, mental and neurological
illnesses.
An increasing number of workers in industrial countries complain
about psychological stress and overwork. These psychological
factors have been found to be strongly associated with insomnia,
depression and fatigue, and burn-out syndromes, as well as with
elevated risks of cardiovascular diseases. Only 5-10% of workers in
developing countries and 20-50% of workers in industrial countries
(with a few exceptions) are estimated to have access to adequate
occupational health services. Even in advanced economies, a large
proportion of work sites are not regularly inspected for occupational
health and safety.

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1.3. Definition of Terms
According to WHO (1995), occupational safety and health can be
defined as a multidisciplinary activity aiming at:
• Protection and promotion of the health of workers by eliminating
occupational factors and conditions hazardous to health and
safety at work
• Enhancement of physical, mental and social well-being of
workers and support for the development and maintenance of
their working capacity, as well as professional and social
development at work
• Development and promotion of sustainable work environments
and work organizations
The ILO/WHO definition of occupational health is “The promotion
and maintenance of the highest degree of physical, mental social
wellbeing of workers in all occupation” and the WHO considers
occupational health service to be responsible for the total of worker
and, if possible, his or her family.
Occupational Health is a diverse science applied by occupational
health professionals engineers, environmental health practitioners,
chemists, toxicologists, doctors, nurses, safety professionals and
others who have an interest in the protection of the health of workers
in the workplace.

5
The discipline covers the following key components:
1. the availability of occupational health and safety regulations
at workplace
2. the availability of active and functional occupational health
and safety committee at workplace
3. monitoring and control of factory hazards to health
4. supervision and monitoring of hygiene and sanitary facilities
for health and welfare of the workers
5. inspection of health safety of protective devices
6. pre-employment, periodical and special health examination.
7. performance of adaptation of work to man
8. provision of First Aid
9. health education and safety training to the worker
10. Advice to employers on the above mentioned items
11. Reporting of occupational deaths, diseases, injuries,
disabilities ,hazards and their related preventive measures
at working
According to a statement by occupational health institutes
collaborating with the WHO (1995) the most important challenges for
occupational health for the future will be:
• Occupational health problems linked to new information
technologies and automation;
• new chemical substances and physical energies;
• health hazards associated with new biotechnologies;
• transfer of hazardous technologies;
• aging working populations;

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• special problems of vulnerable and underserved groups
(e.g. chronically ill and handicapped), including migrants and
the unemployed; and,
• problems related to growing mobility of worker populations
and occurrence of new occupational diseases of various
origins.
Interdisciplinary Relationships
Environmental Managers: are those trying to eliminate hazards
from the workplace cause many environmental problems.
Toxicology: is the science that studies poison ands toxic
substances and their mechanisms and effects on living organisms.
In other words toxicology is the study of adverse effects of chemical
on biologic systems, or when a substance has a capacity to produce
undesirable physiological effect when the chemical reached a
sufficient concentration at a specific site in the body.
Toxicologists: are persons who study poisoning and responsible
defining quantitatively the level of exposure at which harm occurs
and they also prescribe precautionary measures and exposure
limitations so that normal recommended use of chemical substance
does not result in excessive exposure and subsequent harm
Ergonomics: is a multidisciplinary activity dealing with the
interaction between man and his total working environment plus
such traditional environmental elements as atmosphere, heat, light,
and sound as well as all tools and equipment of the work place.

7
Chemical engineers are those who design process plant, they
choose values, decide on how access will be gained and how
cleaning will take place.
Mechanical engineers are those who responsible for choosing
materials handling systems or for specifying noise levels on
machinery.
Environmental health professionals: are those who apply their
knowledge and experience, understand the environmental health
hazards, analyze the technical and social approaches and reduce
and eliminate human exposures and health impacts.
Industrial hygienists are scientists, engineers, and public health
professionals committed to protecting the health people in the
workplace and the community
1.4 Occupational health and development
The health status of the workforce in every country has an
immediate and direct impact on national and world economies. Total
economic losses due to occupational illnesses and injuries are
enormous (WHO 1999). The International Labor Organization (ILO)
has estimated that in 1997, the overall economic losses resulting
from work-related diseases and injuries were approximately 4-5 % of
the world’s Gross National Product.
Workforce is a backbone of a country development. A healthy, well-
trained and motivated workforce, increases productivity and
generates wealth that is necessary for the good health of the
community at large.

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Magnitude of the problem/disease
The difficulty of obtaining accurate estimates of the frequency of
work-related diseases is due to several factors.
1. Many problems do not come to the attention of health
professionals and employers and, therefore, are not
included in data collection systems.
2. Many occupational medical problems that do come to
the attention of physicians and employers are not
recognized as work related.
3. Some medical problems recognized by health
professionals or employers as work- related are not
reported because the association with work is equivocal
and because reporting requirements are not strict.
4. Because many occupational medical problems are
preventive, their very persistence implies that some
individual or group is legally and economically
responsible for creating or perpetuating them.
However, globally, millions of men and women work in poor and
hazardous conditions. According to International Labour
Organization
1.2 million working peoples die of work related accident and
diseases every year
More than 160 million workers fall ill each year due to
workplace hazards

9
UN estimates 10,000,000 occupational disease cases occur
each year globally, severity and frequency is greatest in
developing countries.
Women , children and migrant workers are least protected
and most affected
Micro and small enterprises account for over 90 % of
enterprises where conditions are often very poor and the
workers particularly in the informal sectors are often
excluded from all legal protection.
Reasons for these are:-
Workplace
• Unsafe building
• Old machines
• Poor ventilation
• Noise
• Inaccessible to inspection
Workers
Limited education
Limited skill and training
Employers
Limited financial resources
Low attention and knowledge
In many developing nations, death rates due to occupational
accident among workers are five to six times higher than those in
industrialized countries; yet, the situation in developing countries is
still largely undocumented due to poor recording system.

10
Table 1-1: Estimated Global Burden of Disease from Selected
Environmental Threats
Type of
environmental
and principal
related
diseases
Burden from
these
diseases
(Million of
DALYs per
year)
Reduction
achievable
through
feasible
interventions
(percent)
Burden
averted by
feasible
interventions
(Millions of
DALYs per
year)
Burden
averted per
1,000
population
(DALYs per
year)
Occupational 318 - 36 7.1
Urban air 170 - 8 1.7
Road
transport(mot
or vehicle
injuries)
32 20 6 1.2
All the above 473 - 50 10.0
Source: World Bank, 1993
1.5. Historical background of occupational health
The work place is a potentially hazardous environment where
millions of employees pass at least one-third of their life time. This
fact has been recognized for a long time, although developed very
slowly until 1900.
There has been an awareness of industrial hygiene since antiquity.
The environment and its relation to worker health was recognized as
early as the fourth century BC when Hippocrates noted lead toxicity
in the mining industry. In the first century AD, Pliny the Elder, a
Roman scholar, perceived health risks to those working with zinc

11
and sulfur. He devised a face mask made from an animal bladder to
protect workers from exposure to dust and lead fumes. In the
second century AD, the Greek physician, Galen, accurately
described the pathology of lead poisoning and also recognized the
hazardous exposures of copper miners to acid mists.
In the middle Ages, guilds worked at assisting sick workers and their
families. In 1556, the German scholar, Agricola, advanced the
science of industrial hygiene even further when, in his book De Re
Metallica, he described the diseases of miners and prescribed
preventive measures. The book included suggestions for mine
ventilation and worker protection, discussed mining accidents, and
described diseases associated with mining occupations such as
silicosis.
Industrial hygiene gained further respectability in 1700 when
Bernardo Ramazzini, known as the "father of industrial medicine,"
published in Italy the first comprehensive book on industrial
medicine, De Morbis Artificum Diatriba (The Diseases of Workmen).
The book contained accurate descriptions of the occupational
diseases of most of the workers of his time. Ramazzini greatly
affected the future of industrial hygiene because he asserted that
occupational diseases should be studied in the work environment
rather than in hospital wards.
Industrial hygiene received another major boost in 1743 when Ulrich
Ellenborg published a pamphlet on occupational diseases and

12
injuries among gold miners. Ellenborg also wrote about the toxicity
of carbon monoxide, mercury, lead, and nitric acid.
In England in the 18th century, Percival Pott, as a result of his
findings on the insidious effects of soot on chimney sweepers, was a
major force in getting the British Parliament to pass the Chimney-
Sweepers Act of 1788. The passage of the English Factory Acts
beginning in 1833 marked the first effective legislative acts in the
field of industrial safety. The Acts, however, were intended to
provide compensation for accidents rather than to control their
causes. Later, various other European nations developed workers'
compensation acts, which stimulated the adoption of increased
factory safety precautions and the establishment of medical services
within industrial plants.
In the early 20th century in the U.S., Dr. Alice Hamilton led efforts to
improve industrial hygiene. She observed industrial conditions first
hand and startled mine owners, factory managers, and state officials
with evidence that there was a correlation between worker illness
and exposure to toxins. She also presented definitive proposals for
eliminating unhealthful working conditions.
At about the same time, U.S. federal and state agencies began
investigating health conditions in industry. In 1908, public awareness
of occupationally related diseases stimulated the passage of
compensation acts for certain civil employees. States passed the
first workers' compensation laws in 1911. And in 1913, the New York
Department of Labor and the Ohio Department of Health established

13
the first state industrial hygiene programs. All states enacted such
legislation by 1948. In most states, there is some compensation
coverage for workers contracting occupational diseases.
The U.S. Congress has passed three landmark pieces of legislation
related to safeguarding workers' health: (1) the Metal and
Nonmetallic Mines Safety Act of 1966, (2) the Federal Coal Mine
Safety and Health Act of 1969, and (3) the Occupational Safety and
Health Act of 1970 (OSH Act). Today, nearly every employer is
required to implement the elements of an industrial hygiene and
safety, occupational health, or hazard communication program and
to be responsive to the Occupational Safety and Health
Administration (OSHA) and its regulations.
However, concrete approach to the control of occupational diseases
became valid in most countries after the twentieth century.
Emphasis was then given to the control of working hazards, and
multidisciplinary approach to such effective measures in which at
least triparty: the employer, the employee, and the competent
authority are together participating in the problem solution. Much
improvement in the workers health protection has been made in
developed countries in the field of industrial hygiene and safety, and
occupational medicine. There is still a long distance ahead for
developing countries.

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1.5.1 OSHA and occupational health
Under the OSH Act, OSHA develops and sets mandatory
occupational safety and health requirements applicable to the more
than 6 million workplaces in the U.S. OSHA relies on, among many
others, industrial hygienists to evaluate jobs for potential health
hazards. Developing and setting mandatory occupational safety and
health standards involves determining the extent of employee
exposure to hazards and deciding what is needed to control these
hazards to protect workers. Industrial hygienists are trained to
anticipate, recognize, evaluate, and recommend controls for
environmental and physical hazards that can affect the health and
well-being of workers.
More than 40 percent of the OSHA compliance officers who inspect
America's workplaces are industrial hygienists. Industrial hygienists
also play a major role in developing and issuing OSHA standards to
protect workers from health hazards associated with toxic chemicals,
biological hazards, and harmful physical agents. They also provide
technical assistance and support to the agency's national and
regional offices. OSHA also employs industrial hygienists who assist
in setting up field enforcement procedures, and who issue technical
interpretations of OSHA regulations and standards.
Industrial hygienists analyze, identify, and measure workplace
hazards or stresses that can cause sickness, impaired health, or
significant discomfort in workers through chemical, physical,
ergonomic, or biological exposures. Two roles of the OSHA

15
industrial hygienist are to spot those conditions and help eliminate or
control them through appropriate measures.
1.5.2 National Labor Law Profile: Federal Democratic Republic
of Ethiopia
According to labor proclamation No. 377/2003, the Ministry of Labor
and Social Affairs of Ethiopia is the organ charged with the
responsibility to inspect labor administration, labor conditions,
occupational health and safety
1. Labor regulation
Talking about labor Law in Ethiopia means to basically review the
history of the last 40-50 years. Present-day labor law, as a
specialized law designed to protect employees' welfare, only came
into existence as a result of the modern industrial development and
with the rise of the status of the employee as wage earner. Until
recently, the main source of labor law, the Labor Proclamation,
Proclamation No. 42/1993, was developed in the post-socialist time,
marking the overcoming of the centralized state-economy towards a
market oriented, pluralistic society.
Ethiopia was criticized for several years by the ILO Committee of
Experts, which noted serious discrepancies between the national
legislation and the Freedom of Association and Protection of the
Right to Organize Convention, 1948 (No. 87). It was partly in
response to the observations made by the House of People's
Representatives adopted Labor Proclamation No. 377/2003,

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effective since 26 February 2004. This text repealed Labor
Proclamation No. 42/1993 (as amended by Proclamation 88/1994).
It has become the principal source of labor law in Ethiopia. So far
the Committee of Experts has not published its comments on the
new law.
The new statute represents an important tool for unions and
employers to participate in all labor matters. The innovation
concerns the right of workers, without distinction whatsoever, to form
organizations of their own choosing and the right of these
organizations to organize their activities without interference by the
public authorities and not to be dissolved by administrative authority
(Article 114 (1), (2) and (7)).
Labor Proclamation 377/2003 amends the previous Labor
Proclamation on the following points:
It defines “managerial employees” in Article 3 (2) c);
It introduces an obligation of employers to maintain records;
It tightens the legal procedure by setting several new
deadlines;
It introduces a clear ban for compulsory HIV/AIDS testing
(Article 14 (2) d);
It strengthens the workers' position in case of termination
(Article 27 (2) and (3);

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It clarifies regulations on severance pay and compensation,
disablement payment and dependants benefits (Arts. 39, 40,
109, 110);
It creates the full guarantee of freedom of association by
abolishing trade union monopoly (Article 114), provided that
the number of members of the union is not less than ten;
It recommends regulations on trade union property to be
included into the constitution of workers' organizations
(Article 117 (12) (new));
It clarifies the cancellation of a union to be effective only
after a court decision (new Article 120 (1));
It introduces a simpler system of collective bargaining and
labor dispute settlement, with specified time limits to speed
up the resolution of conflict (Articles 130 (2), 142 (3), 143
and 151);
It intends to improve the efficiency of the Labor Relation
Boards (Articles 145, 1474 (4), 149 (6), 150, 153 and 154);
It restricts the definition of “essential services” (Article 136
(2)), excluding railway and inter-urban bus services, filling
stations and banks, thereby entitling workers or employers
of these undertakings to the right to strike or lockout.

18
Working time
Hours of work
Normal working hours are 8 hours a day or 48 hours a week (Article
61). They should be distributed evenly, but may be even calculated
over a longer period of time (Articles 63 and 64).
Overtime
Any work exceeding the normal working time of 48 hours a week is
overtime. Overtime is only permissible for up to 2 hours a day, or 20
hours a month, or 100 hours a year, in the following cases (Article
67):
Night work
Pursuant to Article 68 (1) b), night work is work realized between 10
PM and 6 AM.
Paid leave
Annual, uninterrupted leave with pay shall be a minimum of 14
working days, plus one working day for every additional year of
service (Article 77). Additional leave is granted for employees
engaged in particularly hazardous or unhealthy work. It is forbidden
to pay wages in lieu of the annual leave (Article 76).
Public holidays
Ethiopia has twelve public holidays – historical memorial days and
holidays of Christian and Moslem origin - described by law.

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Maternity leave and maternity protection
As mentioned in paragraph 2.5, the Constitution of Ethiopia grants
the right to maternity leave with full pay.
Furthermore, the Ethiopian Labor Proclamation provides one part
(Part Six) to the Working Conditions of Women and Young Workers.
Maternity leave and maternity protection are regulated in Articles
87 and 88.
Other leave entitlements
Articles 85 to 86 provide for an entitlement to sick leave after the
completion of the probation period. An employee is entitled to a
maximum of 6 months of sick leave within 1 year of service. An
employer will only be obligated to grant paid sick leave for the first
months, whereas the wage is reduced to 50 % for the second and
third month, and reduced to zero for the third to the sixth month of
sick leave within a year. For any absence for longer than one day
the employee has the obligation to produce a valid medical
certificate.
Moreover, Article 81 to 84 of the Proclamation provide for special
leave for family events, union activities and other special purposes,
such as for hearings before bodies competent to hear labor
disputes, to exercise civil rights, and for training purposes according
to collective agreements or working rules.

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Minimum age and protection of young workers
Under Article 89 of the Labor Proclamation the statutory minimum
age for young workers is 14 years. Beyond the age of 14 years, no
person may employ a child for work that is inappropriate or that
endangers his or her life or health (Article 89 (2) and (3)). Special
measures of protection of young workers (e.g. work in transport,
night work, work in arduous, hazardous or unhealthy activities, such
as mining) may be taken by the Minister. Work performed under the
regime of a vocational training course is exempted from this
protection (Article 89 (5)).
As shown above, the Ethiopian Constitution gives children general
protection from exploitative labor practices – Article 36 – Rights of
Children.
Ethiopia ratified the ILO Worst Forms of Child Labor Convention,
1999 (No. 182), in September 2003.
Equality
The Constitution guarantees the right to equality in employment,
promotion, pay and the transfer of pension entitlement (Article 35 (8)
of the Constitution).
Pay issues
Ethiopian law does not prescribe minimum wages through statute.
Usually wages are fixed by the employer or by collective agreements
or by the employee's contract of employment.

21
2. Legal framework – Federal Democratic Republic of Ethiopia
The Constitution of the Federal Democratic Republic of Ethiopia
(1995) has made a progress in terms of addressing the concern of
persons with disabilities. In Article 41 of the Constitution, it is stated
that the State shall, within available means, allocate resources to
provide rehabilitation and assistance to the physically and mentally
disabled, the aged, and to children who are left without parents or
guardian.
Purpose of the Proclamation
The Right of Disabled Persons to Employment Proclamation
No.101/1994 is the only legislation of its kind which is specifically
concerned with the rights of disabled persons to employment. In
paragraph 3 of the preamble it is stated that the objective of the
Proclamation is to stop such discriminations and protect the rights of
disabled persons to compete for and get employment on the basis of
their qualifications.
Scope of the Proclamation
Article 2(1) of the Proclamation defines a "disabled person" as a
person who is unable to see hear, or speak or suffering from injuries
to his limbs or from metal retardation due to natural or man made
causes provided however that the term does not include persons
who are alcoholics, drug addicts and those with psychological
problems due to socially deviant behaviors.

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Article 3 of the Proclamation provides for a list of protections
pertaining to the rights of disabled persons. Under this article it is
stated that:
1. Disabled person having the necessary qualifications shall,
unless the nature or the work dictates otherwise, have the
right to compete and to be selected for.
a. a vacant post in any office or undertaking through
recruitment, promotion, placement or transfer
procedures;
Model of Disability.
Where disability is understood as a ‘moral’ matter, associated with
shame or guilt, the policy response is generally one of care by the
family or by religious institutions, and solutions often involve charity.
The legal approach associated with this understanding of disability
has been described as ‘Charity Law (c.f. Degener and Quinn, 2000).
This type of law (often called ‘Poor Law’) aims to alleviate complete
destitution and provides for basic services, in segregated settings
which are often stigmatised.
The working group conclusions on this topic are listed below:
• Disability should be regarded as a human rights issue
• Medical provision should be required at the workplace
• Provision should be made for social security benefits

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• Enforcement mechanisms are essential
• Anti-discrimination provisions should be made
• Measures to promote employment opportunities should be
introduced
• Equality should be the basic principle
• People with disabilities should be encouraged to be
independent
• People with disabilities should be represented in workers’
and employers’ organisations
• Education for all people with disabilities should be
compulsory
• A national body to coordinate and consolidate policies and
existing services/activities relating to disability should be
established
• Training of staff to provide services to employers and
workers is required
• ILO Convention No. 159 should be ratified and adapted to
the specificity of each country
• Data on disability should be collected /analysed/
disseminated

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• All disability-related laws should be reviewed and amended
in line with modern law. Implementation should be
persuasive at the beginning
• ‘Disability’ should be clearly defined
• Quota schemes should be provided for
• Equal opportunities should be promoted
• Registration of employers/registration of persons with
disabilities seeking employment is required
• Incentives to employers should be introduced
• Accessibility/reasonable accommodation to buildings
/information/labour market/technical devices should be
provided for
• Personal support service to ease communication barriers
should be provided for
• Measures to promote job retention should be introduced
• A national multi-sectoral mechanism -a Council or
Committee- should be established
• Reservation of posts should be provided for
Session 2: What are the strengths and weaknesses of existing laws
concerning the employment of people with disabilities, and their
implementation measures?

25
The conclusions of the three working groups on this topic are listed
below:
Strengths
• Laws have been introduced
• Provision for the rights of people with disabilities is made in
some national constitutions
• Laws put forward a human rights approach to disability
• Laws are flexible
• Laws make provision for formal, integrative employment
• Specific provisions are made for training
• Some provision is made for social security
• Provision is made for data collection, registration of people
with disabilities, in some cases
• Disabled persons’ organisations are involved in the
development of laws, in some cases
Weaknesses
In the laws themselves
• Laws too general, vague, specific
• No enforcement/implementation mechanisms specified

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• No provision for affirmative action
• No provision for reasonable accommodation
• No provision for equal opportunities
• Definition of disability too narrow
• No provision for representation of people with disabilities
• No consideration of financial implications
• No provisions for coordination mechanisms, in some cases
• Lack of constitutional provision, in some cases
• Narrow scope – only apply to public sector in some cases
• No specific provision for civil service, in some cases
In the wider context
• No policy framework
• Lack of programmes to support laws
• Lack of supportive services and facilities
• Lack of labour market information
• Inability to cope with the implications of globalization,
liberalization

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Session 3: What needs to be done to improve the existing national
laws and their implementation?
Working Groups were formed for each country to identify what
needs to be done in each case to improve the impact of national
laws.
The common problems encountered in the development of
occupational health service include:
1. Lack of awareness among workers, employers, health
planners, policy makers, health professionals and public
at large.
2. Lack of trained human resource.
3. Inadequate, inaccessible, and inequitably distributed
health service institutions.
4. Lack of multidisciplinary staff, absence of field-testing
equipment for conducting environmental and biological
monitoring of the work place and the health of the
workers.
5. Insufficient budget for carrying out regular inspections,
conducting research activities.
6. The characteristics of the workers, the majorities are
poor, illiterate or poorly educated.
7. Poor working environment.
8. No specific regulation/ legislation on occupational health
and safety issues.

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9. Unfavourable climatic condition and heavy load of
endemic disease: such as bilharzia, onchocerciasis,
malaria, leishhuhumaniasis, and trypanosomiasis.
10. Absence of training institution on occupational health
and safety.
11. Little or no collaboration or cooperation among
stakeholders
12. Poor information exchange /net work in the area of OHS
13. Lack of multidisciplinary forum or panel
14. Absence of integration of occupational health and safety
with general health service
Principles of occupational Health and Safety
The basic principles for the development of occupational health and
safety services are as follows:
a) The service must optimally be preventive oriented and
multidisciplinary.
b) The service provided should integrate and complement
the existing public health service.
c) The service should address environmental
considerations
d) The service should involve, participation of social
partners and other stakeholders
e) The service should be delivered on panned approach
f) The service should base up to date information,
education, training, consultancy, advisory services and
research findings
g) The service should be considered as an investment

29
contributing positively towards ensuring productivity and
profitability.
1.6. Scope of occupational health and safety
Factory management spends large amount of expenses for health
insured workers. The workers compensation expenses include
medical payments (hospital and clinic treatment); partial, temporary,
and permanent disability costs; death benefits; and legal costs. The
cost claims may steadily rise up if the employers do not take
measure to intervene the problem. The productivity of the factory will
obviously decline in such situations. The role of occupational health
and safety, therefore, lies in designing ways and means for cost
reduction through workers proper health service provision.
Occupational diseases, accidents, and death prevention are the
issues to be addressed.
The scope of occupational health and safety is three-fold. It begins
with the anticipation and recognition of workers’ health problems in
an industrial atmosphere. The causes of these problems may be
chemical, physical, biological, psychological, and ergonomical
environments. The second scope includes evaluation of the
recognized problem, which encompasses mainly data collection,
analysis, interpretation, and recommendations. Finally, the third
scope involves the development of corrective actions to eliminate or
limit the problem. Generally, the work frame of occupational health
and safety is wide and needs multidisciplinary approach. It requires
the knowledge of physics, biology, chemistry, ergonomics, medicine,

30
engineering, and related sciences. It also requires public health
management skills for proper communication and decision making.
1.7. Elements of the work environment
The basic elements in an occupational setting such as a
manufacturing plant, industry, or offices are four. These are:
1. The worker
2. The tool
3. The process
4. The work environment
1 The worker
In developing countries like Ethiopia, the work force has several
distinct characteristics:-
1. Most people who are employed to work in the informal sectors,
mainly in agriculture, or in small-scale industries, such as
garages, tannery and pottery.
2. There are high rates of unemployment, sometimes reaching
25% or higher. In huhumany developing countries the rates of
unemployment and under employment is increasing each
year.
3. In general, workers are at greater risk of occupational hazards
for a variety of reasons because of low education and literacy
rates; unfamiliarity with work processes and exposures,
inadequate training, predisposition not to complain about
working conditions or exposures because of jobs, whether or
not they are hazardous, are relatively scarce; high prevalence

31
of endemic (mainly infections) diseases and malnutrition;
inadequate infrastructure and human resources to diagnose,
treat, and prevent work - related diseases and injuries.
4. The annual per capita income for Ethiopia is about $ 120
(USD) or less per year which makes it one of the lowest in the
world. Daily wage for all Ethiopian daily laborers is less than
$1 US dollar.
5. Vulnerable populations in any country are at even greater
risks.
These groups are:
a. Women, who make up a large proportion of the work force in
many developing countries and often face significant
physical and psychosocial hazards in their work. Besides
this they also face similar problem at home as mothers and
cooks
b. Children, who account for a significant part of the work force
in many developing countries, often undertake some of the
most hazardous work. In many of these countries, primary
education is not required and there are no legal protections
against child labor.
c. Migrants - both within countries and between countries who,
for a variety of reasons, face significant health and safety
hazards at work.
Industrial workers constitute only a segment of the general
population and the factors that influence the health of the population
also apply equally to industrial workers, i.e., housing, water, sewage

32
and refuse disposal, nutrition, and education. In addition to these
factors, the health of industrial worker, in a large measure, will also
be influenced by conditions prevailing in their workplace. One of the
declared aims of occupational hygiene is to provide a safe
occupational environment in order to safeguard the health of the
workers and to set up industrial production.
The employee plays a major role in the occupational hygiene
program. They are excellent sources of information on work
processes, procedures and the perceived hazards of their daily
operations or activities. The industrial hygienist will benefit from this
source of information and often obtain innovative suggestions for
controlling hazards.
Obviously there is wide variation among workers in genetic
inheritance, constitutions, and susceptibility to disease. Regardless
of the industrial hygienist will start his or her activities in sorting all
those aspects of hazards including the worker himself.
2 The Tool
Tools can range from very primitive tools like a hammer, chisel, and
needle, to automated equipment.

33
Figure.1-1.Simple hand tools are the causes of many accidents.
Source: Deglaville et.al. Occupational Health, a manual for health
workers in developing countries

34
3 The process
In the process, materials used can be toxic. The process itself can
affect the potential harmfulness of the materials. For example, the
particle size or physical state (solid, liquid and gas) of potentially
harmful substances can determine to a large extent what ill effects in
workers may develop from those substances.
4 The work environment.
Occupational environment means the sum of external conditions and
influences which prevail at the place of work and which have a
bearing on the health of the working population. The industrial
worker today is placed in a highly complicated environment and the
work environment is getting more complicated as human is
becoming more innovative or inventive.
Basically, there are three types of interaction in a working
environment: -
1. man and physical, chemical and biological agents.
a. The physical agents. These include excessive level of
noise
heat and humidity
dust
Vibration
Electricity or lighting
Radiation etc.

35
b. Chemical agents. These arises from excessive air borne
concentrations of
Chemical dust
Mists
Fumes
Liquids
Vapors
Gases
dust
C. The biological agents. These include
Presence of insects and rodents
Microorganisms
Poisonous plants and animals
D.Ergonomic hazards. These include excessive improperly
designed tools, work areas, or work procedures. Improper lifting or
reaching, poor visual conditions, or repeated motions in an awkward
position can result in accidents or illnesses in the occupational
environment.
2. Man and machine
An industry or factory uses power driven machines for the purpose
of mass production. Unguarded machines, protruding and moving
parts, poor electrical and machinery installation of the plant, and lack
of safety measures are the causes of accidents. Working for long
hours in an awkward postures or positions is the causes of fatigue,
backache, diseases of joints and muscles and impairment of the
workers health and efficiency.

36
3. Man and his psychosocial environment.
There are numerous psychosocial factors, which operate at
workplace. These are the human relationships among workers
themselves and those in authorities over them.
Examples of psychosocial factors include:-
The type and rhythm of work.
Work stability.
Service conditions.
Job satisfaction.
Leadership style.
Security.
Workers` participation and communication.
Motivation and incentives.
The occupational environment of the worker cannot be considered
apart from his domestic environment. Both are complementary to
each other. The worker takes his worries to his/her home and bring
to his work disturbances that has arisen in his/her home. Stress at
work may disturb his sleep, just as stress at home may affect his
work.

37
1.8. Review Questions
1. Define the following terms:
a. Anticipation
b. Recognition
c. Evaluation
d. Control
2. What are the challenges for the development of occupational
health and safety?
3. Why is occupational health considered as one part of preventive
medicine?
4. What are the three types of interaction in the working
environment?
5. How can work affect health and health affect work? Give
practical examples
6. Mention the main roles of Environmental Health Officers in
occupational health and safety programs

38
CHAPTER TWO
RECOGNITION OF OCCUPATIONAL
HEALTH AND SAFETY HAZARDS
2.1. Learning Objectives
1. Identify the occupational health and safety hazards in
workplace
2. Explain the effects of chemicals such as organic solvents.
3. Discuss the difference between ionizing and non-Ionizing
radiations.
4. Mention the two main effects of noise.
5. Describe the occupational exposure to biohazards.
6. Give examples of some ergonomic hazards
2.2. Introduction
Identification of occupational health and safety hazards has often
come from observations of adverse health effect among workers.
We can say that potential problem areas must be identified and its
extent should be defined.
The purpose of identification is to:
1. Obtain information on occupational health stresses
2. Collect information on working conditions
3. Collect information on processes and products

39
4. Obtain the threshold limit values for substances
5. Collect information on the effects of exposure on human
6. Collect data on exposure levels by conducting elementary
measurements
7. Determine where problem or potential problem area exist
Advantages of Identification
Not all exposure to occupational stresses are hazardous and in
some instances occupational Exposure limits are never reached,
these areas can be eliminated from extensive evaluation, this
reduces the total evaluation and monitoring process with follows.
Identification lays the foundation of the evaluation, which follows as
we have obtained a lot of information we are going to use in the
evaluation phase. Of course it is not necessary to carry out
identification in an area every time one wishes to quantify workers’
exposure in an area that would be like redesigning the wheel.
Identification saves time, effort and eventually money.
Identification of health and safety problems includes the following:
Observe workplace
Investigate complaints from workers
Examine accident and near-miss records
Examine sickness figures
Use simple surveys to ask co-workers about their health
and safety concerns;
Use check-lists to inspect your workplace;
Learn the results of inspections that are done by the
employer, the union or anyone else;

40
Read reports or other information about the workplace
2.3. Classifications of occupational health and safety
hazards
The various hazards which give rise to occupational injuries,
diseases, disabilities or death through work may be classified as: -
2.3.1 Physical Hazards
2.3.2 Mechanical Hazards
2.3.3 Chemical Hazards
2.3.4 Biological Hazards
2.3.5 Ergonomic Hazards
2.3.6 Psychosocial Hazards
2.3.1 Physical Hazards
Physical hazards, which can adversely affect health, include noise,
vibration, ionizing and non-ionizing radiation, heat and other
unhealthy microclimatic conditions. Between 10 and 30% of the
workforce in industrialized countries and up to 80% in developing
and newly industrialized countries are exposed to a variety of these
potential hazards.
Physical hazard has possible cumulative or immediate effects on the
health of employees. Therefore, employers and inspectors should
be alert to protect the workers from adverse physical hazards.
A. Extremes of Temperature
The work environment is either comfortable or extremely cold or hot

41
and uncomfortable. The common physical hazard in most industries
is heat. Extreme hot temperature prevails on those who are working
in foundries or in those industries where they use open fire for
energy. Examples of these include soap factories in large industries
and in the informal sectors that use extreme heat to mold iron or
process other materials.
Effects of hot temperature in work place include:
1. Heat Stress
Heat stress is a common problem in workplace because people in
general function only in a very narrow temperature range as seen
from core temperature measured deep inside the body. Fluctuation
in core temperature about 2 0
C below or 3 0
C above the normal
core temperature of 37.6 0
C impairs performance markedly and a
health hazard exists. When this happens the body attempt to
counteract by:
Increasing the heart rate
The capillaries in the skin dilate to bring more blood to the
surface so that the rate of cooling is increased.
Sweating to cool the body
2. Heat stroke
Heat stroke is caused when the body temperature rises rapidly in a
worker who is exposed to a work environment in which the body is
unable to cool itself sufficiently. Predisposing factors for heat stroke
is excessive physical exertion in extreme heat condition. The
method of control is therefore, to reduce the temperature of the

42
surrounding or to increase the ability of the body to cool itself.
3. Heat Cramp
Heat cramp may result from exposure to high temperature for a
relatively long time particularly if accompanied by heavy exertion or
sweating with excessive loss of salt and moisture from the body.
4. Heat Exhaustion
This also results from physical exertion in hot environment. Signs of
the problem include:
Mildly elevated temperature
Weak pulse
Dizziness
Profuse sweating
Cool, moist skin, heat rash
5. Cold Stress
Cold stress could mainly be defined as the effect of the external
working environment (Very low temperatures i.e. less than 6 0
C)
and the resultant inability of the body to maintain a constant internal
body temperature. High airflow is a critical factor here, as it will
increase cold stress effects considerably. This is commonly referred
to as the wind chill factor.
Special condition that occur in cold weather
1. Trench Foot
An injury which result from long exposure of the feet to
continued wet condition at temperature of freezing 10 0
C with

43
little movement causes changes in the circulation of blood in the
feet.
Result: loss of toes or part of the feet.
Treatment: keep foot dry and worm, do exercise for good
circulation.
2. Immersion foot
Immersion of foot in water that is below 10 0
C, for a prolonged
time, usually in excess of 24 hours
3. Frostbite
Injury of tissue from exposure to intense cold, body parts most
easily frostbitten is cheeks, nose, ears, chin forehead, wrists,
hands and feet.
Prevention
Wearing the proper amount warm, loose, dry
clothing.
Massaging the face, hand, and feet periodically to
promote good circulation.
Troops travelling in cold weather by, particularly in
the rear of trucks should be allowed to dismount and
exercise periodically to restore circulation.
If clothing become wet, it should be dried or change
at once.
B. Vibration Motion Conditions
Vibration causes vascular disorders of the arms and bony changes
in the small bones of the wrist. Vascular changes can be detected by
X-ray examination of the wrist. The most common findings is
rarefaction of the lunate bone.

44
C. Pressure –Atmospheric (high and low)
Exposure to increased atmospheric pressure (under water) leads to
aseptic bone necrosis around the knee, hip and shoulder that can be
detected by X-ray examination
D. Ionizing and Non-Ionizing Radiation
Radiation having a wide range of energies forms the
electromagnetic spectrum, which is illustrated below. The spectrum
has two major divisions: non-ionizing and ionizing radiation.
Radiation that has enough energy to move atoms in a molecule
around or cause them to vibrate, but not enough to remove
electrons, is referred to as "non-ionizing radiation." Examples of this
kind of radiation are sound waves, visible light, and microwaves.
Radiation that falls within the ionizing radiation" range has enough
energy to remove tightly bound electrons from atoms, thus creating
ions. This is the type of radiation that people usually think of as
'radiation.' We take advantage of its properties to generate electric
power, to kill cancer cells, and in many manufacturing processes.
1. Nonionizing Radiation
We take advantage of the properties of non-ionizing radiation for
common tasks:
• microwave radiation-- telecommunications and
heating food

45
• infrared radiation --infrared lamps to keep food
warm in restaurants
• radio waves-- broadcasting
Non-ionizing radiation ranges from extremely low frequency
radiation, shown on the far left through the audible, microwave, and
visible portions of the spectrum into the ultraviolet range.
Extremely low-frequency radiation has very long wave lengths (on
the order of a million meters or more) and frequencies in the range
of 100 Hertz or cycles per second or less. Radio frequencies have
wave lengths of between 1 and 100 meters and frequencies in the
range of 1 million to 100 million Hertz. Microwaves that we use to
heat food have wavelengths that are about 1 hundredth of a meter
long and have frequencies of about 2.5 billion Hertz.
2. Ionizing radiation
Ionizing radiation has many practical uses, but it is also dangerous
to human health. Both aspects are treated below.
Ionizing radiation is either particle radiation or electromagnetic
radiation in which an individual particle/photon carries enough
energy to ionize an atom or molecule by completely removing an
electron from its orbit. If the individual particles do not carry this
amount of energy, it is essentially impossible for even a large flood
of particles to cause ionization. These ionizations, if enough occur,
can be very destructive to living tissue, and can cause DNA damage
and mutations. Examples of particle radiation that are ionizing may

46
be energetic electrons, neutrons, atomic ions or photons.
Electromagnetic radiation can cause ionization if the energy per
photon, or frequency, is high enough, and thus the wavelength is
short enough. The amount of energy required varies between
molecules being ionized. X-rays, and gamma rays will ionize almost
any molecule or atom. Far ultraviolet, near ultraviolet and visible light
are ionizing to some molecules; microwaves and radio waves are
non-ionizing radiation.
However, visible light is so common that molecules that are ionized
by it will often react nearly spontaneously unless protected by
materials that block the visible spectrum. Examples include
photographic film and some molecules involved in photosynthesis.

47
Figure 2-1 Types of radiation
Source: Adapted from a 2005 National Research Council report .
Alpha radiation consists of helium-4 nuclei and is readily stopped by
a sheet of paper. Beta radiation, consisting of electrons, is halted by
an aluminium plate. Gamma radiation is eventually absorbed as it
penetrates a dense material.
Ionizing radiation is produced by radioactive decay, nuclear fission
and nuclear fusion, by extremely hot objects (the hot sun, e.g.,
produces ultraviolet), and by particle accelerators that may produce,

48
e.g., fast electrons or protons or bremsstrahlung or synchrotron
radiation.
In order for radiation to be ionizing, the particles must both have a
high enough energy and interact with electrons. Photons interact
strongly with charged particles, so photons of sufficiently high
energy are ionizing. The energy at which this begins to happen is in
the ultraviolet region; sunburn is one of the effects of this ionization.
Charged particles such as electrons, positrons, and alpha particles
also interact strongly with electrons. Neutrons, on the other hand, do
not interact strongly with electrons, and so they cannot directly
ionize atoms. They can interact with atomic nuclei, depending on the
nucleus and their velocity, these reactions happen with fast neutrons
and slow neutrons, depending on the situation. Neutron radiation
often produces radioactive nuclei, which produce ionizing radiation
when they decay.
The negatively charged electrons and positively charged ions
created by ionizing radiation may cause damage in living tissue. If
the dose is sufficient, the effect may be seen almost immediately, in
the form of radiation poisoning. Lower doses may cause cancer or
other long-term problems. The effect of the very low doses
encountered in normal circumstances (from both natural and artificial
sources, like cosmic rays, medical X-rays and nuclear power plants)
is a subject of current debate. A 2005 report released by the
National Research Council (the BEIR VII report indicated that the
overall cancer risk associated with background sources of radiation
was relatively low.

49
Radioactive materials usually release alpha particles which are the
nuclei of helium, beta particles, which are quickly moving electrons
or positrons, or gamma rays. Alpha and beta rays can often be
shielded by a piece of paper or a sheet of aluminium, respectively.
They cause most damage when they are emitted inside the human
body. Gamma rays are less ionizing than either alpha or beta rays,
but protection against them requires thicker shielding. They produce
damage similar to that caused by X-rays such as burns, and cancer
through mutations. Human biology resists germline mutation by
either correcting the changes in the DNA or inducing apoptosis in
the mutated cell.
Non-ionizing radiation is thought to be essentially harmless below
the levels that cause heating. Ionizing radiation is dangerous in
direct exposure, although the degree of danger is a subject of
debate. Humans and animals can also be exposed to ionizing
radiation internally: if radioactive isotopes are present in the
environment, they may be taken into the body. For example,
radioactive iodine is treated as normal iodine by the body and used
by the thyroid; its accumulation there often leads to thyroid cancer.
Some radioactive elements also bioaccumulate.

50
Example: Electromagnetic radiation
The energy of a photon (i.e., a quantum of electromagnetic
radiation) is given by the Planck equation:
E = hν
where
E is the energy of the photon
h is Planck's constant
ν is the frequency of the photon
The wavelength of a photon is related to its frequency by the
equation of a wave's velocity:
c = λν
where
c is the speed of light
λ is the wavelength of light
Plugging back in and solving for the wavelength, we get,
λ = hc / E
The elements with the lowest and highest ionization potential are
cesium (3.89 eV) and helium (24.6 eV), respectively. Compounds
can have low ionization potentials as well. For example, PMMA has
an ionization potential of 8.1 eV. Photons with energies less than
3.89 eV (λ > 318.8 nm) are non-ionizing radiation, photons with
energies greater than 24.6 eV (λ < 50.4 nm) are ionizing radiation,
and photons with energies between 3.89 eV and 24.6 eV may be
either ionizing or non-ionizing radiation depending on the nature of

51
material (e.g., cesium or helium). Visible light corresponds to
photons with energies from 1.77 eV (λ = 700.6 nm) to 3.10 eV (λ =
400 nm) and are thus non-ionizing electromagnetic radiation.
Ultraviolet (UV) radiation spans the energy range from 3.10 eV (UV-
A) to 12.4 eV (UV-C, λ = 100 nm). Because UV radiation, especially
UV-C, exceeds the ionization energy of many of the elements, it is
often considered ionizing radiation rather than non-ionizing radiation.
2.1. Uses of ionizing radiation
Ionizing radiation has many uses. An X-ray is ionizing radiation, and
ionizing radiation can be used in medicine to kill cancerous cells.
However, although ionizing radiation has many uses the overuse of
it can be hazardous to human health. Shop assistants in shoe shops
used to use an X-ray machine to check a child's shoe size, which
would be a big treat for the child. But when it was discovered that
ionizing radiation was dangerous these machines were promptly
removed.
2.2 Effects of ionizing radiation upon human health
Natural background radiation
Natural background radiation comes from four primary sources:
cosmic radiation, solar radiation, external terrestrial sources, and
radon.

52
Cosmic radiation
The earth, and all living things on it, are constantly bombarded by
radiation from outside our solar system of positively charged ions
from protons to iron nuclei. The energy of this radiation can far
exceed energies that humans can create even in the largest particle
accelerators. This radiation interacts in the atmosphere to create
secondary radiation that rains down, including x-rays, muons,
protons, alpha particles, pions, electrons, and neutrons.
The dose from cosmic radiation is largely from muons, neutrons, and
electrons. The dose rate from cosmic radiation varies in different
parts of the world based largely on the geomagnetic field, altitude,
and solar cycle. The dose rate from cosmic radiation on airplanes is
so high that, according to the United Nations UNSCEAR 2000
Report ,airline workers receive more dose on average than any
other worker, including nuclear power plant workers.
Solar radiation
While most solar radiation is electro-magnetic radiation, the sun also
produces particle radiation, solar particles, which vary with the solar
cycle. They are mostly protons; these are relatively low in energy
(10-100 keV). The average composition is similar to that of the Sun
itself. This represents significantly lower energy particles than come
form cosmic rays. Solar particles vary widely in their intensity and
spectrum, increasing in strength after some solar events such as
solar flares. Further, an increase in the intensity of solar cosmic rays
is often followed by a decrease in the galactic cosmic rays, called a

53
Forbush decrease after their discoverer, the physicist Scott Forbush.
These decreases are due to the solar wind which carries the sun's
magnetic field out further to shield the earth more thoroughly from
cosmic radiation.
External terrestrial sources
Most material on earth contains some radioactive atoms, if in small
quantities. But most of terrestrial non-radon-dose one receives from
these sources is from gamma-ray emitters in the walls and floors
when inside the house or rocks and soil when outside. The major
radionuclides of concern for terrestrial radiation are potassium,
uranium and thorium. Each of these sources has been decreasing in
activity since the birth of the Earth so that our present dose from
potassium-40 is about ½ what it would have been at the dawn of life
on Earth.
Radon
Radon-222 is produced by the decay of Radium-226 which is
present wherever uranium is. Since Radon is a gas, it seeps out of
uranium-containing soils found across most of the world and may
concentrate in well-sealed homes. It is often the single largest
contributor to an individual's background radiation dose and is
certainly the most variable from location to location. Radon gas is
the second largest cause of lung cancer in America, after smoking.

54
Human-made radiation sources
Natural and artificial radiation sources are identical in their nature
and their effect. Above the background level of radiation exposure,
the U.S. Nuclear Regulatory Commission (NRC) requires that its
licensees limit human-made radiation exposure to individual
members of the public to 100 mrem (1 mSv) per year, and limit
occupational radiation exposure to adults working with radioactive
material to 5,000 mrem (50 mSv) per year.
The average exposure for Americans is about 360 mrem (3.6 mSv)
per year, 81 percent of which comes from natural sources of
radiation. The remaining 19 percent results from exposure to
human-made radiation sources such as medical X-rays, most of
which is deposited in people who have CAT scans. One important
source of natural radiation is radon gas, which seeps continuously
from bedrock but can, because of its high density, accumulate in
poorly ventilated houses.
The background rate varies considerably with location, being as low
as 1.5 mSv/a in some areas and over 100 mSv/a in others. People
in some areas of Ramsar, a city in northern Iran, receive an annual
radiation absorbed dose from background radiation that is up to 260
mSv/a. Despite having lived for many generations in these high
background areas, inhabitants of Ramsar show no significant
cytogenetic differences compared to people in normal background
areas; this has led to the suggestion that the body can sustain much
higher steady levels of radiation than sudden bursts.

55
Some human-made radiation sources affect the body through direct
radiation, while others take the form of radioactive contamination
and irradiate the body from the inside.
By far, the most significant source of human-made radiation
exposure to the general public is from medical procedures, such as
diagnostic X-rays, nuclear medicine, and radiation therapy. Some of
the major radionuclides used are I-131, Tc-99, Co-60, Ir-192, Cs-
137. These are rarely released into the environment.
In addition, members of the public are exposed to radiation from
consumer products, such as tobacco (polonium-210), building
materials, combustible fuels (gas, coal, etc.), ophthalmic glass,
televisions, luminous watches and dials (tritium), airport X-ray
systems, smoke detectors (americium), road construction materials,
electron tubes, fluorescent lamp starters, lantern mantles (thorium),
etc.
Of lesser magnitude, members of the public are exposed to radiation
from the nuclear fuel cycle, which includes the entire sequence from
mining and milling of uranium to the disposal of the spent fuel. The
effects of such exposure have not been reliably measured.
Estimates of exposure are low enough that proponents of nuclear
power liken them to the mutagenic power of wearing trousers for two
extra minutes per year (because heat causes mutation). Opponents
use a cancer per dose model to prove that such activities cause
several hundred cases of cancer per year.

56
In a nuclear war, gamma rays from fallout of nuclear weapons would
probably cause the largest number of casualties. Immediately
downwind of targets, doses would exceed 300 Gy per hour. As a
reference, 4.5 Gy (around 15,000 times the average annual
background rate) is fatal to half of a normal population.
Occupationally exposed individuals are exposed according to the
sources with which they work. The radiation exposure of these
individuals is carefully monitored with the use of pocket-pen-sized
instruments called dosimeters.
Some of the radionuclides of concern include cobalt-60, caesium-
137, americium-241 and iodine-131. Examples of industries where
occupational exposure is a concern include:
• airline crew (the most exposed population)
• Fuel cycle
• Industrial Radiography
• Radiology Departments (Medical)
• Radiation Oncology Departments
• Nuclear power plant
• Nuclear medicine Departments
• National (government) and university Research Laboratories

57
2.3. The effects of ionizing radiation on animals
The biological effects of radiation are thought of in terms of their
effect on living cells. For low levels of radiation exposure, the
biological effects are so small they may not be detected in
epidemiological studies. The body repairs many types of radiation
and chemical damage. Biological effects of radiation on living cells
may result in a variety of outcomes, including:
1. Cells experience DNA damage and are able to detect and
repair the damage.
2. Cells experience DNA damage and are unable to repair the
damage. These cells may go through the process of
programmed cell death, or apoptosis, thus eliminating the
potential genetic damage from the larger tissue.
3. Cells experience a nonlethal DNA mutation that is passed
on to subsequent cell divisions. This mutation may
contribute to the formation of a cancer.
Other observations at the tissue level are more complicated. These
include:
1. In some cases, a small radiation dose reduces the impact of
a subsequent, larger radiation dose. This has been termed
an 'adaptive response' and is related to hypothetical
mechanisms of hormesis.
2. Cells that are not 'hit' by a radiation track but are located
nearby may express damage or alterations in normal

58
function, presumably after communication between the 'hit'
cell and neighboring cells occurs. This has been termed the
'bystander effect'.
3. The progeny of a cell that survives radiation exposure may
have increased probabilities for mutation. This has been
termed 'genomic instability'.
Chronic radiation exposure
Exposure to ionizing radiation over an extended period of time is
called chronic exposure. The natural background radiation is chronic
exposure, but a normal level is difficult to determine due to
variations. Location and occupation often affect chronic exposure.
Acute radiation exposure
Acute radiation exposure is an exposure to ionizing radiation which
occurs during a short period of time. There are routine brief
exposures, and the boundary at which it becomes significant is
difficult to identify. Extreme examples include
• Instantaneous flashes from nuclear explosions.
• Exposures of minutes to hours during handling of highly
radioactive sources.
• Laboratory and manufacturing accidents.
• Intentional and accidental high medical doses.

59
The effects of acute events are more easily studied than those of
chronic exposure.
2.4. Minimizing health effects of ionizing radiation
Although exposure to ionizing radiation carries a risk, it is impossible
to completely avoid exposure. Radiation has always been present in
the environment and in our bodies. We can, however, avoid undue
exposure.
Although people cannot sense ionizing radiation, there is a range of
simple, sensitive instruments capable of detecting minute amounts
of radiation from natural and man-made sources.
Dosimeters measure an absolute dose received over a period of
time. Ion-chamber dosimeters resemble pens, and can be clipped to
one's clothing. Film-badge dosimeters enclose a piece of
photographic film, which will become exposed as radiation passes
through it. Ion-chamber dosimeters must be periodically recharged,
and the result logged. Badge dosimeters must be developed as
photographic emulsion so the exposures can be counted and
logged; once developed, they are discarded.
Geiger counters and scintillometers measure the dose rate of
ionizing radiation directly.
In addition, there are four ways in which we can protect ourselves:

60
Time: For people who are exposed to radiation in addition to natural
background radiation, limiting or minimizing the exposure time will
reduce the dose from the radiation source.
Distance: In the same way that the heat from a fire is less intense
the further away you are, so the intensity of the radiation decreases
the further you are form the source of the radiation. The dose
decreases dramatically as you increase your distance from the
source.
Shielding: Barriers of lead, concrete, or water give good protection
from penetrating radiation such as gamma rays and neutrons. This
is why certain radioactive materials are stored or handled
underwater or by remote control in rooms constructed of thick
concrete or lined with lead. There are special plastic shields which
stop beta particles and air will stop alpha particles. Inserting the
proper shield between you and the radiation source will greatly
reduce or eliminate the extra radiation dose.
Shielding can be designed using halving thicknesses, the thickness
of material that reduces the radiation by half. Halving thicknesses for
gamma rays are discussed in the article gamma rays.
Containment: Radioactive materials are confined in the smallest
possible space and kept out of the environment. Radioactive
isotopes for medical use, for example, are dispensed in closed
handling facilities, while nuclear reactors operate within closed
systems with multiple barriers which keep the radioactive materials

61
contained. Rooms have a reduced air pressure so that any leaks
occur into the room and not out of it.
In a nuclear war, an effective fallout shelter reduces human
exposure at least 1,000 times. Most people can accept doses as
high as 1 Gy[citation needed]
, distributed over several months, although
with increased risk of cancer later in life. Other civil defense
measures can help reduce exposure of populations by reducing
ingestion of isotopes and occupational exposure during war time.
One of these available measures could be the use of potassium
iodide (KI) tablets which effectively block the uptake of dangerous
radioactive iodine into the human thyroid gland.
E. Noise
Noise is defined as unwanted sound. Sound is any pressure
variation or a stimulus that produces a sensory response in the
brain. The compression and expansion of air created when an
object vibrates.
Magnitude
Approximately 30 million workers are exposed to hazardous noise
on the job and an additional 9 million are at risk for hearing loss from
other agents such as solvents and metals. Noise-induced hearing
loss is one of the most common occupational disease and the
second most self-reported occupational illness or injury.

62
Industry specific studies reveal:
• 44% of carpenters and 48% of plumbers reported that they
had a perceived hearing loss.
• 49% of male, metal/non-metal miners will have a hearing
impairment by age 50 (vs. 9% of the general population)
rising to 70% by age 60.
While any worker can be at risk for noise-induced hearing loss in the
workplace, workers in many industries have higher exposures to
dangerous levels of noise. Industries with high numbers of exposed
workers include: agriculture; mining; construction; manufacturing
and utilities; transportation; and military.
Industrial Noise
Although the problem of noise was recognized centuries ago, for
example Ramazini in 1700 described how workers who hammer
copper have their ears injured due to exposure to the sound. The
extent of the problem, which was caused by such noise, was not felt
until the industrial revolution in England. The increasing
mechanization in industries, farms, transport and others are likely to
be more intense and sustained than any noise levels experienced
outside the work place.
Industrial noise problems are extremely complex. There is no
“standard " program that is applicable to all situations. However,
industries are responsible to consider and evaluate their noise
problems and to take steps toward the establishment of effective

63
hearing conservation procedures.
The effectiveness of hearing conservation program depends on the
cooperation of employees, supervisors, employers, and others
concerned. The management responsibility is to take
measurements, initiating noise control measures, undertaking the
audiometer testing of employees, providing hearing protective
equipment with sound policies, and informing employees of the
benefits to be derived from a hearing conservation program.
General Class of Noise Exposure
There are three general classes into which occupational noise
exposure may be grouped.
1. Continuous noise: Normally defined as broadband noise of
approximately constant level and spectrum to which an
employee is exposed for a period of eight hours per day or 40
hours a week.
2. Intermittent Noise: This may be defined as exposure to a given
broadband sound pressure level several times during a normal
working day
3. Impact (impulse) type Noise: is a sharp burst of sound. A
sophisticated instrumentation is necessary to determine the
peak levels for this type of noise.
Effects of noise exposure
Noise is a health hazard in many occupational settings. Effects of
noise on humans can be classified into various ways. For example,
the effect can be treated in the context of health or medical problems

64
owing to their underlying biological basis. Noise induced hearing
loss involves damage to the structure of the hearing organ.
The effects of noise on humans can be classified into two types:
Non auditory effect
Auditory effect
Non-auditory effects
This consists of fatigue, interference with communication, decreased
efficiency and annoyance.
Auditory effects
Auditory effects consist of permanent or temporary hearing loss. The
ear is especially adapted and most responsive to the pressure
changes caused by airborne sound or noise. The outer and middle
ear structures are rarely damaged by exposure to intense sound
energy except explosive sounds or blasts that can rupture the ear
drum and possibly dislodge the ossicular chain. More commonly,
excessive exposure produces hearing loss that involves injury to the
hair cells in the organ of corti within the cochlea of the inner ear.
Noise-induced hearing loss
Work-related hearing loss continues to be a critical workplace safety
and health issue. The National Institute for Occupational Safety and
Health (NIOSH) and the occupational safety and health community
named hearing loss as one of the 21 priority areas for research in
the next century. Noise-induced hearing loss is 100 percent

65
preventable but once acquired, hearing loss is permanent and
irreversible. Therefore, prevention measures must be taken by
employers and workers to ensure the protection of workers' hearing.
Prevention of noise exposure
OSHA requires a five phase hearing conservation program for
industry:
1. Noise Monitoring
2. Audiometric (Hearing) Testing
3. Employee Training
4. Hearing Protectors
5. Recordkeeping
E. Illumination
Good and sufficient lighting is aimed at promoting productivity,
safety, health, well being and pleasant working conditions at an
economical cost.
Luminance: is the brightness on an object.
Illuminance: is the amount of light, which falls on the surface. It is
measured in lux.
Purpose of good lighting
• help provide a safe working environment;
• Provide efficient and comfortable seeing
• reduce losses in visual performances.

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Effects of Poor Illumination
Some less tangible factors associated with poor illumination are
important contributing causes of industrial accidents. These can
include:
o direct glare
o reflected glare from the work
o dark shadows which may lead to excessive visual
fatigue
o visual fatigue, it self may be a causative factor in
industrial accidents
o delayed eye adaptation when coming from bright
surroundings into darker ones .
2.3.2 Mechanical Hazards
Mechanical factors include unshielded machinery, unsafe structures
at the workplace and dangerous unprotected tools are among the
most prevalent hazards in both industrialized and developing
countries. They affect the health of a high proportion of the
workforce. Most accidents could be prevented by applying relatively
simple measures in the work environment, working practices, and
safety systems and ensuring appropriate behavioural and
management practices. This would significantly reduce accident
rates within a relatively short period of time. Accident prevention
programmes are shown to have high cost-effectiveness and yield
rapid results. However, ignorance of such precautions, particularly in
sectors where production has grown rapidly, has led to increasing
rates of occupational accidents.

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Workers who use hand tools such as picks, hammers, shovels, or
who habitually kneel at their work may suffer from “beat" condition of
the hand, knee or elbow. Beat hand is subcutaneous cellulites,
which occurs among miners and stoker caused by infection of
tissues devitalized by constant bruising.
Figure .2-1. Moving part of machinery is securely fenced
Source: Deglaville et.al. Occupational Health, a manual for health
workers in developing countries.

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2.3.3 Chemical Hazards
Average annual world production of chemicals amounts to an
estimated 400 million tones. There are between 5 to 7 million known
chemicals, however, only 70,000 to 80,000 are on the market, with
1,000 or so being produced in substantial quantities. In North
America around 1,000 to 1,200 are produced annually (50 % are
polymers).In Western Europe, some 150 to 200 new substances are
registered each year. Of the 70,000 to 80,000 chemicals only 5 to 10
%( i.e., 500 to 7,000 should be considered hazardous; 150 to 200 of
these are carcinogenic.
Chemical hazards are dependent on their amount:-
• Amount
• Concentration
• Time of exposure
• Mode of entry to the body
• Age
• Sex
• Health status
• Resistance of the exposed workers
The effects of chemical agents are as follows:
1. Asphyxiation
2. Systemic intoxication
3. Pneumoconiosis
4. Carcinogens
5. Irritation
6. Mutagencity

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7. Teratogenicity
Among all chemical agents in work place the most notorious and
most in contact with the skin or respiratory system that deserve
attention is solvent
Solvent
In most occupational settings or industries a potential threat to the
health, productivity and efficiency of workers is their exposure to
organic solvents. Exposure to solvents occurs throughout life.
Example, organic solvent vapor inhaled by a mother could reach the
fetus.
Classification of Solvents
The term solvent means materials used to dissolve another material
and it includes aqueous or non-aqueous system. Aqueous solutions
include those based in water.
Example:
Aqueous solution of acids
Aqueous solution of alkalis
Aqueous solution of detergents
Aqueous solutions have low vapor pressure thus the potential
hazard by inhalation and subsequent systemic toxicity is not great.
Examples of non-aqueous solutions
Aliphatic hydrocarbons.
Aromatic hydrocarbons.

70
Halogenated hydrocarbons.
Cyclic hydrocarbons.
The solvent we are concerned in occupational health and safety will
include any organic liquid commonly used to dissolve other organic
material.
These are:
Naphtha
Mineral spirits
Alcohol,etc
Effects of Solvents
The severity of a hazard in the use of solvents and other chemicals
depends on the following factors.
1. How the chemical is used.
2. Type of job operation, which determines how the workers are
exposed.
3. Work pattern.
4. Duration of exposure.
5. Operating temperature.
6. Exposed body surface.
7. Ventilation rates.
8. Pattern of airflow.
9. Concentrations of vapors in workroom air.
10. House keeping

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1 Health Effect
The effect of solvents varies considerably with the number and type
of halogen atoms (fluorine and chlorine) present in the molecules.
Carbon tetrachloride, which is a highly toxic solvent act acutely on
the kidney, the liver, gastro intestinal tract (GIT). Chronic exposure
to carbon tetrachloride also, damages and cause liver cancer. This
solvent should never be used for open cleaning processes where
there is skin contact or where the concentration in the breathing
zone may exceed recommended level.
2. Fire and explosion
Using non-flammable solvents can minimize the potential for this or
solvents with flash point greater than 60 degree Celsius or 140
degree Fahrenheit. However the non-flammable halogenated
hydrocarbons decompose when subjected to high temperature and
give off toxic and corrosive decomposition products. If flammable
solvents with Flash point less than this are used precaution must be
taken to:
Eliminate source of ignition such as flames, sparks, high
temperature smoking etc.
Properly insulate electrical equipment when pollutants are
released outdoors.
Solvent hydrocarbons are important compounds in the formation of
photochemical smog. In the presence of sunlight they react with
oxygen and ozone to produce Aldehyde, acids, nitrates, and other
irritant and noxious compounds. The great portion of hydrocarbons

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contributing to air pollution originates from automobiles and
industries.
Figure 2-2. Pesticides are dangerous wherever used.
Source: Deglaville et.al. Occupational Health, a manual for
health workers in developing countries
Dangerous chemical substances
Many dangerous substances are used in industry, commerce,
agriculture, research activities, hospitals and teaching
establishments.

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The classification of dangerous substances is based largely on the
characteristic properties of such substances and their effects on
man. Legislation on this subject also requires the provision of a
specific pictorial symbol on any container or package.
The following terms are used in the classification of dangerous
substances in the classification, packing and labeling of dangerous
substances regulations 1984.
A. Corrosion B. Oxidizing C. Harmful
D. Very toxic and toxic E. Irritant F. Highly flammable
G. Explosive
A. Corrosive
Hazard: Living tissues as well as equipment are destroyed on
contact with these chemicals.
Caution: Do not breathe vapors and avoid contact with skin eyes,
and clothing
B. Oxidizing
Hazard: ignite combustible material or worsen existing fire and
thus make fire fighting more difficult.
Caution: Keep away from combustible material. Restrict smoking
in that area.
C. Harmful
Hazard: Inhalation and insertion of or skin penetration by these

74
substances is harmful to heath.
Caution: Avoid contact with the human body, including inhalation
of vapors and in cases of malaise consult doctor.
D. Very toxic and toxic
Hazard: The substances are very hazardous to health whether
breathed, swallowed or in contact with the skin and may
even lead to death.
Caution: Avoid contact with human body, and immediately
consult a doctor in case of malaise.
E. Irritant
Hazard: May have an irritant effect on skin, eyes and respiratory
organs
Caution: Do not breathe vapors and avoid contact with skin and
eye
F. Highly Flammable
Hazard: Substances with flash point less than 60 0
C or 140 0
F
Caution: keep away source of ignition.
G. Explosive
Hazard: Substances which may explode under certain condition
Caution: Avoid shock, friction, sparks and heat.

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Figure 2-3. Hazard warning signs and symbols
Source: Barbara A. Plog, Fundamentals of Industrial hygiene, 4th
.
Edition, 1996

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Chemical Hazards Evaluation
• Toxicity assessment
• Work activity/risk assessment evaluation
• Assessment of controls effectiveness to block routes of entry
• Exposure monitoring
• Recommendations for improvement
Chemical Hazards: - Exposure Monitoring
Special instruments - infrared absorption, photo-
ionization, gas
Chromatography
Detector tubes
Air sampling and lab analysis
Professional judgment
Chemical Hazards: Engineering Controls
Substitution (use lower toxicity materials)
Enclose processes and otherwise engineer for low
emission / low risk
Provide local exhaust to remove airborne agents
Local exhaust ventilation
Need to have even air flow for hoods
Need to design for adequate capture velocity -
usually about 100 feet/minute
Need sufficient make up air
Use ACGIH Ventilation Manual for design
Reduce exposure time
Better procedures
Training

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PPE - gloves, face shields, respirators
Remote Operation
2.3.4 Biological Hazards
Many biological agents such as viruses, bacteria, parasites, fungi,
moulds and organic dusts have been found to occur in occupational
exposures. In the industrialized countries around 15 % of workers
may be at risk of viral or bacterial infection, allergies and respiratory
diseases. In many developing countries the number one exposure is
biological agents.
HIV/AIDS, Hepatitis B and C viruses and other blood borne
pathogens, tuberculosis infections (particularly among health care
workers), asthmas (among persons exposed to organic dust) and
chronic parasitic infections (particularly among agricultural and
forestry workers), are the most common occupational diseases that
result from such exposures.
Exposure to biological hazards in workplace results in a significant
amount of occupationally associated diseases.
Biological hazards include viruses, bacteria, fungus, parasites, or
any living organism that can cause disease to human beings.
Biological hazards can be transmitted to a person through:
a. Inhalation
b. Injection
c. Ingestion
d. Contact with the skin

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The contract of biohazard depends on:
a. The combination of the number of organisms in the
environment.
b. The virulence of these organisms
c. The susceptibility of the individual
d. Concomitant physical/chemical stresses in the environment.
Classification of Biohazard Agents
Knowing the biohazard and their groupings is important to decide on
what to do to safeguard the workers from the hazards. There are two
points that are important to remember. These are:
1. Any accident involving biohazard material can result in
infection.
2. When working with biological agents or materials for which
Epidemiology and etiology is not known or not completely
understood, it must be assumed that the materials present a
biological hazard.
Occupational Exposure to Biohazards
The most obvious work place in which employees are subjected to
hazards as a result that the work requires handling and manipulation
of biological agents include: surgery, autopsy, contaminated
discharges, blood, pipettes, laboratory specimens, etc.

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1. Research Laboratory
Health personnel such as laboratory technicians and scientists
working on biological specimens are at risk with biological hazards in
the laboratory. Specimen such as blood, pus, stool and other tissue
samples may expose the workers to hazards such as HIV, Hepatitis,
etc.
2. Health care facilities
Many potential biological agents exist in hospital environment.
These are bacterial infection and viral agents. Those working in
laundry, housekeeping, laboratory, central supply, nursing station
and dietary are highly exposed to biohazard from the patient they
handle, from the specimen they collect and from the cloth, needle
and pans they handle and from their general day to day activities.
A/Laundry
Workers in laundry are exposed to discharges from patients by
virtue of the fact that contact with linen (bed sheet), nightdresses
and washable articles that are sent to the laundry for cleaning every
day.
Control of infection or exposure is possible only if workers and
hospital administration adhere to the following:
All linen should be placed in plastic or other bags at the bed side
rather than carried carelessly across the corridor or through the
halls to where collection bags or the laundry is collected.
Laundry bags should be color coded in order to alert laundry
workers that, what is contained in the bags is potentially

80
hazardous.
When the soiled laundry item reached the laundry the contents
of the bags should be emptied directly into the washing basin,
machine or trough.
Employees responsible for sorting and folding linens can also be
sources of infection as a result of poor personal hygiene.
Thorough hand washing and the use of rubber gloves are
essential and basic infection control methods.
B/Housekeeping
Housekeepers in hospitals are the single highest group exposed to
infectious biological agents.
The areas and condition of contamination are:
Contact with discarded contaminated disposable materials
during all general cleaning activities.
Widespread use of disposable materials, especially those used
in intravenous administration and blood collection.
Contaminated hypodermic needles and intravenous catheters
Dry sweeping of the floor does not remove many microbes. It
rather pushes dust and other materials from one area to the
other. When mops and brooms are improperly treated dust is
dispersed back into the air.
C/Central Supply
The most serious problem in this department is the cleansing of
surgical instruments. Grossly contaminated materials should be
sterilized in an autoclave before any handling or rinsing.

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Scrubbing action is much more efficient than soaking, but it is during
scrubbing that exposure to biohazard is the greatest. Direct injection
of microorganisms is possible if the skin is punctured with dirty
instruments or if the skin has a lesion that comes into contact with
contaminated instruments.
D/Health care staff
The possibility of exposure to infection of health care professionals
that have direct contact with patients is always present. Infection
can be spread in health care facilities through:-
• Patient to patient
• Patient to other staff
• Patient to his/her own family
• Patient to visitors especially if consulting with family
members of the patient
Health care workers are not the only person to spread infection.
Others are
• Patient
• Waste handlers, transporters
• Laundry staffs
Poor health care waste management system hazardous to:-
• Health care workers
• Patients
• Visitors
• Community

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• Environment
To avoid such contamination health care workers should:
Dispose of contaminated equipment properly so that no health
hazard is exposed to infect others.
Hands should be thoroughly washed with soap and water after
visiting each patient to minimize the chance of spreading
harmful infection or organisms from patient to patient.
Gowns, masks and caps must be worn whenever necessary and
removed before entering clean areas such as rest areas and
lunchrooms.
E/Dietary
Staffs involved in food preparation are exposed to infection from
infectious agents such as salmonella, botulism, amoeba and
staphylococcus, which can result from contact with raw fish, meat,
and some vegetables contaminated by sewage or human waste or
dirty water.
Primary prevention against infection or contamination of the food
include:
Proper handling of food products (raw or cooked)
Use clean hands and garments in the food processing areas
No skin lesion of the food handlers
Refrigeration of the food products at a safe temperature level in
order to prevent growth of bacteria.
Adequate cooking of foods.

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The problem of biological hazard in health care delivery system is
increasing because of:
1. Inadequate sanitation, disinfection and sterilization methods.
2. Increase in drug as well as chemical resistant strains of
microbes.
3. Increase of high-risk patients (HIV/AIDS and TB).
3. Agriculture
Occupational exposures to biohazard also occur in agriculture.
There are three types of relationships in terms of disease
transmission between humans and animals. These are:
Disease of vertebrate animals transmissible to human and other
animals (Zoonosis)
Disease of humans transmissible to other animals
(Anthropozooonois)
Disease of vertebrate animals chiefly transmissible to humans
(Zooanthroponosis)
Zoonosis
It consists of viral, bacterial, rickettsial, fungal, protozoal, and
helminthic disease. Among the most important through out the world
are: Anthrax, brucellosis, tetanus, encephalitis, leptospirosis, rabies,
and salmonellosis. The infection could enter the body through
inhalation, ingestion, or through the skin or mucus membrane.

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Biohazard Control Program
1. Employee health.
Pre-placement examination for new employee.
Periodic physical examination as part of a surveillance
program.
Vaccination.
2. Laboratory safety and health.
Employee training
Avoid if possible entering into a biohazard areas.
Avoid eating, drinking, smoking and gum chewing in
biohazard areas
Wearing personal protective equipment is always advisable.
3. Biological safety cabinet
To protect workers from exposure to aerosols especially when
there is contact with biohazards in laundry activities.
4. Animal care and handling
Periodic examination, disposal of manure, cleanliness,
collection of medical history and treatment.
2.3.5 Ergonomic Hazards
2.3.5.1 Ergonomics
Ergonomics, also known as human engineering or human factors
engineering, the science of designing machines, products, and
systems to maximize the safety, comfort, and efficiency of the
people who use them. Ergonomists draw on the principles of

85
industrial engineering, psychology, anthropometry (the science of
human measurement), and biomechanics (the study of muscular
activity) to adapt the design of products and workplaces to people’s
sizes and shapes and their physical strengths and limitations.
Ergonomists also consider the speed with which humans react and
how they process information, and their capacities for dealing with
psychological factors, such as stress or isolation. Armed with this
complete picture of humans interact with their environment,
ergonomists develop the best possible design for products and
systems, ranging from the handle of a toothbrush to the flight deck of
the space shuttle.
Ergonomists view people and the objects they use as one unit, and
ergonomic design blends the best abilities of people and machines.
Humans are not as strong as machines, nor can they calculate as
quickly and accurately as computers. Unlike machines, humans
need to sleep, and they are subject to illness, accidents, or making
mistakes when working without adequate rest. But machines are
also limited—cars cannot repair themselves, computers do not
speak or hear as people do, and machines cannot adapt to
unexpected situations as humans. An ergonomically designed
system provides optimum performance because it takes advantage
of the strengths and weaknesses of both its human and machine
components.
In general, ergonomics deals with the interaction between humans
and such additional environmental elements such as heat, light,
sound, atmospheric contaminants and all tools and equipment

86
pertaining to the work place.
Ergonomics or the proper designing of work systems based on
human factors has the following advantages:
1. There will be more efficient operations
2. There will be fewer accidents
3. There will be reduced training time
4. There will be fewer costs of operations
5. There will be more effective use of workers or personnel.
The goal of "ERGONOMICS" or human factors ranges from making
work safe to humans, and increasing human efficiency and well-
being. To ensure a continuous high level performance, work system
must be tailored to human capacities and limitations measured by
anthropometry and biomechanics.
2.3.5.2 Ergonomic Hazards
Between 10% and 30% of the workforce in industrial countries and
between 50% and 70% in developing countries may be exposed to
heavy physical workload or to unergonomic working conditions such
as lifting and moving of heavy items or repetitive manual tasks.
Repetitive tasks and static muscular load are found in many
industrial and service occupations. In many industrial countries
musculoskeletal disorders are the main cause of both short-term and
permanent work disability, which can cause economic losses that
may amount to 5% of the GNP.

87
Most exposures can be eliminated or minimized through
mechanization, improvement of ergonomics, and better organization
of work and training. In particular, the growing numbers of elderly
workers and the female workforce require constant vigilance from
those responsible for the work organization.
Improving the conditions of the work environment and opportunities
for providing workers’ health, safety and wellbeing essentially means
contributing to sustainable improvement of ergonomics. Local
perceptions about ergonomics in many countries have not captured
headlines in the newspapers. However safe and hygienic
workplaces contribute to sustainable development and this issue can
be raised through proper media exposure.
Principles of biomechanics
It deals with the functioning of the structural element of the body and
the effect of external and internal forces on various parts of the
body.
Taking an example of "lifting" an object from the ground bio-
mechanics seek relevant information:
1. What is the task to be performed (task variable)
2. Would the person be able to do the task (human variable)
3. What is the type of work environment (environmental variable)

88
Task variable
• Location of object to be lifted
• Size of object to be lifted
• Height from which and to which the object is to be lifted
• Frequency of lift
• Weight of object
• Working position
Human Variable
• Sex of worker
• Age of worker
• Training of worker
• Physical fitness of worker
• Body dimension of worker
Environmental variable
• Extremes of temperature (hot/cold)
• Humidity
• Air contaminants
Work physiology
People perform widely different tasks in daily work situation. These
tasks must be matched with human capabilities to avoid "over
loading" which may cause the employee to breakdown, suffer
reduced performance capability or even permanent damage.

89
Matching people with their work
It is important to match human capabilities with the related
requirements of a given job. If the job demands are equal to the
worker's capabilities or if they exceed them, the person will be under
much strain and may not be able to perform the task.
Work classification
The work demands are classified from light work to extremely heavy
in terms of energy expenditures per minute and the relative heart
rate in beats per minute. For example the energy requirement for
light work is 2.5 Kcal/minute and the heart rate is 90 beats rate per
minute, while it was extremely heavy work energy requirement is 15
Kcal/minute and heart beat is 160/minute.
Workstation design
Workstation means the immediate area where the person is
performing his/her duties. The goal of designing a workstation is to
promote ease and efficiency of the person’s performance.
Productivity will affected if the operator is uncomfortable and the
workstation is awkwardly designed.
Workplace design
Workplace is the establishment or department where the person or
worker is performing his/her duties. The most basic requirement for
a workplace is that it must accommodate the person working in it.
Specifically this means that:

90
1. The workspace for the hands should be between hip and
chest height in front of the body.
2. Lower location are preferred for heavy manual work.
3. Higher locations are preferred for tasks that require close
visual observations.
Another key ergonomic concept is that workplace should be
designed relating the physical characteristics and capabilities of the
worker to the design of equipment and to the layout of the work
place.
When this is accomplished:
- There is an increase in efficiency
- There is a decrease in human error
- Consequent reduction in accident frequency.
Design is accomplished after learning what the worker's job
description will be, kind of equipment to be used for that process and
the biological characteristic of the person (worker).
Workspace dimension
Workspace dimension can be grouped in three basic categories:
minimal, maximal, and adjustable dimensions.
Minimal workspace provides clearance for ingress and egress in
walkways and doors.
Maximal workspace dimensions permit smaller workers to see
the equipment.

91
This is ensured by selecting workspace dimension over which a
small person can reach or by establishing control forces that are
small enough so that even a weak person can operate the
equipment.
Adjustable dimensions permit the operator to modify the work
environment and equipment so that it conforms to those
individuals on particular set of anthropometric characteristics.
Effects of non ergonomic working conditions
• Tendosynovitis
• Bursitis
• Carpal tunnel syndrome
• Raynaud’s syndrome (“white fingers”)
• Back injuries
• Muscle strain
To avoid ergonomic hazards the following points should be
considered:-
• Sensibility and perceptibility (visual,audible,tactile)
• Kinetic ability and muscular power or strength
• Intelligence
• Skill
• Ability to learn a new technique of skill
• Social and group adaptability
• Kinetic conditions (body size or physical
constitution)

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• Effect of environmental conditions on human ability
• Long term short term or short term adaptable limits
of man(desirable or normal, compensatory or fatal)
• Reflexion and reaction patterns
• Mode of living (custom) and sex distinction
• Racial differences
• Human relationship
• Factors that affect on synthetic judgment
2.3.6 Psychosocial hazards
Up to 50% of all workers in industrial countries judge their work to be
“mentally heavy”. Psychological stress caused by time pressure,
hectic work, and risk of unemployment has become more prevalent
during the past decade. Other factors that may have adverse
psychological effects include jobs with heavy responsibility for
human or economic concerns, monotonous work or work that
requires constant concentration.
Others are shift-work, jobs with the threat of violence, such as police
or prison work, and isolated work. Psychological stress and overload
have been associated with sleep disturbances, burn-out syndromes,
stress, nervousness and depression. There is also epidemiological
evidence of an elevated risk of cardiovascular disorders, particularly
coronary heart disease and hypertension.
Within the work environment emotional stress may arise from a
variety of psychosocial factors, which the worker finds
unsatisfactory, frustrating, or demoralizing.

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For example:
A peasant who migrates from the rural areas to a city will face
entirely different environment if he/she start to work in an
industry. In his /her rural life he used to work at his /her own
speed but in the factory he may have to work continuously at
speeds imposed by the needs of production.
Workers may be working in shifts that will expose them to
unusual hours. They may upset their family’s life as a result of
their work conditions.
Workers may be working with a person who is paid more but
who is incapable of working.
Financial incentives are too low etc.
These and other stresses will have adverse psychosocial problems
on workers.
Reduction of occupational stresses depends not only on helping
individuals to cope with their problems but also on:
Improved vocational guidance,
Arrangement of working hours,
Job design, and work methods;
Good management.

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2.4 Review questions
1. Select ten occupations common to your community. List the
potential and real occupational risks associated with each type
of employment.
2. What are the common health hazards of organic solvents?
3. Explain the reasons why the magnitude of occupational health
hazards is increasing in health care industries (hospitals, health
centers, laboratory etc).
4. What are the main health effects of Noise?
5. How does the occupational environment of the worker affect the
health of his or her families and the general population?
6. What are the criteria to state that substances are hazardous or
dangerous?
7. What are the advantages of hazard warning symbols or signs?
8. Give two examples each for task, human and environmental
variables
9. What are hazards in hospital environment?
Note to the Instructor
Please take your students to an occupational setting (industries,
factories, workshops, hospitals, classrooms, laboratories etc) and
ask them to indicate health and safety hazards in the work
environment. Discuss their findings and your observation with the
students. The assignment in the setting could be in teams. If so, ask
the group leaders to present their findings to a plenary in the
classrooms.

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CHAPTER THREE
OCCUPATIONAL ANATOMY AND
PHYSIOLOGY
1. Discuss the functionality of human physiology
2. Explain the principles of occupational anatomy and
physiology anatomy.
3. Identify the occupational physiology related problems
3.2. Introduction
Before we attempt to assess the effect of work on the health of man,
it is expedient to summarise briefly our knowledge of the human
body and the working of its organs. Of Course, all the organs of the
body take part in the life, and hence in the work, of human.
However, certain parts of the body that determine working capacity
are more particularly involved; they can therefore be considered as
representative, and only they need to be studied.
3.3 Anatomy and physiology
Muscles
All physical work is done by muscles, in which the necessary energy
is created. The first task of the muscles is to maintain the body in the

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required posture (upright, seated, kneeling, and so on) and then to
effect the various movements. It is through them that useful work is
finally done.
Muscles work by alternating contraction and relaxation of the
component fibres, resulting from chemical action. Muscle fibres,
which are mostly arranged in groups or bundles in different parts of
the body, cause various movements by acting on the bones.
Muscles also cause movements in internal organs.
The energy required to contract the muscle fibres is provided by the
oxidisation of glucides. The combustion residues include lactic acid,
water and carbon dioxide. Since the chemical reactions take place
within the fibres themselves, it becomes necessary for the oxygen
and the fuel to be brought to these fibres and for the waste products
of combustion to be removed, either to be discharged outside or to
be reintroduced in a regeneration cycle. The working capacity of
muscle therefore depends on the number of fibres (musculature),
the capacity of the transport routes (arteries and veins), the speed of
the transport (blood flow), the functioning of the regulatory system
which has to harmonise the physiological phenomena with the effort
exerted, and the pulmonary function which ensures the renewal of
the oxygen in the blood and the elimination of gaseous waste.
Bones and joints
To effect movements of the body, muscles require a firm anchorage;
bones may therefore be considered as being practically rigid. To a
certain extent they are also elastic, especially in young persons. This

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elasticity, however, does not play any part in work, it is needed to
take the strain of heavy loads. If the elasticity is insufficient, as is
often the case in accidents, a bone will break. Most bones in the
body are connected by joints (such as the knee, the hip and the
elbow), or they are semi-rigidly connected by ligaments or cartilage
(as the ribs are to the upper part of the spinal column), or they are
fastened together like the bones of the skull, whose purpose is to
protect the brain. The spinal column has quite a special structure.
The vertebrae are so shaped that the upper part of the body can
assume the most widely differing positions in relation to the lower
part, and it can also rotate independently. There is a special reason
for this structure, in that the spinal column protects the abdominal
organs. Since it can only move by arching and cannot bend like the
knee, these organs always have enough room. It does happen that
in certain positions of the torso some organs are slightly
compressed, but their functions are only very slightly impaired on
this account. In order to leave the organs with the space that they
require and to maintain the torso in a suitable position, the vertebrae
are connected by joints that are only slightly mobile and by
ligaments called meniscuses or intervertebral discs. Because of their
inelasticity, the meniscuses are very sensitive to repeated jolts, such
as those caused by the bumping of a vehicle that has neither springs
nor shock absorbers.
The spinal column protects only the hinder part of the abdomen; the
rest is protected by a wall of ligaments and muscles. The muscles
are superimposed and the fibres are criss-crossed so as to
constitute an envelope that is both elastic and strong. This enables

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the body to bend forwards and sideways, and hence allows it to
work in a bent position. When the abdominal wall is overloaded,
especially when heavy weights are lifted, the weakest points may
give way and this may lead to hernias.
The thorax, which can move only a little, protects not only the vital
organs-the heart and the lungs-but also the top of the stomach, the
liver, the gall bladder and the spleen. The vertebrae are connected
by muscles and ligaments, and the shoulder-bones and collar-bones
are connected to the chest by the same means. The back muscles
play an important part in maintaining the position of the body. The
less they are developed, the more the vertebrae are pressed
together, and consequently the greater the risk of deformation of the
spinal column. The back muscles are also needed to compensate
for the efforts made when the arms are working.
The strength of bones is invariable over a good part of a person's life
span, and it is wrong to suppose, as often happens, that because
old people are particularly subject to bone fractures they have soft
and weak bones. In fact, a predisposition to bone fractures is the
result of poor musculature that is no longer able to hold the bones
together adequately, coupled with vagueness and lack of co-
ordination of movements.
Circulation of the blood and respiration during work
One of the principal determinants of the power of muscles is the
amount of blood flowing through them. The total amount of blood

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may be considered as a personal constant because normally it is
subject to only slight variations. The amount of red pigment
(haemoglobin) determines the amount of oxygen that can be fixed in
the blood. The velocity of the bloodstream and the volume of the
vessels (arteries and veins) govern the quantity of oxygen available
in muscles. The blood is moved by the heart, first through the lungs
where it fixes the oxygen, and then through the muscles and the
organs where part of the oxygen is consumed. From these it returns
to the heart and lungs. It is not only the size of the heart but also,
and directly, the rate at which it beats (pulse) that determines the
blood flow. Hence, measurement of the rate of beating or pulse is of
great importance in assessing the strength required to perform a
given job. Naturally, the amount of oxygen consumed is directly
proportionate to the muscular energy produced. It is, however, more
difficult to measure this than the heart rate. All that is usually done is
to compare the oxygen content of the inhaled and exhaled air,
whereas at the same time it is necessary to measure the respiration,
which is proportionate to the effort expended.
During inhalation the lungs fill with fresh air, rich in oxygen; this air
passes through the membranes of the alveoli of the lungs, enters the
blood stream and is fixed by the haemoglobin. Each cell can fix and
transport only a certain amount of oxygen. Muscular work depends
on the amount of oxygen that the blood can convey to the muscles;
similarly, the rate of elimination of carbon dioxide depends on the
blood flow through the body. Consequently, good circulation and
respiration are of essential importance to working capacity.

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The heavier the demands made on muscle power, the faster the
blood must flow and the faster the human must breathe, because
the concentrations of energising substances and cells transporting
oxygen are almost constant. When the composition of the blood is
normal, the amount of oxygen that it transports is sufficient for
combustion. However, if it is too poor in haemoglobin the oxygen
flow is insufficient and the muscle cannot do as much work; if, in
such a case, it is desired to intensify muscular work, the circulation
of the blood must be accelerated and the shortage of haemoglobin
must be compensated by an acceleration of the rate of oxygen
exchange in each muscle. In a person whose blood is poor in
haemoglobin, the amount of muscular work will be less than in a
person whose blood contains a normal amount of haemoglobin. The
requirements of a muscle considered in isolation naturally depend
on the work it has to do.
During periods of rest, at each heart beat the pumped blood is
distributed among the different organs in accordance with a fixed
pattern. During work, an additional flow of blood must irrigate the
regions producing the energy so as to feed the muscles and remove
the waste products. The regulatory mechanism of the circulatory
system works with extraordinary precision and sensitivity. Its
reaction to change must be almost instantaneous, because the
movements of the body alter very quickly. One needs only to think,
for example, how quickly the different muscles of the legs act in turn
when one is walking; and the same, of course, applies to the
muscles of the arms and legs, or the hands and arms, in other
movements. The blood flow per minute is regulated by the rate at

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which the heart pumps; this can be measured by the pulse, and is
only slightly influenced by variations in the size of the heart. The
quantity of blood flowing towards any particular part of the body
depends on the cross-section of the blood vessels concerned. The
blood arrives through the arteries and leaves through the veins.
When the blood supply to a certain region has to increase, the
arteries carrying it have to dilate in order to increase their carrying
capacity, as do the veins when the blood is returning to the heart.
When certain regions of the body need intense irrigation, the arteries
and veins contract in other regions, in which irrigation is thereby
reduced so that the circulation can meet the increased needs of the
first-mentioned regions. It is true that the vital organs continue to
receive just enough blood to enable them to function, but in these
conditions they are not particularly active. It is, however, very
important to maintain the irrigation of the brain. Of course, the
amount of blood required there is small in comparison with that
required by the large muscles, such as those of the thighs when they
are working at full capacity. But the brain needs blood that is rich in
oxygen, and its activity declines when the demand for blood
becomes too high in other parts of the body. Naturally, other organs,
such as those of the digestive system, may compete with the
muscles for blood supply. After meals the digestive system needs a
large quantity of blood, not only to make its own muscles work but
also to transport and distribute the products of digestion. Man should
therefore stop working during and immediately after meals so as not
to hinder the working of the digestive tract. This is also the reason
why the zeal for work declines even before the meal break. This

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changing blood distribution between organs and muscles is also due
to the regulation of circulation. The system is so responsive to the
variations with which it has to deal that it can work for several
decades without breaking down. Thus, working capacity depends
also on the proper working of the regulatory mechanism of the
circulation.
Basal metabolism
A minimum expenditure of energy is always required, independently
of any activity, and even during sleep. This is "basal metabolism". It
is the minimum energy exchange that is essential for the
maintenance of life. Basal metabolism (measured in calories)
depends on the weight of the body and its surface area (temperature
regulation) and varies slightly with sex and age. Such determinations
of basal metabolism as may be necessary for medical reasons or for
work study must be carried out in a specially equipped laboratory.
Static work
So far we have spoken only of dynamic muscular work-that is, work
done by movements of the body. There is, however, another kind of
work: static work, or the work of maintaining a position. Such work
entails constant effort by the muscles that maintain certain parts of
the body in particular positions (crouching, kneeling, sitting, and so
on). Carrying loads on outstretched arms or on the head are
examples of static work. If the body is to maintain a certain posture,
the first requirement is that the head is in such a position that the
functioning of the brain is not hampered. Second, the posture should
be such that the reactions of dynamic work (for instance, when

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walking or making tractive effort) can be absorbed without loss of
balance.
As we have discussed, muscles work by alternating contraction and
relaxation of their component fibres. However, the work of
maintaining a position cannot be accomplished by continuous
contraction, since muscular relaxation is indispensable to irrigation
by the blood and to the removal of the waste products of oxidisation.
In static work, the contraction phase of each fibre is much longer
than the relaxation phase, and there are therefore always more
contracted than relaxed muscles. Consequently, the time available
for removing waste products is much shorter than in dynamic work,
and static work causes fatigue much more quickly -indeed, a given
group of muscles produces 15 per cent less effort in static than in
dynamic work. Carrying an object with outstretched arms soon
causes fatigue, and standing still for a long time may cause fainting
due to imbalance of the circulation. Work done by the hand in static
contraction, on a tool, a work-piece, a pen or other object often
causes pain, indicating an accumulation of waste products in the
muscles. Posture during work and the manner of working therefore
have a considerable effect on output.
Thermal regulation
If all the vital functions of the human body are to remain unimpaired,
the body's internal temperature must be maintained at or about
37°C. If a human lives in a cool or cold environment, he/she is
constantly dissipating a certain amount of heat. This leads to the
intensification of basic combustion in order to make up for the

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constant loss of calories. In adults, the basal metabolism needed for
the functions of the various organs represents between 1,200 and
1,600 kcal per day, or between 0.85 and 1.1 kcal per minute. But
this amount of heat is not enough to compensate for the losses
unless the environmental temperature is at least 20°C. In agricultural
work it is practically impossible to regulate the environmental
temperature, and the clothing must therefore be adapted to the
working conditions.
The additional heat produced by physical work is sometimes very
great and may amount to several times that of basal metabolism.
For an eight-hour day, depending on the effect required, the
expenditure of energy ranges from 2,000 to 3,000 kcal. The average
is therefore 4-6 kcal/min, with peaks which may reach 12 kcal/min.
This great amount of heat has to be eliminated as quickly as
possible. The body dissipates heat by radiation, convection or
evaporation (sweat). Radiation and convection, by which the body
can dissipate only 2-2.5 kcal/min, are restricted by clothes. The heat
losses by radiation and convection depend primarily on the
difference in temperature between the skin and the environment,
and this is regulated to a certain extent by the circulation of the
blood.
The greater the amount of excess heat to be removed, the more the
circulation increases at the level of the skin and the faster the heat
exchange with the environment becomes. The thermal conductivity
of the skin is different in the two sexes, being lower in women than in
men. This is why women can generally bear to be more lightly

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clothed than men. The dissipation of body heat increases in a
draught, which is constantly bringing cooler air into the vicinity of the
skin.
If the work generates more heat than can be dissipated by radiation
and convection, sweat is produced, which evaporates on the skin.
The phenomenon of sweat evaporation enables large quantities of
heat to be dissipated in the environment. The larger the sweating
area of the skin and the drier the environmental air, the greater the
dissipation of heat by sweat. While for light work the humidity of the
air is of no great significance, intensive work can be done only if the
air is not saturated with humidity (that is, if it is comparatively dry),
as otherwise the sweat cannot evaporate. Sweat can remove excess
calories only by evaporating, and this is why streaming sweat
represents a useless waste of energy.
As evaporation depends on the environmental temperature and air
movements, clothing is an important factor here too. Since sweating
is not uniform over the whole surface of the body, underclothes may
facilitate the dissipation of heat if they are completely soaked with
sweat. Thus underclothes should rapidly absorb sweat, distribute it
and ensure uniform and regular evaporation. The larger the surface
of the garments, the more effectively will they fulfil these tasks.
Natural fibres such as wool and cotton are impregnated more slowly
than synthetic fibres. Closely woven materials are less effective than
loose materials, such as knitted garments.

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Equatorial and tropical countries are normally regarded as "hot
countries". They may nevertheless have temperate seasons and
cool upland regions (for instance, the east central African plateau,
which is at an average altitude of 1,500 m and has intensively
cultivated areas up to an altitude of about 3,000 m near the equator).
As a rule, workers in hot climates cannot be expected to have the
same output as those in temperate countries.
Co-ordination of physiological functions
The foregoing very brief description of some physiological functions
suggests the existence of a very precise regulatory system for the
necessary harmonisation of these functions. This regulation is
controlled by the nerves, which receive their impulses from widely
differing centres, most of them in the brain. It is almost entirely
unconscious and involuntary, and depends on the physiological
automation that keeps the body alive. The over-all co-ordination of
the maintenance of body balance, the adaptation of respiration and
circulation and the dissipation of heat are automatic reflex functions
that do not require any voluntary interference. Automatic regulation
is surer and more precise than conscious regulation and also seems
to need a smaller expenditure of energy. This is in fact the reason
why, whenever possible, man tends to replace certain processes,
movements and actions by reflexes. Advantage is taken of this fact
in training and working. However, this natural tendency, imposed on
man as it were by his physiology, has as its counterpart an attitude,
varying in degree, of inertia towards changes in working habits. In
fact every new process has first to be controlled by the will; only later
does it come within the province of reflexes, which, if necessary, will

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succeed and replace reflexes controlling the processes adopted
hitherto.
The precision of regulatory functions varies with the importance of
each in the maintenance of vital equilibrium, health and welfare.
While internal temperature is regulated very precisely, the oxygen
content of the blood is less so, and the water content of the body still
less. Some types of regulation, such as that of blood supply to
muscle, are almost instantaneous; others, such as the reconstitution
of energy reserves, sometimes take several hours. Some have a
daily rhythm-for instance, the alternation of activity (day) and rest
(night)-and others have a periodicity of a year or more (duration of
sleep in summer and winter, variation of activity with age). The
organs can retain their vitality only by functioning regularly; they
have no need of prolonged rest. On the contrary, inaction may
atrophy them and put an end to the corresponding regulatory
function.
The proper working of the regulatory system depends on healthy
development in childhood and adolescence, suitable training during
growth and continuous exercise later.
Adaptation to environment
The co-ordination of the different functions of the body is not the sole
task of physiological regulation; it must also ensure the correct
adaptation of the individual to the environment. This is of capital
importance for the maintenance of maximum working capacity in
face of the enormous variations that may occur in the nature and

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place of work. For example, the muscular energy must correspond
to the effort demanded, and the dissipation of heat to the
environmental temperature. This adaptation can be easily observed:
if the intensity of the effort increases, the pulse and breathing rates
will steadily increase too. The eye adapts itself automatically to the
luminosity and distance of objects. These are only a few of the
countless regulatory activities induced by stimulation from the
environment.
Working capacity
State of health and working capacity
Human's working capacity depends on the sum total of his
physiological functions. It is based to some extent on a certain
natural predisposition, but more on the development and training of
the body, muscles and regulatory organs and centres. A person's
working capacity is thus closely bound up with his state of health.
Physical work calls for certain qualities that human, if he enjoys
good health, can develop fully by training. It requires well developed
muscles, a robust skeleton, sound organ (circulatory, respiratory,
renal, digestive, etc.) and a good neuro-endocrinian regulatory
system.
Diet and work
An adequate and balanced diet is one of the indispensable
conditions of satisfactory working capacity. The more muscular work
a human does, the greater must be his consumption of the
substances required for chemical combustion. Energy reserves must

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therefore be replenished by a diet rich in carbohydrates. Most of the
carbohydrates in a diet come from cereals: wheat in Europe and
North America, rice in Asia and maize in Latin America.
Human other plants are rich in carbohydrates, such as sorghum,
manioc and potato. In making bread and paste, cereals must be
treated to make them more digestible; they also undergo
transformation in the body. On the other hand, sugar can be
absorbed without any preparation and quickly passes into the blood,
so that it is a very important food in intensive work.
When a human does less strenuous work, his diet should contain
correspondingly fewer carbohydrates. It is a problem peculiar to
modern nutrition in industrial countries (in which muscular work is
steadily declining and consequently the consumption of
carbohydrates should decline to the same extent) that because of
habit or appetite people still consume large quantities of
carbohydrates. This leads to obesity, which is not only inimical to
work but is also at the origin of human diseases. In addition to
carbohydrates, food should contain proteins and fats, the latter
contributing to the energy balance, more especially in the internal
organs. Protein is needed in the formation of cell tissue, which is
constantly being renewed; this is why muscle too needs a supply of
protein. It is obvious that an adolescent whose muscular growth is
not completed will need more protein than an adult; but the adult
must have a certain minimum amount to maintain his energy
balance. The body needs various proteins, and if a diet is to be
balanced it must be adequate in quantity and quality. If it is not,

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there will be a food deficiency. Above all, there must be a minimum
proportion (about 30 per cent) of animal protein for persons doing
heavy, difficult or intellectual work.
All food is transformed in the digestive tract before being conveyed
to the organs for which it is intended. Digestion is a cyclic and not a
continuous process, but since requirements in muscular energy are
either continuous (in the heart muscle, for example) or spread
evenly over the hours of the day (as in the muscles of locomotion),
reserves have to be constituted. Thus food can be absorbed and
digested at the intervals fixed by meals. In healthy persons the body
has sufficient reserves to enable it to burn, over a period of several
days, more substance than is supplied by the food consumed during
those days. In the long run, however, the food intake must restore
the balance or exhaustion will ensue. The more energy the work
demands, the richer and more frequent the meals should be; but
meals should be spaced out if the work falls off. Thus a human doing
heavy work needs five meals a day, while a tractor driver, for
example, if he is comfortably seated, is so little affected by eight
hours of work that he should easily be able to manage with three
meals a day. The proper working of the digestive system is just as
important for working capacity as are the soundness of the skeleton
and the development of muscles.
Training
Working capacity is determined by muscular development as well as
by food and by the adaptation of the circulatory and respiratory
systems and their regulatory mechanisms. It is possible to develop

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individual predispositions by training, up to an advanced age, and to
maintain them at a high level.
In physical training stimulations are produced by muscular work, the
maximum stimulation corresponding to overwork up to the limit of
fatigue. A short spell of overwork-from two to five minutes, for
example-is the best form of physical training. Naturally, persons
suffering from pathological changes or disorders should avoid such
efforts.
The stimulation produced by training may be deliberate, as in sport,
and be intended to develop the muscles of a particular part of the
body, but it occurs automatically in all work. The greater the amount
of work required of the different parts of the body, the better will be
the physical condition. Thus varied muscular work, as encountered
in many agricultural activities, is one of the best means of achieving
a harmonious development of the body. The physical development
of adolescents should therefore be promoted systematically, by
means of work suited to their body strength and their age. Muscular
stimulation that is due to training and causes muscles to develop
also strengthens certain organs that participate indirectly in muscular
work. Both the heart muscle and the regulatory mechanism of
circulation benefit from the training constituted by steady work.
The functions of each are decisive for the maintenance of a person's
working capacity. The regulation of the circulation is a very good
example of the organisation of an aggregate of physiological

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reflexes designed to produce the requisite effect at any point and
moment.
Physiological regulation operates at two different levels. One is
independent of the will and is essentially concerned with the
maintenance of life. It comprises the regulation of the heart, the
circulation and the respiration, the regulation of the digestive system,
the co-ordination of circulation and respiration, and so on. The other
consists of regulatory mechanisms that depend on the will and
govern processes bound up with voluntary action. But as a result of
exercise and training, the control of work very soon passes into the
domain of automatic reflexes. It must be supposed that unconscious
regulation is more economical, and at the same time quicker and
more precise, than conscious regulation. The performance of any
job requires a rapid and precise system of regulation. This system
also is subject to the laws of training: the more it is used, the better it
is trained and the more serviceable it becomes.
There are limits in both directions to these biological processes. The
science of work has long concerned itself with discovering human's
optimum working capacity. The permanent optimum rate is attained
when the energy supply just balances the loss.
There is also a lower limit to physical work. We all know that after a
long spell in bed the body has lost strength and must be laboriously
retrained for work. This is because the stimulation of training has
been absent for too long, and consequently the muscles, muscular
movements and organic regulation have all become too weak. The

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optimum working capacity lies between insufficient work and
excessive work; however, frequent alternation of working intensities-
light work, normal work, heavy work-is, within certain limits, probably
more beneficial to the body than working at uniform intensity for a
very long spell.
If training is to be effective, the same exercises must be repeated
often and correctly. In simple work the effects of training are felt very
soon, generally after a few hours. It is not necessary to repeat the
exercises without a break; they can be performed on alternate days.
This is very important in agricultural operations, some of which
cannot be carried on for long without a break. However, in all the
repetitions the course of the process must be identical. Operations
calling for very close co-ordination of various movements or
perceptions, and those involving analogous but very varied actions,
need longer training periods (up to 50 or 60 hours). Here too,
however, one may count on a sufficient degree of assimilation,
which means that the work is performed correctly under the control
of the unconscious.
This sufficiency of assimilation of operations is particularly important
for the agricultural worker, who can rarely concentrate on the actual
work, being frequently obliged to watch the results so as to control
quality. The farmer, acting both as the head of an undertaking and
as a worker, is even more bound to watch the result of the work, so
that he has no time to see how the work is actually being carried on.
Thus, for the farmer, the introduction of new processes means a

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heavy psychological strain, and attempts should be made to lighten
it by all possible means.
Age and aptitude for work
If the individual limits for these various factors are not exceeded,
working capacity can be maintained over the whole span of active
life. With age, it is true, many functional capacities decrease, as well
as aptitude for training, but this does not matter much if the work
done remains fairly constant. Moreover, the elderly worker often
replaces failing strength by greater skill. Retraining elderly persons
for new and arduous operations is difficult, but a man of 60 can do
most field work just as well as a man of 30, except for those
operations wherein man reaction time may be critical. If ability to
work is to be measured by age, it may be said that it can equally well
begin relatively early and continue well beyond 65 years. The quality
declines only slowly with age if activity is regularly maintained. There
is practically no wear on muscles and organs, as was once thought.
However, the effects of illness increase with the years, because the
aptitude of the body and its functions for training continuously
decline. This is why convalescence in old people is more prolonged
than in the young.
Curve of physiological work and biological rhythm
The working capacity of an individual varies in the course of the day,
and does so in a rhythm that is independent of the actual work. It
increases in the morning from 6.30 to 8 a.m., reaches its maximum
about 10 a.m. and declines towards 11 a.m. In the middle of the day,
between noon and 1 p.m., it is low, whatever the meal taken, and

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then it rises again. The afternoon maximum, between 2:00 and 3:00
p.m., is a little lower than the morning maximum. After 4 p.m.
working capacity falls rapidly. At night it is always lower than in the
daytime. No training can alter this natural rhythm. It persists even
among persons who have worked only at night for several years;
their working capacity remains greater during the day than during
the night.
Fatigue
Whatever the tempo of work, human tires in the course of the day.
Fatigue is a complex physiological condition entailing a reversible
lowering of working capacity. In addition to muscle fatigue due to
work, which is the more acute the more the work is concentrated in a
few muscle groups, human usually experiences general fatigue.
There are days when a person feels very tired after work; there are
others when after the same work he is less tired. Fatigue is thus a
subjective phenomenon that depends on both physiological and
psychological factors. Normal fatigue occurring at the end of the day
is usually overcome by sleep, so that when a human wakes up he is
ready to resume work. However, matters are not always so simple;
after the night's rest some fatigue may remain, but this may be
eliminated one or two days later by a good night's sleep. On the
average, daily fatigue due to work should not exceed the maximum
that can be overcome by a night's sleep. If overwork persists, fatigue
accumulates and may cause serious trouble, or at least reduce
working capacity. Even purely muscular fatigue is overcome by rest,
chiefly by nightly rest. However, local phenomena may also occur in

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muscles; they are mostly due to insufficient elimination of waste
products, which is often the result of the manner of working as much
as of the intensity of the work.
Static effort is always particularly arduous and tiring, and this is why
attempts should always be made to eliminate it from methods of
working. If this is impossible, spells of static work must be shortened
and interrupted by spells of dynamic work. If static work lasts too
long, the minimum results will be local cramp (for example, tractor
drivers suffer from cramp in the right calf when the accelerator pedal
is badly placed and requires excessive effort by the foot).
Intense muscular fatigue and stresses on the brain and the sense
organs (eye, ear and so on) lead to considerable strain on the
central nervous system and consequently to general fatigue, which
in turn is characterised by a general lowering of working capacity. It
will even affect body organs that have taken scarcely any part in the
effort.
The working environment can also affect the functioning of the
central nervous system and contribute to the development of fatigue.
This is more particularly so in workplaces that are dark, noisy and
hot to an unhealthy extent.
Monotonous work causes drowsiness and can lead to extremely
serious problems in many kinds of work.

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Measurement of physical work
Oxygen consumption
Since the degree of fatigue is not always directly proportionate to the
work done, and since even today it cannot be measured, other
criteria have been sought for measuring human work. One that has
been applied for a long time, and is very suitable for measuring
dynamic work, is the amount of oxygen consumed. This amount is in
fact directly related to the energy consumed, so that the amount of
oxygen consumed is a direct indication of the intensity of the work.
Naturally, it can be used only to measure dynamic muscular work, to
the exclusion of static work and intellectual work which consume
comparatively little oxygen.
The consumption of oxygen is measured as follows: the subject,
whose nose is pinched, has in his mouth a valve that allows him to
inhale fresh air. All the exhaled air passes through a volumetric
counter which gives a reading of the amount of air breathed. Part of
the exhaled air is collected in a vessel and then analysed in the
laboratory. The carbon dioxide content and the oxygen content are
determined and compared with the content of the inhaled air. This
latter content need not be specially determined unless the air has
been contaminated by exhaust or other gases, but can be taken
from tables. The difference between the oxygen content multiplied
by the volume of air inhaled gives the oxygen consumption, from
which, with the aid of tables, the calorie production can be found. To
find the number of calories produced by the work, the number due to
basal metabolism must be deducted from this result. Although the

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apparatus used is much less cumbersome than formerly, the valve
for breathing does inconvenience the subject and he needs a certain
time to get used to it before exact measures can be taken.
Table 3-1. Work classification according to oxygen uptake and
calorie expenditure
Physiological variables Work intensity
Very light (1/min) Cal/min
Light <0.5 < 2.5
Moderately heavy 0.5-1.0 2.5-5.0
Heavy 1.0-1.5 5.0-7.5
Very heavy 1.5-2.0 7.5-10
Extremely heavy 2.0-2.5 10.0-12.5
Oxygen uptake > 2.5 > 12.5
Source: E. H. Christensen: human at work: studies on me
application of physiology to working conditions in a subtropical
country, Occupational safety and health series, No.4 (Geneva, ILO,
1964).
Heart rate
As the intensity of physical work gradually diminished, it became
necessary to find another method of measurement independent of
oxygen consumption. A good indicator of work is the pulse. Since
the amount of blood delivered by each heart beat is almost constant
for an individual, within certain limits, the pulse rate is a direct
indication of the amount of blood demanded by a particular part of

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the body. Measuring instruments are used for pulse counting during
work. In simple investigations integrating instruments count the
pulsations during a minute or a number of minutes. For more precise
investigations instruments that record each pulsation are used.
Some have a small lamp which is placed under the lobe of the ear
and the light of which is momentarily dimmed as each surge of blood
passes. The variation in the light is converted into electric impulses
that are shown on the recording instrument. Other instruments pick
up the nervous impulses directly by means of electrodes. Heartbeats
can be recorded electrically on magnetic tape or mechanically on
paper reels. It is essential to obtain recordings that are as accurate
as possible, for it is not at all easy to interpret them. In fact, the pulse
rate does not depend solely on the oxygen consumption, and hence
on the amount of dynamic work. Static effort will accelerate the
pulse, and hence measuring the heart rate usefully supplements the
measurement of oxygen consumption. Mental and intellectual
activities also affect the heart rate, as do many other factors,
especially psychological factors such as anguish, bad temper, joy
and mental effort. Their influence is seen in the circulation.
Moreover, regulation of the heart rate is subject to quite precise laws
that are related to work. For example, the rate increases before work
begins; during work it decreases to correspond with the intensity of
the work. When the work is finished, the rate decreases slowly until
it corresponds to the rest conditions prevailing before the work
began. If this does not occur, it must be supposed that some fatigue
remains after the work. To measure this, the method just described
can be used. When it is desired to measure the pulse rate during

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work, the rest rate must be subtracted from the rate measured. The
rest rate can be measured when the subject has rested for a
sufficient time lying down. It varies greatly from one person to
another, and so must be determined not only for each person
separately but also several times for the same person, before and
after work. In many measurements it is better to count only the
pulsations above the number corresponding to the period
immediately preceding the work; for example, for work done in a
sitting position the pulse rest rate in that position would be
subtracted, for work done in a standing position the rest rate would
be subtracted, and so on. This "starting rate" is useful in most effort
tests. The "effort" pulse rate is the difference between the aggregate
rate during work and the rest rate or starting rate.
Table 3-2. Classification of physical work by heart beat
Degree of effort Heart rate (pulse/min)
Very light <75
Light 75-100
Moderately heavy 100-125
Heavy 125-150
Very heavy 150-175
Extremely heavy >175
Source: Adapted from Christensen.
Measurement of the heart rate, rather than measurement of the
oxygen consumption, makes it possible to determine the limit of
continuous work (see table 2). If the pulse remains constant during

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the work, this is within normal limits; but if the pulse rate
continuously rises while the work remains constant, the work is
exceeding the limits of normal effort. This test often brings to light
organic defects or functional troubles that render a person unfit for
heavy work.

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3.4 Review Questions
1. Discuss the functionality of human physiology
2. Explain the principles of occupational anatomy and
physiology and anatomy.
3. Identify the occupational physiology related problems

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CHAPTER FOUR
INDUSTRIAL TOXICOLOGY
1. Define toxicology
2. Describe toxicological health problem.
3. Explain dose-Response Relationships
4.2. Introduction
Toxicology is the study of harmful interactions between chemicals
and biological systems. Man, the other animals and plants in the
modern world are increasingly being exposed to chemicals to
enormous variety. These chemicals range from metals and inorganic
chemicals to large complex organic molecules, yet they are all
potentially toxic.
There are now many thousands of chemical substances used in
industry ranging from metals and inorganic compounds to complex
organic chemicals. The people who work in the industries which use
them are therefore at risk of exposure. Fortunately, exposure is often
minimized by using chemicals in closed system so that operators do
not come into contact with them, but this is not always the case. In
third world countries, however, some of which are rapidly
industrializing, exposure levels are higher and industrial diseases
are more common than in the fully developed countries.

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Consequently exposure to toxic substances in the workplace is still a
very real hazard. Furthermore even in the best regulated industrial
environment, accidents may happen and can lead to excessive
exposure to chemicals.
Industrial diseases have existed ever since man began
manufacturing on a large scale, and during the industrial revolution
occupational disease became common. Some were well known to
the general public and are still known by their original, colloquial
names. These diseases were, and some still are of great importance
socially, economically and medically. Many occupations carry with
them the risk of a particular disease or group of disease. Thus,
mining has always been a hazardous occupation and miners suffer
silicosis, while asbestos workers suffer asbestosis and
mesothelioma, and paper and printing workers are prone to disease
of the skin. A man spends on average one-third of his life at work
and, therefore, the environment in that workplace can be a major
factor in determining his health. Although the working environment
has improved immeasurably over the last century, some occupations
are still hazardous despite legislation and efforts to improve
conditions.
4.3 Routes of Entry into the Body
There are three main routes by which hazardous chemicals enter
the body:
1. Inhalation. For industrial exposure, a major, if not
predominant route of entry is inhalation. Any airborne

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substance can be inhaled. The total amount of a toxic
compound absorbed via the respiratory pathways depends
on its concentration in the air, the duration of exposure, and
the pulmonary ventilation volumes, which increase with
higher work loads.
2. Skin Absorption. An important route of entry for some
chemicals is absorption through skin. Contact of a
substance with skin results in these four possible actions.
The skin can act as an effective barrier
The substance can react with the skin and cause local
irritation or tissue destruction
The substance can produce skin sensitization
The substance can penetrate skin to reach the blood
vessels under the skin and enter the bloodstream
a. Ingestion. The problem of ingesting chemicals is
not widespread in the industry; most workers do not
deliberately swallow materials they handle.
Nevertheless ,workers can ingest toxic materials as
result of eating in contaminated work areas;
contaminated fingers and hands can lead to
accidental oral intake when a worker eats or smokes
on the job
b. Injection. Although infrequent in industry, a
substance can be injected into some part of the

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body. This can be done directly into the
bloodstream, peritoneal cavity, pleural cavity, skin,
muscle, or any other place needle or high-pressure
orifice can reach
Figure 4-1: Routes of entry into the body
4.4. Dose-Response Relationships
Dose
The dose is the actual amount of a chemical that enters the body.
The dose received may be due to either acute (short) or chronic
(long-term) exposure. An acute exposure occurs over a very short

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period of time, usually 24 hours. Chronic exposures occur over long
periods of time such as weeks, months, or years. The amount of
exposure and the type of toxin will determine the toxic effect.
What is dose-response?
Dose-response is a relationship between exposure and health effect
that can be established by measuring the response relative to an
increasing dose. This relationship is important in determining the
toxicity of a particular substance. It relies on the concept that a dose,
or a time of exposure (to a chemical, drug, or toxic substance), will
cause an effect (response) on the exposed organism. Usually, the
larger or more intense the dose, the greater the response, or the
effect. This is the meaning behind the statement "the dose makes
the poison."
Threshold dose
Given the idea of a dose-response, there should be a dose or
exposure level below which the harmful or adverse effects of a
substance are not seen in a population. That dose is referred to as
the ‘threshold dose'. This dose is also referred to as the no observed
adverse effect level (NOAEL), or the no effect level (NEL). These
terms are often used by toxicologists when discussing the
relationship between exposure and dose. However, for substances
causing cancer (carcinogens), no safe level of exposure exists,
since any exposure could result in cancer.

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Individual susceptibility
This term describes the differences in types of responses to
hazardous substances, between people. Each person is unique, and
because of that, there may be great differences in the response to
exposure. Exposure in one person may have no effect, while a
second person may become seriously ill, and a third may develop
cancer.
Sensitive sub-population
A sensitive sub-population describes those persons who are more
at risk from illness due to exposure to hazardous substances than
the average, healthy person. These persons usually include the
very young, the chronically ill, and the very old. It may also include
pregnant women and women of childbearing age. Depending on
the type of contaminant, other factors (e.g., age, weight, lifestyle,
sex) could be used to describe the population.
Dose Response Assessment
The characteristics of exposure to a chemical and the spectrum of
effects caused by the chemical come together in a correlative
relationship that toxicologists call the dose-response relationship.
This relationship is the most fundamental and pervasive concept in
toxicology. To understand the potential hazard of a specific
chemical, toxicologists must know both the type of effect it
produces and the amount, or dose, required to produce that effect.
The relationship of dose to response can be illustrated as a graph
called a dose-response curve. There are two types of dose-

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response curves: one that describes the graded responses of an
individual to varying doses of the chemical and one that describes
the distribution of responses to different doses in a population of
individuals. The dose is represented on the x-axis. The response is
represented on the y-axis. The following graph shows a simple
example of a dose-response curve for an individual with a single
exposure to the chemical ethanol (alcohol), with graded responses
between no effect and death.
Figure 4-2. Individual Dose-Response Curve
[Source: Institute for Environmental Toxicology, Michigan State
University]
A simple example of a dose-response curve for a population of
mice in a study of a carcinogenic chemical might look like the
following graph:

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Figure 4-3. A dose-response curve for a population of mice in a
study of a carcinogenic chemical
[Adapted from: Eaton, D.L., and Klaassen, C.D. 1996.
Principles of toxicology]
An important aspect of dose-response relationships is the concept of
threshold. For most types of toxic responses, there is a dose, called
a threshold, below which there are no adverse effects from exposure
to the chemical. The human body has defenses against many toxic
agents. Cells in human organs, especially in the liver and kidneys,
break down chemicals into nontoxic substances that can be
eliminated from the body in urine and feces. In this way, the human
body can take some toxic insult (at a dose that is below the
threshold) and still remain healthy.

131
The identification of the threshold beyond which the human body
cannot remain healthy depends on the type of response that is
measured and can vary depending on the individual being tested.
Thresholds based on acute responses, such as death, are more
easily determined, while thresholds for chemicals that cause cancer
or other chronic responses are harder to deter-mine. Even so, it is
important for toxicologists to identify a level of exposure to a
chemical at which there is no effect and to determine thresholds
when possible.
Figure 4-4. Dose-response curves for a chemical agent administered
to a uniform population of test animals
Source: adapted from Ref.4
When a threshold is difficult to determine, toxicologists look at the
slope of the dose-response curve to give them information about the
toxicity of a chemical. A sharp increase in the slope of the curve can

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suggest increasingly higher risks of toxic responses as the dose
increases.
A comparison of dose-response curves among chemicals can offer
information about the chemicals as well. A steep curve that begins to
climb even at a small dose suggests a chemical of high potency.
The potency of a chemical is a measure of its strength as a poison
compared with other chemicals. The more potent the chemical, the
less it takes to kill. In the previous dose-response graph, line A
describes a chemical that is more potent than the chemical
described by line B, as can be seen by the relative positions of the
lines along the dosage axis and their slopes.
Dose Estimates of Toxic Effects (LD, EC, TD)
Dose-response curves are used to derive dose estimates of
chemical substances. A common dose estimate for acute toxicity is
the LD50 (Lethal Dose 50%). This is a statistically derived dose at
which 50% of the individuals will be expected to die. Other dose
estimates also may be used. LD0 represents the dose at which no
individuals are expected to die. This is just below the threshold for
lethality. LD10 refers to the dose at which 10% of the individuals will
die.
For inhalation toxicity, air concentrations are used for exposure
values. Thus, the LC50 is utilized which stands for Lethal
Concentration 50%, the calculated concentration of a gas lethal to
50% of a group. Occasionally LC0 and LC10 are also used.

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Effective Doses (EDs) are used to indicate the effectiveness of a
substance. Normally, effective dose refers to a beneficial effect
(relief of pain). It might also stand for a harmful effect (paralysis).
Toxic Doses (TDs) are utilized to indicate doses that cause adverse
toxic effects.
The knowledge of the effective and toxic dose levels aides the
toxicologist and clinician in determining the relative safety of
pharmaceuticals. As shown above, two dose-response curves are
presented for the same drug, one for effectiveness and the other for
toxicity. In this case, a dose that is 50-75% effective does not cause
toxicity whereas a 90% effective dose may result in a small amount
of toxicity.
Most exposure standards, Threshold Limit Values (TLVs) and
Permissible Exposure Limits (PELs), are based on the inhalation
route of exposure. They are normally expressed in terms of either
parts per million (ppm) or milligrams per cubic meter (mg/m3
)
concentration in air.
If a significant route of exposure for a substance is through skin
contact, the MSDS will have a "skin" notation associated with the
listed exposure limit. Examples include: some pesticides, carbon
disulfide, phenol, carbon tetrachloride, dioxane, mercury, thallium
compounds, ethylene, and hydrogen cyanide.

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4.5 Health Effects
Acute poisoning is characterized by rapid absorption of the
substance and the exposure is sudden and severe. Normally, a
single large exposure is involved. Examples: carbon monoxide or
cyanide poisoning.
Chronic poisoning is characterized by prolonged or repeated
exposures of a duration measured in days, months or years.
Symptoms may not be immediately apparent. Examples: lead or
mercury poisoning or pesticide exposure.
“Local” refers to the site of action of an agent and means the action
takes place at the point or area of contact. The site may be skin,
mucous membranes, the respiratory tract, gastrointestinal system,
eyes, etc. Absorption does not necessarily occur. Examples: some
strong acids or alkalis.
“Systemic” refers to a site of action other than the point of contact
and presupposes absorption has taken place. For example, an
inhaled material may act on the liver. Example: arsenic affects the
blood, nervous system, liver, kidneys and skin.
Cumulative poisons are characterized by materials that tend to build
up in the body as a result of chronic exposure. The effects are not
seen until a critical body burden is reached.
Example: heavy metals (such as Lead).
Synergistic responses: When two or more hazardous material
exposures occur, the resulting effect can be greater than the effect

135
of the individual exposures. Example: exposure to asbestos and
tobacco smoke, producing lung cancer or mesothelioma.
Types of Interactions
There are four basic types of interactions. Each is based on the
expected effects caused by the individual chemicals. The types of
interactions are:
1. Additivity: is the most common type of interaction.
Examples of additivity reactions are:
Organophosphate insecticides interfere with nerve
conduction. The toxicity of the combination of two
organophosphate insecticides is equal to the sum of
the toxicity of each.
Chlorinated insecticides and halogenated solvents
both produce liver toxicity. The hepatotoxicity of an
insecticide formulation containing both is equivalent
to the sum of the hepatotoxicity of each.
2. Antagonism: is often a desirable effect in toxicology and is
the basis for most antidotes. Examples include: The same
combination of chemicals produces a different type of
interaction on the central nervous system. Chlorinated
insecticides stimulate the central nervous system whereas
halogenated solvents cause depression of the nervous
system. The effect of simultaneous exposure is an
antagonistic interaction.
3. Potentiation: occurs when a chemical that does not have a
specific toxic effect makes another chemical more toxic.

136
Examples are: The hepatotoxicity of carbon tetrachloride is
greatly enhanced by the presence of isopropanol. Such
exposure may occur in the workplace.
4. Synergism: can have serious health effects. With
synergism, exposure to a chemical may drastically increase
the effect of another chemical. Examples are:
Exposure to both cigarette smoke and radon results
in a significantly greater risk for lung cancer than the
sum of the risks of each.
The combination of exposure to asbestos and
cigarette smoke results in a significantly greater risk
for lung cancer than the sum of the risks of each.
Factors Influencing Toxicity
The toxicity of a substance depends on the following:
form and innate chemical activity
dosage, especially dose-time relationship
exposure route
species
age
sex
ability to be absorbed
metabolism
distribution within the body
excretion
presence of other chemicals

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Systemic Toxic Effects
Toxic effects are generally categorized according to the site of the
toxic effect. In some cases, the effect may occur at only one site.
This site is referred to as the specific target organ. In other cases,
toxic effects may occur at multiple sites. This is referred as
systemic toxicity. Following are types of systemic toxicity:
1. Acute Toxicity
Acute toxicity occurs almost immediately (hours/days) after an
exposure. An acute exposure is usually a single dose or a
series of doses received within a 24 hour period. Death is a
major concern in cases of acute exposures. Examples are: In
1989, 5,000 people died and 30,000 were permanently disabled
due to exposure to methyl isocyanate from an industrial accident
in India. Many people die each year from inhaling carbon
monoxide from faulty heaters. Non-lethal acute effects may also
occur, e.g., convulsions and respiratory irritation.
2. Sub-chronic Toxicity
Subchronic toxicity results from repeated exposure for several
weeks or months. This is a common human exposure pattern
for some pharmaceuticals and environmental agents. Examples
are: Ingestion of coumadin tablets (blood thinners) for several
weeks as a treatment for venous thrombosis can cause internal
bleeding. Workplace exposure to lead over a period of several
weeks can result in anemia.

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3. Chronic Toxicity
Chronic toxicity represents cumulative damage to specific organ
systems and takes many months or years to become a recognizable
clinical disease. Damage due to subclinical individual exposures
may go unnoticed. With repeated exposures or long-term continual
exposure, the damage from these subclinical exposures slowly
builds-up (cumulative damage) until the damage exceeds the
threshold for chronic toxicity. Ultimately, the damage becomes so
severe that the organ can no longer function normally and a variety
of chronic toxic effects may result.
Examples of chronic toxic affects are:
• cirrhosis in alcoholics who have ingested ethanol for
several years
• chronic kidney disease in workmen with several years
exposure to lead
• chronic bronchitis in long-term cigarette smokers
• pulmonary fibrosis in coal miners (black lung disease)
4. Carcinogenicity
Carcinogenicity is a complex multistage process of abnormal cell
growth and differentiation which can lead to cancer. At least two
stages are recognized. They are initiation in which a normal cell
undergoes irreversible changes and promotion in which initiated
cells are stimulated to progress to cancer. Chemicals can act as
initiators or promoters.

139
The initial neoplastic transformation results from the mutation of
the cellular genes that control normal cell functions. The
mutation may lead to abnormal cell growth. It may involve loss
of suppresser genes that usually restrict abnormal cell growth.
Many other factors are involved (e.g., growth factors, immune
suppression, and hormones).
A tumor (neoplasm) is simply an uncontrolled growth of cells.
Benign tumors grow at the site of origin; do not invade adjacent
tissues or metastasize; and generally are treatable. Malignant
tumors (cancer) invade adjacent tissues or migrate to distant
sites (metastasis). They are more difficult to treat and often
cause death.
5. Developmental Toxicity
Developmental Toxicity pertains to adverse toxic effects to the
developing embryo or fetus. This can result from toxicant exposure
to either parent before conception or to the mother and her
developing embryo-fetus.
6. Genetic Toxicity (somatic cells)
Chemicals cause developmental toxicity by two methods. They can
act directly on cells of the embryo causing cell death or cell damage,
leading to abnormal organ development. A chemical might also
induce a mutation in a parent's germ cell which is transmitted to the
fertilized ovum. Some mutated fertilized ova develop into abnormal
embryos.
Genetic Toxicity results from damage to DNA and altered genetic

140
expression. This process is known as mutagenesis. The genetic
change is referred to as a mutation and the agent causing the
change as a mutagen. There are three types of genetic change:
If the mutation occurs in a germ cell the effect is heritable. There is
no effect on the exposed person; rather the effect is passed on to
future generations. If the mutation occurs in a somatic cell, it can
cause altered cell growth (e.g. cancer) or cell death (e.g.
teratogenesis) in the exposed person.
Types of organ specific toxic effects are:
Blood and Cardiovascular Toxicity results from xenobiotics acting
directly on cells in circulating blood, bone marrow, and heart.
Examples of blood and cardiovascular toxicity are:
hypoxia due to carbon monoxide binding of hemoglobin
preventing transport of oxygen
decrease in circulating leukocytes due to chloramphenicol
damage to bone marrow cells
leukemia due to benzene damage of bone marrow cells
Dermal Toxicity may result from direct contact or internal
distribution to the skin. Effects range from mild irritation to severe
changes, such as corrosivity, hypersensitivity, and skin cancer.
Examples of dermal toxicity are:
Dermal irritation due to skin exposure to gasoline
Dermal corrosion due to skin exposure to sodium hydroxide
(lye)

141
Skin cancer due to ingestion of arsenic or skin exposure to
UV light
Eye Toxicity results from direct contact or internal distribution to the
eye. The cornea and conjunctiva are directly exposed to toxicants.
Thus, conjunctivitis and corneal erosion may be observed following
occupational exposure to chemicals. Many household items can
cause conjunctivitis. Chemicals in the circulatory system can
distribute to the eye and cause corneal opacity, cataracts, retinal
and optic nerve damage.
For example:
Acids and strong alkalis may cause severe corneal corrosion
Corticosteroids may cause cataracts
Methanol (wood alcohol) may damage the optic nerve
Hepatotoxicity is toxicity to the liver, bile duct, and gall bladder.
The liver is particularly susceptible to xenobiotics due to a large
blood supply and its role in metabolism. Thus it is exposed to high
doses of the toxicant or its toxic metabolites.
Immunotoxicity is toxicity of the immune system. It can take
several forms: hypersensitivity (allergy and autoimmunity),
immunodeficiency, and uncontrolled proliferation (leukemia and
lymphoma). The normal function of the immune system is to
recognize and defend against foreign invaders. This is
accomplished by production of cells that engulf and destroy the

142
invaders or by antibodies that inactivate foreign material. Examples
are: immunosuppression by cocaine
Nephrotoxicity The kidney is highly susceptible to toxicants for two
reasons. A high volume of blood flows through it and it filtrates large
amounts of toxins which can concentrate in the kidney tubules.
Nephrotoxicity is toxicity to the kidneys. It can result in systemic
toxicity causing:
decreased ability to excrete body wastes
inability to maintain body fluid and electrolyte balance
Neurotoxicity represents toxicant damage to cells of the central
nervous system (brain and spinal cord) and the peripheral nervous
system (nerves outside the CNS). The primary types of
neurotoxicity are:
neuronopathies (neuron injury)
axonopathies (axon injury)
demyelination (loss of axon insulation)
interference with neurotransmission
Reproductive Toxicity involves toxicant damage to either the male
or female reproductive system. Toxic effects may cause:
infertility
interrupted pregnancy (abortion, fetal death, or premature
delivery)
infant death or childhood morbidity
chromosome abnormalities and birth defects
childhood cancer

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Respiratory Toxicity relates to effects on the upper respiratory
system (nose, pharynx, larynx, and trachea) and the lower
respiratory system (bronchi, bronchioles, and lung alveoli). The
primary types of respiratory toxicity are:
pulmonary irritation
asthma/bronchitis
reactive airway disease
emphysema
allergic alveolitis
Pneumoconiosis
lung cancer

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4.6 Review Questions
1. What is occupational toxicology
2. Discuss toxicological health problem.
3. Explain dose-Response Relationships

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CHAPTER FIVE
RECOGNITION OF OCCUPATIONAL
DISEASES AND DISORDERS
5.1. Learning Objectives
1. Identify the magnitude of the problems due to
occupational injuries, disorders and diseases.
2. List epidemiological descriptions of Occupational
related health problems.
3. List possible determinants of work related injuries.
4. Discuss the difference types of occupational
disorder and diseases.
5. Explain prevention and control methods of
Occupational disorders .
6. Describe the principles of disability evaluation
methods.
5.2. Introduction
It is difficult to estimate the number of workers involved in meeting
the energy requirements of communities. As noted, in poor
communities much of this work is carried out by family members,
particularly women, who are not formally employed. In addition,
much of this work is carried out by small industries that are not
always recorded in national employment statistics.

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Occupational mortality rates in energy jobs in industrialized countries
are generally 10-30 times lower than in developing countries
(Kjellstrom, 1994; ILO, 1998), indicating that more effective
prevention programs could eliminate more than 90 percent of the
deaths referred to above. Still, energy-related jobs have inherent
health risks that need to be considered when assessing the full
impact of energy production and distribution.
Although too often ignored in discussions of environmental health
risks, the burden of occupational disease and injury is substantial on
a global scale. It is conservatively estimated that with well over 1
million deaths a year, nearly 3 percent of the global burden of ill
health is directly attributable to occupational conditions (Leigh and
others, 1996). This is substantial, accounting for more than motor
vehicles, malaria, or HIV and about equal to tuberculosis or stroke.
Although the fraction due directly to supplying energy is unclear,
energy systems employ many millions of people worldwide in jobs
substantially riskier than average-particularly in jobs producing solid
fuels.
In the early days of the development of employment injury
protection, attention was concentrated on accidents at work. It was
only later that protection was widened to include diseases
contracted during work processes. It proved difficult to define the
diseases which ought properly to be within the protection of the
employment injury law, while excluding common conditions which
are prevalent among the general population.

147
Usually the national legislation contains a list of diseases which are,
beyond dispute, of an occupational origin, at least when they are
contracted by a person who has worked in a process, or in contact
with a substance, which can cause the listed disease. In 1925 the
International Labour Conference was able to agree on only three
diseases which could be so prescribed - lead poisoning, mercury
poisoning and anthrax. But research establishes new criteria of
proof, and the accelerating development of industrial chemistry and
physics brings in its train new hazards. Thus, the Employment Injury
Benefits Convention, 1964 (No. 121), contained a list of 15
occupational diseases and the list was further revised in 1980 to
include a total of 29.
In Ethiopia there is no systematized recording and reporting on work
related injuries organized the national level. If there is, then only few
manufacturing industries provide some information to the Ministry of
Labour and Social Affairs. Hence, the data gathered from these few
industries are incomplete and neither represents all industries nor
show the actual magnitude of work related injuries of the country.
The few studies carried out by individuals in Textile industries in
1991, 1988, and in tobacco factories, revealed an accident rate of
200/1000 person/ year, and 183/1000/year respectively. The only
reliable study which can represent all the manufacturing industries in
the one carried out in January 1988 in 105 manufacturing industries
by the occupational health and safety sector, In this study, 11
corporations each representing a group of factories were studied for
a year, using standardized work related injury reporting system
adopted from ILO. In one year, a total of 13,796 accidents were

148
reported making an over all work related accident rate of 178/1000
person/ year with a range varying from 10-390/1000 person/year,
depending on the nature of industries. The highest work related
accident rate was detected to be among the sugar plantation
workers, followed by workers in Beverage, Textile and metal work
industries. Out of these 0.08% were fatal, 46.2% moderate (injuries
that required sick leave of a day or more) and 53.7% mild (injuries
that did not require sick leave).
5.3. Epidemiology
1. Part of body affected, type, causes and day of the week of
work related injuries
• Among the parts of body affected Brazilian
steel workers, the commonest were hands;
arms and eye.
• The commonest part of body affected among
eleven industrial workers in Addis Ababa was
fingers (37.3%) and hands (11.6%).
• In textile factory study in Addis Ababa, the
most common part of body affected by work-
related injuries were fingers (42%), lower leg
(18.95), and hands (13.3%).
• Reports from Department of Environmental
Health of Ministry of Health of Ethiopia listed
eye, hand and finger as the most affect parts
of the body.

149
Different studies have shown different causes of work-related
injuries.
• According to the study done in eleven urban industries
in Addis Ababa, hit by or against object and fall were the
commonest causes of work-related injuries.
• Findings from textile factory study in Addis Ababa,
demonstrated that the most frequent causes of work-
related injury were machinery 42(29.4%), hit by or
against objects 29 (20.3%).
• Department of Environmental Health of Ministry of Health
of Ethiopia reported that striking (25.5%), falling (12.8
%) and flying objects from machines (8.5%) were the
major causes of work-related injury.
Regarding the distribution of work-related injuries by the days
of the week, most studies revealed:
• The highest injury rates occurred on Monday’s and the
lowest on Thursday’s and Friday’s.
• Absenteeism is higher on Monday’s than other days of
the week in most industrialized countries, which results
in workers to stand in for absent workers and undertake
unfamiliar jobs on that day.
• The most common time of injury is from 8 am to 10 am.
2. Factors related to work related injuries
• Many authorities believe that work-related injuries
result from a complex interplay of multiple risk factors.

150
• Exposure to physical, mechanical and chemical
hazards and the performance of unsafe practices by
workers are the leading causes of work-related
injuries.
• Similarly, psychosocial factors, work organization,
socio demographic characteristics of workers and
environmental and social conditions are other
potentially risk factors
• Reports form France, U.S and China revealed that
men have the highest rates of work-related injuries
than women.
• Study done in eleven urban factories in Addis Ababa
revealed that the highest rate of work-related injury
was observed in the age group 15-19 years.
• Age groups less than 30 years were more affected by
work-related injuries according to textile factory study
in Addis Ababa (9).
• Ministry of Labour and Social Affairs of Ethiopia has
reported that the majority (18 %) of work related
injuries were observed in the age group of 25-
29(27).These studies emphasized that work-related
injuries in young subjects were more common due to
lack of experience, lack of job knowledge and know-
how than in other subjects. Furthermore, many
workers begin working at an early age and often
without safety training.

151
• Different investigations reported that low education
status, low monthly salary, low working experience (5
years or less) in present job, lack health and safety
training, sleep disorders, job category and alcoholic
drink consumption were common risk factor for work-
related injuries.

152
Figure 5-1. Determinants of work-related injuries-A Conceptual
Framework for study of Work-related injury prevalence.
Source: Adapted from Ref.1
Socio demographic
factors
• Sex of workers
• Age of workers
• Level of
education
• Salary of workers
• Job category
• Length of
employment
Behavioural Factors
• Alcoholic drink
consumption
• Chat chewing
• Sleep disorder
• Job satisfaction
• Use of personal
protective equipment
Work environment
• Type of industry
• Health and safety
training
• Hours worked
per week
• Supervision of
workplace
Work Related Injury

153
5.4. Occupational disorder by system
Respiratory Disorders
Work-related respiratory disease is frequently a contributory cause-
and commonly a primary cause-of pulmonary disability. The clinical
evaluation of pulmonary disease includes a minimum of four
elements: 1/a complete history including occupational and
environmental exposures, a cigarette-smoking history, and a careful
review of respiratory symptoms; 2/ a physical examination with
special attention to breath sounds; 3/ a chest x-ray with appropriate
attention to parenchymal and pleural opacities, and 4/ pulmonary
function tests.

154
Table 5-1 Major types of occupational pulmonary disease
Pathophysiologi
c process
Occupational
disease
example
Clinical history Physical
examination
Chest x-ray Pulmonary function
pattern
Fibrosis Silicosis Dyspnea on
exertion,
shortness of
breath
Clubbing,
cyanosis
Nodules
Asbestosis Dyspnea on
exertion,
shortness of
breath
Clubbing
cyanosis,
rales
Linear
densities,
pleural
plaques,
calcifications
Restrictive or mixed
obstructive and
restrictive
DLCO normal or
decreased
Reversible
airway
obstruction
(asthma)
Byssinosis,
isocyanate
asthma
Cough, wheeze,
chest tightness,
shortness of
breath, asthma
attacks
Respiratory
rate ,
wheeze
Usually
normal
Normal or obstructive
with bronchodilator
improvement Normal
or high DLCO
Emphysema Cadmium
poisoning
(chronic)
Cough,
sputuma,
dyspnea
Respiratory
rate
expiratory
phase
Hyperaeration
bullae
Obstructive low DLCO
Granulomas Beryllium
disease
Cough, weight
loss, shortness
of breath
Respiratory
rate
Small nodules Usually restrictive with
low DLCO
Pulmonary
edema
Smoke
inhalation
Frothy, bloody
sputum
production
Coarse,
bubbly rales
Hazy, diffuse
air-space
disease
Usually restrictive with
decreased DLCO,
hypoxemia at rest
DLCO= diffusing capacity; = increased.

155
Musculoskeletal disorders
Work-related musculoskeletal disorders commonly involve the back,
cervical spine, and upper extremities. Understanding of these
problems has developed rapidly during the past decade. Prevention
of a low back pain is a complex challenge. Low back pain prevention
in work settings is best accomplished by a combination of measures,
such as: a/ Job design (ergonomics); b/ Job placement (selection);
Training and education ( training of workers, managers, labour union
representatives and health care providers).
Prevention and Control
Job design (ergonomics)
Mechanical aids
optimum work level
Good workplace layout
Sit/stand workstations
Appropriate packaging
Job placement (selection)
careful history
Through physical examination
No routine x-ray
Strength testing
Job-rating programs
Training and education
Training workers
Biomechanics of body movement (safe lifting)
Strength and fitness
Back schools

156
Training managers
Response to low back pain
Early return to work
Ergonomic principles of job design
Training labour union representatives
Early return to work
Flexible work rules
Reasonable referrals
Training health care providers
Appropriate medication
Prudent use of x-rays
Limited bed rest
Early return to work (with restrictions, if necessary)
Skin disorders
Any cutaneous abnormalities or inflammation caused directly or
indirectly by the work environment is an occupational skin disorder.
Work-related cutaneous reaction and clinical syndromes are as
varied as the environments in which people work. Skin disorders are
the most frequently reported occupational diseases. A basic
understanding of occupational skin disorders is therefore essential
for everyone involved in occupational health. Occupational skin
diseases are often preventable by a combination of environmental,
personal, and medical measures.
Eye disorders
Every working day, there are over 2,000 preventable job-related eye
injuries to workers in the United States. Occupational vision

157
programs, including pre-placement examinations and requirements
for appropriate eye protectors in certain occupations, can prevent
many of these injuries.
Symptoms and signs of serious eye injury
Symptoms of serious eye injury indicating immediate referral are the
following:
1. Blurred vision that does not clear with blinking.
2. Loss of all or part of the visual field of an eye
3. Sharp stabbing or deep throbbing pain
4. Double vision
Signs of eye injury that require ophthalmologic evaluation are
the following:
1. Black eye
2. Red eye
3. An object on the cornea
4. One eye that does not move as completely as the other
5. One eye protruding forward more than the other
6. One eye with an abnormal pupil size, shape, or
reaction to light, as compared to the other eye
7. A layer of blood between the cornea and the iris
(hyphema)
8. Laceration of the eyelid, especially if it involves the lid
margin.
9. Laceration or perforation of the eye

158
Disorders of the Nervous System
The nervous system comprised of the brain, spinal cord, and
peripheral nerves, is a complex system responsible for both
voluntary and involuntary control of most body functions. These are
accomplished through a process of receiving and interpreting stimuli
as well as transmitting information to the effectors organs. The
adverse impacts of stressors from the work environment (physical,
chemical, and psychological) are experienced in a variety of ways.
Of the many means by which these effects can be categorized,
somewhat like arbitrary distinctions between neurology and
behavioural effects on the one hand, and psychiatric effects on the
other, to organize this information for the reader-ed
Prevention
Because work-related psychological disorders have been identified
as a leading occupational health problem, NIOSH has proposed a
national strategy to protect and promote the psychological health of
workers. The strategy focuses mainly on reducing job stress and
providing employee mental health services (see Annex 1).
Efforts to prevent stress-related disorders focus on ameliorating
major areas of job stress; providing job security and career
opportunity, a supportive social environment, and meaningful,
creative, rewarding work; and making every effort to ensure worker
participation in decision making and control of the work environment.
Reproductive disorders

159
The prevention of reproductive disorders is an important public
health priority. These problems include abnormalities that affect the
reproductive function of both men and women as well as a wide
range of unwanted pregnancy outcomes. In the United States,
approximately one in seven married couples is involuntarily infertile.
On the same area among newborns, approximately 7 percent are of
low birth weight (<2,500gm), and 3 percent have major congenital
malformations.
There are two ways by which occupational specialists can prevent or
reduce work-related health risks. The first is through patient
education and counselling. The second is by intervening in the work
place to reduce or eliminate deleterious exposures.
Cardiovascular disorders (CHD)
Risk factors associated with CHD can be divided into three
categories: personal, hereditary and environmental. Personal risk
factors include sex, age, race, high serum cholesterol, high blood
pressure, and cigarette smoking. There are strong interactions
between these factors that act synergic ally, such that a smoker with
high blood pressure and high serum cholesterol is eight times more
at risk developing CHD than a non smoker who has normal serum
cholesterol and blood pressure.
While the association between personal risk factors and CHD is well
documented, our knowledge of the role of occupational risk factors is
still limited. Several chemical and physical agents have been
suspected of causing CHD in workers chronically exposed to them.

160
However scientific evidence indicates a direct causal relationship for
every few of them. For most of these agents, the evidence is based
on isolated case reports or on a few unconfirmed studies.
Table 5-2. Personal risk factors associated with CHD
Risk factor Feature
Sex
Age
Race
High serum
cholesterol
High blood pressure
Cigarette smoking
Mortality for women lags behind that of men
by about 10 years
Risk increases with age
Before age 60, white men have lower death
rates than non white men; the inverse is
true after 60
Risk estimated at 1.7-3.5
Hepatic Disorders
High-Risk Occupations
Occupations with exposure to hepatotoxins are found in huhumany
different industries including munitions, rubber, cosmetics, perfume,
food processing, refrigeration, paint, insecticide and herbicide,
pharmaceutical, plastics, and synthetic chemicals. Usually these
workers are exposed by inhalation of fumes. Most hepatotoxins have
pungent odors that warn of their presence, preventing accidental
oral ingestion of large amounts; however, ingestion of imperceptible
amounts of hepatotoxins over long periods of time may cause injury.
Skin over long periods of time may cause injury. skin absorption has

161
been a significant cause of disease only with trinitrotoluene (TNT)
exposure in munitions workers and with methylenedianiline
exposure in epoxy resin workers.

162
Table 5-3 some causes of occupational liver disease
Disease produced Type of agent Example Types of workers exposed
ACUTE HEPATITIS
Acute toxic hepatitis
Acute cholestatic hepatitis
Acute viral hepatitis, type B
Subacute hepatic necrosis
HCRONIC LIVER DISEASE
Fibrosis/cirrhosis
Angiosarcoma
Biliary tree carcinoma
Chlorinated
hydrocarbons
Nitroaromatics
Ether
Halogenated
aromatics
Epoxy resin
Inorganic element
Virus
Nitroaromatic
Alcohol
Virus
Inorganic element
Haloalkene
Haloalkene
Unknown agents
Carbon tetrachloride
Chloroform
Dinitrophenol (DNP)
Dinitrobenzene
Dioxin
Polychlorinated biphenyls
(PCBs)
DDT
Chlordecone (kepone)
Chlorobenzenes
Halothane
Methylenedianiline
Yellow phosphorus
Hepatitis B
TNT
Ethyl alcohol
Hepatitis B and C
Arsenic
Vinyl chloride
Vinyl chloride
-
Solvent workers, degreasers,
cleaners, refrigeration workers
Chemical indicator workers
Dye workers, explosives workers
Herbicide and insecticide workers
Electrical component assemblers
Insecticide workers, fumigators,
disinfectant workers
Solvent workers, dye workers
Anesthesiologists
Rubber workers, epoxy workers,
synthetic fabric workers
Pyrotechnics workers
Health care workers (see Chap. 18)
Munitions workers
Imbibing bartenders, wine producers,
whiskey producers
Day care workers, health care
workers (see Chap.18)
Vintners, smelter workers
Vinyl chloride workers
Vinyl chloride workers
Rubber workers

163
Renal and Urinary Tract Disorders
The kidney is a target organ for a number of toxic chemical
compounds. Renal excretion is the major route of elimination for
many toxic compounds. The relatively high renal blood flow, about
one-fourth of total cardiac output, exposes the renal structures to a
relatively high toxic burden. Concentration of toxins in the glomerular
ultra-filtrate through active re-absorption contributes further to the
intensity of toxic exposures. The considerable endothelial surface
represented by the extensive capillary network in the kidney, the
presence in renal tubular cells of numerous important enzyme
systems, the local synthesis of active peptides (for example, rennin
and prostaglandin), and the generally high metabolic rate of the
organ are additional factors increasing the vulnerability of the
kidneys to chemical toxins. These agents can adversely affect the
delicate balance between blood flow, glomerular filtration, tubular re-
absorption, and filtrate concentration.
5.5. Disability evaluation and ability to work
Over the years, industrialized societies have taken two basic
approaches to dealing with the problems of poverty and social
isolation that frequently befall people with disabilities who have been
unable to achieve gainful employment. One approach, disability
compensation, provides income support for those who are unable to
work because of a disability.
An increasingly popular approach seeks to promote the
independence of people with disabilities to obtain rehabilitation

164
services intended to facilitate or maintain employment and remove
barriers to employment by regulating employment practices and
workplace conditions that have tended to exclude people with
disabilities.
Clinicians’ effectiveness in dealing with work ability and disability
evaluations will be enhanced by a clear understanding of (1) key
definitions related to the evaluation process, (2) common features of
insurance plans and antidiscrimination legislation affecting disabled
workers, (3) the clinician’s role in the evaluation of work ability, and
(4) unresolved controversies and potential role conflicts for the
clinician.
In reviewing the variety of compensation plans and the associated
roles for the health care provider, it is important to recognize a few
key concepts. Most important is the distinction between impairment
and disability.
Impairment is commonly defined as the loss of function of an organ
or part of the body compared to what previously existed. Ideally,
impairment can be defined and described in purely medical terms
and quantified in such a way that a reproducible measurement is
developed (for example, severe restrictive lung disease with a total
lung capacity of 1.6 litres).
Disability, on the other hand, is usually defined in terms of the
impact of impairment on societal or work functions. A disability
evaluation would therefore take into account the loss of function

165
(impairment) and the patient’s work requirements and home
situation. Certain agencies use a more restrictive definition of
disability; for example, the Social Security Administration defines
disability as “inability to perform any substantial gainful work.” Often,
private disability insurance defines disability as an “inability to
perform the essential tasks of the usual employment.” However, the
determination of disability is always predicated on an assessment of
impairment, followed by a determination of the loss in occupational
or societal functioning that result from the impairment. In general,
the determination of impairment is performed by a health care
professional (usually a physician); most often, non-physician
administrators use this information to determine the presence and
extent of disability.
Disability compensation systems frequently request a determination
of the extent and permanence of a disability condition. An injured
worker who cannot do any work because of a medical condition is
considered to be totally disabled. If this person can work but has
some limitations and cannot do his or her customary work, a partial
disability exists. Either type of disability is considered to be
temporary as long as a resolution of the disability is expected. When
no significant functional improvement is expected, or a condition has
not changed over a one-year period, it is inferred that a medical end-
result (sometimes called maximal medical improvement) has been
achieved. A temporary (partial or total) disability would then be
regarded by most systems as a permanent disability.

166
Workers’ compensation insurance systems usually require
determination of the work-relatedness of a disability. A work-related
injury or disease refers to conditions; however, it may be difficult to
be certain of the relationship of the injury to the workplace is usually
clear. In chronic conditions, however, it may be difficult to be certain
of the relationship between work and disease. It is recommended
that the physician’s determination of work-relatedness should be
based on the evidence of disease, the exposure history, and the
epidemiologic evidence linking exposure and disease.
Health professionals must be aware, however, that the legal
definition of cause may be less exacting than the medical definition,
and that most disability systems are based on the legal standard.
One legal definition of a work-related condition is one “… arising out
of or in the course of employment” or “caused or exacerbated by …
employment”. Thus, a pre-existing condition, unrelated to work, that
becomes substantially worse because of work may legally be work-
related. A typical legal standard of proof is that a condition is work-
related if it is “more likely than not” that the condition would not have
been present or would have been substantially better had the work
exposure not occurred.
Disability compensation systems
Some of the confusion regarding disability assessment stems from
the multitude of disability compensation systems and plan, since
each may have its own definition of disability and criteria for
assessing impairment. Different countries have designed verifying

167
approaches to providing income security to those who find their
wage-earning capacity compromised by injury or disease.
Occupational physicians are most familiar with workers’
compensation insurance, which provides coverage of most federal,
state, and private employees. These plans compensate for medical
expenses and lost wages due to work-related conditions.
The federal government sponsors the major compensation programs
for the severely disabled, through Social Security Disability
Insurance. These programs pay a limited amount of compensation
to those who are unable to achieve any gainful employment,
regardless of the cause of disability.
Private disability insurance is often purchased by individuals or
provided as an employer or union benefit and is designed to provide
compensation for those who are unable to work at their regular jobs
regardless of the cause of disability, or to supplement Social
Security benefits.
Thus, a patient who can no longer work because of injury or illness
might receive support from his or her employer’s insurer, a federal or
state agency, and /or an insurance policy that has been purchased
privately.

168
Although each plan has different eligibility criteria and levels of
payment, all share a few common features:
1. Every plan incorporates shared risk. Many people or
employers at risk of financial losses contribute to a pool,
from which a few individuals are reimbursed. The cost of
entering the pool is partially determined by the actuarial risk
of future events for that person or insured group. Thus,
private disability insurance is much more expensive per year
for a 55-year-old than for a 20-year-old, since the older
worker has a higher risk of disabling medical illness.
Workers’ compensation insurance is more expensive per
employee for a construction company (higher risk of injury to
employees) than for a stock brokerage firm.
2. Because payments into the pool are predictable, finite
resources are available to all potential recipients of each
plan. Therefore, eligibility criteria are structured so that the
limited resources go to those in greatest need. Workers’
compensation plans often do not replace lost wages for
fewer than 6 days of absence from work, since doing so
might greatly increase the cost of the program. Many private
disability insurance plans do not begin coverage until 30
days to 6 months of illness absence has occurred.
3. Before medical evaluation of impairment, a potential
recipient of benefits must first demonstrate legal eligibility.
The basis for eligibility is different in each plan. One must
have worked and contributed to Social Security for 5 of the
past 10 years. Workers’ compensation covers only regular

169
employees, not consultants or subcontractors. Private
disability insurance often does not cover illness that occurs
during the first 60 to 90 days of enrolment.
4. Medical information on impairment is requested once a legal
basis for a claim has been established. In every system, a
medical diagnosis is necessary; in the worker’s
compensation system, physicians are often asked their
opinions on the work-relatedness of employees’ conditions,
the prognosis for eventual return to work, and the
restrictions or job accommodations that might be necessary
to return the worker to employment.
5. The information from the physician, however, does not
determine whether benefits are awarded or how much is
paid; all of these systems are under administrative control.
In the Social Security system, an administrator-physician
team reviews medical information from the evaluating
physician and compares it with specific criteria for eligibility.
In the worker’s compensation systems, if there is a
significant discrepancy between the employer’s report of an
injury and the physician’s report, benefits may be withheld
pending an investigation by the insurance company.
6. Benefits are limited and are intended to provide only a
proportion of lost wages, medical expenses related to the
specific impairment, and vocational rehabilitation. Only in
rare circumstances are worker’s compensation benefits
intended to punish gross negligence by an employer in
causing the injury; in all other instances, fault has no bearing
on benefit levels.

170
7. Applicants generally have a right of appeal of an
administrative or medical decision, with review by a third
party. In the Social Security system, applicants who are
initially denied benefits can appeal to a second
administrator-physician team, then to an administrative law
judge, and finally to the federal courts, if desired. In most
worker’s compensation plans, the claimant can request an
administrative hearing and be represented by an attorney.
The agencies that provide benefits also conduct periodic
reviews of cases to verify that continued eligibility (disability)
exists.
8. Recently, there has been an increased emphasis on
developing resources for retraining and rehabilitation,
closely allied with each system. Beneficiaries are often
required to participate in programs to maximize their
potential for return to alternative, gainful employment.
The purpose of each plan is to reimburse workers for medical
expenses, rehabilitation expenses, and lost wages that result from a
work-related injury or illness. Plans are generally designed to be
non-adversarial so that, in most cases, limited benefits are paid to
injured workers without the necessity of a formal hearing. In most
cases of acute traumatic injuries (for example, fractures or
lacerations occurring at work), the relationship to work is
unquestionable and the system works reasonably well at
compensating the injured worker. In many cases, however, the
relationship to work is less clear, and the demand on the clinician
more complicated, as the following case illustrates.

171
A 50-year-old truck driver followed by his physician for 6 years
because of chronic low back pain came to the physician stating “I
cannot take it anymore.” Although he could not recall a specific
injury, he found that the requirements of driving a long-haul tractor
trailer caused him severe discomfort that was no longer relieved by
rest or analgesics. His back discomfort generally improved while he
was on vacation but was clearly aggravated after more than 2 hours
of driving or after any heavy lifting (at home or at work). He had
been out of work for one week because of his discomfort and
required a note from the physician before returning to work. Physical
examination revealed a mild decrease in forward flexion. X-rays
were consistent with osteoarthritis of the spine. The patient wanted
to know the physician’s opinion on whether his back problems were
due to his work as a truck driver, whether he should change his
vocation because of his discomfort, and whether he should file a
workers’ compensation claim for work-related injuries.
The case illustrates some of the difficulties in evaluating and treating
the patient with work in capacity. The patient went to the physician
because his back discomfort was interfering with his ability to do his
job. Like most patients with chronic low back pain, his symptoms
and examination findings were non-specific. The standard
recommendations of rest and avoidance of exacerbating activities
met with transient success, but his symptoms reappeared with his
return to work. It is logical at this point to explore with the patient any
opportunity for job accommodations at work, and, if no alternatives

172
are available, for him to seek employment that would not exacerbate
the symptoms. The patient, for a variety of reasons, however, may
be reluctant to consider changing to another line of work, despite the
discomfort associated with the current job.
With regard to causality, the high prevalence of non-specific low
back pain in the general population and the multi-factional etiology of
this common condition make it impossible to say with medical
certainty that this patient’s back discomfort was caused in its entirety
by his work. Several epidemiologic studies, however, have linked
truck driving with a higher incidence of chronic disabling low back
pain and have attributed this increase to excessive vibration, sitting,
and heavy lifting. Despite medical uncertainty, it is likely that most
compensation systems would recognize this patient’s low back pain
as a condition that is aggravated by work and that the patient’s
medical bills and lost wages related to his back pain would be
converted by workers’ compensation insurance.
A patient with severe chronic lung disease was being evaluated for
disability under Social Security. His exposure history was significant
for occupational exposure to asbestos and non-occupational
exposure to cigarette smoke. His physical examination, chest x-ray,
and pulmonary function tests were consistent with diagnoses of (1)
severe obstructive lung disease and possible restrictive lung
disease, and (2) asbestos-related pleural plaques.
The patient’s occupational exposure to asbestos might have played
a small etiologic role in the development of pulmonary insufficiency.

173
It is worth noting, however, that this would have no effect on the
patient’s application for SSDI.
Steps in the Disability Evaluation Process
The following questions are involved in disability evaluation:
1. What is the patient’s medical diagnosis?
2. Does the individual have any impairment is present, is it
temporary or permanent?
3. What is the extent of any impairment?
4. Is the patient’s impairment or disease caused or aggravated
by work?
5. What is the impact of this impairment on the individual’s
ability to obtain employment in specific occupations and to
perform specific jobs? Might accommodations allow for
employment?
6. What other sources of information on work capabilities or
possible accommodations should be considered?
7. In consideration of the answers to the previous questions, to
what, if any, economic benefit is the individual entitled?
In workers’ compensation and in private insurance disability cases,
the physician is often asked whether the impairment is disabling and
to describe how the impairment impedes the performance of usual
job tasks. A clear job description is the basis for evaluating whether
the employee can perform the essential functions of the job. Often,
this cannot be determined without knowing what accommodations at

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work might be available. Thus, in the second case, it cannot be
determined whether the patient is totally disabled until it is known
whether any alternate work or accommodations are available. The
same considerations apply to determining disability for private
insurance. A visit to the workplace usually will resolve the lack of
clarity that frequently is present in standard job descriptions and may
have an important role in encouraging an employer to provide
accommodations for the disabled employee.
Most insurance systems reimburse individuals for loss of earning
capacity caused by objective impairment. It is often difficult to
determine whether sufficient impairment exists for one to qualify for
benefits under a given plan. Physicians usually lack the experience,
technical facilities, and ability to accurately estimate vocational
potential; in these situations, early involvement with a qualified
vocational rehabilitation specialist is worthwhile. Specialized skills
and a broad database are required to predict residual caring
capacity when an employee is no longer able to return to previous
work. For example, factors related to worker autonomy, such as the
availability of self-paced work, educational and experience levels,
and self employment, have been shown to be more important in
determining disability status in patients with rheumatoid arthritis than
the extent of medical findings.
In workers’ compensation plans and in most private disability plans,
the treating or reviewing physician is required only to determine that
the impairment is sufficient to prevent work. However, in the Social
Security, Veteran’s Administration, and Black Lung programs, there

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are often specific criteria for impairment that determine whether one
is eligible for benefits, which vary from plan to plan. For example, the
Black Lung and Social security programs have threshold pulmonary
function values; if an applicant’s lung function is better than the
threshold, then he or she does not qualify for disability. In the
veteran’s Administration system, the degree of lost function is
expressed as a percentage of total lung function. Benefits are
assigned based on the percentage of function lost; in contrast, the
Social Security and Black Lung programs usually provide a fixed
amount of benefits only if a worker is totally disabled according to
the threshold criteria. Physicians are often frustrated with the
arbitrary nature of the determination process. Under these criteria,
some individuals with truly disabling impairments will be refused
compensation, while others capable of gainful employment will
receive benefits.

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1. What variables would you use to measure the magnitude of the
problems due to occupational health?
2. What are the determinant factors for work related injuries?
3. Describe what occupational disorders mean?
4. Describe what occupational diseases mean?
5. Explain the principle of disability evaluation?
6. List the challenges of disability evaluation
7. List the preventive and control measure of Occupational
disorders?

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CHAPTER SIX
SMALL-SCALE ENTERPRISES AND
INFORMAL SECTORS IN ETHIOPIA
At the end of this chapter, the student will be able to:-
1. Define small-scale enterprises and informal sectors
2. Describe the common problems of SSE and IS
3. Discuss the general actions to be taken on SSE and IS
6.2. Introduction
Most workers in developing countries like Ethiopia are employed in
small industrial or agricultural setting. Small-scale industrial and
service enterprises often have few resources, heavy workloads and
multiple tasks for each worker. Work usually takes place in an
environment that does not always meet required standards. Family
members of the entrepreneurs and workers, including children,
pregnant women and elderly people, share the work in small-scale
enterprises, such as home industries, small farms and cottage
industries, particularly in developing countries. In such situations,
most workplace exposures also affect family members because
most of the time is spent in the combined home and work
environment.

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The ccommon features of these enterprises and informal sectors
are:
There is no clear boundary between the working and the living
environment
Unsafe building or work places which are often associated with
poor working designs, which may have inadequate light and
ventilation
Unsatisfactory hygiene and sanitation facilities
Cramped and ergonomically inadequate work spaces and safety
The work processes involve often low technology and budget
which are operated by employees with limited training and
education
Protective clothing such as respirators, gloves, apron, boot and
other safety equipment are seldom available or used
Inappropriate working hand tools and equipment
Poor access to information, lack of knowledge about hazards,
their effects and control measures, low degree of mechanization
Majority of them have no permit.
Employment and insurance polices are nil.
Management of health is absolutely unknown.
Vocation and salary is absolutely unknown.
Low capital resources
Not followed for compliance by regulation.

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6.3. Types of small scale enterprises and informal
sectors
Examples of some small-scale enterprises and informal sectors
where the inspection, education and evaluation of the Sanitarian is
needed are. However, some of these could also be considered large
enterprises in some areas.
1. Tannery (SSE)
2. Pottery (IS)
3. Wickery (wickerwork) (IS)
4. Bakery (SSE)
5. Weaver (IS)
6. Oil-seed crushers (SSE)
7. Blocket, pipe, tile makers (IS)
8. Stone crushers (IS)
9. Brick-makers (IS)
10. Carpentry (IS)
11. Welders (IS)
12. Miller (IS)
13. Garage (SSE)
14. Glass cutters (IS)
15. Butchers (IS)
16. Blacksmith (IS)
17. Charcoal producers ((IS)
18. Carpet makers (IS)
19. Dairy farm (IS)
20. Chicken farm (IS)

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21. Soap makers (IS)
22. Bee farm (honey) (SSE)
23. Animal fattening farm (SSE)
24. Mining (SSE)
25. Foundries (SSE)
26. Grinding (IS)
27. Boiling (IS)
28. Painting and paint making (IS)
29. Dying and dye products (SSE)
30. Quarrying (IS)
31 Cutting (IS)
32. Burning (IS)
33. Cleaning (IS)
34. Digging a hole (shallow well)(IS)
Example :health hazards associated with pottery
a. Clay soil digging
Falling
Mechanical accidents
Land sliding (collapse)
Diseases from soil such as Tetanus, URTI, Pneumoconiosis,
Silicosis, Asbestosis
Poisoning - Arsenic, lead, silica.

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b. Clay preparation
The raw clay prepared by burning as the result there may be
Air pollution
Heat
Dust
Fume.
c. Clay forming (shaping)
Since they do have direct contact with water
Water related disease
Food borne diseases
d. Clay drying
Heat
Burn
Cram
Rash (excessive heat)
e. Firing and glazing
Air pollution
Accidents (falling)
Psychological problem.
Poisoning
Lack of transportation for market is the cause for fatigue and
other health problems.
Low selling price.
Deforestation

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6.4. General action on small-scale enterprises and
informal sectors.
1. Survey must be made on
Types
Numbers
Potentiality of resources in terms of money
Problem
Economical
managerial
2. What type of
• Organization
• Establishment
• Cooperation
• Communication
• Transportation
3. On job and off job training
4. Provision of health facilities.
• Basic environmental sanitation.
• Hospitals, Health center, clinics /health post/
• Nutritional counseling.
5. General and Health education on
• Scientific facts
• Technologies
• Production and marketing.
• Salary and transaction
• Employment

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1. What are the main differences between small-scale
enterprises and informal sectors?
2. What are problems of SSE and IS?
3. What are actions to be taken to improve the status of SSE
and is in Ethiopia?
4. Mention the health hazards associated with pottery and
tannery?
5. Prepare a checklist and conduct survey on small scale
enterprise and informal and

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CHAPTER SEVEN
EVALUATION OF OCCUPATIONAL
HEALTH AND SAFETY HAZARDS
1. Define the objectives of hazard evaluation in workplace.
2. Explain methods used to evaluate workplace hazards
3. Discuss types of sampling
4. Interpreter the results
7.2. Introduction
The previous chapters briefly traced the concepts of occupational
health and safety. Moreover, the type of hazards in the workplace
and how they happen were discussed. Following this it will be
logical to discuss in s how we can actually evaluate the hazards in
the work place. In this chapter we will discuss instrumentation and
scientific or non scientific methods of evaluating the nature and
extent of some health problems arising in occupational setting.
Health and safety issues are concerned with the evaluation of the
human workforce, and the design of the working environment to
obtain maximum satisfaction in productivity, and workers' health,
safety and well being. The recognition and subsequent identification
of the specific contaminants (dust, fume, gas, vapor, mist,

185
microorganisms, and sound pressure level etc) is the first stage in
the sequence. A number of spot check devices are used such as
detector stain tubes for gases, or in the case of noise, a sound
pressure meter.
Once the contaminants have been identified, it is necessary to
measure the extent of the contamination. Evaluation is an important
part of the procedure for measurement. Measured level of
contamination must be compared with existing hygiene standards
(always assuming there is such a standard applicable to the material
in question), such as exposure limits, control limits and
recommended limits. In addition, the duration and frequency of
exposure to the contaminants must be taken into account. Following
a comprehensive evaluation, a decision must be made as to the
actual degree of risk to workers involved. This degree of risk will
determine the control strategy to be applied.
7.3. Evaluation of occupational hazards
The basic principles to evaluate occupational health and safety
hazards, and the philosophical basis for establishing safe levels of
exposure to chemical, physical and biological agents is based on
evaluation of occupational environment.
Evaluation can be defined as the decision making process that
results in an opinion as to the degree of risk arising from exposure to
chemical, physical, biological, or other agents. It also involves
making a judgment of the magnitude of these agents and

186
determines the levels of contaminants arising from a process or
work operation and the effectiveness of any control measures used.
Method of sampling
Grab Sampling Vs integrated Sampling
Air sampling can be conducted for long or short periods depending
upon what type of information is needed.
Instantaneous or grab Sampling is the collection of an air sample
over a short period whereas longer period of sampling is called
integrated sampling.
1. Grab samples represent the environmental concentration at a
particular point in time. It is ideal for following cyclic process
and for determining airborne concentration of brief duration
but it is seldom used to estimate eight-hour average
concentration.
2. In integrated sampling, a known volume of air is passed
through a collection media to remove the contaminant from the
sampled air stream. It is the preferred method of determining
time weighted averages exposure(.explain)

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Types of sampling
Area or environmental sampling Vs personal sampling
Environmental sampling includes sampling for gases, vapors,
aerosol concentrations, noise, temperature etc. Which are found on
the worker or the general work area or environment.
Area or general room air samplings are taken at fixed locations in
the work place. This type of sampling does not provide a good
estimate of worker exposure. For this reason it is used mainly to
pinpoint high exposure areas, indicate flammable or explosive
concentrations, or determine if an area should be isolated or
restricted to prevent employees from entering a highly contaminated
area.
Personal sampling
The objective of personal sampling is to see the extent of exposure
of the person working on a particular contaminant while he/she is
working at a location or work place. For example, if the worker is
working in a garage where cars are painted the area as a whole is
sampled to see how much lead which is present in all car paints, is
on the air but with personal sampling one can determine how much
are inhaled by the person performing the work or those who are
working near by. In short it is the preferred method of evaluating
workers exposure to air contaminants.

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Health surveillance
The Occupational Health and Safety act requires medical
surveillance of workers for the protection of worker’s health At its
simplest health surveillance might just be to keep medical records
but there is also sophisticated tests that can be used
Biological measurements
Biological effect measurements
• Medical tests e.g. Kidney function tests, Lung function tests,
Chest x-rays, etc.
• Biological Sampling
Biological sampling provides us with different information than air
sampling. It indicates exactly what has been absorbed into the body
rather than what is in the environment. Biological Sampling can be
defined as the measurement of a substance or it’s metabolites in
body tissues or fluids to assess the working environment or the risk
to exposed workers.
7.4 Measurement of occupational hazards
a. Particulate matter measurement
To measure dust exposure, it is necessary to determine the
composition of dust that are suspended in the air where workers
breathe. Operation that involves the crushing, grinding, or polishing
of minerals or mineral mixtures frequently do not produce airborne
dusts that have the same size composition.

189
When air samples are collected in the immediate vicinity of dust
producing operation, larger particles that have not yet had time to
settle from the air may be collected. If a larger number of these
particles appear in the dust sample, the effect of their presence may
have to be evaluated separately.
To evaluate either the relative hazard to health posed by dusts or
effectiveness of dust control measures, one must have a method of
determining the extent of the dust problem. Ideally the method
employed should be as closely related to the health hazard as
possible. The basic methods are briefly discussed below.
1. Count Procedure
The concern of industrial hygienists has been to measure the
fraction of dust that can cause pneumoconiosis. Since it has been
recognized that only dust particle smaller than approximately 10
micrometer are deposited and retained in the lung method were
sought to measure the concentration of these tiny particles.
Microscopic counting of dust collected has long been used for this
purpose.
2. " Total” Mass Concentration Method
The simplest method of measuring dust concentration is to
determine the total weight of dust collected in a given volume of air.
The “total" mass, however, is determined to a considerable extent by
the large dust particle, which can not penetrate to the pulmonary
space and cause adverse health effect. Thus the total dust

190
concentration by weight is not a reliable index of "respirable" dust
concentration. This is because in this method of measurement the
proportion of dust that is small enough to penetrate into the
pulmonary space (respirable dust 2.5-micrometer) is extremely
variable ranging from 5 percent to 60 percent.
3. Respirable Mass Size Selection Measurement (Personal
sampling)
When measuring respirable dust the method now commonly used is
personal or breathing zone respirable mass sampling? Dust
collection devices now available for this method of sampling also
provide a means for a size frequency analysis of the collected dust.
Respirable mass samples are preferably taken over a full 8 hour
shift. However, multiple, shorter period samples (over a 2-4 hour
period) may be collected during an individual full shift period.
In general, any dust particle producing activity will have respirable
dust. For example road construction, cotton ginning, stone crushing
and milling site, farm sites etc all produce same amount of dust. By
practice 30-40% of dust are respirable. Even if we cannot measure
the particle size using instrument, we can tell by the mass produced
in a certain work site that the worker is exposed to respirable dust
particle.

191
Air sampling instruments
The sampling instruments are geared to the type of air contaminants
that occur in the work place that will depend upon the new materials
used and the processes employed.
Air contamination can be divided into two broad groups depending
upon physical characteristics.
Gases and vapors
Particulate

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Type of Air Sampling
The type of air sampling to be used depends upon a number of
factors.
The type of sampling
The equipment available
The environmental condition
The nature of the toxic contaminants

193

194
b. Noise Evaluation
The purposes of a detailed noise survey are:
1. To obtain specific information on the noise levels existing at
each employee Workstation
2. To develop guidelines for establishing engineering and/or
administrative Controls.
3. To define areas where hearing protection will be required.
4. To determine those work areas where audiometric testing of
employees is desirable and/or required.
Surveys will help us to determine:
Whether noise problems exist or not;
How noisy is created in each work place or station,
What equipment or process is producing the noise,
Which employees are exposed to the noise often,
Duration of exposure to the noise, etc.
Therefore, for evaluation purposes noise measurement is conducted
using such strategy such as:
1. Measuring noise levels using area measurement methods
2. Work station measurement

195
Sound Survey
Sound measurement falls into two broad categories.
1. Source measurement
2. Ambient-noise measurement
Source measurement involves the collection of acoustical data for
the purpose of determining the characteristics of noise radiated by a
source.
Ambient noise measurement ranges from studying a single sound
level to making a detailed analysis showing hundreds of components
of complex variations.
Because of the fluctuating nature of many industrial noise levels, it
would not be accurate or meaningful to use a single sound level
meter reading. For this reason a preliminary and a detailed noise
survey has to be conducted in the industry.
There are wide assortments of equipment available for noise
Measurement. Some of these instruments are:
1. Sound Survey meter / Sound level meter/
2. Octave band analyzers
3. Narrow band analyzers
4. Tape and graphic level recorders
5. Impact sound level meters

196
6. Dosimeter
For most noise problems encountered in industries, the sound level
meter and octave band analyzer, and if available noise dosimeter
provide ample information.
Sound level Meter/Sound survey meter/
This is one of the basic instruments used to measure sound
pressure variations in air. This instrument contains a microphone,
an amplifier with a calibrated attenuator, a set of frequency response
networks, and an indicating meter. It is an electronic voltmeter that
measures the electrical signal emitted from a microphone attached
to the instrument. Exposure duration at workstation where the
regular noise levels varies above 85 dBA.
Assessing the thermal environment Heat stress
This is a real challenge as there is not only one but four
environmental parameters which must be considered. The extent of
stress suffered depends on:
Air temperature: commonly what we would call the room
temperature. At its simplest we could measure it with ordinary
mercury in glass thermometer.
Radiant Temperature: This is measured by using a globe
thermometer. This consists of a hollow copper sphere measuring
about 15cm in diameter, and painted black. A mercury-in-glass
thermometer is inserted into the sphere to a point such that the bulb

197
of the thermometer is at its center. Radiant heat is absorbed by the
sphere, which gives this as a higher reading.
Humidity:
The classical instrument for determining humidity is the whirling
hygrometer. It contains two thermometers side by side. The bulb of
one thermometer is covered with a wetted fabric, whereas that of the
other is left dry. As the instrument is whirled the water evaporates
from the fabric and the evaporative effect cools the thermometer
bulb referred to as the wet-bulb thermometer. The wet bulb reading
is usually lower than the dry bulb reading. The differences between
these two thermometers depend upon the amount of moisture
already in the air. The greater the difference between the
thermometers the drier the air and the greater the potential to cool
down through sweating.
Air movement
This is commonly measured with hot wire anemometers and vane
anemometers. The older but still very accurate instrument is the kata
thermometer.
Kata thermometer: This is an alcohol filled thermometer with a large
bulb coated with silvery material. When used, the bulb is heated in
warm water until the alcohol rises into the upper reservoir. Then the
bulb is dried with a clean dry cloth and suspended in the air. The
time the alcohol takes to fall from the upper limit to the lower limit on
the stem is timed using a stopwatch. From the cooling time, the dry-
bulb temperature and the kata factor, which is usually printed on the

198
stem, air speed can be read from the monogram provided with the
instrument.
Illumuinance
Use photocells based upon silicon or selenium and they also
incorporate colour-correcting filters to match the sensitivity of the
human eye. The photocell also needs to be cosine corrected.
Without this, light arriving at glancing angles is underestimated.

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7.5. Questions and Exercises
1. What variables would you use to determine the level of safety in
a given Occupational settings?
2. Take a walk around your college or university. Assess the
safety of your campus. Look at traffic, lighting, accessibility,
indoor air, obstruction, classroom conditions, sanitation, and
related factors. Make suggestions to improve the safety of
campus and submit the suggestions to the responsible body in
your campus.
3. Explain the difference between grab sampling and integrated
sampling?
4. How can you evaluate the level of noise in occupational setting?
5. Mention the occupational exposure to noise in your college or
university ”Community”.
6. Evaluate your classroom in terms of biological hazard, noise,
dust, ergonomic and other physical hazards.

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CHAPTER EIGHT
PREVENTION AND CONTROL OF
OCCUPATIONAL HEALTH AND
SAFETY HAZARDS
At the end of this chapter, the student will be able to
1. Describe the objectives of prevention and control of
occupational health and safety hazards.
2. Explain the prevention and control methods of Occupational
hygiene.
3. List types and importance of personal protective equipment
4. Discuss the difference between local exhaust ventilation and
general ventilation
5. Explain the reasons for misutilization of personal protective
equipment.
8.2. Introduction
Occupational diseases and injuries are, in principle, preventable.
Among the approaches to prevent these include, developing
awareness of occupational health and safety hazards among
workers and employers assessing the nature and extent of hazards,
introducing and maintaining effective control and evaluation
measures. These approaches are undertaken by employers,

201
workers and the government. This can range from encouragement
by appropriate individuals or agencies outside the specific workplace
to the promulgation and rigorous enforcement of occupational health
and safety regulations. Working conditions, type of work, vocational
and professional status, and geographical location of the workplace
also have a profound impact on the social status and social
wellbeing of workers. Historically, occupational health programmes
have been developed hand-in-hand with the improvement of social
conditions for underserved and unprivileged workers.
The classic occupational hygiene model of controlling a hazard,
indicates that the ideal situation is to prevent exposure altogether.
This is known as control at the source and utilizes substitution or
enclosure of the hazard, as well as other means. If this can not be
achieved, exposure should be reduced along the path, through
ventilation, protective barriers, or related measures, only thirdly,
should exposure be controlled at the person, using personal
protective equipment, administrative controls, or other primary
prevention measures such as training or even biological measures
such as immunization. The final measure of controlling a hazard is
secondary prevention, i.e. early detection of effects of exposure and
subsequent remediation.

202

203
Table 8-1: General diagram of methods of control
Source Air path Receiver
1. Substitution with a less harmful
material (water in place of organic
solvent)
2. Change of process(Airless
paint spraying)
3. Enclosure of process
(Glove-box)
4. Isolation of process
space of time.
5. Wet methods (hydro Blast)
6. Local exhaust
ventilation(capture at source)
7. Adequate maintenance
program
1. House Keeping (immediate
clean up)
2. General exhaust ventilation
(Roof fans)
3. Increase distance between
source and receiver (semi
automatic or remote control)
4. Dilution ventilation (supplied
air)
5. Continuous area monitoring
(pre-set alarms)
6. Adequate maintenance
program
1. Training and education
2. Rotation of workers (split up dose)
3. Enclosure of workers (air
conditioned crane cabs)
4. Personal monitoring devices
(Dosimeters)
5. Personal protective
devices9respirators)
6. Adequate maintenance program.
Source: Barbara, A.P. Fundamental of industrial hygiene united States of America: National Safety Council,
1988.

204
To determine the extent of the exposure, locate the contaminant
source, its path to the employee, and the employee’s work pattern
and use of protective equipment.
8.3. Hierarchy of Prevention and control methods
Generally, there are five major categories of prevention and control
measures: elimination, substitution, engineering controls,
administrative controls and personal protective equipment.
1. Elimination
Eliminating the hazard completely is the ideal solution, but it is
seldom easy to achieve. Usually there are good reasons why a
process or operation has to be carried out and why it has to be done
in a certain way. Elimination therefore challenges to find an
alternative method of achieving the same goals. Some of the
barriers commonly encountered are as follows:
The quality of the product may have a service life of many years,
and even a small defect in quality could cause it to fail in use. This
might lead to liability claims. Sometimes quality standards may also
have been set or approved by the customer or a regulatory authority.
Applications to change the production method may then be difficult
or expensive.
The cost of the product may be increased. Raw materials or energy
costs may be higher or the production time may be increased if the
new method is slower.

205
It is important to consider workers health and safety when work
processes are still in the planning stages. For example, when
purchasing a machine, safety should be the first concern but not
cost.
Machines should confirm to national safety standards – they should
be designed with the correct guard on them to eliminate the danger
of a worker getting caught in the machine while using it. Machines
that are not produced with the proper guards on them may cost less
to purchase, but cost more in terms of accidents, loss of production,
compensation, etc. Unfortunately, many machines that do not meet
safety standards are exported to developing countries, causing
workers to pay the price with accident, hearing loss from noise, etc.
1. Substitution
If a practically dangerous chemical or work processes cannot be
completely eliminated, then it should be applied with a safer
substitute. This could involve, for example, using less hazardous
pesticides such as those based on pyrethrins (prepared from natural
product), which are considered to be less toxic to humans than
some other pesticides. This particular substitution is practiced in
some countries because the substitute chemicals do not leave
residues on food and therefore reduced long-term costs. The
substituted materials may cost more to buy and may cause
resistance in insects. So you can see there are many factors to be
considered when choosing a chemical or chemical substitute?

206
It is not easy to find safer chemical substitute (in fact, no chemical
should be considered completely safe). It is important to review
current reports every year on the chemicals used in the work places
so that safe chemicals could be considered for the future.
When looking for safer substitute a less volatile chemical is selected
of a highly volatile one or solid, instead of liquid. Other examples of
substitutions include using:
Less hazardous instead of toxic ones.
Detergent plus water cleaning solutions instead of organic
solvents
Freon instead of methyl bromide chloride as a refrigerant
Leadless glazes in the ceramics industry
Leadless pigments in paints
Synthetic grinding wheels (such as aluminum oxide, silicon
carboide) instead of sandstone wheels.
3. Engineering controls
An engineering control may mean changing a piece of machinery
(for example, using proper, machine guards) or a work process to
reduce exposure to a hazard; working a limited number of hours in a
hazardous area ; and there are number of common control
measures which are called engineering control. This includes
enclosure, isolation and ventilation.

207
3.1 Enclosure
If a hazardous substance or work process cannot be eliminated or
substituted, then enclosure the hazard is the next best method of
control. Many hazards can be controlled by partially or totally
enclosing the work process. Highly toxic materials that can be
released into the air should be totally enclosed, usually by using a
mechanical handling device or a closed glove system that can be
operated from the outside.
The plant can be enclosed and workers could perform their duties
from a control room. Enclosing hazards can minimize possible
exposure, but does not eliminate them. For example, maintenance
workers who serve or repair these enclosed areas can be still
exposed. To prevent maintenance workers from being exposed,
other protective measures (such as protective clothing, respirators,
proper training, medical surveillance, etc) must be used as well as
safety procedures.

208
Machine guarding is another form of enclosure that prevent workers
coming into contact with dangerous parts of machines. Workers
should receive training on how to use guarded machine safely.
Figure 8-1. Guarded circular saw
Source: Deglaville etal. Occupational Health, a huhumanual for
health workers in developing countries.
3.2 Isolation
Isolation can be an effective method of control if a hazardous
material can be moved to a part of work place where fewer people
will be exposed, or if a job can be changed to a shift when fewer
people are exposed (such as weekend or midnight shift). The
worker can also be isolated from hazardous job for example by
working in an air-conditioned control booth.
Whether it is the job or the worker that is isolated access to the
dangerous work areas should be limited to few people as much as

209
possible to reduce exposures. It is also important to limit the length
of time and the amount of substance (s) to which workers are
exposed if they must work in hazardous area. For example, dust
producing work should be isolated from other work areas to prevent
other worker from being exposed. At the same time, workers in the
dusty areas must be protected and restricted to only a short time
working in those areas.
Remember: isolating the work process or the worker does not
eliminate the hazard which means workers can still be exposed.
3.3 Ventilation
Ventilation in work place can be used for two reasons: 1) to prevent
the work environment from being too hot, cold, dry or humid. 2) to
prevent contaminates in the air from getting into the area where
workers breathe.
Generally there are two categories of ventilation.
1. General or dilution Ventilation
2. Local Exhaust ventilation
1. General or dilution Ventilation
This adds or removes air from work place to keep the concentrations
of an air contaminant below hazardous level. This system uses
natural convection through open doors or windows, roof ventilators
and chimneys, or air movement produced by fans or blowers.

210
It is recommended to use the general ventilation system if the
following criteria are fulfilled.
1. Small quantities of air contaminants released into the workroom
at fairly uniform rate.
2. Sufficient distance between the worker and the contaminant
source to allow sufficient air movement to dilute the contaminant
to a safe level.
3. Only contaminant of low toxicity are being used
4. No need to collect or filter the contaminants before exhaust air is
discharged into the community environment.
5. No corrosion or other damage to equipment from the diluted
contaminants in the workroom area.
2. Local Exhaust Ventilation
Local exhaust Ventilation is considered the classical method of
control for dust, fumes, vapors and other airborne toxic or gaseous
pollutants. The ventilation system captures or contains the
contaminants at their source before they escape into the workroom
environment. A typical system contains one or more hoods, ducts,
air cleaners and a fan. Such systems remove but do not dilute like
general exhaust ventilation although removal may not be 100
percent complete. This method is very useful especially for the
chemical or contaminants that cannot be controlled by substitution,
changing the process, isolation or enclosure. One other major
advantage in such system requires less airflow than dilution
ventilation system.

211
Figure 8-2. Local exhaust ventilation
Source: Deglaville etal. Occupational Health, a manual for health
4. Administrative Controls
Administrative controls limits the amounts of time workers spend at
hazardous job locations. Administrative control can be used together
with other methods of control to reduce exposure to occupational
hazards.

212
Some examples of administrative controls include:
Changing work schedules, for example two people may be able
to work 4 hours each at a job instead of one person working for
8 hours at that job.
Giving workers longer rest periods or shorter work shits to
reduce exposure time
Moving a hazardous work process so that few people will be
exposed
Changing a work process to a shift when fewer people are
working
Workers promotion
Provision of health and sanitation facilities
An example of administrative controls being used together with
engineering controls and personal protective equipment is: a four-
hour limit for work in a fully enclosed high noise area where ear
protectors are required.
Remember: administrative controls only reduce the amount of time
you are exposed to hazard – they do not eliminate exposure.
5. Personal protective equipment
Personal protective equipment (PPE) is the least effective method of
controlling occupational hazards and should be used only when
other methods cannot control hazards sufficiently. PPE can be
uncomfortable, may decrease work performance and may create
new health and safety hazards. For example, ear protectors can

213
prevent hearing warning signals, respirators can make it harder to
breathe, earplugs may cause infection and leaky gloves can trap
and spread hazardous chemicals against the skin.
Personal protective equipment includes:
a. Eye protection
Eye protection embraces spectacles, goggles and handled screens.
No eye protection is effective if it is not worn. Common complaints
from users are:
• discomfort
• restricted vision
• impaired vision ( caused by misting or scratching)
1. Safety goggles
Figure 8-3. Safety goggles protects the eyes

214
2. Face shield and gloves
Gloves are perhaps the most common personal protective
equipment, being an almost automatic reaction to the idea of a
hazardous agent in contact with the hands. Selection should take
into account a wide range of parameters.
• The dexterity required to perform the work
• Physical protection against cuts, grazes and bruises
• Whether the wrist and arm needed protection as well.
• Permeability to chemicals
• Dust retention characteristics
Figure .8-4.protective face shield and gloves
Source: Deglaville et.al. Occupational Health, manual for health

215
2. Helmet
Figure 8-5. A safety helmets protects the head from possible injury.
Protective clothing
At its simplest term protective clothing means overalls or lab coats
for general-purpose use. They are intended to protect the user (or
the user’s own clothing) from everyday wear, tear or dirt. There are

216
a number of special hazards that may be encountered against which
such basic clothing may not be adequate:
Corrosive liquids: could soak into the clothing and so come in
contact with the skin, causing serious damages. Impermeability is
an important factor here.
Dust retention: When working with powders, a fabric that holds dust
could generate an airborne exposure hazard as the person moves
around.
Thermal environment: normal clothing may be too warm or too cold
for a particular environment. In extremes cases, chemical protective
clothing might be necessary. Typically this comprises a one-piece
suit made from an impervious material.
Respiratory protective Equipment (RPE)
In selecting RPE you should take into account:
•The physical nature of contaminant- whether it is gaseous or
particulate
•The chemical nature of the contaminant – whether it is reactive or
corrosive
• Wearability and comfort factors

217
Figure 8-6. Respiratory protective equipment
Hearing Protection
Hearing protection is perhaps a more descriptive term than the
commonly used ear defenders since it is the hearing that is at risk,
not the ears. Protection can take two forms.
Ear muffs- fit over and around the ears. A fluid of foam filled cushion
seals them against the head.

218
Earplugs – fit snugly inside the ear. There are a variety of types,
including foam and soft rubber plugs.
As the noise is produced over a range of frequencies the choice of
hearing protection must be based on the measured spectrum of the
noise to be attenuated. Choosing hearing protection is only partly a
matter of finding protectors with the right attenuation. It is equally
important to find ones that are comfortable and practicable for the
work.
Other administrative services
Provision of health and sanitation facilities
Workers health, physical and psychological developments are
associated with the working and the external environment.
The general sanitation of the industry and the healthful conditions
are necessary for conserving health or to ensure the protection of
occupational health safety and hygiene and measuring or providing
the efficiency of the work place.
Therefore, an industrial plant should satisfy the following conditions
and facilities.
The provision of safe potable and adequate water supply.
Proper collection and disposal of liquid waste.
The provision of adequate sanitary facilities and other personal
services.

219
General cleanness and maintenance of industrial establishment
of protecting good house keeping of the plant.
Maintaining good ventilation and proper lighting systems.
Water Supply
The provision of safe and adequate water supply is the most
important element in industrial settings.
Water can be used for the following purposes in an industrial plant:
It may be used as raw material in the production process.
Used for cooling purposes in the machines
Used for cleaning and washing of equipment
Used by employees to keep their personal hygiene
Serve as a means for waste disposal in water carrying systems
For drinking and cooling purposes
In general the water supply should be safe, adequate and
wholesome and which satisfy public health standards. The number
of taps or fountains required varies from 1 for 50 men to 1 for 200
men, depending upon the plant arrangement. However the standard
is an average of 1 tap or fountain for 75 persons.
Sanitary Facilities
Excreta disposal facilities: observation of many plants or industries
indicated that latrines and toilets used by the workers are of a
primitive and unsanitary nature or in some cases there are none at
all.

220
In some countries the public health services and labor legislation lay
down regulations concerning sanitary facilities to be provided
including the number for male and female workers.
Example. - At least 1 suitable latrine for every 25 females
- At least 1 suitable latrine for every 25 males
In a factory where the number of males employed exceeds 500, it is
sufficient to provide 1 toilet or latrine for every 60 males provided
that sufficient urinals are provided.
Washing Facilities: adequate, suitable and conveniently accessible
washing facilities should be provided for employees. There should
be a supply of running water; in addition soap and clean towels
should be supplied and common towels should be discouraged as
much as possible.
The recommended standards:-
1 wash basin for every 15 workers for clean work
1 wash basin for every 10 workers doing dirty work
1 wash basin for every 5 workers handling poisonous
substances or engaged in handling food stuffs
The walls of washing rooms should preferably be glazed tiles and
the floor made of the same tiles or hard asphalt. The washing basin
should be preferably of vitreous china.

221
Points to be considered in providing shower services.
All showers should be separated for male and female workers to
guarantee privacy
Emergency facilities must be available where there is a danger
of skin contamination by dangerous or poisonous substances
Emergency shower or eye wash facility
Accessory materials
Refuse disposal
Proper solid waste management starting from the source to
generation to the final disposal site is highly required in industries
where different kinds of wastes are generated.
Industrial solid wastes may contain hazardous materials that
required special precaution and procedures. But combustible solid
wastes except poisonous and flammable or explosive materials can
be handled in the convenient manner.
Liquid waste collection and disposal
Industrial liquid wastes if not properly disposed could pollute rivers,
lakes, environment and drinking water supply.
Toxic liquid wastes should be diluted, neutralized and filtered, settled
or other wise chemically treated before being discharged into a
stream or river or on open land. Under no circumstances should be
toxic, corrosive, flammable or volatile materials be discharged into a
public drainage system.

222
Illumination/lighting
The intensity of light source is measured by the standard candle.
This is the light given by a candle, which has been agreed upon so
that it is approximately uniform.
The intensity of illumination is measured by the foot-candle. This is
the illumination given by a source of one candle to an area one foot
away from the source.
For checking illumination, the foot-candle meter is very useful.
Inspectors in determining and measuring illumination at the factory
workers bench can use it.
The window glass area of the workroom should be (usually) 15-20 %
of the floor area.
Advantage of good lighting
• Safeguards eye sight
• Reduce accident and hazards
• Saves the workers time and cut down the amount of spoiled
work and therefore it is economically profitable.
Good Housekeeping and Maintenance
This includes cleanliness of the work place, waste disposal and
adequate washing, adequate toilet, clean eating facilities, and
independent cloakroom. Good housekeeping play a key role in the
control of occupational health hazard.
Immediate cleanup of any accidental spill of toxic materials is a very

223
important control measure. A regular clean up schedule preferably
using vacuum cleaners or using wet methods when vacuum is not
available is an effective method of removing dirt that is probably
laden with harmful substances form the work area.
Good house keeping is essential where solvents are store, handled
and used. It is also very important to provide a cleaning and
maintenance schedule to any work place so that harmful dust may
not accumulate on ceilings, pipes, and other objects within the work
area.Highly trained individuals under strict supervision must carry
out disposal of hazardous materials.

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1. What are the principles of prevention and control of
occupational health and safety problems?
2. What does health promotion mean in the workplace and who
is responsible to deliver it?
3. What are the reasons for misutilization of personal protective
devices among the workforce?
4. Discuss on the roles of safety rules in a certain occupational
settings.

225
GLOSSARY
Acute. Health effects that show up a short length of time after
exposure.
Administrative control. Methods of controlling employee
exposures by job rotation, work assignment or training in specific
work practices designed to reduce exposure.
Aerosols. Liquid droplets or solid particles dispersed in air that is
fine enough particle size (0.01-100mm) to remain so disposed for a
period of time.
Asbestos. A hydrated magnesium silicate in fibrous form.
Asbestosis. A disease of the lungs caused by inhalation of fine
airborne asbestos fibres.
Asphyxia. Suffocation from lack of oxygen.
Asphyxiate. A gas whose primary or most acute health effect is
asphyxiation.
Biohazard. organisms or products of organisms that present a risk
to humans.
Chronic. Persistent, prolonged, repeated.

226
Contact dermatitis. Dermatitis caused by contact with a substance
gaseous liquid or solid
Climatic stressor: heat radiation problems from tin-roof shed of the
factory and other source.
Confounding factor: factors those are not directly visible but have
risks at workplace, an endpoint determinant that is not under primary
consideration but is correlated in the data with the determinant under
study and it may thus confound or bias the estimated effect
of determinant (or exposure).
Contributing factor: more visible factors that are long lasting risks
at workplace due to poor workplace layout, old equipment, critical
posture, excessive muscle exertion, heat, noise, vibration, smokes,
dusts, and other hazards.
Determinant: risk factors that include exposure level and influences
probability of cumulative exposures, peak or remote exposures,
recent or lagged exposures according to duration, place,
environment, etc.
Ergonomics: preventative measures, which help in designing
workstations, work processes, tools or equipment to fit the individual
worker, and an innovative tool for increasing safety, efficiency, and
productivity.

227
Excessive heat: heat is recorded as excessive if a worker is found
sweating when naked or with light clothing; if investigator feels as
sudden heat wave when entering into the industry.
Excessive noise: noise that makes it difficult to communicate with
your neighbour without shouting
Good workplace: ergonomic workplace with the potential to
increase workers’ health, safety and work performance or
productivity.
Hazard: occupational or environmental exposure sometimes to
individual susceptibility that increase risk, a source of possible injury
to workers or damage to the environment or material assets, and
disturb work process.
Hazardous workplace: workplaces in which a worker interacts with
hazards.
Heat stress: a situation when human body feels thermal discomforts
(e.g., heat load) in dissipating excess heat and sweating to the
surrounding (nearby) environment.
Heat strain: result of heat load or physiological response to heat
stress, differences between internal or metabolic heat production
and heat loss due to a hot and humid climate, or occurrence of heat
exhaustion with change of excessive sweating, heart rate, body
temperature, high blood pressure, feeling of thirst, etc.

228
Hours of exposure: total number of hours worked in a particular job
task, shift or time spent (how many hours) in a specific work
environment.
Implementation: carry out various steps to provide health and
hygiene measures, as well as safety and ergonomic applications for
workplace improvement or intervention.
Industrial hygienist. are occupational health professionals who are
concerned primary with the control of environmental stress or
occupational health hazards that arise as a result of or during the
course of work.
Information system: system that provides the data needed for
decisions relating to safety, health and the work environment.
Intervention: an instrument of something that enhances way of
modification, increase work value and control measures to minimize
work-related problems, and/or to find some changes for
improvement in the workplace.
Job-safety analysis: a series of logical steps to enable systematic
assessment of job tasks for implementing health, safety and hygiene
measures as well as ergonomic applications.
Management system: organizational structure, procedures,
processes and resources needed to implement health and safety
management.

229
Medium scale industry: any industry that uses power driven
machine and employ more than 10 workers.
Monitoring: systematically testing, measuring or observation
aspects of working conditions over a certain period of time in order
to find some changes (improve) in the workplace.
Nonergonomic condition: poor manipulation (incorrect use) of
machinery or tools, intense work with frequent movement of arms,
legs or trunks, handling of heavy materials or carrying a heavy load
without using ergonomic aid such as lifting device, wheel barrows,
push or pull carts.
Occupation: when a person engages in a job-task that brings
livelihood (salary, fringe benefits or other facilities), or work
experience, the identity of a profession, designation or employee
status.
Occupational health: workers’ physical, social, and cognitive
elements for better efficiency in job-tasks.
Occupational safety: working situations where injury risks or
production loss have not begun, or unsafe act, poor work
environment, or non-ergonomic practices are minimised by safety
measures and adopting ergonomic means to control work hazards.
Occupational health/safety: competence of a healthy work force,
safe handling operation, clean or hygienic workplace, suitable work

230
schedule, provision of labour welfare through a maintaining of work
regulation and labour legislation.
Physical fatigue: the result in muscle pain, postural discomfort,
symptoms of musculoskeletal disorders from heavy physical work, or
tired from long working hours without enough food or nutrition,
drinking of water, tea or coffee, and sufficient rest.
Physical stress: results from a relatively high work exposure (heavy
manual work or strenuous tasks, muscle force without using
powered hand tools), physically tired from poor working posture, or
from long working hours without sufficient rest, etc.
Poor workplace: when the work environment is hazardous, non-
hygienic, unsafe, non-ergonomic and/or unproductive.
Psychosomatic symptom: symptom arises from a situation of
poverty, poor salary, family burden, mental fatigue, working on a
non-suitable shift, lack of cognition, bad relation with co-workers,
factory owners and managers, for instance.
Prevention: the act of reducing work-related problems and work
injuries or hindering the obstacles (physical or chemical hazard,
radioactive substance, or biological exposure) in the workplace.
Risk: probability of an adverse endpoint (cumulative risk of hazards
in workplace, for instance).

231
Severity of injury: characterized by death, hospitalization more
than 24 hours and absence from work over three days in the last
one year.
Shift design: making the shift schedule in some way (course or
direction of time) or replace a worker that it brings less work stress
(both from physical and mental), minimize sleep debts and fatigue.
Shift work: activity carried out by several workers in different
periods of day or night, a portion of an extended production process
covered by two or more teams for an equal number of working hour
per shift that relieve each other over a period of 24 hours by day and
night.
Small scale industry: any industry that uses power driven machine
and employ less than 10 workers .
Symptom: a deviation of the normal health of workers due to
abnormal environment, condition or hazardous system at workplace.
Strenuous task: hard work, intolerable task, and a heavy workload
for excessive physical exertion (e.g., stressful manipulation with
nonergonomic tools) in hot and humid work environment.
Sustainable workplace: poverty alleviation through gradual
improvement of workplace safety and health since it contributes to
clean or hygienic work environment as well as productivity and
welfare.

232
Thermal comfort: a state when a worker feels comfortable in a
climate or specific environment without any change of a worker’s
physiological or metabolic parameters such as sweating rate,
variation of oral temperature, heart rate, etc.
Thermal discomfort: feeling of heat exhaustion and thirst, heat
cramps from the effects of excessive heat-load either from direct
heat source, or radiation temperature at workplace.
Thermoregulatory response: physiological response within a hot
and humid working climate that results in the greater sweat loss, or
evaporation of sweat to the local environment or change in oral
temperature or heart rate increase.
Threshold Limit value. is concentration by volume in air under
which it is believed that nearly all workers may be repeatedly
exposed day after day without adverse effect.
Permissible Exposure Limit. is amount permitted for a specific
period within a working day
Variety: type and number of state or situation of a
system/environment
Workplace: a location, place or environment where a worker
normally performs his/her job tasks, or spends a reasonable time
working in that place, location or environment.

233
Workplace assessment: a systematic investigation of job-tasks or
evaluation of work related factors in order to find ergonomic solution
to reduce and control of accidents and injuries, or ill health, or to
improve health, hygiene and safety.
Working condition: a job, task, machinery, tools, layout, factory
premises or working climate that covers factory environment. It can
be also workers’ physical, social and mental workload, psychosocial
and organizational context of job-tasks under which job-task has to
be performed or influences the work (or job tasks), or work
environment.
Working environment: work space, illumination, noise, dust, fumes,
or humidity level at workplace, climate or environment inside factory
premises.
Work hazard: source of risks of an activity, conditions of a system,
or other local situations that result in a work injury, damage to or loss
of equipment, materials, etc.
Workplace improvement: process of improving workplace or the
state of improved work environment, or the act of and process of
improving working conditions (e.g., task, activity, tools).
Workplace intervention: improved health, safety and ergonomic
applications through collaborative efforts from all the parties
concerned, or an efficient use of local resources for good work,
increased productivity and less injuries in the workplace.

234
Work-related injury: an accident that gives rise to poor health,
musculoskeletal disorders or other bad symptoms that results in sick
leave production losses or increased compensation claims.
Work-related risk: the incidence rate combined with the severity of
work hazard, probability or possibility of a mishap in terms of hazard
severity, activation of a hazard that can result injury in workplace, or
result in accident or loss of production.

235
REFERENCES
a. Dembe AE, Erickson JB, Delbos R. Predictors of work-
related injuries and illness: National Survey findings Occup
Environ Hyg. 2004; 8:542-550.
b. Ministry of Labor and Social Affairs. Labor proclamation
No.377/2003.Federal Negarit Gazeta. No12, Addis Ababa,
Ethiopia 2004; pp.2476-2477.
c. WHO. Occupational Health program of WHO Headquarters,
Geneva, Switzerland. The Global Occupational Health
Network 2003
d. Barbara A. Plog. Fundamentals of Industrial Hygiene. 5th
edition. National Safety Council Chicago. 2002
e. WHO/ILO. Occupational Health and safety in Africa.
Meeting report. World Health Organization with input of
WHO/ILO Joint Effort Taskforce 2001
f. WHO, Geneva, "An international journal of health
development", volume 19, No.4, 1998, pp.390-396
g. Mathew Cahill. Diseases.2nd
edition. Springhouse
Corp.Pub.USA.1997
h. Barry S.Levy and David H.Wegman. Occupational Health.
Recognizing and Preventing Work-Related Diseases.3rd
edition.London.1988.
i. David L.Bever. Safety. Personal focus, 2nd edition .mosby
College pub.Toronto.1988.
j. Dedglaville, H., R.S.F Schillings and C.H. Wood, editors,
Occupational Health, A manual for health Workers in
developing countries, AMREF. 1987.

236
k. National safety council. Fundamentals of industrial
hygiene.3rd
edition.USA.1987
l. Jeremy Stranks and Malcolm Dewis. RoSPA. Health and
safety practice.2nd
edition. Great Britain .1986
m. H.A.Waldron. Occupational Hygiene: An Introductory Text.
Blackwell Science (UK).1980
n. H.A.Waldron. Lecture Notes on occupational medicine.
Blackwell Scientific Publications 1979

237
ANNEXES
Annex 1: Points of Reference *measured in dBA or
decibels
• 0 The softest sound a person can hear with normal
hearing
• 10 normal breathing
• 20 whispering at 5 feet
• 30 soft whisper
• 50 rainfall
• 60 normal conversation
• 110 shouting in ear
• 120 thunder

238
Annex 2: Personal Monitoring Equipment
• Fold-down earmuff
• Minor’s lamp
• Lamp cord
• Hard hat
• Safety glasses
• Thermoluminescent (TLD)badge
• Gloves
• Reflective stripes
• Gamma meter
• Safety belt
• Radio
• Lamp battery
• Radon dust pump
• Coveralls
• Rubber steel-toed boots

239
Annex:-3 NIOSH Pocket Guide to Chemical Hazards
First Aid Procedures
Code Definition
Eye: Irrigate immediately If this chemical contacts the eyes, immediately
wash the eyes with large amounts of water,
occasionally lifting the lower and upper lids.
Get medical attention immediately. Contact
lenses should not be worn when working with
this chemical.
Eye: Irrigate promptly If this chemical contacts the eyes, promptly
wash the eyes with large amounts of water,
occasionally lifting the lower and upper lids.
Get medical attention if any discomfort
continues. Contact lenses should not be worn
when working with this chemical.
Eye: Frostbite If eye tissue is frozen, seek medical attention
immediately; if tissue is not frozen, immediately
and thoroughly flush the eyes with large
amounts of water for at least 15 minutes,
occasionally lifting the lower and upper eyelids.
If irritation, pain, swelling, lacrimation, or
photophobia persist, get medical attention as
soon as possible.
Eye: Medical attention Self-explanatory
Skin: Blot/brush away If irritation occurs, gently blot or brush away

240
excess.
Skin: Dust off solid;
water flush
If this solid chemical contacts the skin, dust it
off immediately and then flush the
contaminated skin with water. If this chemical
or liquids containing this chemical penetrate
the clothing, promptly remove the clothing and
flush the skin with water. Get medical attention
immediately.
Skin: Frostbite If frostbite has occurred, seek medical
attention immediately; do NOT rub the affected
areas or flush them with water. In order to
prevent further tissue damage, do NOT
attempt to remove frozen clothing from
frostbitten areas. If frostbite has NOT occurred,
immediately and thoroughly wash
contaminated skin with soap and water.
Skin: Molten flush
immediately/solid-liquid
soap wash immediately
If this molten chemical contacts the skin,
immediately flush the skin with large amounts
of water. Get medical attention immediately. If
this chemical (or liquids containing this
chemical) contacts the skin, promptly wash the
contaminated skin with soap and water. If this
chemical or liquids containing this chemical
penetrate the clothing, immediately remove the
clothing and wash the skin with soap and
water. If irritation persists after washing, get

241
medical attention.
Skin: Soap flush
immediately
If this chemical contacts the skin, immediately
flush the contaminated skin with soap and
water. If this chemical penetrates the clothing,
immediately remove the clothing and flush the
skin with water. If irritation persists after
washing, get medical attention.
Skin: Soap flush
promptly
If this chemical contacts the skin, promptly
flush the contaminated skin with soap and
promptly remove the clothing and flush the skin
with water. If irritation persists after washing,
get medical attention.
Skin: Soap
promptly/molten flush
immediately
If this solid chemical or a liquid containing this
chemical contacts the skin, promptly wash the
contaminated skin with soap and water. If
irritation persists after washing, get medical
attention. If this molten chemical contacts the
skin or nonimpervious clothing, immediately
flush the affected area with large amounts of
water to remove heat. Get medical attention
immediately.
Skin: Soap wash If this chemical contacts the skin, wash the
contaminated skin with soap and water.
Skin: Soap wash If this chemical contacts the skin, immediately

242
immediately wash the contaminated skin with soap and
immediately remove the clothing, wash the
skin with soap and water, and get medical
attention promptly.
Skin: Soap wash
promptly
wash the contaminated skin with soap and
promptly remove the clothing and wash the
skin with soap and water. Get medical
attention promptly.
Skin: Water flush If this chemical contacts the skin, flush the
contaminated skin with water. Where there is
evidence of skin irritation, get medical
attention.
Skin: Water flush
immediately
flush the contaminated skin with water. If this
chemical penetrates the clothing, immediately
remove the clothing and flush the skin with
water. Get medical attention promptly.
Skin: Water flush
promptly
If this chemical contacts the skin, flush the
contaminated skin with water promptly. If this
remove the clothing and flush the skin with
water promptly. If irritation persists after

243
washing, get medical attention.
Skin: Water wash If this chemical contacts the skin, wash the
contaminated skin with water.
Skin: Water wash
immediately
wash the contaminated skin with water. If this
remove the clothing and wash the skin with
water. If symptoms occur after washing, get
medical attention immediately.
Skin: Water wash
promptly
wash the contaminated skin with water. If this
chemical penetrates the clothing, promptly
remove the clothing and wash the skin with
water. If irritation persists after washing, get
medical attention.
Breath: Respiratory
support
If a person breathes large amounts of this
chemical, move the exposed person to fresh
air at once. If breathing has stopped, perform
mouth-to-mouth resuscitation. Keep the
affected person warm and at rest. Get medical
attention as soon as possible.
Breath: Fresh air If a person breathes large amounts of this
air at once. Other measures are usually
unnecessary.

244
Breath: Fresh air, 100%
O2
If a person breathes large amounts of this
air at once. If breathing has stopped, perform
artificial respiration. When breathing is difficult,
properly trained personnel may assist the
affected person by administering 100%
oxygen. Keep the affected person warm and at
rest. Get medical attention as soon as
possible.
Swallow: Medical
attention immediately
If this chemical has been swallowed, get
medical attention immediately.

245
Annex 4: Checklist for observation of working
environment
Checklist identification number: ______________
Identification
Name of industry ____________Type of industry(by size) ________.
Major hazardous raw material in use_______________________
Final product______________________________
Address: Kebele__________________
Total number of employees directly involved in production
processes_______________
Hazards in working environment
1 Is there excessive heat in the workplace? 1. Yes 2. No: A
yes requires that a worker is found sweating when naked or
with light clothing; if investigator feels as sudden heat wave
when entering into the industry.
2 Is there excessive dust in the workplace? 1. Yes 2. No. A
yes requires if the investigator experiences sudden sneezing
upon entering the industry or if the worker’s eye brows, hair,
nostrils and cloths is observed by investigators to be
covered with dust particle.
3 Is there excessive noise in the workplace? 1. Yes 2.
No. A yes requires that it difficult to communicate with
nearby worker without shouting.
4 Is there warning signs or safety rules? 1. Yes 2. No. A yes
requires no lack of such arrangement at inspection around.

246
5 Do the employees use the necessary personal protective
equipment? 1. Yes 2. No. A yes requires no lack in use of
safety devices seen at inspection around.
6 Does all production equipment have the appropriate
protective arrangements?
1. Yes 2.No .A yes requires no lack of such arrangement
(poorly installed electric wire or unguarded machine or equipment) at
inspection around.
7 What is the most dangerous incident in the industry during
the last 12 months, and any preventive measures been
implemented? 1. Yes 2. No. Attainment of yes requires
specification of the incident and preventive measures.
8 Does the industry have copy of the most important safety
and health regulations?
1. Yes 2.No. A yes requires a copy of the regulation.
9. Does the industry have of health and safety personnel? 1.
Yes 2.No. Attainment of yes requires either implementation as
result of initiative from heath and safety personnel or written
programme for action worked out with them.
10. Does the industry follow written health and safety plan for
action in the workplace?
1. Yes 2.No.A yes requires completion of at least one of
the measures in the plan.
11. Does the industry have meetings to discuss safety and
health factors with the employees in the last six months? 1. Yes
2.No. A of yes requires minutes with written conclusions.
12. Are training needs considered in connection with new
employment, equipment or other changes? 1. Yes 2.No. A

247
yes requires an example of training given as a consequence of a
change.
13. Does the industry have first aid equipment? 1. Yes 2.No. A
yes requires that first –aid equipment be available in the
production area and that content be as prescribed
Name of inspector ______________________
Signature____________________Date___________________

Ln occ health_final

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