PINE ISLAND — A major source of the chemical that has been found contaminating fish in Lake Zumbro is a Pine Island plating plant.
Ironically, DS Manufacturing Inc. used perfluorooctane sulfonates as a way to control pollution because it helped stop chromium from contaminating the air inside or letting it get into the air outside, said Paul Hoff, supervisor of the Environmental Reporting and Special Studies Unit.
Use of the chemical was completely legal and the company quit using it many months ago, he said. The company and the Pine Island Wastewater Treatment Plant, which receives wastewater from the DS, have been cooperating with the MPCA, he said. The plating plant is using another chemical to control chromium, one that doesn’t contain PFOS.
Because the chemical was found in high enough concentrations in the lake, the Minnesota Department of Health tightened its recommendation for people eating fish caught from the lake from unrestricted for the general population to once a week.
The MPCA began looking for PFOS, which can cause cancer and developmental problems, after they were found in a lake on the south side of Minneapolis, Hoff said. It came from 3M, which has stopped making it.
The agency looked at wastewater plants that have manufacturing plants, such as DS Manufacturing, feeding into them, he said. They found the chemical in Pine Island. The plant discharges into a branch of the Zumbro River and from there, into Lake Zumbro.
Because the company quit using the chemical, the amount coming out of the wastewater plant has been dropping, Hoff said. It will take a while for it to completely get out.
It will take even longer for it to leave the lake, he said. One of the reasons it was used in things like firefighting foam is that it doesn’t break down easily. So it will take a while for it to be either washed out of the lake or buried in sediment, he said.
How fast isn’t known. “This is kind of new territory,” he said.
Also, the MPCA has found lower levels of PFOS coming from the Rochester Wastewater Treatment Plant, he said.