still other cases, affected individuals may be the initial source of knowledge about multiple exposures or confounding physical conditions (e.g., compromised health because of disease or nutritional problems, as is observed in iron deficiency and lead absorption). In all of these cases, these individuals are first-hand observers, with unique and essential knowledge about the activities or places that may lead to exposure.
An organized, methodical system of collecting these experiential data is an essential part of the scientific process (National Research Council, 1991b, 1996, 1997). Frequently, affected individuals bear the burden of proof for establishing the legitimacy of their problems (see for example, Box 3-2). Without the assistance of those with scientific training and financial resources, this can be an impossible task. If early data are ignored pending conclusive confirmation, however, there is a risk of presuming a hazard to be safe on the basis of inadequate data, thereby subjecting exposed people to unnecessary harm.
Public health officials and researchers need to develop ways to help community activists and local medical personnel document health outcomes and health status in a reliable and unbiased manner. Even if the methods are imperfect, they could produce evidence for the justification of more thorough medical surveillance and measurement. Epidemiologic data obtained by laypeople cannot supplant data obtained by epidemiology professionals; they can, however, help identify issues or supplement the data obtained by professionals (National Research Council, 1991b, 1997).
One of the best methods for capitalizing on local knowledge is participatory research. Participatory research has been defined as research that involves the affected community in the planning, implementation, evaluation, and dissemination of results (Banner et al., 1995; Drevdahl, 1995). In this regard, scientists serve as a resource to the community and work with the community in identifying and finding solutions to environmentally related health problems. In addition to allowing researchers to capitalize on local knowledge, the involvement of the affected community ensures that the research addresses the issues that are important to the community and reinforces the social validity of "the goals, procedures, and effects" of the research—that is, participatory research ensures that the community truly benefits from the research being done (Fawcett, 1991, p. 235). Although participatory research can greatly benefit and advance environmental health sciences, it still poses unique challenges.
Cultural differences between a minority community exposed to an environmental health hazard and the majority of Americans may be a barrier to communication and may affect the collection of data and the understanding of the relationship between exposure and disease. For example, the American Indian and Alaskan Native communities hold as sacred free-ranging animals, wild herbs, and other flora and fauna, values that have resulted in the discussion of endangered