Healthcare Management
Helpm31990
51589_PPTx_CH13.pptxChapter 13
Epidemiologic Aspects of Work and the Environment
Learning Objectives
Define the term environmental epidemiology
Give examples of environmental agents that are associated with human health effects
Provide examples of study designs used in environmental epidemiology
State methodologic difficulties with research on environmental health effects
Environmental Epidemiology
Study of disease and health conditions (occurring in the population) that are linked to environmental factors
Environmental exposures—outside the control of the exposed individual
Two Examples of Environmental Catastrophes
Deepwater Horizon oil spill, Gulf of Mexico, April 20 to July 15, 2010
Fukushima nuclear reactor meltdown following earthquake in Japan, March 11, 2011
Human Exposures to Environmental Hazards
Chemical agents
Electromagnetic radiation
Ionizing radiation
Heavy metals
Air pollution
Temperature increases from global warming and climate change
Health Effects Attributed to Environmental Exposures
Cancer
Infertility
Reproductive impacts
Infectious diseases such as malaria
Occupation-specific adverse outcomes
Study Designs Used
Descriptive study designs
Helpful for setting priorities
Hypothesis formulation
Analytic study designs
Effects of low-level exposures
Exposure-effect relationships
Retrospective cohort designs
Hazardous Agents in the Work Environment
Ionizing radiation
Infectious agents
Toxic substances
Drugs
Carcinogenic agents
Health Effects Associated with Work Environment
Health risks for pregnant workers and the unborn fetus
Various lung diseases
Dermatologic problems
Bladder cancer among dye workers
Leukemia among workers exposed to benzene
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Study Designs Used in Environmental Epidemiology
Descriptive studies provide information for setting priorities, identifying hazards, and formulating hypotheses for new occupational risks.
Etiologic studies can be used to show exposure-effect relationships.
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Retrospective Cohort Studies
Various end points are used to study the effects of occupational exposures.
Morbidity: self-reports of symptoms and results of clinical examinations
Mortality: comparison of mortality rates of exposed workers with nonexposed workers in the same industry
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Collection of Exposure Data
Employment records often are used and may include:
Personal identifiers to permit record linkage
Demographic characteristics
Work history
Information about potential confounding variables, e.g., medical history, smoking habits
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The Healthy Worker Effect
Observation that employed populations tend to have a lower mortality experience than the general population.
The healthy worker effect may reduce the measure of effect for an exposure that increases morbidity or mortality.
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Ecologic Study Designs
One use is the study of the health effects of air pollution.
Researchers measure the association between average exposure to air pollution within census tracts and the average mortality in those census tracts.
Unable to controI for individual factors, e.g., smoking habits
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Case-Control Studies
Compared with cross-sectional study designs, case-control studies can provide more complete exposure data.
However, precise quantitation of exposure and unobserved confounding may be difficult to achieve.
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Toxicologic Concepts Related to Environmental Epidemiology
Dose-response
Threshold
Latency
Synergism
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Dose-Response Curve
Graph that is used to assess the effect of exposure to a chemical or toxic substance upon an organism.
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Threshold
The lowest dose at which a particular response may occur
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Latency
The time period between initial exposure and a measurable response
Latency can range from seconds (acute toxic agents) to years (mesothelioma).
The long latency of health events in environmental research makes the detection of hazards difficult.
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Synergism
A situation in which the combined effect of several exposures is greater than the sum of the individual effects.
Example: Study conducted among asbestos insulation workers demonstrated a synergistic relationship between asbestos and smoking in causing lung cancer.
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Types of Agents
Chemical agents
Metallic compounds
Electric and magnetic fields
Ionizing radiation
Allergens and molds
Dusts
Physical and mechanical energy
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Chemical Agents
Many types used at home and at work
Household cleaning agents
Automotive chemicals
Paints
Pesticides
Bisphenol A (BPA) in plastics
Chemical Agents (cont’d)
Potential effects on human health through acute toxicity, direct skin irritation, contact dermatitis, or long-term effects such as cancer
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Pesticides: Used to Control Pests
Insecticides
Herbicides
Rodenticides
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Four Classes of Insecticides
Organophosphates
Organocarbamates
Pyrethroids
Organochlorides (organochlorines)
Organochloride Insecticides
DDT
Toxic to wildlife and persistent in the environment
Lindane
Chlordane
Chemical Agents (cont’d)
Asbestos
Strictly speaking, a mineral fiber
Was used commonly for ship building, construction, insulation, and automobiles
Associated with asbestosis, mesothelioma, and lung cancer
Metallic Compounds
Arsenic
Mercury
Lead
Metallic Compounds (cont’d)
Arsenic
A crystalline metalloid
Exists as inorganic compounds in the environment
Many uses
Used as a preservative for residential lumber outlawed
Potential carcinogen, e.g., bladder cancer
Metallic Compounds (cont’d)
Mercury
Used for the treatment of syphilis, as an agricultural fungicide, and in dental amalgams
Responsible for Minamata disease, which occurred in the mid-1950s in Minamata Bay, Japan
A neurological condition linked to the consumption of fish contaminated with mercury
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Metallic Compounds (cont’d)
Lead
Once widely used in paint and gasoline
Associated with serious central nervous system effects even at low levels
Has adverse effects on intelligence, behavior, and development
Between 1988 and 2002, percentage of children with elevated blood lead levels declined steeply
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Electric and Magnetic Fields
Sources include power lines, microwave ovens, stoves, clocks, cellular phones.
Los Angeles and Swedish studies found an association between residential proximity to power lines and childhood cancer risk.
U.S. and Norwegian studies found an increased risk for male breast cancer among male electrical workers.
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Ionizing Radiation
Consists of either particle energy (e.g., highly energetic protons, neutrons, and α and β particles) or electromagnetic energy (e.g., γ-rays and X-rays)
Sources of ionizing radiation can be natural or synthetic.
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Ionizing Radiation (cont’d)
Natural sources--examples are radon and cosmic rays.
Radon is one of the largest sources of human exposure to ionizing radiation and may be the cause of about 21,000 deaths from lung cancers in the U.S.
Synthetic sources--examples are medical x-rays and nuclear generators.
Allergens and Molds
Allergens--substances that provoke an allergic reaction in susceptible individuals
Allergic reactions range from dermatitis, asthma, and itchy eyes to anaphylactic shock.
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Physical and Mechanical Energy
Include agents associated with unintentional injuries
Unintentional injuries are a leading cause of death within the age group 1-44 years in the U.S.
Also include such factors as noise, vibration, and extremes of temperature
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Global Warming
Possible association with extreme heat waves
Climate changes in the eastern U.S.
Deaths associated with heat waves
Monitoring and Surveillance of Occupational Hazards
Hazard surveillance--characterization of known chemical, physical, and biologic agents in the workplace
Sentinel health event--a case of unnecessary disease, unnecessary disability, or untimely death whose occurrence is a warning signal that the quality of preventive or medical care may need to be improved
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Environmental Hazards Found in the Work Setting
Biologic hazards--Hospital employees, sewage workers, and agricultural workers may be exposed to hazardous biologic agents. For example, HIV may infect hospital workers through accidental needle sticks.
Mineral and organic dusts--Examples include coal dust (mining and black lung disease) and rubber dust (COPD).
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Environmental Hazards Found in the Work Setting (cont’d)
Vapors and fumes are likely to become increasing hazards due to the growing use of chemical substances.
Vapors--Include organic solvents such as benzene, which may cause cancer and damage internal organs (particularly the liver)
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Mineral and Organic Dusts
Silicosis
Pulmonary emphysema
Chronic obstructive disease
Coal workers’ pneumoconiosis
Industrial Chemicals
Exposure in occupational settings is up to 100 times higher than in the ambient environment.
Vinyl chloride—angiosarcoma of the liver
Pesticides
Noteworthy Community Environmental Health Hazards
Hazardous waste sites
Air pollution
Nuclear facilities
Drinking water
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Sick Building Syndrome
Dryness of the skin and mucous membranes
Mental fatigue
Headaches
Symptoms diminish when affected person leaves the building.
Hazardous Waste Sites
Notorious sites in the U.S. include: Love Canal, NY; Valley of the Drums, KY; Times Beach, MO; Stringfellow acid pits, CA; Casmalia Waste Disposal Facility, CA.
Of great concern is the contamination of water supplies by toxic wastes.
Some possible adverse effects of hazardous waste exposure include birth defects, neurologic disease, and cancer.
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Air Pollution
Constituents of air pollution include sulfur oxides, particles, ozone, and lead and other heavy metals.
Lethal air pollution episodes have occurred worldwide.
Studies conducted in New York City, St. Louis, and Tennessee have shown a correlation between increases in daily mortality and increased air pollution.
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Environmental Tobacco Smoke (ETS)
Nonsmokers who work in a smoking environment have reduced pulmonary function compared to nonsmokers in a smoke-free work environment.
ETS causes 3,000 lung cancer deaths annually among nonsmokers.
ETS is associated with children’s bronchitis, pneumonia, and asthma.
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Nuclear Facilities
Include weapons production plants, test sites, and nuclear power plants
Studies of living in close proximity to nuclear installations have shown conflicting results regarding cancer rates.
Following the Chernobyl nuclear power plant accident, thyroid cancer rates increased near the reactor.
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Drinking Water
Chemical plants and nuclear facilities may contaminate ground water.
Chlorination of water supply has helped to decrease the incidence of gastroenteric diseases.
Lead and asbestos particles may be present in water and have potential for toxicity.
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