Eleven Orange County water agencies have joined in a lawsuit seeking hundreds of millions of dollars from DuPont, 3M and others whose carcinogenic chemicals have leached into groundwater aquifers and forced the closure of more than three dozen wells in the central and northern parts of the county.

The money would compensate the water districts — and the hundreds of thousands of residents they serve — for costs associated with the contamination, including the treatment plants being designed to remove the PFAS contaminants targeted in the lawsuit. Those chemicals were long used in Scotchguard, Teflon, and other waterproofing and stain-proofing products.

The chemicals are believed to end up in county wells as product residue that finds its way into Inland Empire wastewater. That water is then released as treated sewage into the Santa Ana River, which eventually settles into the county’s groundwater basin, according to water officials. Additionally, the lawsuit lists a 3M plant in Corona and Corona-based roofing company, Decra Roofing Systems, that used 3M products, as possible sources.

“Defendants 3M Company and E.I. du Pont de Nemours … knew or reasonably should have known that these harmful compounds would reach groundwater, pollute drinking water supplies, render drinking water unusable and unsafe, and threaten public health and welfare,” according to the suit, filed Tuesday, Dec. 1, in Orange County Superior Court.

The PFAS toxins — the acronym stands for per- and polyfluoroalkyl substances — encompass a family of chemicals that includes two compounds regulators have focused on, PFOA and PFOS. Those two have been linked to a variety of health problems, including cancer, liver and kidney damage, and ulcerative colitis. Regulators have steadily been lowering the threshold at which the chemicals may have health consequences to ever more miniscule amounts, which has led to growing attention on their presence in Orange County and elsewhere in the state.

Water districts statewide began shutting down wells last year and shifting to more costly imported water. Orange County was particularly hard hit: Of the 195 wells in the 11 Orange County water agencies’ turf, more than three dozen have been closed and the number eventually determined to be contaminated could reach more than 70.