Mercury and PCBs were detected in every fish sample from all 500 lakes and reservoirs tested.
The data showed mercury concentrations in game fish exceeding EPA’s recommended consumption levels at 49 percent of all lakes and reservoirs nationwide, and polychlorinated biphenyls, PCBs, in game fish at levels of potential concern at 17 percent of lakes and reservoirs.
The findings are based on a comprehensive four-year national study using more data on levels of contamination in fish tissue than any previous study.
Bass caught in a Wisconsin lake (Photo credit unknown)
For four years, EPA staffers worked with 47 states, three tribes, and two other federal agencies to collect fish from 500 lakes and reservoirs selected randomly from the estimated 147,000 target population of lakes and reservoirs in the 48 states.
The study excluded the Great Lakes and Great Salt Lake. Delaware is the only state in the Lower 48 where no fish were tested.
For the first time, based on these results, EPA is able to estimate the percentage of lakes and reservoirs nationwide that have fish containing potentially harmful levels of chemicals such as mercury, PCBs, arsenic, dioxins and furans, DDT, and chlordane.
Peter Silva, assistant administrator for EPA’s Office of Water, said the agency is taking action to lower toxic concentrations in fish.
"EPA is aggressively tackling the issues the report highlights," said Silva. "Before the results were even finalized, the agency initiated efforts to further reduce toxic mercury pollution and strengthen enforcement of the Clean Water Act – all part of a renewed effort to protect the nation’s health and environment," Silva said.
Burning fossil fuels, primarily coal, accounts for nearly half of mercury air emissions caused by human activity in the United States, and those emissions are a significant contributor to mercury in water bodies.
From 1990 through 2005, emissions of mercury into the air decreased by 58 percent. Yet, fish in 48.8 percent of the sampled lakes had mercury tissue concentrations that exceeded the 300 ppb human health screening values for mercury - a total of 36,422 lakes.
Silva said the EPA is committed to developing a new rule to substantially reduce mercury emissions from power plants, and the Obama Administration is supporting a new international agreement that will reduce mercury emissions worldwide.
The EPA emphasizes that women of child-bearing age and children should follow fish consumption advisories for mercury issued by federal agencies and state governments.
Because these findings apply to fish caught in lakes and reservoirs, it is particularly important for recreational and subsistence fishers to follow their state and local fish advisories, the EPA warns.
Silva says this study is a "strong message" to state and local governments to redouble their efforts in looking for opportunities to reduce mercury discharges, as well as developing fish advisories, especially to reach those in sensitive and vulnerable populations.
The National Study of Chemical Residues in Lake Fish Tissue is based on the work of teams of biologists who used consistent methods nationwide to collect composite samples of a predator fish species, such as bass or trout, and a bottom-dwelling species, such as catfish or carp, from each lake or reservoir.
Whole fish and fillets were analyzed for 268 persistent, bioaccumulative, and toxic chemicals, including mercury, arsenic, dioxins and furans, the full complement of polychlorinated biphenyl congeners, and a large number of pesticides and semivolatile organic compounds.
Dioxins and furans were detected in 81 percent of the predator fish tissue and 99 percent of the bottom-dweller fish tissue tested.
Forty-three of the 268 target chemicals were not detected in any samples, including all nine organophosphate pesticides, such as chlorpyriphos and diazinon, one PCB congener (PCB-161), and 16 of the 17 polycyclic aromatic hydrocarbons analyzed as semivolatile organic chemicals. There were also 17 other semivolatile organic chemicals that were not detected.
EPA is 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.
Copyright Environment News Service (ENS) 2009. All rights reserved.