Pollution and the nervous system

Relation between
Environmental POLLUTION and
mental disability

By Dr. Shewikar El Bakry
Lecturer of Neuropsychiatry
Benha University.

The Developing Brain
 Brain development begins very early in human

gestation and continues well after birth through
adolescence. It depends on a tightly orchestrated
cascade of sequential and concurrent events.

 The abnormalities observed after exposure to a single

toxic agent may vary with the timing of the exposure.1
The nature of the neurotoxicant, the extent of
exposure, and the timing of exposure are, therefore,
each important determinants of outcome.

Although genetic inheritance plays a
prominent role in fetal brain
development, environmental factors
also significantly contribute to final
outcomes through their direct impact on
developing tissues, by alteration of
signaling chemicals that are essential
mediators of brain development
(neurotrophins), or by modifying gene
expression

Environmental Influences
 Physical
 Toxins
 Nutrition
 Sick buildings
 Noise pollution
 Second-hand smoke
 Lead

 Social
 Violence
 Substance abuse
 Child rearing

practices

 Poverty

Environmental Factors
Attributable to DD
 25% of developmental and

neurological deficits in children are
due to the interplay between
chemicals and genetic factors

 3% of DD can be attributed to

chemical exposure alone

Known Causes of
Developmental Disabilities
 Lead
 Alcohol
 Nicotine
 Mercury
 PCBs

Pollution and the nervous system

MENTAL RETARDATION
DSM4 (Diagnostic and Statistical Manual for Psychiatric
Disorders, American Psychiatric Association)
1. Score of 70 or below on a standard IQ (intelligence
quotient) test
3. Adaptive functioning: how well the individual meets
age and culture specific standards
3.

Age of onset before 18
Degrees of severity:

Mild: 55-70
Moderate: 35-55
Severe: 20-35
Profound: below 20

The cause of approximately 80 percent
of developmental disorders of
childhood is not known; and in the
absence of knowledge about causal
factors, environmental exposures
should be considered prime suspects
for causing such problems or
interacting with other factors (e.g.
physical, genetic or psychosocial
factors) to cause or exacerbate these
conditions.

Mercury Exposure:
Sources

Major

 Seafood: larger fish have most mercury, due to eating

smaller fish

 Vaccines: many childhood vaccines used to contain 12.5-25

ug of thimerosal, so that a fully-vaccinated child could
receive up to 237.5 ug of thimerosal injected into them

 Dental amalgams: usually emit 1-10 ug/day; amount of

mercury in brain strongly correlated with number of dental
fillings; could release much more when first placed or
removed

OFFICIAL STATEMENT:
US Centers for Disease Control
and Prevention (CDC)
 “Mercury occurs naturally and is found

everywhere in the environment.”

 “The level of mercury exposure from vaccines is

low.”

 “Evidence is accumulating of lack of harm

resulting from exposure to thimerosal in
vaccines.”

KNOW YOUR MERCURY (Hg)
TYPE SOURCE

EXPOSURE

Elemental Hg Thermometers

Vapor

Amalgams
Lights/batteries
Inorganic Hg Coal power plants Air pollutants
(hydrophilic) Volcanoes
Organic Methyl Hg

Fish Ingestion

(lypophilic)
Organic Ethyl Hg Thimerosal
(lypophilic)

Fish(?)

Vaccines

OTC Topicals

The LDA is convinced that there
is a direct relationship between
human exposure to mercury
pollution-especially for women
of child-bearing years- and the
rising incidence of cognitive
disabilities.

Mercury Exposure
Low Dose Prenatal
 Impairments of:
 motor skills
 attention
 visual spatial skills
 language
 memory

 Blood pressure, heart rate variability

Mercury Exposure
Prenatal High-Dose Effects
 Mental retardation
 Seizures

 Cerebral palsy
 Disturbances of vision, hearing, sensation
 Abnormal gait
 Abnormal speech
 Disturbances of swallowing

and sucking
 Abnormal reflexes

Mercur y Toxicity
 “Mercury is considered to be a developmental toxicant.

… The symptoms observed in offspring of exposed
mothers are primarily neurological in origin and have
ranged from delays in motor and verbal development to
severe brain damage.”

 “The infant may be born apparently normal, but later

show effects that may range from the infant being
slower to reach developmental milestones, such as the
age of first walking and talking, to more severe effects
including brain damage with mental retardation,
incoordination, and inability to move.”

“Other severe effects observed in
children whose mothers were exposed
to very toxic levels of mercury during
pregnancy include eventual blindness,
involuntary muscle contractions and
seizures, muscle weakness, and
inability to speak.”
“It is important to remember, however,
that the severity of these effects
depends upon the level of mercury
exposure and the time of dose.”

Maximum Hg exposure in 1st year of life US Childhood Schedule - 1992-200?
AGE

SHOTS

BIRTH

Hep B

HG CONTENT

12.5mcg

8lb infant (3.6kg)– EPA Hg limit: 0.36mcg = 35 times over
4lb infant (1.8kg) – EPA Hg limit: 0.18mcg = 70 times over

2 MONTHS

Hep B

12.5mcg

HIb 25.0mcg
DTaP

25.0mcg

(subtotal for visit):
62.5mcg
Avg. weight: 10lbs/4.5kg EPA limit: 0.45mcg = 138 times over

4 MONTHS
DTaP

HIb 25.0mcg
25.0 mcg

(subtotal for visit):

50.0 mcg

Avg weight: 14lbs/6.5kg EPA limit: 0.65mcg = 72 times over

ETHYL VS METHYL
 Main chemical difference: Ethyl form contains extra carbon compound on molecule,

making it larger.

 Some scientists contend extra carbon compound makes ethylmercury less likely to

cross the blood-brain barrier.

 Methylmercury shown to remain in blood longer than ethyl (1/2 life of 50 days vs. 7 days

for ethyl); it accumulates more readily in the body. But ethyl converts more readily to
inorganic Hg, which appears to remain in brain longer.

 Despite these differences, FDA researchers assumed that the two forms of mercury

were equal in toxicity.

 Arsenic is “less toxic” than cyanide.

Bolus vs. Chronic Exposure
FDA’s “Interpretation”

 FDA totaled 4 large “bolus” doses at birth, 2, 4, & 6 months

(162.5mcg) and divided by 180 days.

 162.5mcg divided by 180 = 0.9mcg per day.
 This “average” daily exposure was just above the EPA limit, but

below FDA and CDC limits.

 Analogy: You can take 2 tylenol a day for 60 days and be fine.

But 120 tylenol in one day is a lethal dose.

CHILD WITH ACRODYNIA CHILD WITH AUTISM
(Mercury poisoning)
(Will Redwood)

Impact of Pb on human health
Pb is a highly toxic, heavy metal and remain stable
over time (entering into ecological systems, water
supply, plants, …)
Pb accumulates in the body over time causing health
problems.
Pb has been confirmed to hamper neurological and
physical development (harmful for children below 6
years)

Low level of exposur e to lead can
result in
physical r etar dation
low IQ
hyperactivity
hearing loss
behavioural changes
insomnia
High level of exposur e (blood contains
> 25 mg Pb/dl) can cause
lead poisoning
Anemia, hypertension, mental
r etar dation, convulsions, coma

PCB Exposure
Developmental Effects
Infant


Birth weight



Head circumference



Performance on Brazelton Neonatal Behavioral Assessment
(BNBA) - motor immaturity, inc. startle

Early Childhood


Memory, attention, verbal ability, information processing



Delayed psychomotor development; changes in play behavior



Hyperactivity

Preteen


Word and reading comprehension



Full scale and verbal IQ



Memory and attention

Nicotine
 Reduced IQ
 Learning disabilities
 Attention deficits

Noise pollution:


non-auditor y ef fects on health

 auditor y ef fects

Hearing Impairment
 Hearing is essential for well-being and safety.

Hearing impairment is typically defined as an
increase in the threshold of hearing as
clinically assessed by audiometry.

 Studies suggest that children seem to be

more vulnerable than adults to noise induced
hearing impairment

non-auditor y effects on
health
 1-Interference with the spoken

communication.

 2- Sleep Disturbances.
 3- Cardiovascular Diseases.
 4- Disturbances in Mental Health.
 5- Impaired Task Performance.
 6- Negative social Behaviour and Annoyance

Reaction.

Missing the Dark: Health
Effects of Light Pollution
 Electric lighting has become an integral part of

modern society. When such light is inefficient,
annoying, or unnecessary, it is known as light
pollution. Many environmentalists, naturalists, and
medical researchers consider light pollution to be one
of the fastest growing and most pervasive forms of
environmental pollution. Moreover, a growing body
of scientific research suggests light pollution can
impair biologic functions in both

Pollution and the nervous system

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