Rural water utilities are accusing 3M Co., E.I. du Pont de Nemours and Co. and other companies of potentially contaminating groundwater wells with firefighting foam containing chemicals that take forever to degrade.

The city of Millington, Tenn., joined by the National Rural Water Association, alleged in a complaint Tuesday that the companies developed, marketed, and sold chemicals known as per- and polyfluoroalkyl substances, or PFAS, despite knowing about the environmental and health risks they posed.