The “forever chemicals” are used by the oil and gas industry, but a lack of transparency and accountability makes it impossible to know how widespread contamination could be.

Last year it was revealed that these chemicals, collectively referred to as PFAS (per-and polyfluoroalkyl substances), have been used in U.S. oil and gas wells for decades. As far as the experts we spoke with know, this is the first time PFAS that may be linked to fracking have been detected in household drinking water.

The chemicals don’t break down naturally, so they linger in the environment and human bodies. Exposure is linked to health problems including kidney and testicular cancer, liver and thyroid problems, reproductive problems, lowered vaccine efficacy in children and increased risk of birth defects, among others.