DuPont de Nemours Inc., Chemours Co. and DuPont spinoff Corteva Inc. said they have agreed to pay $1.2 billion to resolve hundreds of pollution claims filed by cities, towns and local water agencies over "forever chemicals" that allegedly fouled groundwater across the U.S.

The pollution comes from a class of chemicals called PFAS found in firefighting foam used in the cities.

3M, a litigant and the company that made the most PFAS chemicals, is not part of the settlement and is set to go to trial Monday on a big case involving contamination in Florida from firefighting foam. Bloomberg News reported that the Maplewood-based company is in talks for a $10 billion or more settlement in the cases.

The three companies in the settlement will set up a fund to settle lawsuits claiming that per- and polyfluoroalkyl substances made by DuPont tainted drinking water and subjected consumers to higher rates of cancer, according to a statement Friday. The compounds are known as PFAS.

Under a cost-sharing agreement between the three companies, Chemours will cover about $592 million of the settlement, DuPont approximately $400 million and Corteva roughly $193 million, the companies said. The settlement amounts will be deposited into the water district settlement fund within 10 business days after the court's preliminary approval of the pact, according to the statement.

"This is an impressive step toward righting a corporate wrong that threatened the health of all Americans," said Scott Summy, one of the lawyers leading the consolidated PFAS litigation in federal court. "DuPont has decided to put money into water systems' hands today rather than delaying payment for years of trial. We applaud the company for this proactive move for cleaner water for all of us."

Holly Froum, a Bloomberg Intelligence analyst who has been following the PFAS litigation, said in a note Friday that "it remains to be seen" how many water authorities will sign off on the deal.

3M and other makers of PFAS including DuPont last month agreed to pay more than $100 million to resolve a Georgia city's lawsuit claiming the chemicals polluted its drinking water.

Researchers have found that PFAS, an industrial product used since the 1950s in products ranging from computer chips and nonstick frying pans to cosmetics, never breaks down naturally and has to be removed from waterways to landfills or destroyed by burning.

They say PFAS runoff into groundwaters across the country means more than 200 million Americans may have the allegedly toxic substance in their drinking water. The compounds have been linked to increased cancer risks and other ailments.

The federal trial set to start Monday in South Carolina involves firefighting foam pollution in Stuart, Fla. It is the first of more than 1,000 lawsuits against 3M regarding firefighting foam.

The judge in the case, Richard Gergel, said 3M faces an existential threat from lawsuits over the PFAS claims. Analysts say the company's liability could hit $143 billion for cleanup alone.

The city of Stuart claims 3M failed to warn of PFAS' risks and design-defective products. A verdict for Stuart could help determine what 3M must pay to settle other cases.

Lawyers for Stuart are seeking $105 million to cover the cost of removing PFAS and as much as $500 million in punitive damages, court filings show.

3M maintains that PFAS are safe and that PFAS contamination poses no significant threat to public health and welfare. The company, which already stopped making many PFAS types, will stop making the chemicals by 2025 because of "regulatory trends focused on reducing or eliminating the presence of PFAS in the environment." The company started winding down production of some of the compounds in 2000, court filings show.

In a statement, a 3M spokesman said the company would contest claims by cities, states and individuals but also held out the possibility of settlement.

"We are in active, ongoing and confidential mediation sessions regarding the resolution" of the Stuart case and "multiple other water supplier cases and claims," he said.

The three companies in the settlement, which agreed in 2021 to set up a $4 billion fund to handle the burgeoning wave of PFAS suits, noted in their statement that the accord doesn't cover claims by state attorneys general about pollution of rivers and streams or any claims by the federal government.

Also excluded from the deal are smaller water providers that haven't found "the presence of PFAS and are not currently required to monitor for it under federal or state requirement," according to the statement.