Three major chemical companies say they’ve reached a tentative settlement with cities suing them for water contamination linked to PFAS.

PFAS are a group of human-made chemicals known as forever chemicals, because they don’t break down naturally. They’re used in a host of consumer and industrial products, from waterproof coating to firefighting foam. Exposure to certain types of the chemicals is associated with health issues like cancers, liver and problems.

Cities around the U.S. that are suing chemical giants Chemours, DuPont and Corteva say the companies produced products containing PFAS that contaminated drinking water and other parts of the environment. 

In an article published in Market Screener, the companies say they’ll set up a more than $1 billion fund as part of the agreement, though it has not been finalized.

3M, another chemical company that produces a firefighting foam containing PFAS, has also been named in class action suits from cities, including Tucson. The city and the town of Marana filed suit against 3M and four other chemical producers, which seeks to recover the costs of treating water contaminated with PFAS.

Tucson Water officials detected the chemicals in higher concentrations in some groundwater back in 2021 and has been spending city money to address the contamination.  Municipal officials have tied the contamination to a special firefighting foam used for years and the Davis-Monthan Air Force Base and the Tucson International Airport nearby.

City Council member Steve Kozachik says it’s unclear how the settlement plan announced this week will impact the city, since it's only a principle agreement right now. Earlier this year, the EPA proposed its first-ever legal limits on six types of PFAS in drinking water, but the limits are not yet finalized.