(Reuters) - Los Angeles County sued Monsanto Co on Thursday, seeking to force the unit of Germany’s Bayer AG to help pay for reducing PCB contamination in dozens of bodies of water.

FILE PHOTO: Logo of Bayer AG is pictured at the annual results news conference of the German drugmaker in Leverkusen, Germany February 27, 2019. REUTERS/Wolfgang Rattay/File Photo

The most populous U.S. county, which has about 10.1 million people, said the presence of polychlorinated biphenyls (PCBs) in products sold by Monsanto many decades ago has caused widespread environmental contamination, forcing it to spend money to retrofit its stormwater systems and prevent further damage.

Los Angeles County said Monsanto had long concealed its knowledge that PCBs were harmful, and created a public nuisance because their presence interferes with commerce, fishing, navigation, swimming and other water-based activities.

In a statement, Bayer said it believed Los Angeles County’s lawsuit had no merit, and that it would defend itself aggressively. Bayer said in its most recent annual report that it had “meritorious defenses” against PCB-related claims.

The lawsuit filed in Los Angeles federal court seeks compensatory and punitive damages that Scott Kuhn, a lawyer for the county, said in an interview could reach hundreds of millions of dollars.

Kuhn called PCB contamination “a big problem in our county. It’s a significant overall cost to clean that up.”

PCBs have been linked to cancer, immune system difficulties and other health problems. The U.S. government outlawed them in 1979.

Monsanto produced PCBs from 1935 to 1977, and has said it stopped making them because they were not readily biodegradable.

Los Angeles County joined many other U.S. municipal entities to sue the company over PCBs.

The lawsuit adds to Bayer’s legal problems tied to Monsanto, which it bought last year for $63 billion.

Bayer also faces claims by more than 13,400 plaintiffs that Monsanto’s Roundup weed killer causes non-Hodgkin’s lymphoma, and that Monsanto concealed the link.

A jury in Oakland, California, on May 13 awarded $2.055 billion to a couple who said Roundup caused their cancer, though that award will likely be reduced.

PCBs were once used widely to insulate electrical equipment, helping reduce fire risk. They were also used in such products as carbonless copy paper, caulking, floor finish and paint.

The case is County of Los Angeles et al v Monsanto Co et al, U.S. District Court, Central District of California, No. 19-04694.