Our nation's environmental laws developed piecemeal without a holistic view of the totality of environmental and other stressors that an individual or community may confront. Statutes adopted in the 1970s such as the Clean Air Act, the Clean Water Act, and the Resource Conservation and Recovery Act addressed air, water, and waste disposal as separate problems. Within each programmatic silo, environmental laws often regulate each pollutant separately.

Although this approach has successfully established emission standards that have reduced the concentration of pollutants to which individuals are exposed, it has an obvious drawback. The burden on human health and ecosystems depends on the totality of environmental and nonenvironmental stressors. Community members may be exposed to multiple pollutants in all environmental media, and the interaction of these pollutants may have a synergistic effect. In addition, factors particular to a community or individual, such as nutrition, health conditions, age and socioeconomics, may constitute vulnerabilities that increase the adverse impact of exposure to pollutants.