This story was updated at 2:30 p.m.

The chemical giant Monsanto will pay the District of Columbia $52 million dollars, as part of a settlement over toxic contamination in D.C. waterways. It’s one of the largest environmental settlements ever in the city.

D.C. Attorney General Karl Racine filed suit against Monsanto in May, alleging the company had polluted all 36 waterways in the city with toxic polychlorinated biphenyls, or PCBs. The company knew how harmful the chemicals were for decades, according to the lawsuit, but continued to promote and sell them.

PCBs were outlawed in 1979, but prior to that ban, they were used in all sorts of products, including caulking, fluorescent lights, and floor finish. Monsanto produced 99% of the PCBs used by U.S. industry in their Illinois facility.

“We sued Monsanto because they knowingly sold these chemicals, they misled the public,” says Jason Downs, D.C.’s Chief Deputy Attorney General. “They misled regulators for the purpose of maximizing profits. In other words, they put profits over people.”

PCBs can stick around in the environment for decades—and the lawsuit claims they can still be found in high levels in all the waterways in D.C. The chemicals can cause cancer, damage the immune system and reproductive system, and lead to many other health problems, according to the Environmental Protection Agency.

The majority of the $52 million will help fund cleanups of the Potomac and Anacostia Rivers, per the suit. The District is currently working on a lengthy and expensive plan to remediate PCB contamination in the sediment of the Anacostia River.

D.C. is not the only jurisdiction to reach a settlement with Monsanto over PCB pollution recently. Last month, a $550 million settlement was announced between Monsanto and 13 governments around the country, including Baltimore City and Baltimore County.

Monsanto was acquired by Bayer in 2018. In a statement, Bayer said the recent settlements with D.C. and other governments over PCB pollution were fair. “To be clear, Monsanto legally manufactured PCBs until voluntarily ceasing their production in 1977, two years before the EPA banned its manufacture, and the company never manufactured or disposed of PCBs near or in any D.C. waterways.

PCBs can be found all over the world — even the arctic — and far from where they were manufactured. The chemicals can enter the water and air when products containing them are put in landfills, or through leaks or spills.

This story was updated to include a statement from Bayer.