The 3M Co. is refusing to pay for providing clean water to some 200 homeowners in the southeastern Twin Cities suburbs who were advised last fall to drink bottled water because their wells are contaminated by toxic chemicals once used at the company’s operations nearby.

3M, which has paid similar costs for those neighborhoods for a decade, sent a letter to the Minnesota Pollution Control Agency (MPCA) blaming others for some of the contamination. That includes the state itself, for long ago mishandling a Washington County landfill where the toxins — PFCs — were dumped before the drinking water problem was known.

3M also said Minnesota officials haven’t supplied sufficient proof that the water contamination came from the other three sites 3M used, as outlined in a 10-year-old legal agreement between the company and the state.

In an e-mail Wednesday, officials from the agency said 3M is reinterpreting the deal they cut in 2007, and that its lawyers have refused to meet to resolve the dispute. They said that for now the costs, $376,000 so far, will fall on Minnesota taxpayers.

The standoff comes at a time when mitigation costs are escalating for the affected communities — Cottage Grove, Oakdale, Woodbury and St. Paul Park. New and far more stringent government health standards designed to protect pregnant women and infants, who are most at risk, have increased the number of homes requiring bottled water or reverse osmosis treatment systems; 3M argues that the more stringent limits are unnecessary.

“We do not believe there is a health-related public health issue in Minnesota,” the company’s letter said.

Minnesota has yet to issue a significantly larger bill to 3M to pay for another 120 homeowners who were advised to drink bottled water in April, plus municipal drinking systems that were affected in the communities. The water is safe to drink, but Cottage Grove has imposed water use restrictions because its supply is reduced, and it’s planning to install an expensive filtration system.

It’s possible that the dispute won’t be resolved until the conclusion of a long-awaited lawsuit Minnesota filed against 3M alleging damage to groundwater and the Mississippi River. That case is expected to go to trial next year.

State Sen. Dan Schoen, DFL-Cottage Grove, issued a blistering statement Wednesday in response to 3M’s letter.

“After contaminating the environment and laudably paying for this contamination, it appears that 3M does not want this ongoing cost on their books anymore,” Schoen said. He asked why citizens should “be stuck with the consequences of a company that decides they no longer want to stand by their word?”

In a statement Wednesday, an attorney for the company responded, “3M will, as always, honor its legal obligations under its agreement with the State. That said, 3M requests evidence that the environmental presence of the PFCs in question emanates from disposal sites for which it has some responsibility. 3M is eager to resolve these concerns and work with others to develop a deeper understanding of these issues.”

The toxins, primarily PFOA and PFOS, were invented by 3M and made for decades at its manufacturing plant in Cottage Grove. They were used in Teflon, firefighting foam, industrial solvents and many other consumer products, becoming one of the most widely used class of chemicals in the world.

But since the early 2000s, research has increasingly linked exposure to PFCs in drinking water to certain cancers, liver and thyroid ailments, and developmental problems in infants.

Since the 2002 discovery that the compounds had contaminated groundwater from the 3M plant and dump sites in Washington County, east metro cities and hundreds of homeowners have had to add filtration and treatment systems to protect their drinking water, at a cost of about $13 million — which 3M paid until this week.

There are dozens of similarly contaminated sites across the country from military and firefighting facilities and other manufacturers.

Last year, after new research heightened concerns about the chemicals’ health risks, the U.S. Environmental Protection Agency advised states and municipalities to set a sharply lower safety threshold for the compounds. Following that, some 200 more east metro homeowners were advised not to drink or cook with their well water.

Then in April, Minnesota set its own standard, which was even lower, in an effort to protect pregnant women and children. The number of affected wells increased again.

Now 3M says “the actions of the state were unwarranted and unnecessary.” The health risk levels adopted by Minnesota and the EPA are “nonenforceable and non-regulatory tools,” the company said. It hired an expert to study the groundwater flow, and said in its letter that some homes were contaminated by flows from the landfill. The company paid $8 million years ago to help clean it up, and now it’s the state’s responsibility, not 3M’s, the letter said.

3M also says the state is ignoring possible contributions from firefighting foam once used to put out a blaze at a nearby plastics factory, plus training exercises by local fire departments and chemicals used at the Marathon refinery.

Until the PCA provides evidence that the costs are clearly tied to contamination from the three sites in its legal agreement with the state, 3M won’t pay, the letter said.