Chemical levels in male walleye worry scientists

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Capital News Service
LANSING — Male walleye in Saginaw Bay contain three times more flame retardant chemicals than females, a new study shows, and animal tests suggest that the chemicals could damage people’s liver, thyroid and brain.
The reason: Male walleye hang out in the wrong places.
“Males use the Saginaw River and its tributaries to feed in and for habitat, while the females mostly stay out in the bay,” said Charles Madenjian, a fisheries biologist with the U.S. Geological Survey based in Ann Arbor, and the study’s lead author.
The chemicals, polybrominated diphenyl ether (PBDEs), have been used in plastics, foams and fabrics as flame-retardants since the 1970s, according to the federal Environmental Protection Agency (EPA).
The river empties into the bay near Essexville. The river has much higher levels of PBDEs than the bay, Madenjian said. Once in the river, the chemicals are ingested by small fish that the walleye eat. Gobies and other small fish from the river had 10 times more PBDEs than those dwelling in the bay.
But industries don’t discharge PBDEs into the Saginaw River, which means the chemicals are so-called “non-point source pollutants” that drain from landfills and other waste sites. And it appears they stick in the river sediment.
“The Saginaw River is a large drainage basin,” said Richard Rediske, a professor at the Annis Water Resources Institute at Grand Valley State University and co-author of the study. “As these plastics get old and breakdown, the dust gets airborne and the river collects the pollutants.”
Since the area is heavily farmed, erosion worsens the river’s contamination, Rediske said.
PBDEs are considered an emerging contaminant — chemicals that could hurt people or the environment but haven’t been exhaustively studied. They are increasing in regional waters and fish. They don’t appear to damage fish health, but the risks to human aren’t fully understood, Rediske said.
“They’re like PCBs (polychlorinated biphenyls) where there are over 200 different forms of the chemicals,” Rediske said. “We’re just starting to get a handle on impacts, and while there’s no human health standard, we’re starting to see that this could be a significant pollutant.”
Most people are exposed to low levels of PBDEs, usually by breathing in or eating them, according to the federal Agency for Toxic Substances and Disease Registry in Atlanta. In addition to fish, scientists have found the chemicals in milk, cheese and beef because cows can eat contaminated grass.
Great Lakes fish advisories don’t include PBDEs, but state agencies consider them an emerging contaminant. The Michigan Department of Community Health tests fish for PBDEs but doesn’t give consumption recommendations for them.
The Saginaw Bay historically has been a hotspot for walleye. After population dips about a decade ago, the Department of Natural Resources started stocking them in the bay. The recovery has been credited largely to a decreasing number of alewives that compete with young walleye for food.
Madenjian said researchers don’t know why male walleye spend so much time in the Saginaw River.
And it’s not the first time male walleye have shown higher chemical levels than females.
A 2009 study showed Saginaw Bay male walleye with 2.5 times higher concentrations of PCBs than females. Those findings were even more ominous because PCB levels were 15 times higher than the PBDE levels reported in the new study.
Researchers also attributed that result to the fact that males spent more time in the Saginaw River than females did.
But industries used to spew PCBs directly into the river, which makes the recent study all the more interesting, Rediske said.
“There is no industrial drainage of PBDEs — it’s all atmospheric deposition,” Rediske said. “The Saginaw River really is a hotspot for its ability to collect sediments and pollutants from the outside environment.”
Brian Bienkowski writes for Great Lakes Echo.
© 2012, Capital News Service, Michigan State University School of Journalism. Nonmembers cannot reproduce CNS articles without written permission.

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