Environmental Epidemiology

Lecture PPt

1. HawassaUniversity College of Medicine andHealth
SciencesDepartment of Environmental health Sciences
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2. Introduction to Environmental Epidemiology
for 4
th
yrBSc Environmental Health Sciences students
by AdaneE (BSc, MSc)
[email protected]
March, 2019
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3. Definitions of terms
Health:Astateofcompletephysical,mentalandsocialwell-
beingandnotmerelytheabsenceofdiseaseorinfirmity
(WHO,1948)
Disease:A physiological or psychological dysfunction
Illness:A subjective state of not being well
Sickness:A state of social dysfunction
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4. Definitions…
Epidemiology
Itisthestudyoffrequency,distribution,anddeterminantsofdiseases
andotherhealth-relatedconditionsinahumanpopulation
and
theapplicationofthisstudytothepreventionofdiseaseandpromotion
ofhealth
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5. Components of the definition
1.Study: Systematic collection, analysis and interpretation of data
Epidemiology involves collection, analysis and interpretation of
health related data
Epidemiology is a science
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6. Components…
2. Frequency: the number of times an event occurs
•Epidemiology studies the number of times a disease occurs
•It answers the question How many?
•Epidemiology is a quantitative science
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7. Components…
3. Distribution: Distribution of an event by person, place and time
•Epidemiology studies distributionof diseases
•It answers the question who, where and when?
•Epidemiology describes health events
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8. Components…
4. Determinants: Factors the presence/absence of which affect the
occurrence and level of an event
•Epidemiology studies what determines health events
•It answers the question how and why?
•Epidemiology analyzes health events
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9. Components…
5. Diseases & other health related events
•Epidemiologyisnotonlythestudyofdiseases
•ThefocusofEpidemiologyarenotonlypatients
•Itstudiesallhealthrelatedconditions
•Epidemiologyisabroaderscience
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10. Components…
6. Human population
•Epidemiology diagnoses and treats communities/populations
•Clinical medicine diagnoses and treats patients
•Epidemiology is a basic science of public health
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11. Components…
7. Application
•Epidemiological studies have direct and practical applications
for prevention of diseases & promotion of health
•Epidemiology is a science and practice
•Epidemiology is an applied science
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12. Environmental Epidemiology
•The study of the determinants of the distributions of disease that are
exogenousto and nonessentialfor the normal functioning of human
beings
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13. Environmental epidemiology
•Epidemiology is one of the core disciplinesused to examine the
associations between environmental hazards and health outcomes.
•Study of diseases and health condition (occurring in the population)
that are linked to environmental factors.
studiesenvironmentalriskfactorsandtheirimpactonthehealthof
exposedpeople
Thesefactorsmaybenaturaloranthropogenic
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14. Types of Environmental Exposures
✔Point sources
•Pollution from a factory, municipal solid waste site
✔Line sources
•EMF exposures from high tension power lines
•Combustion pollutants around high density motorways
✔Area sources
•Airborne combustion products from traffic and long-range transport
•Volatile organic compounds contaminating underground water
reservoirs
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15. •Epidemiology is one of the fundamental disciplines used in the study
of environmental health.
•One of the research toolsthat seeks to answer the following questions:
What is the impact of air pollution on children’s lung function?
Is there a relationship between exposure to agents in the
environmentand degenerative brain diseases such as Alzheimer’s
disease?
What environmental exposuresmight act in combination with
genetic factors to cause breast cancer?
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16. What are the health effects of consuming seafood contaminated
with Mercury?
Is it safe to eat tuna, because it could contain chemical pollutants
that were dissolved in the ocean?
What are the long-term consequences of beach pollution?
Does secondhand cigarette smoke cause lung cancer in
nonsmokers?
Are death rates higher in geographic regions that have higher air
pollution levels in comparison with regions that have lower levels?
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17. Thereisconsiderableconcerntodayaboutthechronichealth
hazardsofradiation.
Wouldyouconsiderchemicalstobeanequalhazard?
Howlargeanincreaseincancerincidence(occurrence)wouldbe
necessarybeforeachemicalcouldbeidentifiedasaproblem?
Severalyearsago,peoplewereconcernedthatdaughtersexposed
fordiethylstilbestrol(DES)woulddevelopcancer.
Whatarethechancesthatthisdiseasewilldevelopin10or20
yearsinaDES-exposeddaughterwhodoesnothavecancernow?
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18. 18
Interaction
The study of how the environment affects human health.
Food
Air
Water
Sunlight
Noise
Soil
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19. 19
…with good things
There are many things around us that help us stay healthy.
Family &
friends
Beautiful
scenery to
look at
Medicine &
vitamins
Oxygen
in the air
Nutrients
in food
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20. 20
….with hazards
A hazardis anything in the environment that can hurt or make
humans sick.
Bacteria
& viruses
Tobacco
smoke
Stress
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21. 21
Parts of exposure for environmental hazards
Source
of the hazard
(bus exhaust)
Environmental
Pathway
(air)
Contact
(inhaled fumes)
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22. Environmental Exposures
•Not genetic
•Pollution as opposed to life style
•Passive as opposed to active
•Involuntary as opposed to voluntary
•External as opposed to internal
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23. Pollutants in the Ambient Environment
•Ubiquitous
Hard to identify unexposed people
•Low levels
Tight range
Measurement error
•Passive
Potentially unknown to participant
Hard to identify unexposed AND exposed people
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24. 243/5/2019

25. Risk factors interaction
The added risk from environmental factors interacts with non
environmental risk factors:
•Behavioural(smoking, drugs, alcohol abuse)
•Socio-health(hygiene, nutrition, stress)
•Genetic(hereditary susceptibility)
•Anamnestic(previous diseases and medication)
•Physiological(age, sex, pregnancy, weight, height and
respiration)
•Professionalexposure
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26. Exposure
•The timing of exposure, both of populations and individuals, may take
three basic forms:
1.Acute
2.Sub-acute and
3.Chronic
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27. Exposure…
•Sub-acute-less than one month by whatever route and repetition
•Sub-chronic-doses between one and three months
•Chronic-exposure for more than three months to lifetime
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28. Exposure…
Acute–doseoccursinlessthan24hour
•Usuallyduetosomeaccidentalreleaseofmaterial,perhapsfroman
industrialaccidentorfire.
•Otherthaninanecdotalorpubliclyreportedform,nolong-term
recordsarecurrentlykeptofincidentsleadingtoexposureof
populations,andlittleaccurateinformationabouttheprecisenatureof
thematerials,theexposurelevelsorthepeopleexposed.
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29. Exposure…
•Clearly, there are a number of potential victims of a sudden chemical
releasein this way:
oemployees and others in the immediate vicinity when the release
takes place;
othe population within the exposure area; and
othe emergency services and others who have to deal with the
immediate problem and effects of the release.
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30. Exposure…
Sub-acute exposure
•Less than one month by whatever route and repetition
•May take place where a population lives in houses built on
contaminated land or near an old industrial waste tip.
•There may be a continuous low-level exposure that is episodically
increased by development or climatic causes.
•In such environments, children are particularly at risk because of
their play activities.
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31. Exposure…
Chronic exposure
•Exposure for more than three months to lifetime
•Mayoccurwhereawell-controlledindustrialprocessmakeslow-level
releasesintotheatmosphere,orwherethereisacontinuousdietaryor
occupationalexposure,forexample,
•drinkingwatersuppliescontainingchloroform
•increasedMercurydosageduetoanoverlargeconsumptionoftuna,or
•Benzpyrenesaccumulatingincookingoilthathasbeenusedattoo
highatemperatureandnotchangedregularly.
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32. Theamountofexposurecanbeassessedinsixways:
1.Interviews,questionsanddiariestorecordwhatpeopleobserveof
theirownexposure,bothintimeanddegree
2.Physical,chemical,ormicrobiologicalmeasurementsonwater,air
orsoil
3.Samplingthepersonalenvironment,forexample,foodseatenorair
breathed
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Exposure…

33. 3.Measurementofdoseofexposure(individualradiationmonitorsare
oneexample)
4.Concentrationofchemicalsinhumantissues
E.g.leadinbloodorteeth
5.Markersofthephysiologicaleffectsofexposure
E.g.carboxyhaemoglobinasanindicatorofexposuretotobacco
smoke
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Exposure…

34. History of Environmental Epidemiology
•It has a long history that dates back 2000 or more years.
1.In about 400 BC the ancient Greek authority Hippocratesexplained
(recognized) the role of environmental factors such as waterquality
and the aircausing diseases.
•He produced the well known book On Airs, Waters, and Places.
•Historical corner stone of Environmental Epidemiology
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35. History…
2.SirPercivalPott(Surgeon,London),thoughttobethefirst
individualtodescribeanenvironmentalcauseofcancer.
•In1775,heobservedthatchimneysweepershadahighincidence
ofscrotalcancerincomparisonwithmaleworkersinother
occupation.
•Inhisbook(ChirurgicalObservationsRelativetotheCataract,the
PolypusoftheNose,theCanceroftheScrotum,theDifferent
KindsofRuptures,andtheMortificationoftheToesandFeet,
1775),hewroteachaptercalledAshortTreatiseoftheChimney
Sweeper’sCancer
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36. History…
•provided the first clear description of an environmental cause of
cancer,
•suggested a way to prevent the disease, and let indirectly to the
synthesis of the first known pure carcinogen and the isolation of the
first carcinogenic chemicals
•Established an occupational hygiene control measures-bathe once a
week
3.John Snow, English Anesthesiologist-linked a cholera outbreak in
London to contaminated water from the Thames River.
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37. Contributions of Epidemiology to Environmental Health
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38. Contributions…
•Epidemiologyisimportanttothestudyofenvironmentalhealth
problemsbecause
manyexposuresandhealtheffectsassociatedwiththeenvironment
occuratthepopulationlevel(concernwithpopulations)
theepidemiologicmethodsofnaturalexperimentsand
observationaltechniquesareappropriate(useofobservationaldata)
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39. thestudydesignsusedinepidemiologicresearchcanbeapplied
directlytothestudyofenvironmentalhealthissues(methodology
forstudydesigns)and
epidemiologyaidsinthedevelopmentofhypothesesandthestudy
ofcausalrelationships(descriptiveandanalyticstudies).
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Contributions…

40. Concern with Populations
•Incontrastwithclinicalmedicine’straditionalfocusonthe
individual,auniquecharacteristicofepidemiologyisthatit
studiestheentirepopulationandhenceissometimescalled
populationmedicine.
E.g.theoccurrenceoflungcancermortalityacrosscountries
oramongregionalgeographicsub-divisions-censustracts.
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41. Concern…
•Whetherlungcancermortalityishigherinareaswithhigher
concentrationsof“smokestack”industriesincomparisonwithareas
thathavelowerlevelsofairpollutionorarerelativelyfreefromair
pollution.
•Thealternativeapproachoftheclinicianwouldbetoconcentrateon
thediagnosisandtreatmentoflungcanceramongspecificindividuals.
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42. Use of Observational Data
•Ethicalissuessuchaspotentialdangerstosubjectsprohibittouse
experimentalmethods
•Studies of the population’s health present a challenge that is partially
met by epidemiology because it is an observational science that takes
advantage of naturally occurring situations in order to study the
occurrence of disease.
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