New year, old pollutants for popular Great Lakes sport fish
Still on their slow decline, long-banned pollutants still “dominate” chemical loads for predator fish such as walleye, trout
January 11, 2016
By Brian Bienkowski
Environmental Health News
Toxic banned chemicals like DDT and PCBs are declining in the Great Lakes food chain, but the long-lived compounds still dominate the chemical load in top predators such as walleye and lake trout, based on a new review.
“We realized 35 years ago that these might build up and be harmful," said Thomas Holsen, an engineering professor at Clarkston University who studies Great Lakes chemicals. "The lesson is we have to be careful about what we use going forward … the impact of using chemicals we probably shouldn’t use can last a long time.”
Walleye are one of the most popular sport fish in the Great Lakes. Here young and old target them on Lake Erie. (Credit: the rube/flickr)
The findings are further evidence of the long shadow cast by pollution from decades ago. It also suggests that mandatory and voluntary elimination of some newer contaminants, such as flame-retardants, seems to be working: they aren’t building up in fish as much as legacy pollutants have.
Looking at information on lake trout and walleye from all five Great Lakes from 2008-2012, U.S. and Canadian researchers reported last month that polychlorinated biphenyls, or PCBs, were by far the most abundant contaminant in every lake.
The next two most common contaminants across the lakes were organochlorine pesticides, such as DDT, and mercury.
PCBs and DDT were phased out in the 1970s after they began building up in the environment, particularly in the Great Lakes. Because they are slow to break down, they persist in the lakes’ sediments and accumulate in fish and other wildlife.
But after initial dramatic declines, the decreases in PCB and DDT contamination leveled off. They are now getting into the lakes mostly through what’s released in sediment and circulating through the air and food chain.
The researchers also looked at trends for contaminants of “emerging concern”—stain- and water-proofing compounds, different types of flame retardant chemicals, and siloxanes, which are used in cosmetics and dry cleaning liquids. None came close to the ubiquity of the older, banned compounds.
Manufacturers realized relatively early that certain flame retardants, called PBDEs, were building up in the lakes' food chain. Voluntary phase-outs followed. And they've worked, said Holsen, who was not involved in the current study.
“We’ve seen a turnaround with those [flame retardants] starting to decline across the basin. It initially didn’t even take regulatory action but manufacturers realizing that this may be a problem,” Holsen said.
PCBs have been linked to impaired reproduction in fish, although it’s unclear what impact the chemicals might currently have in populations.
Elizabeth Murphy, senior author of the current study and environmental scientist with the U.S. Environmental Protection Agency, said the agency is trying to determine if any predator fish in the basin are experiencing reproductive problems or population declines from the contaminants. But such projections are difficult, since Great Lakes fish are exposed to a robust mix of chemicals that scientists are still unraveling, she said.
Fish consumption warnings remain throughout the basin for PCBs, which have been linked to an array of health effects, including cancer and reduced IQs in people.
Deborah Swackhamer, a professor emeritus at the University of Minnesota’s Water Resource Center, cautioned that concentrations don’t tell the whole story on how toxic it might be to eat walleye or lake trout.
While PCBs are known to be harmful to humans, the chemicals found in smaller concentrations, such as stain- and water-proofing compounds called perfluorinated chemicals, have been linked to certain cancers, hormone disruption, brain and liver problems and lower birth weights.
Daryl McGoldrick, lead author of the new study and environmental scientist at Environment and Climate Change Canada, expects the legacy chemicals to eventually decline until they’re no longer a threat to people eating fish. But it will take a long time.
Murphy said given current declines and cleanup efforts, they project that PCBs will no longer be a concern for those eating Great Lakes lake trout around 2035.
But Swackhamer said other models project it out much longer—another 50 or maybe 100 years.
Helping the cause is the federally funded Great Lakes’ Restoration Initiative, which Congress plans to maintain at $300 million this year.
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