The 3M Co. and other major manufacturers of firefighting foams that have contaminated drinking water near military bases should have known they were making and selling products that presented a health risk, according to a suit filed Friday in U.S. District Court in Philadelphia against six foam makers.

The foam - known as Aqueous Film Forming Foam or AFFF - was sold to the military and used at two naval air bases in Warminster and Horsham Townships, among hundreds of sites nationwide.

During the last two years, chemicals contained in the foam known as PFOS and PFOA have been found in public and private drinking wells in Warminster, Horsham, and Warrington Townships, where wells have been shut off and are being treated.

PFOS and PFOA are linked to certain cancers, and research on their effects is still evolving. The contaminants have been found at other military sites in Pennsylvania, but not in the drinking-water supply. The foam was used at military bases across the country, and hundreds of sites yet to be tested could be contaminated.

The class-action suit, filed in U.S. District Court by the New York law firm Weitz & Luxenburg on behalf of seven residents from Bucks and Montgomery Counties, alleges that the companies that made the foam and sold it to the military knew that potentially harmful chemicals "would be introduced, in large quantities, into the environment."

"They put a dangerous product into the stream of commerce, and they put the blinders on," said Donald Soutar, a Weitz & Luxenburg attorney.

An attorney for 3M, which manufactured the foam through 2002, said the AFFF was used because it "saves lives."

"We believe these claims lack merit. 3M sold these products with instructions regarding their safe use and disposal," William A. Brewer III said in a statement. "3M is proud of its record of responsible stewardship in connection with its manufacturing and sales of AFFF."

Officials with Angus Fire, Ansul Co., Chemguard, and National Foam declined to comment. A call to Buckeye Fire Protection Co. was not returned.

The six companies' foams are listed on the Department of Defense's list of products qualified for use. However, because the military does not keep records of contracts beyond a certain period of years, it is not known which companies sold foam to these bases.

"Part of what we hope to learn through this lawsuit is exactly who was selling to the military," Soutar said.

The suit seeks funding from the companies for a medical monitoring program and blood tests for affected residents, in addition to monetary damages.

Meanwhile, water bills for local residents have gone up to cover the costs of bringing in water from new sources. Congressmen Mike Fitzpatrick (R., Pa.), Brendan Boyle (D., Pa.), and Patrick Meehan (R., Pa.) on Thursday wrote a letter urging the Navy to provide funding that would cover the rate increases for residents. Politicians have also asked the Navy to fund blood tests for residents, which it has said it would not do.

The Navy is paying for treating the contaminated wells and getting them back online, but the three townships have also chosen to bring in water from North Wales.