Pressure vessels hold an ion exchange resin media that filters out PFAS at a new water treatment plant along Kimberly Ave. in Fullerton, CA. The plant is used to remove PFAS, a family of chemicals used for waterproofing and stain-proofing among other uses.

California’s attorney general on Thursday sued 3M Co, DuPont de Nemours Inc and several other companies to recoup the “staggering” clean-up costs from toxic pollutants known as “forever chemicals.”

Attorney General Rob Bonta said the lawsuit followed a multiyear probe that found the companies marketed products containing polyfluoroalkyl and perfluoroalkyl substances (PFAS) for decades despite knowing they cause cancer, developmental defects and other health problems. Bonta said the lawsuit could ultimately seek hundreds of millions of dollars in penalties and costs.

DuPont has never manufactured PFOA, PFOS or firefighting foam, said spokesperson Daniel Turner, referring to two PFAS substances. He added the company believes the complaint incorrectly names it as a defendant. “We believe these complaints are without merit … We look forward to vigorously defending our record of safety, health and environmental stewardship.”

3M spokesperson Carolyn LaViolette said in a statement the company “acted responsibly in connection with products containing PFAS and will defend its record of environmental stewardship.”

The substances are known as forever chemicals because of how long they stay in the human body and environment.

They have been mass produced since the 1950s, and used in products such as firefighting foams, nonstick pans and personal care items.

Bonta said the defendants created a public nuisance and demanded they pay to clean up PFAS, which he said has been found in drinking water, rivers, lakes, wildlife and the bloodstreams of about 98% of California’s approximately 39 million people.

“The damage caused by 3M, DuPont, and other manufacturers of PFAS is nothing short of staggering, and without drastic action, California will be dealing with the harms of these toxic chemicals for generations,” Bonta said.

Thousands of lawsuits have been filed against chemical companies in the last two decades for health and environmental damage from PFAS, potentially leading to billions of dollars in liabilities.

Thursday’s lawsuit was filed in Alameda County, which includes Oakland, and is the first statewide legal action over PFAS contamination.

It alleges violations of state consumer protection and environmental law violations and invokes the federal Superfund law, which establishes a path to recoup the costs of cleaning up hazardous substances.

In June, the US Environmental Protection Agency warned that forever chemicals could be dangerous even at undetectable levels.

The Biden administration is expected to issue the first enforceable drinking water regulations for PFAS in public water systems this year.