District of Columbia Attorney General Brian L. Schwalb has filed a lawsuit against more than 25 chemical companies for manufacturing, marketing, distributing and selling products containing dangerous PFAS chemicals, which the suit claims now pollute the District’s natural resources including its water system.

The firms being sued include 3M Co. and DuPont.

The complaint alleges that as early as the 1950s, 3M and DuPont knew the PFAS chemicals they manufactured, commonly used by the U.S. military and at airports to fight fires, posed health and environmental risks, but “actively hid” that information from the public and government regulators and falsely maintained that their products were safe.

PFAS substances — or per-and polyflouroalkyl substances — have been manufactured and used since the 1940s. PFAS have been used primarily by the military and at airports, for fighting liquid-based fires like those from jet fuel. PFAS have been called “forever chemicals” because they do not readily break down and once released into the environment can cause widespread contamination.

The suit claims that research has linked human exposure to PFAS with reproductive and developmental defects, increased cholesterol levels, liver damage, decreases in body vaccine response, lower infant birth weights, and higher risks of kidney and testicular cancer.

The Environmental Protection Agency (EPA) has found that even low levels of the chemicals can be harmful.

“The District and its residents will be forced to deal with the adverse impacts of these ‘forever chemicals’ for years to come. Through this lawsuit, we will hold polluters accountable for the damage their conduct has caused and will continue to cause,” Schwalb said.

The District seeks to recover the costs to fully investigate and clean-up PFAS contamination in the District’s natural resources and waterways and to monitor and treat PFAS in the stormwater, drinking water and wastewater.

The District also seeks punitive damages.

Other firms targeted in the D.C. lawsuit include Tyco Fire Products, Chemguard, Carrier Fire & Security, Fire Service Plus, Amerex, Arkema, BASF, ChemDesign Products, Corteva and Dynax.

Chemical firms are facing thousands of lawsuits in the U.S. over PFAS contamination. In June, Chemours, DuPont de Nemours and Corteva said they had reached an agreement to settle claims for $1.19 billion. Also, 3M said it reached its own $10.3 billion settlement. These agreements involve claims made against them by hundreds of water providers across the country. Those lawsuits have been consolidated in South Carolina’s federal court.

A number of states have also sued chemical manufacturers over PFAS. They include New Mexico, New Jersey, Maryland, Georgia, Rhode Island, Maine, Massachusetts, California and Wisconsin.