Store-bought freshwater fish contain elevated levels of mercury, arsenic and selenium

November 7, 2007

White bass wild-caught and sold commercially contained significantly higher levels of mercury, arsenic and selenium than fish caught near former industrial areas. The University of Pittsburgh study, abstract number 161184, is being presented at a special session on “Contaminants in Freshwater Fish: Toxicity, Sources and Risk Communication,” on Wednesday, Nov. 7, at the annual meeting of the American Public Health Association in Washington, D.C.

According to study results, mercury levels were 2.2 to 4.8 times higher in fish caught in the Canadian Lake Erie and available commercially than in fish caught near former iron and steel mills on the Allegheny and Monongahela rivers in Pittsburgh. While several of these mills have been closed for many years, the nearby rivers continue to contain high levels of pollution from sewer overflows and active industrial operations.

For the study, researchers used local anglers to catch 45 white bass at two locations in Pittsburgh and bought 10 white bass locally that were caught in the Canadian Lake Erie. They analyzed the fish for levels of mercury, arsenic and selenium. In addition to higher levels of mercury, the store-bought fish had levels that were 1.7 times higher for arsenic and 1.9 times higher for selenium.

“We were surprised by our results since we had hypothesized that levels of contaminants in fish would be higher in specimens caught near once heavily polluted sites,” said Conrad D. Volz, Dr.P.H., M.P.H., principal investigator, department of environmental and occupational health, University of Pittsburgh Graduate School of Public Health. “These results indicate to us that purchasing fish from a local market cannot guarantee food safety. We recommend a more rigorous testing program for commercial freshwater fish with particular attention to fish entering the U.S. from other countries.”

According to Dr. Volz, the results also may indicate that sediments in Lake Erie remain contaminated because of only relatively recent reductions in industrial pollution and active coal-fired power plant air emissions from facilities located around and to the southwest of Lake Erie, as well as wastewater from plants located on the lake. Mercury, arsenic and selenium are markers for coal-burning pollution through air emissions and water pollution and from fly ash piles that are absorbed into surrounding soil. Fly ash is the residue left after coal burning that is often stored at the plant site.

Source: University of Pittsburgh

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