U.S. manufacturing and chemical industry groups have filed a lawsuit seeking to block a federal rule announced this year setting the first-ever drinking water standard to protect people against toxic “forever chemicals.”

The rule is intended to reduce exposure to the group of 15,000 chemicals known as per- and polyfluoroalkyl substances (PFAS) for approximately 100 million people. It would avoid deaths that have been linked to PFAS, according to the EPA.

Dubbed “forever chemicals” because they do not easily break down in the human body or environment, PFAS are found in hundreds of consumer and commercial products, including non-stick pans, cosmetics, firefighting foams and stain-resistant clothing. In a brief petition against the U.S. Environmental Protection Agency (EPA) filed Monday in the U.S. Court of Appeals for the D.C. Circuit, the National Association of Manufacturers and the American Chemistry Council said the rule is “arbitrary, capricious, and an abuse of discretion”.

The groups said the rule exceeds the EPA’s authority under the federal Safe Drinking Water Act, a 1974 law empowering the agency to pass water-quality regulations. The lawsuit followed a similar challenge filed on Friday in the same court by two associations representing water utilities, which are directly responsible for ensuring that drinking water meets the new standards. The American Water Works Association and Association of Metropolitan Water Agencies also said that the EPA “did not rely on the best available science” in developing the rule. A spokesperson for the EPA, which announced the rule in April, declined to comment.

The agency has estimated that between 6% and 10% of 66,000 public drinking water systems in the United States will have to take action as a result of the rule. While the new rule directly regulates public water systems, experts say it could bolster existing lawsuits or lead to new claims against companies that make PFAS from systems trying to recover their cleaning costs because the rules create an unambiguous standard for what levels of PFAS in drinking water are acceptable. Lawsuits against chemical companies over PFAS led to $11 billion in settlements in 2023.