The 3M Co. should pay for environmental harm done by its chemicals, according to state officials.

The Minnesota Pollution Control Agency said this week that it is negotiating with 3M over compensation for damage done by perfluorochemicals that leaked into Washington County groundwater.

The state attorney general’s office, acting as the agency’s lawyer, confirmed it is interviewing city officials in Washington County to gauge the public cost of the chemical leaks.

Agency officials said they hope to have an agreement with 3M by the end of the year.

Usually, Mother Nature doesn’t have a way to strike back at polluters. Animals have no claim in most courts — no one can sue a polluter on behalf of wildlife injured by a chemical or oil spill.

But in a process called Natural Resources Damage Assessment, spelled out in the federal Superfund law, state agencies can ask polluters for repayment.

The MPCA has used the process in the past to make polluters pay. The paybacks have been in the form of cash or sponsorship of environmental projects such as restoring wetlands or building trails.

Officials would not speculate about the potential amount of the 3M settlement, but the agency provided details of settlements in earlier cases:

• In 2006, Conoco Oil Co. paid $68,000 and agreed to extend a multi-use nature trail near Duluth. The company was penalized for allowing oil to leak into groundwater.

• In 2009, after a fire in a petroleum tank in Newport, Marathon Petroleum Co. agreed to retrofit a number of diesel engines to make them cleaner.

• In 2009, Enbridge Energy Co. agreed to pay for a study of crude-oil spills, after a break in one of its oil lines near Pinewood, Minn.

Kathy Sather, director of the agency’s remediation division, said damages in the 3M case will be difficult to assess.

The area affected by the spill is huge — a 15-mile swath of Washington County, affecting the drinking water of 67,000 people. The chemicals are unique, and it’s difficult to tell what — if any — harm has come to people or animals because of them.

PFCs have been found in lower concentrations in fish in lakes and the Mississippi River and in animals and people around the world. 3M has been making PFCs since the 1940s, for use in products including fire extinguishers, Scotchgard stain repellent and nonstick cookware. The company legally dumped PFCs in landfills and dumps, ending in the 1970s.

Megadoses of the chemicals cause thyroid problems and birth defects in mice. That’s why officials were alarmed in 2004 when traces of the chemicals were found in drinking water in Lake Elmo and Oakdale.

But the question of damages is complicated by the lack of evidence that PFCs are harmful to people, especially in the tiny concentrations found in Washington County. A judge presiding over a five-month trial in 2009 threw out claims that PFCs harmed any of the people trying to sue 3M for damages.

3M has spent tens of millions of dollars cleaning PFCs out of drinking water, and the efforts to remove tainted soil and to filter groundwater in Washington County are ongoing.

“The broad issue of PFCs in the environment is being addressed,” said 3M spokesman Bill Nelson.

The yet-to-be-negotiated payments won’t cover all public costs, though.

The state of Minnesota was legally liable for most of the $21 million cost of digging up a landfill in Lake Elmo last year, to line it with sheets of plastic to keep PFCs from leaching into groundwater.

3M wasn’t liable for those costs but contributed $8 million to the cleanup.

Regardless of the settlement, said Sather, the important thing to remember is that the level of PFCs has dropped to safe levels for water-drinkers in the county.

“They all have safe water now,” she said.