Environmental and Occupational Epidemiology

Environmental and occupational epidemiology are subdisciplines of epidemiology and use the same standard epidemiologic research approaches, study designs, and analytical methods in estimating disease occurrence, relative risk, and statistical variability. These two disciplines focus on studying the effects on human health attributable to chemical, particulate, metallic, physical, infectious, and psychosocial agents in the workplace and general environment. Occupational and environmental epidemiology involves a wide variety of methodological techniques that are used to evaluate associations between workplace or community exposures and health outcomes. This entry reviews the study designs used in occupational and environmental research and also examines sources of bias in such studies.

Occupational and environmental epidemiology are closely linked by the nature of the many common exposures of concern. Epidemiologic studies in these fields often consider other factors such as genetics, nutrition, and behavioral patterns, although in the context of their confounding influence on the workplace or environmental-exposure/outcome relationship rather than as primary exposure factors. For example, in a study of radiation exposure and risk of lung cancer, smoking in this context would be considered as a confounder (not a primary risk factor), whereas in a study of health risks due to secondhand smoke, smoking by family, friends, or coworkers would be considered as an environmental or occupational exposure. Several important causal relationships have been identified through occupational and environmental research, such as benzene exposure and acute myeloid leukemia, vinyl chloride and angiosarcoma of the liver, and ultraviolet radiation and melanoma.

Diseases of concern in occupational and environmental epidemiology include virtually the entire spectrum of health events, including cancer and cardiovascular, neurological, respiratory, immunological, and dermal diseases, as well as injuries, reproductive health, and mental health. Infectious disease and nutritional disorders are typically the domain of other epidemiologic subdisciplines, but they are also studied in occupational or environmental epidemiologic research (e.g., the evaluation of health care of food-processing workers, or the evaluation of health impacts of environmental disasters [weather, earthquakes] or sociopolitical conditions [war, political unrest]). The well-known John Snow natural experiment study is a classic example of an environmental epidemiologic study, in which mortality rates of cholera were found to be attributable to different sources of residential water.

The occupational setting offers several advantages for conducting epidemiologic research. Often occupational epidemiologic study results can provide a ‘sentinel’ for the potential health effects for a particular agent because exposures are often higher in the workplace and frequently are better characterized there than in the general environment. Also, because the population at risk (a workforce) can be more accurately enumerated, occupational studies may be less vulnerable to potential biases. However, because these studies examine adult working populations, certain limitations exist. Typically, only adult health issues are assessed, and since working populations generally present with a better health profile than the general public, the likelihood for detecting certain health risks may be lower than if the study were conducted in a general population. Environmental epidemiologic studies often examine involuntary exposures and can be useful in providing guidance for public health policy. Epidemiologic methods applied to occupational and environmental settings, particularly in the area of exposure assessment, will continually evolve to keep pace with rapidly changing and more complex environmental exposures.

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