'Forever chemicals' are everywhere. The battle over who pays to clean them up is just getting started.

State and local governments across the country are suing manufacturers of toxic chemicals that are contaminating much of the nation's drinking water, aiming to shield water customers and taxpayers from the massive cost of cleaning them up.

These pervasive “forever chemicals,” known as PFAS, are linked to a variety of health hazards, including cancer. Now, as state lawmakers and federal regulators get serious about removing them, scores of governments and water suppliers are in pitched court battles over who is on the hook for hundreds of billions of dollars in damage — the companies that created the chemicals or the customers who are drinking them.

Key rulings starting later this year could determine which side has the upper hand in these cases, which are part of an unfolding legal saga that could become the most expensive in U.S. history.

Early estimates of the cost of removing PFAS from drinking water nationwide are about $400 billion — dwarfing the cost of settlements and cleanup costs from environmental contamination like asbestos and lead pipes or other public health settlements tied to tobacco and opioids.

And if the chemical companies can't be forced to pay, water customers and taxpayers will have to foot the bill.

“The manufacturers of PFAS are in effect creating a water affordability problem for the people of New Jersey,” said Shawn LaTourette, the head of New Jersey's Department of Environmental Protection, which was one of the first states to regulate the chemicals in drinking water and has filed several lawsuits seeking hundreds of millions of dollars for damages to the state’s natural resources.

The reasons why the chemicals are so favored by manufacturers — they’re found in cosmetics, nonstick cookware and medical devices, and are key to brands like Scotchgard and Gore-tex — are the same reasons why they’re so hard to clean up: They’re long-lasting and resistant to fire, wind and water.

Costs are almost certain to mount as the hazards become clearer and more regulators set removal requirements. The Environmental Protection Agency is just starting to address risks by setting non-binding limits for PFAS in drinking water and moving to designate two kinds as hazardous substances — moves that could lead to more cleanup costs nationwide and that the industry is fighting fiercely.

In the absence of firm EPA action, states have moved faster. In those that already have drinking water limits for PFAS, including New Jersey, Massachusetts, Michigan and New York, compliance costs are starting to show up in rates. Water providers are warning that rates must rise and some are going into debt.

Officials from across the political spectrum are targeting a small number of companies, including 3M, DuPont and its spinoffs, that made most of the per- and polyfluoroalkyl substances that are now ubiquitous in water, soil, and even human blood. One nonprofit, the Environmental Working Group, estimates 200 million Americans are drinking water known to be laced with PFAS.

In Florida, Republican Attorney General Ashley Moody sued more than a dozen companies in April, alleging water supplies throughout the state are contaminated by PFAS. She wants companies to pay an unspecified amount to investigate the pollution and then clean it up.

More than a dozen other states, including Michigan, Alaska, Pennsylvania, North Carolina, New York and Colorado, are also suing based on the contamination of drinking water or natural resources such as lakes and groundwater. They're plaintiffs alongside two U.S. territories, one Native American tribe and at least 150 water districts and local governments seeking reimbursement for PFAS pollution.

In Orange County, Calif., water managers found PFAS in dozens of wells that draw from a vast groundwater basin that supplies 2.5 million people. They estimate technology to filter the chemicals from the wells will cost $1 billion, on top of the costs for replacement water in a state already pinched by drought.

The federal infrastructure law set aside $10 billion to help agencies such as the Orange County Water District, which is moving to build and upgrade treatment plants with the help of a federal loan. But attorneys suing the chemical companies argue taxpayer money shouldn't be used to let those corporations evade responsibility.

“That money shouldn’t be coming from those of us who are the victims here, the exposed people,” said Robert Bilott, an attorney whose decades-long crusade over PFAS pollution in the Ohio River highlighted DuPont's knowledge that it was sickening its own workers in West Virginia and inspired the film "Dark Waters."

Since then, a rash of cases has established some health effects of the chemicals and resulted in significant payouts from companies. An initial $107 million settlement with DuPont funded a study in West Virginia and Ohio that found links between one kind of PFAS and several conditions, including high cholesterol, thyroid disease, and kidney and testicular cancer.

Manufacturers concede PFAS is now in the blood of nearly every living person but argue they are not harmful. A leading industry trade group advertises the class of chemicals as beneficial, even as some that were used in firefighting foam are no longer being made.

Lawsuits on behalf of 3,500 Ohio River Valley residents resulted in a $671 million settlement with DuPont and a spinoff company, Chemours, in 2017. Another settlement with Chemours includes a mile-long underground wall to keep PFAS from getting further into drinking water drawn from North Carolina's Cape Fear River. A 2018 settlement between 3M and the state of Minnesota includes $850 million to clean up public drinking water as well as private wells.

Smaller jurisdictions are particularly vulnerable. Hoosick Falls, N.Y., and state agencies have received more than $5 million from Saint-Gobain SA and Honeywell Inc. over the last six years to clean up PFAS from the village's water supply. Without the settlement, the cleanup costs for the village's 3,500 residents “would have decimated us," said Mayor Rob Allen.

“I don’t see a way where our village would have remained financially solvent and viable,” he said.

Many of the lawsuits don’t yet seek specific damages, but the American Water Works Association, a trade group, estimated that it would take $370 billion to remove the chemicals from the nation’s drinking water. Insurance risk analysis firm Praedicat estimates the cleanup costs could exceed $400 billion.

The largest set of cases targets pollution caused by firefighting foam. Orange County's suit is one of around 3,000 consolidated in federal court in South Carolina alleging damage from the foam, which is considered a prime legal target because it’s tied to specific locations, like military installations and airports.

Sean Lynch, a spokesperson for 3M, which manufactured the firefighting foam for decades, said it was a “critical tool developed to serve an important need for military service members facing potentially life-threatening challenges.”

Chemours declined to comment on the litigation, while DuPont de Nemours, as DuPont is now known, argues that it never manufactured PFAS or firefighting foam and is being improperly named in litigation.

3M and other companies are also arguing in South Carolina that if there are health risks, they should be partly shielded from liability because the government agencies that bought the foam knew about the hazards. A similar argument worked to shield the makers of Agent Orange from lawsuits by Vietnam War veterans.

U.S. District Court Judge Richard Gergel's ruling on the liability defense will determine the scope of the companies’ exposure and how much money the water districts and states can try to collect. At an August hearing, Gergel expressed skepticism that anyone outside the companies was fully aware of the risks of PFAS, raising advocates' hopes that he would reject one of the companies’ key defenses.

“We’re spending a lot of money to clean up existing sites and filter people’s drinking water,” said Liz Hitchcock, director of federal policy at the environmental advocacy group Toxic-Free Future. “By we, I mean taxpayers and ratepayers. And water utilities are left holding the bag."