- More than 200 million Americans could have the toxic fluorinated chemicals known as PFAS in their drinking water at a concentration of 1 part per trillion, or ppt, or higher. PFAS contamination has raised alarms among a bipartisan group of lawmakers in Congress. https://www.ewg.org/release/study-more-200-million-americans-could-have-toxic-pfas-their-drinking-water 34 comments science