Geographic information system application of environmental epidemiology

Geographic Information System-
Application of Environmental
Epidemiology
Dr. Ali Jafar Abedi
7/10/2014 1

Introduction: Location Matters
• The concept that location can
influence health is a very old one in
medicine. As far back as the time
of Hippocrates (c. 3rd century BC),
physicians observed that certain
diseases tend to occur in some
places and not others.
7/10/2014 2

Introduction: Location Matters
• In fact, different locations on Earth are
usually associated with different profiles:
physical, biological, environmental,
economic, social, cultural and sometimes
even spiritual profiles, that do affect and
are affected by health, disease and
healthcare.
• These profiles and associated health and
disease conditions may also change with
time (the longitudinal or temporal
dimension).
7/10/2014 3

Introduction: The Origins of Spatial
Analysis
• In 1854, a major cholera outbreak in
London had already taken nearly six
hundred lives when Dr John Snow, using a
hand-drawn map, showed that the source
of the disease was a contaminated water
pump.
7/10/2014 4

Analysis
• By plotting each known cholera
case on a street map of Soho
district (where the outbreak took
place), Snow could see that the
cases occurred almost entirely
among those who lived near the
Broad Street water pump.
7/10/2014 5

Analysis
• This pump belonged to the Southwark and
Vauxhall Water Company, which drew
water polluted with London sewage from
the lower Thames River.
• The Lambeth Water Company, which had
relocated its water source to the upper
Thames, escaped the contamination.
7/10/2014 6

Analysis
• Snow recommended that the
handle of this pump be
removed, and this simple action
stopped the outbreak and
proved his theory that cholera is
transmitted through
contaminated drinking water.
7/10/2014 7

Analysis
• People could also see on this map that
cholera deaths were not confined to the
area around a cemetery of plague victims
and were thus convinced that the infection
was not due to vapours coming from it as
they first thought.
7/10/2014 8

This map is a
digital recreation
of Dr Snow’s hand-
drawn map. The
1854 cholera
deaths are
displayed as small
black circles. The
grey polygon
represents the
former burial plot
of plague victims.
The Broad Street pump (shown in the centre of the map)
proved to be the source of contaminated water, just as Snow
had hypothesised7/10/2014 9

Analysis
• By using a map to examine the geographical
(spatial) locations of cholera cases in relation
to other features on the map (water pumps
and cemetery of plague victims), Snow was
actually performing what is now known as
spatial analysis.
< Dr John Snow (1813-1858), a legendary
figure in the history of public health,
epidemiology and anesthesiology
7/10/2014 10

Geographic information systems
• A geographical information system (GIS) is a
computer system for capturing, storing,
checking, integrating, manipulating, analysing
and displaying data related to positions on the
Earth's surface.
• It is thus a way of linking databases with
maps, to display information, perform spatial
analyses or develop and apply spatial models.
7/10/2014 11

Why use maps?
• Maps and spatial information technologies
have three main advantages:
• They can be a means of recording and storing
information
• They can be used to identify and investigate
spatial patterns
• They are effective in presenting information
and communicating findings
7/10/2014 12

Commonly mapped environmental
information of relevance to the health
sector
• pollution sources and affected areas (including sewage, solid
waste, hazardous waste, industrial pollution, smoke and other
emissions, and radiation);
• land cover and use (including vegetation type, vegetation change
and condition, agriculture, forestry, and soil type and condition);
water availability and quality;
• energy sources and use (including fossil fuel use, electrical
connectivity, biomass use, and renewable energy sources); and
• biological resources (including protected areas and recreational
sites, endangered species, and medicinal resources).
7/10/2014 13

• Mapping techniques can be used to show the
links between environment and health.
• Simple overlays (comparisons) of environmental
and socioeconomic (health) data can be used to
identify patterns, which can then be investigated
later for correlations
• Once the causal relationship is known, however,
spatial models can also be developed to predict
changes in health based on environmental
changes.
7/10/2014 14

• An example :
• vulnerability to disease outbreaks based on
water quality information, temperature, and
rainfall.
7/10/2014 15

Steps to GIS
Data Capture
Data Storage
Data Retrieval Display
Query
Analyze
7/10/2014 16

• Data capture. A GIS cannot analyze the information in a map, if the
data are not already in digital form, which the computer can
recognize. Maps can be digitized (hand-traced with at computer
mouse) to collect the coordinates of the map features.
•
Data retrieval. With a GIS we can point at a location, object, or area
on the screen and retrieve recorded information about it from the
Database Management System (DBMS) which holds the information
abut the map’s features.
•
Spatial measurements. GIS makes spatial measurements easy to
perform. Spatial measurements can be the distance between two
points, the area of a polygon or the length of a line or boundary.
7/10/2014 17

• Overlays (data integration). Overlaying is an important procedure
in GIS analysis. Overlaying involves superimposing two or more map
layers to produce a new map layer.
• Consider the following example: a new genetically engineered
variety of wheat grows well in dry environments, with long growing
seasons and alkaline soils. Given the availability of data on the
length of the growing season, moisture regime and soil alkalinity,
where is the best place to plant the wheat?
• The answer can be found by overlaying (superimposing) several
maps showing (separately) water-budget, growing season length,
soil pH, sodium content, and so on. The GIS analysis can establish
the locations where all the favorable soil conditions coincide, as the
places where the wheat will grow best.
7/10/2014 18

• Spatial interpolation. A GIS can be used to estimate the
characteristics of terrain or ecological conditions from a
limited number of field measurements. For example, a
rainfall map can be created from the interpolation of
rainfall point measurements taken at a number of different
locations on a map.
•
Buffering and corridors. Buffers are used when the
distance from a point or line is important to measure. For
example a classic use of GIS in earth sciences involves
estimating the damage caused by an earthquake, in terms
of distance belts away from the epicenter.
7/10/2014 19

• Registration Before they can be used in GIS, maps and images
should be geometrically rectified. The process begins by registering
the raw maps and images to known (control) coordinates.
•
Map projection. Map projection is a fundamental aspect of
mapmaking. A map projection is essentially a geometric model that
transforms the locations of features on the Earth's surface to
corresponding locations on a two-dimensional map.
• It is impossible to project a spheroid perfectly onto a plane; but
some projections can preserve shape, while others preserve area,
distance, or direction.
• Different projections are used for different types of maps because
each projection is particularly appropriate for certain uses. For
example, a projection that preserves the shape of the continents
may distort their relative size.
7/10/2014 20

Strengths
• visual impact and thus effective communication
of the issues
• deliver a message without pages of text, and are
therefore ideal for busy people or those who
want a strategic view of the situation
7/10/2014 21

Strengths Contd...
• geo-referenced information gives a
spatial dimension to environment–
health linkages – not only
pinpointing issues but also
describing the intensity or extent of
the cause or effect
• Maps can highlight localized issues
(for example, exposure to disease
from location of disposal sites) as
well as more diffuse issues (for
example, exposure to radiation
from reductions in atmospheric
ozone).
• Both types of information are
useful in planning (ex ante) and
assessment (ex post) of health
impacts.
7/10/2014 22

Maps of environmental
information can be used as
early-warning tools for
health planners.
For example, mapping
environmental criteria in
the determination of
malaria prevalence may
give insights into areas
where malaria may be
occurring but is currently
not well reported, as well
as into possible changes in
the distribution of the
disease under altered
climate regimes.
7/10/2014 23

Other examples include
• mapping land degradation, together with
long-term rainfall variability, to indicate
potential future food production changes;
• mapping forest fires as an indication of air
pollution;
• mapping flood-prone areas as early
determination of potential cholera outbreaks.
7/10/2014 24

Some maps can be used to indicate
trends over time if the same
variables are mapped in the same
way and at the same scales at regular
intervals.
Land cover or land use change is
often mapped over time intervals,
and can be used to track changes in
environmental health issues (for
example, the rate of urban
expansion, agricultural expansion, or
infrastructure development).
Some data sets can be recorded and
displayed in near-real time, such as
air pollution dispersion.
This enables planners to issue
warnings or to take mitigatory
actions (such as UV warnings for
holidaymakers).
7/10/2014 25

Weaknesses
• A map is primarily a means of display; it cannot
predict the patterns of distribution or
relationships between resources
• does not infer a causal relationship, it merely
points out that there are some spatial
coincidences that are worth exploring, to see if a
causal relationship exists.
• Likewise, to show how changes in one resource
may impact distribution of another resource, the
relationship must be known and put into the
model creating the map.
7/10/2014 26

Weaknesses
Contd..
• Most maps, unless they use data that are recorded in real
time or near-real time , represent only a snapshot of the
situation at a particular time in history.
• As the environment is extremely dynamic, and conditions
(many of which impact on health) are constantly changing,
maps can quickly become outdated.
• Updating maps can be expensive in terms of the time
required to make the maps and the cost of the information
inputs required.
• In cases where current information is required (for
example, monitoring of pollution dispersal from accidents
or leaks), obtaining spatial information may be difficult or
costly.
7/10/2014 27

Weaknesses
Contd..
• access is often limited
• data may be available for only a portion of
the required area, or for the whole area but
taken from two or more different sampling
exercises which may have used different
sampling methodologies, scales, or accuracy
levels.
7/10/2014 28

Weaknesses
Contd..
• costs : generating maps, and in printing,
disseminating, and updating them.
• requires specialized hardware and software,
trained personnel, and often expensive and
time-consuming means of acquiring, checking,
interpreting, and inputting information.
7/10/2014 29

Weaknesses
Contd..
• technology is rapidly advancing, and thus new
applications and training courses are required on an
almost annual basis.
• not all people can readily relate to information in a
two-dimensional spatial format, especially if the map is
of an unfamiliar area or is presented in an unusual
projection.
• different cultures place different importance or
meaning on symbols and colours- western cultures may
use the colour red to symbolize danger or an area
where conditions are bad, but in China this colour
would symbolize luck or a favourable area.
7/10/2014 30

Summary
• maps are useful communication tools if they
have been developed according to the best
available information (about both the
environmental conditions and the targeted
users).
• However, they should be used together with –
– other information, such as documents,
discussions, and models.
7/10/2014 31

Commonly-used environmental spatial
information relevant to health
Geological
• These maps could be used to detect radiation
sources and potential for seismic activity.
• They can therefore be useful in planning and
assessment in the health sector, particularly in
the location of vulnerable population groups
and the calculation of risks.
7/10/2014 32

Topographical
• Contour maps or digital elevation models can
be used to calculate steepness of slope and
resultant vulnerability to flooding, landslides
and mudslides, erosion, and dust pollution.
This is relevant for determining risk and
planning emergency services.
7/10/2014 33

Soils
These maps can be useful in locating areas of
food insecurity or malnutrition as a result of
low agricultural potential or mineral
deficiency, but are perhaps more useful when
used in models in combination with other
variables such as rainfall and hours of
sunshine.
7/10/2014 34

Land cover and use
• These maps are usually informative when
used in modelling environmental change and
impacts for human health.
• Land cover change could signify an increase in
agricultural activity resulting in greater food
security, or it could signify changes in climate
and spread of new diseases.
7/10/2014 35

Biodiversity
• These maps are usually based on forest cover or
protected areas, but specific species or habitat
atlases exist.
• These can be useful as indicators of
environmental change – for example, a
worldwide decline in amphibian species is
thought to signify atmospheric or climatic
changes such as increased pollution. These
indicators may also be relevant to human health.
7/10/2014 36

Water resources
• Maps of both surface and groundwater
resources exist; in some cases water quality is
indicated.
• These maps can be useful in planning water
supply and sanitation schemes related to
health planning.
7/10/2014 37

Air quality
• Most commonly monitored are emissions of
sulfur oxides and nitrous oxides, and smoke,
ambient concentrations of carbon monoxide
and carbon dioxide, sulfur and nitrogen
oxides, lead, and ozone.
• These are useful for health assessment and
planning with relation to respiratory diseases,
cancers, and stunting in children.
7/10/2014 38

Poverty
• They are most commonly used by planning
and development agencies, to target specific
areas with specific needs.
• A classic example is provided by a case-study
by Friends of the Earth UK, which showed that
the residents downwind of industrial sites in
the United Kingdom had significantly lower
income levels than the residents upwind of
these sites.
7/10/2014 39

WHO (World Health Organisation) GIS Programmes
• HealthMap (http://www.who.int/csr/mapping/en/) is a joint
WHO/UNICEF GIS Programme that was initially created in 1993 to provide
GIS support for the management and monitoring of the Guinea Worm
Eradication Programme. But since 1995, the scope of the work has been
expanded to cover other disease control and public health programmes.
• The HealthMap project has successfully contributed to the surveillance,
control, prevention and eradication of many communicable diseases,
including Guinea worm, onchocerciasis, lymphatic filariasis, malaria,
schistosomiasis, intestinal parasites, blinding trachoma and HIV.
• The programme has developed its own HealthMapper application
(http://www.who.int/health_mapping/tools/healthmapper/en/ ) and is
providing it at no cost to developing countries. This is a database
management and mapping system that simplifies the collection, storage,
retrieval, management, spatial and statistical analyses, and visualisation of
public health data through its user-friendly interface.
7/10/2014 40

WHO (World
Health
Organisation) GIS
Programmes
7/10/2014 41

Reference
• Oxford TEXTBOOK OF PUBLIC HEALTH
• http://www.who.int/heli/tools/maps/en
7/10/2014 42

Geographic information system application of environmental epidemiology

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