ENVIRONMENTAL DETERMINANTS OF HEALTH

An environmental determinant of health is, in general, any external agent (biological, chemical, physical, social, or cultural) that can be causally linked to a change in health status. However, since virtually everything that is not genetically determined could be considered "environmental," this general definition is too all-encompassing to be useful. Rather, environmental epidemiologists have narrowed the term to include only those environmental influences that are involuntary. For example, breathing secondhand tobacco smoke would be an environmental hazard, whereas active tobacco smoking would be considered a behavioral determinant.

In the developed world, environmental epidemiologists are concerned about such things as gene-environment interactions, environment-environment interactions, particulate air pollution, nitrogen dioxide, ground-level ozone, environmental tobacco smoke, radiation, lead, video display terminals, cellular telephones, and persistent organic pollutants (POPs) that act as endocrine disruptors. Exposures to these types of environmental vectors are known as downstream, or proximate, determinants of health (that is, the exposures are closely related in time and space to the ill effects they produce), and they impact both health and well-being.

In the developing world, the primary environmental determinants of health are biological agents in the air, water, and soil that account for most deaths, and for most deaths in the world. Four million children die annually from diarrheal diseases acquired from contaminated food or water. Over one million people die from malaria each year. Hundreds of millions of people suffer from debilitating intestinal parasitic infestations. Hundreds of millions of people suffer from respiratory diseases caused by biological and chemical agents in the air, both indoors and outdoors. According to the World Health Organization (WHO), over one billion people are unable to meet their basic needs (i.e., adequate food, clean water, and shelter) because they lack the necessary income or land. These are environmental hazards that take a far greater toll on human life and suffering in absolute terms compared to those environmental determinants of concern in the developed world.

To understand approaches needed to address environmental health concerns, a distinction is made between infectious and chronic causes of disease. A distinction also is made between short-term, acute exposures resulting in epidemic outbreaks of illness, and long-term, low-dose exposures resulting in chronic diseases. Such classifications are necessary to ensure appropriate methods for researching and understanding the extent of health problems in the world. The workplace often serves as a laboratory for understanding the relationship between environmental exposures and health. It serves as a laboratory because, in their occupational environment, workers tend to be exposed to measurable amounts of pollution. This fact allows occupational health researchers and epidemiologists to link adverse health outcomes to these environmental factors. If no link between a workplace pollutant and worker ill-health can be demonstrated, then that pollutant is unlikely to have measurable consequences for human health beyond the work environment owing to comparative lack of frequency and concentration of exposure experienced by those not working in that specific environment. One notable exception, however, is that class of people who are more susceptible to ill-effects even from low levels of exposure.

An emerging concern with great potential impact on public health relates to upstream, or distant, determinants of health (the exposures are far apart in time or space from the witnessed ill-effects) including as policies that drive current levels of population growth, consumption and waste issues, and the uses of technology. For example, the environmental, transboundary transport of contaminants through the food chain has resulted in global chemical contamination. Other transboundary issues include acid precipitation, ozone, greenhouse gasses, and hazardous wastes. Global ecological integrity (i.e., the ability of life-support systems to sustain themselves in the presence of polluting forces) and global change (including concerns about climate change from global warming, ozone depletion, and the loss of biodiversity) have given people reason to adopt the WHO maxim: "Think globally, act locally." Reducing wastes and consumption at the local level can have positive effects on the entire earth's ecosystems.

Colin L. Soskolne

Lee E. Sieswerda

(see also: Acid Rain; Ambient Air Quality [Air Pollution]; Ambient Water Quality; Behavioral Determinants; Biodiversity; Chronic Illness; Climate Change and Human Health; Environmental Justice; Environmental Movement; Environmental Protection Agency; Environmental Tobacco Smoke; Global Burden of Disease; Population Growth )

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