This study is a national screening-level survey of chemical residues in fish tissue from lakes and reservoirs in the lower 48 United States, excluding the Laurentian Great Lakes and Great Salt Lake. It is unique among national assessments of fish contamination in lakes because the sampling sites were selected according to a statistical (random) design. Study results allow EPA to estimate the percentage of lakes and reservoirs in the United States with chemical concentrations in fish tissue that are above levels of potential concern for humans or for wildlife that eat fish. This study also includes the largest set of chemicals ever studied in fish. Whole fish and fillets were analyzed for 268 persistent, bioaccumulative, and toxic (PBT) chemicals, including mercury, arsenic, dioxins and furans, the full complement of polychlorinated biphenyl (PCB) congeners, and a large number of pesticides and semivolatile organic compounds.
The data showed mercury concentrations in game fish exceeding EPA recommended levels at 49 percent of lakes and reservoirs nationwide, and PCBs in game fish at levels of potential concern at 17 percent of lakes and reservoirs. These findings are based on a comprehensive national study using more data on levels of contamination in fish tissue than any previous study.
EPA is currently conducting other statistically based national aquatic surveys that include assessment of fish contamination, such as the National Rivers and Streams Assessment and the National Coastal Assessment. Sampling for the National Rivers and Streams Assessment is underway, and results from this two-year study are expected to be available in 2011. Collection of fish samples for the National Coastal Assessment will begin in 2010.
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