Fish containing potentially harmful levels of chemicals are widespread throughout the United States. Almost every state in the country has lakes and reservoirs containing fish with potentially harmful concentrations of toxic chemicals, such as mercury and PCBs, in their tissue, according to a U.S. Environmental Protection Agency (EPA) news release.
For the National Study of Chemical Residues in Lake Fish Tissue, the first national assessment of freshwater fish contamination in the United States, concentrations of target chemicals, such as mercury, or chemical groups, such as PCBs, were examined in the tissue of two groupings of fish: predators and bottom-dwellers.
This study uses more data on levels of chemical concentrations in fish tissue than any previous study. During a 4-year sampling period, field teams collected 486 predator composites and 395 bottom-dweller composites from 500 sampling locations out of the estimated total of 147,000 lakes and reservoirs in 48 states, according to the EPA Web site.
The study revealed five commonly detected chemicals, including mercury, PCBs, dioxins and furans, DDT, and chlordane. Dioxins and furans were detected in 81% of the predator samples and 99% of the bottom-dweller samples.
Mercury, PCBs, and dioxins and furans are widely distributed in lakes and reservoirs in the lower 48 states. Burning fossil fuels, primarily coal, accounts for nearly half of mercury air emissions, which are a significant contributor to mercury in water, according to the news release. Mercury and PCBs were detected in every fish sample from all 500 lakes and reservoirs, the release says.
Mercury concentrations exceeded EPA’s recommended tissue-based water quality criterion of 0.3 ppm in 49% of the sampled waterbodies. Further, PCB concentrations exceeded EPA’s recommended criterion in 17% of the sample waterbodies, according to the news release.
In predator fish, 16.8% of sampled waterbodies’ PCB tissue concentrations exceeded the 12-ppb human health standard; in 7.6% of the sampled waterbodies, dioxin and furans concentrations exceeded the 0.15-part-per-trillion human health standard; in 1.7% of the sampled waterbodies, DDT tissue concentrations exceeded the 69-ppb human health standard; and in 0.3% of the sampled population of waterbodies, chlordane concentrations exceeded the 67-ppb human health standard, according to the EPA Web site. However, 43 of the 268 target chemicals were not detected in any of the samples.
The study is designed to inform the public, water quality specialists, natural resource managers, and government officials about the distribution and prevalence of potentially harmful chemicals in freshwater fish, the executive summary of the study report says. For the public, EPA recommends following the advice of EPA and the U.S. Food and Drug Administration on fish consumption as it relates to mercury. For state and local government, EPA recommends further efforts in looking for opportunities to reduce mercury discharges and develop fish advisories to reach those people deemed as the sensitive or vulnerable populations.
EPA is conducting other national aquatic surveys that include fish contaminant assessment, such as the National Rivers and Streams Assessment, which should have results available in 2011, and the National Coastal Assessment, which will begin in 2010. For more information, see www.epa.gov/waterscience/fishstudy.
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