environmental epidemiology introduction to occupational · environmental epidemiology a science...
TRANSCRIPT
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Introduction to Occupational & Environmental Epidemiology
Thanawadee Chantian, MD, MPHJoint Introductory Course for Epidemiology and Statistics: July 9, 2019
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Learning objectives
1. Understand basic concepts and terminology in environmental and occupational health
2. Discuss role of epidemiology in environmental health and challenges
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Outline
◍ Terminology and concept○ Environmental health and occupational health○ Environmental and occupational diseases○ Environmental and occupational epidemiology ○ Risk assessment
◍ Difference between environmental and occupational epidemiology
◍ Challenges in environmental and occupational epidemiology○ Common bias
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“Most living things require water, food, oxygen, and sunlight for a healthy existence why would this not apply to humans?”
Carlos A Camargo, MD,DrPHDepartment of Epidemiology, Harvard Medical School
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What is environmental and occupational health?
Environmental health ◍ Focusing on the relationships between people and their
environment; promotes human health and well-being; and fosters healthy and safe communities 1
Occupational health ◍ Identification and control of the risks arising from physical,
chemical, and other workplace hazards in order to establish and maintain a safe and healthy working environment 2.
Reference. 1.American Public Health Association. Retreived from https://www.apha.org/topics-and-issues/environmental-health 2. National Institute of Environmental Health Science. Retreived from https://www.niehs.nih.gov/health/topics/science/index.cfm
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Occupational diseases
Occupational diseases ◍ Any disease contracted primarily as a result of an exposure to
risk factors arising from work activity◍ Listed by International Labor Organization (ILO)◍ Examples: Silicosis, Asbestosis,
Work-related diseases◍ Multiple factors cause the disease ◍ The work can aggravate the symptoms ◍ Examples: Musculoskeletal disorder, Asthma
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◍ Environmental diseases ○ Diseases caused by directly result from the environment
(as distinct from infection or genetic factor) ○ I.e. exposure to toxic chemicals, and physical factors in
the environment◍ Pollution-related diseases
○ attributed to exposure to toxins in the air, water, and soil
Environmental diseases
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Environmental epidemiology◍ A science primarily concerned with environmental
causes of health outcomes
Occupational epidemiology◍ Focusing on workers exposed to a variety of
chemical, biological or physical (e.g., noise, heat, radiation) agents to determine if the exposures result in the risk of adverse health outcomes
Environmental and occupational epidemiology
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Concept in occupational and environmental epidemiology
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Epidemiological triad
Host (Human)-Dose-Genetics
Agent (Hazard)-Physical-Biological-Chemical-Psycholoogical-Ergonomics
Environment
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Human risk assessment
◍ Quantitative estimate of the potential effects on human health and environmental significance of various types of chemical exposure
◍ Four steps:○ Hazard identification○ Dose-response assessment○ Exposure assessment○ Risk characterization
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Risk assessment and envi epi
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Hazard identification
◍ Hazard Identification○ The process of determining whether exposure to a stressor
can cause an increase in the incidence of specific adverse health effects (e.g., cancer, birth defects).
◍ Hazards○ Any source of potential damage, harm or adverse health
effects on something or someone
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Hazards
Ergonomics
Psychological
ChemicalPhysical
Biological
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Dose-response assessment◍ Dose-response assessment
○ Process quantitates the hazards to determine the relationship between different level of dose and incidence of effects in humans
◍ Dose○ Amount of material taken into the body
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Dose-response curve
The Linearized Multistage Model is used to extrapolate cancer risk from a dose-response curve using the cancer slope factor(Image Source: NLM)
Carcinogenic risk assessment Non-carcinogenic risk assessment
Dose-response curve for noncarcinogenic effects(Image Source: NLM)
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Exposure Assessment
◍ Exposure assessment○ Study of distribution and determinants of the
substances or factors affecting human health◍ Exposure
○ Any contact between environmental medium (i.e. water, air, soil) and the surface of human body
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Source of Exposure◍ Air◍ Soil◍ Water
Route of exposure•Inhalation•Ingestion•Dermal Absorption•Ionizing radiation
Exposure assessment
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Conceptual diagram
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Exposure assessment approachExposure assessment
approach
Direct methods Indirect methods
QuestionnairesDiaries
Environmental monitoring/
modeling
Personal monitoringBiomonitoring
Exposure model
Dose model
PBPK modeling
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Hierarchy of exposure data
1. Quantified personal measurement2. Quantified area measurement in the sites of activity3. Quantified surrogate of exposure i.e estimates of
drinking water use4. Distance from the site and duration of exposure5. Residence or employment in a defined geographical
area of the site
Best
Worst
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Risk characterization
◍ To summarize and integrate information from the proceeding steps of the risk assessment to synthesize an overall conclusion about risk.
◍ Risk○ probability of effects
likely to occur in humans exposed under similar conditions.
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Environment◍ Low dose exposure◍ Most of exposure are
long term of exposure ◍ Focusing on general
population and most susceptible i.e. children ,elderly
Occupation◍ Higher exposure level◍ Shorter duration of
exposure◍ Focusing on adult
(worker)◍ Healthier
Difference characteristics between environmental and occupational epidemiology
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Common bias
◍ Healthy effect◍ Measurement error◍ Collinearity ◍ Lagging time windows
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Healthy worker effect
◍ Special type of selection bias that can occur in cohort studies of occupational exposures when the general population is used as the comparison group
◍ Why is such a comparison biased?○ Because the general population also contains many people
who cannot work due to ill health○ Work force tends to have fewer sick people
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Measurement error of exposure
◍ Instruments: lab, equipment◍ Variation
○ Within and between subject variability○ Low exposure > lab level below limits of detection
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Collinearity
Distribution of asthma-related hospital emergencies and air pollution levels in Madrid during 1995–1998.
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Lagging time windows
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Q & A ?