Seven Montgomery County residents have sued 3M and several other chemical companies over the contamination of their drinking water by firefighting foam used at a nearby military base.

The lead plaintiffs in the lawsuit, Kevin and Elizabeth Voelker, claim that the chemicals used in training exercises at the former Naval Air Station Joint Reserve Base in Horsham and the former Naval Air Warfare Center in Warminster seeped into the groundwater flowing to their home and poisoned them.