For the first time, Minnesota is directing 3M to limit the amount of PFAS it sends into the Mississippi River from its 76-year-old factory in Cottage Grove. The industrial chemicals detected near the factory's discharge pipe have been blamed for contaminating fish that pose a threat to people who eat them.

3M is challenging the new requirement for its wastewater permit, asking the Minnesota Pollution Control Agency for a hearing for its argument that the restriction is neither legal nor justified by the science.

The regulation is the first front in a new battle over how to manage chemicals used in dental floss, firefighting foam, waterproof clothing and many other common products. They have built up for many decades in the environment, and don't break down.

Minnesota has already enacted a ban on the use of these chemicals in almost all applications, which will roll out gradually until 2032. Until now, however, the state has not ordered manufacturers to keep PFAS out of their wastewater.

The shape of 3M's permit could set a standard for many other entities that release the chemicals, even if they didn't create them. The Metropolitan Council, with multiple plants that discharge treated sewage from the Twin Cities into the Mississippi River, expressed concern to the MPCA about setting a precedent for controlling a pollutant that is difficult to capture and destroy.

Environmentalists welcomed the MPCA's action. The draft permit is "a long overdue step and an important milestone," said Carly Griffith, water program director for the Minnesota Center for Environmental Advocacy. The group has urged MPCA to tighten restrictions on some of the PFAS chemicals in the permit.

PFAS, or per- and polyfluoroalkyl substances, are a class of thousands of chemicals that contain carbon-fluorine bonds. They have built up in the environment, wildlife and humans after decades of use. Some of the chemicals have been linked to certain cancers and other health problems.

The Cottage Grove site, which opened in 1948, was the original manufacturer of Scotchgard, a fabric protector composed of PFAS. The plant also produced waste that was later dumped around the east metro, polluting drinking water supplies for thousands of people.

The plant now produces specialty tapes and films, chemicals and abrasive materials used in auto body repair. In recent years, MPCA has been probing PFAS emissions to the air and water at the plant. In 2020, the state investigated after 3M disclosed to the agency that there were "compliance issues" at the site. One finding resulted in a $2.8 million fine for mishandling hazardous waste.

The water quality standards that Minnesota is now trying to enforce at Cottage Grove are derived from a 10,000-page report 3M was required to compile as a part of MPCA's investigation. It extensively sampled the Mississippi and the fish in it near the plant's pipe, finding specific chemicals linked to 3M's manufacturing. MPCA concluded in its water standards that this section of the river, which includes parts of Pool 2 and Pool 3, is "demonstrably impacted by discharge from 3M."

The state now warns that women who are pregnant or could become pregnant and children should not eat fish from this section of the river, in part because of PFAS contamination.

3M said it will end all its PFAS production by the end of 2025, but the chemicals will still be flowing through wastewater at Cottage Grove because the company is treating contaminated groundwater at the site. It is building a $300 million water treatment system at Cottage Grove, which would use four filtering technologies to remove PFAS.

In an email, MPCA spokesman Adam Olson said that only monitoring will show "if the configuration of technologies 3M has chosen can meet the limits needed to protect water quality."

Despite its own plans to filter out PFAS, the company wrote in comments to MPCA that state regulators want "to impose requirements for the operation of the advanced wastewater treatment system that are legally impermissible and unsupported by the record."

It's not the only group posing a challenge to the new regulation.

In public comments on the draft permit, the Metropolitan Council, whose Empire Wastewater Treatment Plant releases treated effluent into the same part of the river, wrote that the permit "may be viewed as precedent for how other facilities, including the Met Council, will be regulated."

The Met Council and several industry groups also said in comments that MPCA's process for putting together the permit was improper. The state should first decide what level of reduction is feasible, these groups said, and then apply those numbers to the factory.

There is no timeline for when MPCA may issue a final permit, Olson wrote.