Environmental Chemical Mixtures: A Field Approach to Assessing Exposure and Effects

摘要

Assessing the human and ecological health risks associated with exposure to complex chemical mixtures is acknowledged as a significant environmental health challenge. A major limitation to addressing this issue is the scant data on actual environmental chemical mixtures. This presentation describes a field-based approach to identifying chemical mixtures and biological activity associated with stream waters affected by a wide range of contaminant sources. The results will (1) document the mixtures and levels of chemicals found in the environment, (2) help identify potential human and ecological exposures, (3) guide prioritization of toxicological studies of chemical mixtures, and (4) provide insight into potential biological interaction of multiple contaminants. Stream sites were selected from environments that are vulnerable to multiple contaminant sources, including industrial and municipal wastewater discharges, crop and animal agriculture, land-applied manures and biosolids, urban runoff, and other point and nonpoint contaminant sources. Data from previous U.S. Geological Survey (USGS) studies of contaminants of emerging environmental concern provide a basis for site selection. The approach combines comprehensive chemical characterization, which includes sensitive and specific direct analysis for over 700 dissolved organic and inorganic chemicals, identification and quantitation of unknown contaminants (environmental diagnostics), and a battery of bioassays to evaluate biological activity and toxicity. Sample collection and analysis, and data interpretation in this study are inherently complex. Therefore, this pilot study also will test the feasibility of future expansion in terms of sites, environmental media, and exposure and effects pathways. The study is a collaborative effort between the USGS, which leads the site selection, sample collection, and chemical characterization, and the U.S. Environmental Protection Agency, which leads the biological testing.