The Metropolitan Council is considering legal action against 3M Co. after state regulators said the agency may have to spend millions of dollars on wastewater treatment plants to clean up a toxic pollutant connected to the corporation's manufacturing sites.

The development brings yet another player into the decades-long battle over perfluorochemical (PFC) contamination in the Mississippi River and groundwater in the east metro area, which already has cost 3M millions of dollars in cleanup and remediation.

PFCs are industrial compounds widely used in the manufacture of household products, but which are viewed as an emerging environmental health concern. In high concentrations the compounds are toxic, especially the one at issue in the Met Council's plants, known as perfluorooctane sulfanate or PFOS.

3M stopped using the compounds in 2002, but last year the Minnesota attorney general filed suit against the company after 3M and the state were unable to reach agreement on future cleanup costs and water treatment related to many years of contamination in the east metro area.

Now, the council is considering joining in that lawsuit, as the city of Lake Elmo did after it was filed.

Council members have become alarmed that the agency might be saddled with enormous costs for treated water that goes back into the Mississippi River. The council oversees seven large Twin Cities wastewater treatment plants, including the Metro plant near downtown St. Paul and the Eagles Point plant near Cottage Grove.

The problem is that PFOS levels in the river already exceed regulatory standards. Adding more would violate the federal Clean Water Act, which has forced the hand of state regulators, said Katrina Kessler, a PCA supervisor.

"We can't have anything above the standard coming in," she said.

At a meeting this week, environmental staff told Met Council members that achieving the legal standard would cost tens of millions of dollars, and might not be possible. Now, the two treatment plants emit PFOS at a concentration of about 200 nanograms per liter. The PCA said in the future it might require that level to come down to 10 nanograms per liter. Even the most sophisticated filtration systems can't achieve that, Met Council officials said.

A 3M spokesman said the company would be happy to discuss the issue with the council.

The PFOS at the water treatment plants doesn't come from the 3M sites, according to the council, but from industrial customers that still use the compounds. The council is reviewing those customers to see if they can reduce their emissions into the water treatment system.

A decision on legal steps is on hold for the time being. Council officials said they hope sediment cleanup already underway in the river will solve the PFOS problem.

Josephine Marcotty • 612-673-7394