3M is nearing a settlement with scores of cities and water agencies over firefighting foam made with PFAS, the "forever chemicals" that have tainted groundwater across the country.

3M and plaintiffs' lawyers Sunday asked that a big trial scheduled to start Monday in Charleston, S.C., be delayed while mediation continues. U.S. District Court Judge Richard Gergel Monday granted a motion for the trial's continuance.

"Counsel for the plaintiff and counsel for 3M Co. have been in serious settlement discussions to reach a global resolution of the claims of the water district plaintiffs pending against 3M," Gergel wrote in an order Monday.

"The parties informed the court last evening that they have reached a stage in those discussions where they believe a final binding agreement is achievable in the near future."

Both 3M and plaintiffs' lawyers told the court Sunday "that they believe their time could be more effectively spent finalizing the agreement and obtaining the necessary approvals rather than commencing the trial of this case."

Last week, DuPont de Nemours Inc., Chemours Co. and DuPont spinoff Corteva Inc. agreed to a $1.2 billion settlement before the trial, which pits over 3,000 plaintiffs — including cities, towns and public water agencies — against several firefighting foam manufacturers.

Maplewood-based 3M was the largest of those foam makers, and any settlement is expected to be several times higher than the DuPont agreement. Bloomberg News, citing unnamed sources, Friday reported that a 3M settlement could be at least $10 billion.

3M faces a flood of lawsuits — and potentially tens of billions of dollars in liabilities — over myriad consumer and industrial products that contained PFAS, an acronym for per- and polyfluoroalkyl substances.

But no single case is more significant in terms of size, combined with possible damages, than the firefighting foam litigation in South Carolina.

A series of bellwether trials were expected to kick off Monday with the city of Stuart, Fla., as the plaintiff. Bellwether trials are common in multidistrict litigation (MDL) cases, such as the firefighting foam litigation.

Such trials are aimed at encouraging settlements in MDLs, which are used in the federal court system for complex product liability matters with many separate claims.

Gergel ordered mediation of the PFAS firefighting foam litigation in October. Gergel wrote Monday that if 3M and the plaintiffs' lawyers don't reach a binding settlement within 21 days, he would promptly reschedule the Stuart case for trial.

The firefighting foam case against 3M is akin to a tidal wave of PFAS lawsuits filed in the past few years. Plaintiffs claim that 3M knew of the chemicals' risks for years, yet did not fully disclose them to government regulators.

In the 1960s, 3M and the U.S. Navy developed a new firefighting foam that was particularly good at quenching oil-related fires. The U.S. Air Force adopted the foam after the Navy and so did fire departments of all stripes nationwide.

3M's fluorocarbon-based film blanketed an oil fire, smothering flames, keeping vapors from igniting and fireproofing unburned fuel. The suppressant was dubbed "aqueous film-forming foam" — AFFF for short.

But what made the firefighting foam so effective were PFAS chemicals. However PFAS chemicals don't biodegrade, tainting the environment. They have been linked to cancer, liver damage, decreased fertility and other maladies.

3M stopped making firefighting foam around 2000 because of potential environmental risks. The company stands by its handling of PFAS, arguing that the chemicals are safe to humans in the levels that exist in the environment.

3M's stock closed Monday down 4.5% to $97.96. However, the stock jumped 8.5 % on Friday on the Bloomberg report of a possible settlement.

3M's stock has been trading recently at 10-year lows, partly because of the financial threat of PFAS lawsuits and litigation over 3M-made earplugs that were once standard issue for the military.

Veterans and service members claim the earplugs were defective, causing hearing loss. 3M maintains they were safe.