A lawsuit filed last week in Dane County Circuit Court seeks unspecified damages from dozens of companies — including DuPont, 3M and Johnson Controls as well as unknown manufacturers — that the county says sold products for decades despite knowing the contents were toxic and do not break down once released to the environment.

Assistant Corporation Counsel Amy Tutwiler said the county is prepared to pursue the case individually in state court, though the defendants may try to move the case to the federal courts and consolidate it with about 500 similar cases — including one filed last year by the city of La Crosse — in pending multijurisdictional litigation.

“Under either scenario, we are prepared to take the action that is in the best interest of the county,” Tutwiler said.

According to the complaint, the defendants began selling a water-based foam in the 1960s known as AFFF made with PFOA and PFOS, two of thousands of fluorinated compounds generally known as PFAS.

Highly effective for extinguishing liquid fuel fires, the foam continues to be used at airports and military bases, though the complaint claims AFFF can be made with different PFAS compounds.

The suit claims the defendants knew — or should have known — since the early 1980s that using AFFF according to their instructions would release PFAS to the air, soil and groundwater and that the chemicals could damage the liver, kidneys and nervous system, among other negative health effects.

Under pressure from the Environmental Protection Agency, 3M stopped producing PFOS-based foam in 2002.

DuPont began studying the toxicity of PFOA in the 1960s but kept the information from the public and government regulators. In 2005 the company agreed to pay the EPA more than $10 million for failing to communicate the risks. DuPont later spun off its chemical division — and associated liabilities — as a new company called Chemours.

The lawsuit alleges the manufacturers produced defective products and failed to warn consumers and the public of their dangers, creating public and private nuisances that persist to this day.

Because of the manufacturers’ failures, the suit alleges the airport continues to be contaminated, creating an environmental hazard and forcing the county to investigate, monitor, and clean up the damage “at significant expense.”

It’s been four years since the state Department of Natural Resources informed the county, Wisconsin National Guard and the city of Madison that they were responsible for PFAS contamination on and around the airport, including several “burn pits” where firefighters trained with the toxic foam.

The National Guard Bureau is heading the remediation using a federal process under which actual cleanup may not begin for at least a decade.

But last month a Waukesha County judge said the DNR lacks authority to enforce the state’s spills law without first going through the Legislature to establish a definitive list of hazardous substances or an explanation of how it makes those determinations.

The ruling is on hold until June 6 and will likely be appealed.

Last year the state retained a private law firm to investigate and sue those responsible for PFAS pollution. In March, the state sued Johnson Controls over PFAS contamination near Marinette.