Conceptual Environmental Justice Model for Evaluating Chemical Pathways of Exposure in Low-Income, Minority, Native American, and Other Unique Exposure Populations

摘要

Risk assessment determines pathways, and exposures that lead to poor health. For exposures that fall disproportionately on urban low-income communities, minorities, and Native Americans, these pathways are often more common than in the general population. Although risk assessors often evaluate these pathways on an ad hoc basis, a more formal way of addressing these nonstandard pathways is needed to adequately inform public health policy. A conceptual model is presented for evaluating nonstandard, unique, or excessive exposures, particularly for environmental justice communities that have an exposure matrix of inhalation, dermal, ingestion, and injection. Risk assessment can be improved by including nonstandard and unique exposure pathways as described in this conceptual model. Environmental hazards, exposures, and risks are not uniformly distributed across populations, and multiple biological and social factors, including age, poverty, and minority status, intersect to create unique exposures that place some individuals at disproportionately high risk of environmental disease. The interplay of poverty, race/ethnicity, life stages, and health (including pregnancy status) is pervasive, complex, and well documented. 1 – 11 However, it is easier to find data on disparities in health outcomes 12 than on the environmental exposure disparities associated with health disparities. Many circumstances expose individuals to hazardous substances or conditions at levels above those accounted for in standard risk assessment paradigms. 13 These high-end exposures (above 95th or 99th percentile) to common agents or unique pathways are usually not encountered in the general population. Some groups have nonstandard exposures because of where and how they live. For some groups, uniqueness lies in the multiplicity of exposure pathways, mixed exposures, or the interplay of cultural–psychosocial and economic factors with toxicants. 14 The importance of exposure to multiple stressors has been recognized for 30 years but remains difficult to study, although study of the interplay of nonchemical stressors and chemical toxicology is developing rapidly. 15 Conventional methods of risk assessment often exclude outliers or log-transform them into submission; these methods must be supplemented with identification of unique pathways. We propose a conceptual framework for identifying important but unique pathways that risk assessors, public health personnel, and the public can use to adequately incorporate the exposures of minority, low-income, and tribal population groups in risk and health assessments, and to examine how these exposures contribute to health disparities. Although measuring chemicals in human tissues is the gold standard for assessing exposure, 16 examining risk factors, nonstandard vulnerabilities, unique pathways, and behaviors that lead to excessive exposures is also critical. Exposure assessment is becoming increasingly complex, from consideration of single exposure pathways with single contaminants, to complex evaluations of cumulative chemical exposures occurring in different environmental settings. 17 , 18 We examined exposure sources that result in disproportionate environmental burdens on low-income populations, minorities, children, Native Americans, and Native Alaskans, and combinations thereof. References were identified through Medline using the keywords environmental justice, vulnerable populations, and exposure pathways, as well as through table of contents searches of environmental exposure, risk, and public health journals, and US Environmental Protection Agency (EPA) documents. 19 We also searched for exposure pathways and specific environmental justice communities (those exposed disproportionately), such as Native Americans, low-income populations, and minorities. After identifying specific exposure pathways leading to high exposure, we searched for key words such as fish and wildlife consumption, cosmetics, and Asian medicine. Our synthesis was based on literature review, study of environmental health and exposure for 35 years, and constructing an exposure route and pathway model to synthesize possible pathways for unique exposures.