A former 3M chemical has been found in fish taken from more metro area lakes, including Cedar, Calhoun and Lake of the Isles in Minneapolis.
The compound, known as PFOS, was measured at levels of concern in 13 of 22 lakes, mostly in bluegills, black crappies and largemouth bass.
The Minnesota Pollution Control Agency (MPCA) released the data Monday from fish tested in 2008, the agency’s third year of checking fish.
Pat McCann, research scientist for the Minnesota Department of Health, said that the data are being reviewed and that the department may issue advice about eating fish less often from some of the lakes.
“The concern that we have about contaminants in fish in general is people’s long-term exposure,” McCann said. In some cases health officials advise that people eat no more than one meal per week, or one meal per month, of certain species. McCann said some of the lakes already have such advisories because of mercury found in fish.
The study also detected PFOS in Fish Lake and Wild Rice Lake near Duluth, and in the Mississippi River near 3M’s Cottage Grove plant. The company manufactured PFOS and similar chemicals for decades until 2002. The compounds were used in hundreds of products including stain-resistant fabric coatings and firefighting foam.
The chemical continues to show up in unexpected places, some of them far from where 3M manufactured or disposed of the compound, said Paul Hoff, MPCA supervisor of environmental reporting and special studies. “It’s really kind of unpredictable,” Hoff said.
The chemical was used in so many products that it seems to be generally present in much of the environment, said Hoff. PFOS does not break down.
A handful of lakes with the highest concentrations may have had extra doses of the chemical at some point in history, he said, such as chemicals that washed off streets and were taken into lakes through stormwater pipes. The two northern lakes are near the Duluth airport, said Hoff, where foam with the chemical may have been used in firefighting drills.
The testing of metro lakes began with a surprise finding of PFOS in bluegills in Lake Calhoun. Researchers began checking fish in other areas to see whether Calhoun was unusual or typical of other lakes. During the past three years, MPCA has tested about 1,450 fish in 55 lakes, and in the Mississippi and St. Croix rivers.
Hoff said the agency will analyze that data further. Besides trying to find hot spots for the chemical and possible sources of how it got into lakes, scientists are also trying to learn why it seems to accumulate in some fish species more than others.
“We’re always cautious about drawing conclusions,” said Hoff. “We have a lot more questions than answers.”
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