'Forever Chemicals' in Philly-area waterways

4 AND ABOVE: A U.S. Geological Survey study sampled streams across Pennsylvania for chemicals in the PFAS family of compounds. Although the study did not sample drinking water — only raw stream water — many locations were found to exceed newly proposed federal contaminant levels in drinking water for the compounds set at 4 parts per trillion. A separate proposed index includes other PFAS compounds and flags anything over 1 as a hazard.