LIMESTONE, Maine (AP) Researchers exploring the presence of so-called forever chemicals around the former Loring Air Force Base are asking residents how they use the local waters.

Wood Environment and Infrastructure will interview residents of Limestone, Caswell and Caribou about water used for swimming, farming and fishing, as well as drinking water from private wells, the Bangor Daily News reported.

“We want to know if kids have waded or swam in a stream or lake or if farmers have used the water for irrigation,” Amy Quintin, from Wood Environment, said during a public meeting Wednesday.

Officials are concerned that PFAS contamination from firefighting foam used on Loring’s runway may have spread elsewhere.

Initial investigations that began in 2015 found non-dangerous PFAS levels in 21 of 22 sites of groundwater, surface water, soil and sediment.

Wood’s researchers have not found contamination of private wells or local water supply but more samples will be collected.

Research sites will encompass the waterways on the more than 9,000-acre former base.

PFAS, or per- and polyfluoroalkyl substances, are known to cause cancer, birth effects and other health risks. They’ve been found in soil on farms, in fish and in deer in Maine.