The Minnesota Pollution Control Agency has decided that two 3M chemicals are hazardous substances, giving it extra legal muscle if necessary to force the company to clean up the pollution spreading underground in the east metro.

The chemicals, which were dumped in three Washington County locations decades ago, have seeped into the groundwater and polluted wells in Lake Elmo and Oakdale. The company has cooperated with the state in its investigation since the pollution was discovered in 2004, but legislators have criticized the MPCA for not being aggressive enough.

The state’s intentions, communicated in letters from MPCA Commissioner Brad Moore to top 3M officials on Tuesday, are to declare that PFOS and PFOA are hazardous substances and that three sites owned by 3M are subject to cleanup under the state Superfund law.

The pollution agency acted after the Minnesota Department of Health determined that the two chemicals, once used to make Teflon, Scotchgard and other products, were more of a health risk than previously thought.

“It has become clear to me that these chemicals are going to be in the groundwater for a long time, probably decades,” Moore said Wednesday. “I want a very solid legal framework to assure that we protect the citizens and the environment.”

The decision does not affect another chemical, PFBA, that has been found in the drinking water supplies of six other east metro communities.

The agency’s action brought a thank-you from state Sen. Katie Sieben, DFL-Cottage Grove, who told a legislative panel Wednesday that the MPCA’s decision largely accomplishes what she had proposed in a bill: to look out for citizens and ensure that the public would not be left paying cleanup costs.

3M officials testified that they disagree with the state’s conclusion. Michael Santoro, director of environmental regulatory affairs, said the company is willing to move forward with cleanups, but under some other agreement with the agency. “We do not believe these substances are hazardous substances, but we are willing to discuss this directly with the Minnesota Pollution Control Agency,” Santoro said.

Determining which laws pertain to the pollution problems is important, because 3M would have greater potential liability under the Superfund law. It allows the state to clean up the pollution if necessary, and recover the costs from 3M, said Tim Scherkenbach, the MPCA’s assistant commissioner.

He said he does not anticipate the need for that, since 3M has cooperated with the agency so far in investigating the extent of the problems. It has also voluntarily financed water filtering and hookup projects for public wells in Oakdale and private wells in Lake Elmo.

Scherkenbach said the agency is acting now because state health officials recently lowered the maximum concentration levels of the two chemicals that are considered to be safe in drinking water, and because of public concern about exposure to the chemicals.

He said that it is very unusual for the agency to declare that chemicals are hazardous, but that he expects it to become more common as scientists learn more about new groups of chemicals in the environment.

The MPCA’s conclusions about PFOA and PFOS affect three former disposal sites: the Oakdale and Woodbury dumps and the company’s Chemolite plant in Cottage Grove. A different state program is involved with the potential cleanup of another 3M dump site, the former Washington County landfill in Lake Elmo.

Maplewood-based 3M manufactured the chemicals for decades until 2002. They were used in stain-resistant fabrics, firefighting foams, nonstick cookware and other products.