to adverse health effects. Rios and colleagues (1993) have reviewed inborn and acquired variations among minority populations in their susceptibilities to the effects of environmental exposures. They reported that susceptibility can be affected by genetic factors (e.g., the sickle cell trait may increase one's susceptibility to the toxic effects of carbon monoxide), dietary factors (e.g., lower calcium intake among African American children may act to increase gastrointestinal absorption of ingested lead), other lifestyle factors (e.g., smoking increases lung cancer susceptibility in asbestos-exposed workers), or other environmental exposures (e.g., concurrent solvent exposure may increase the likelihood of hearing loss due to high levels of noise) that may be associated with variations among minority populations. Additional factors that Rios and colleagues concluded may differentially affect minority populations include compromised health status (e.g., people with diabetes may be less able to detoxify organic solvents), social inequality of access to health care (e.g., poor control of asthma by primary care providers may increase susceptibility to particulate air pollution), and inadequate education and communication skills (e.g., non-English-speaking workers may not be able to read health and safety warnings at work).

Frumkin and Walker (1997) also reviewed some of the mechanisms that act to increase the risk of environmental and occupational diseases among minority workers and communities. In addition to disparities in exposures and susceptibilities to environmental agents in the community and workplace, the investigators pointed out that the racial or ethnic and socioeconomic disparities that exist in access to health care in general may contribute to observed differences in occupational and environmental illnesses, although further research is needed to clarify this.

One tool that can be used to identify increased susceptibility is biomarkers. Biomarkers are measurements of the body's response to external events or substances such as environmental hazards. A biomarker of susceptibility would measure limitations, either inherited or acquired, in a person's ability to mount a protective response to a hazard. The development of biomarkers of susceptibility would allow further analysis of differentials in susceptibility among minority or, possibly, low-income populations. A more complete discussion of biomarkers is provided later in this chapter.

Establishment of the causal relationship between exposure to environmental hazards and adverse health outcomes and measurement of the scope and severity of such outcomes are critical steps in the analysis of environmental justice issues. As noted at the beginning of this chapter, a better understanding of the disease mechanisms and the processes involved is needed. The committee's principal focus, however, is the use of epidemiologic studies in communities of