Colorado Attorney General Phil Weiser sued 15 manufacturers of a foam used by firefighters, arguing it contains “toxic forever chemicals” that might be associated with an increased risk of cancer.

Weiser’s office asked the Denver District Court to order the companies to pay for the cost of investigating, cleaning up, restoring and monitoring sites where the chemical was used, stored or disposed of.

Weiser’s office said the aqueous film forming foam, which is widely used to fight fires, contains polyfluoroalkyl substances, which the attorney general described as “forever chemicals” because “they persist in the environment and accumulate in living organisms, including people.”

“Research shows that exposure to high levels of PFAS chemicals may be associated with serious diseases including an increased risk of cancer,” Weiser said in a statement. 

In his complaint, Weiser said the 15 companies should have known their products “harmed the environment and human health.” The attorney general also cited sampling by the Colorado Department of Public Health & Environment, which he said detected the chemical in water across the state, as well in military facilities in Colorado Springs, the Suncor oil refinery, airports, and fire districts.

“Colorado now has forever chemicals in our soil and drinking water systems and people’s health is at risk,” Weiser said in a statement. “These companies knew that these chemicals posed significant threats to human health and the environment and nonetheless put Colorado at risk; it is important that they pay for the harm they caused.”