State pollution officials have solved a four-year-old mystery about the source of fish contamination in Lake Calhoun.
A St. Louis Park company used a chemical formerly made by 3M, and it entered the southwest Minneapolis lake through a storm water system, said Ralph Pribble, spokesman for the Minnesota Pollution Control Agency.
Although the PCA didn’t identify the company, Douglas Corp., which has five manufacturing plants in Minnesota, acknowledged Thursday that air emissions from its St. Louis Park plant may have contributed to the chemical, known as PFOS, being found in the sewer system leading to Lake Calhoun. Company spokesman Blois Olson said the company is cooperating with the investigation.
The contaminant is part of a family of man-made chemicals known as perfluorochemicals (PFCs). Olson said the company, which provides plating services, used the chemical for a “significant” number of years but stopped using it this year at the plant 1 1/2 miles west of the lake. He said the company hasn’t violated any law or permit, noting that the use of PFCs is not regulated under any state or federal law.
A University of Minnesota researcher first detected PFOS in Lake Calhoun’s water in 2004. It was formerly used in Scotchgard and other products. State scientists did additional testing in 2006 and found the chemical both in the water and some fish in 2007.
Early on, researchers couldn’t explain the source of the contamination, because Lake Calhoun is not near any known areas where 3M manufactured or disposed of the chemical.
Minnesota health officials said the lake’s water is no danger to boaters, swimmers, or pets, but they issued a fish consumption advisory in 2007 that remains in effect. It recommends that anglers eat no more than one meal per month of bluegills or crappies from Calhoun, and no more than one meal per week of the same species caught in nearby Lakes Harriet, Brownie, Cedar and Lake of the Isles.
The MPCA also has tested fish in more than four dozen other metro lakes, and several also have similar limits on eating panfish, said Pat McCann, research scientist with the Minnesota Health Department.
Discovering the source of Calhoun’s pollution may make it easier to track how the same chemical has entered other lakes, she said.
Pribble said the agency is “actively taking steps to reduce continuing runoff from the facility into the lake.” However, it may be months before the investigation is complete, he said.
PCA officials will determine whether the contamination came from an illegal connection to the storm sewer or from normal runoff from the company’s property. Company officials said Thursday that the contamination would have come from normal runoff.