Careful with the Fish

New research shows a continuing decline in PCB levels in key Lake Michigan sport fish, more than 30 years after regulations on manufacture, use and disposal were put into place.

Wisconsin Department of Natural Resources researchers Paul Rasmussen, Candy Schrank and Meghan Williams, in a paper published in the June 16 online edition of the Journal of Great Lakes Research, described a statistical model based on fish samples collected from 1975 to 2010 that quantified how toxic polychlorinated biphenyls have diminished in Chinook and Coho salmon. The researchers found that over time, the rate of decline has moderated to decreases of four percent per year in Chinook and 2.6 percent per year in Coho from the mid-1980s to 2010.

“Although the rate of decline has slowed from the early days of the ban, the continuing improvement is significant,” said Candy Schrank, an environmental toxicologist and fisheries expert with DNR. “PCBs remain the contaminant of greatest concern for the health of people who eat fish from Lake Michigan and these findings will help us evaluate ongoing efforts to reduce the amount of chemical contamination entering the lake and to learn about how PCBs move in the environment.”

PCBs were used to make electrical transformers, carbonless papers, cutting oils and hydraulic fluids. However, because the man-made PCBs are slow to break down in the environment, they remain a problem today.

The current advisory recommends that people should eat no more than one meal per month of Chinook and Coho salmon from Lake Michigan. While the new PCB data are not expected to result in a short-term advisory change, they signify an important, positive trend.