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Approximately 40 million people live within a 4-mile radius of waste sites that the Agency for Toxic Substances and Disease Registry (ATSDR) has assessed to date. Human populations living in the vicinity of such sites are often subjected to complex chemical exposures that may contribute to the total body burden of oxogenous chemicals. Apart from the contaminants found at waste sites, exposure may also include environmental, occupational, and personal agents. Concurrent exposure to chemicals such as welding fumes, indoor air pollutants, tobacco smoke, alcohol, and prescription and nonprescription drugs makes the health assessment of exposure to waste site chemicals a more complex task. Voluntary exposures such as these frequently entail exposures to relatively high chemical concentrations and can usually be well defined and quantified. Conversely, involuntary exposures from waste sites may be at low concentrations and hence difficult to characterize and quantify. Of the approximately 1450 waste sites evaluated by the ATSDR, 530 (37%) had either completed or potentially completed exposure pathways. Results of public health assessments conducted at 167 sites during 1993 to 1995 show that about 1.5 million people have been exposed to site-specific contaminants. At 10% or more of the sites that had either completed or potentially completed exposure pathways, 56 substances were identified. Of these, 19 are either known or anticipated human carcinogens, and 9 are associated with reproductive or endocrine-disrupting effects. In this paper we present important concerns regarding hazardous waste sites including the impact on human health, ecology, and quality of life. To address such human-health related issues, the ATSDR has established a mixtures program that consists of three components: trend analysis to identify combinations of chemicals of concern, experimental studies to identify data that would be useful in the development and implementation of predictive decision support methodologies, and development of assessment methodologies and guidance to provide health assessors with the tools to incorporate the evaluation of multiple-chemical exposure into site assessments.

BACKGROUND: Abundant historical evidence demonstrates how environmental changes can affect social stability and, in turn, human health. A rapidly growing body of literature, largely from political science and economics, is examining the potential for and consequences associated with social instability related to current climate change. However, comparatively little of this research incorporates the effects on human health or the role of health systems in influencing the magnitude and types of instability that could occur. OBJECTIVE: The objective of this commentary is to articulate a conceptual framework incorporating health outcomes and health systems into theorized and observed linkages between climate change and social instability, illustrating in particular the health effects of natural resource shortages, infectious disease outbreaks, and migration. DISCUSSION: Although increasing evidence exists that climate change, health, and social instability are related, key questions remain about the pathways linking these factors, as well as the magnitude, causality, and directionality of relationships across spatial and temporal scales. Models seeking to explain and predict climate-related social unrest should incorporate the many linkages between climate change, human health, and social instability. Members of the environmental health research community should work closely with those in the political science and economics communities to help deepen understandings of climate-related stressors and shocks that affect instability and worsen health outcomes. [ABSTRACT FROM AUTHOR]

BACKGROUND: Recent research highlights the promise of remotely sensed aerosol optical depth (AOD) as a proxy for ground-level particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5.). Particular interest lies in estimating spatial heterogeneity using AOD, with important application to estimating pollution exposure for public health purposes. Given the correlations reported between AOD and PM2.5., it is tempting to interpret the spatial patterns in AOD as reflecting patterns in PM2.5.. OBJECTIVES: We evaluated the degree to which AOD can help predict long-term average PM2.5. concentrations for use in chronic health studies. METHODS: We calculated correlations of AOD and PM2.5. at various temporal aggregations in the eastern United States in 2004 and used statistical models to assess the relationship between AOD and PM2.5 and the potential for improving predictions of PM2.5. in a subregion, the mid-Atlantic. RESULTS: We found only limited spatial associations of AOD from three satellite retrievals with daily and yearly PM2.5.. The statistical modeling shows that monthly average AOD poorly reflects spatial patterns in PM2.5. because of systematic, spatially correlated discrepancies between AOD and PM2.5. Furthermore, when we included AOD as a predictor of monthly PM2.5. in a statistical prediction model, AOD provided little additional information in a model that already accounts for land use, emission sources, meteorology, and regional variability. CONCLUSIONS: These results suggest caution in using spatial variation in currently available AOD to stand in for spatial variation in ground-level PM2.5. in epidemiologic analyses and indicate that when PM2.5. monitoring is available, careful statistical modeling outperforms the use of AOD. [ABSTRACT FROM AUTHOR]