The MPCA says Brainerd's effluent sample contained 1.5 parts per billion of PFOS -- that's several times higher than the safe limit for human exposure to the chemical over a lifetime.
But agency supervisor Paul Hoff says it's unlikely that Brainerd residents are ever directly exposed to treatment plant water.
"There's not any kind of immediate health threat from this finding, because nobody's drinking the discharged water -- that's what the sample was from -- or no one otherwise is directly exposed. But the concern is about the long-term exposure and bioaccumulation of PFOS in fish," says Hoff.
PFOS is from a family of perfluorinated chemicals that have contaminated drinking water supplies in some east metro communities. The compound has also been found in the tissue of bluegills in Lake Calhoun in Minneapolis.
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"There's not any kind of immediate health threat from this finding, because nobody's drinking the discharged water."
The MPCA doesn't know yet if fish in the Mississippi River near Brainerd contain PFOS or other perfluorinated chemicals. Hoff says agency staff will take river and fish samples in the area starting next week. They will also begin searching for the source of the contamination.
3M was the sole manufacturer of PFOS until 2002, when it stopped making the chemical after finding it widely dispersed in the environment. Other companies still make PFOS.
Contamination in the east metro has been traced to former 3M dump sites and 3M's production plant in Cottage Grove. But Hoff says Brainerd doesn't have any direct ties to 3M operations.
"There's no known disposal site from 3M in that area, or manufacturing operations that would have been related to PFOS, so we really do think that it's some other kind of contribution," says Hoff.
Like consumer, commercial or industrial products. PFOS has been used in products to protect fabrics and carpets. It can be found in shampoos, insecticides and paper coatings.
Brainerd does have a paper mill. But officials say the plant's wastewater does not funnel into the city's treatment plant.
University of Minnesota researcher Matt Simcik, who has been studying PFOS in Minneapolis's Lake Calhoun, says it may be impossible to pinpoint the source of the chemicals in Brainerd because they have been used so widely in society. But he says it's still important to search.
"It's incumbent on scientists and regulatory agencies to find these things, find their sources, to determine if they need to be removed from the waste stream and then how to do it. So that they can focus their efforts on removing these things," says Simcik.
The PFOS discovery is a setback for the city of Brainerd. Officials say they need to get approval to expand their wastewater treatment facility before the end of August in order to qualify for a low interest loan.
"It has a potentially a very large economic impact to us by not issuing the permit," says Brainerd City Administrator Daniel Vogt. "However, the environment as we all know, is very, very important, and we're all concerned about that as well."
The Minnesota Pollution Control Agency has tested other wastewater treatment facilities around the state for PFOS and a related chemical called PFOA. So far the agency has found low levels of the compounds in most of the facilities it has tested.
The MPCA is also sampling landfills, and plans to test air emissions and rainfall.