Fish can accumulate high levels of per- and polyfluoroalkyl substances (PFAS), even far from sources of contamination, according to a new study by researchers at The Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS). The research highlights the need for expanded monitoring in watersheds affected by large PFAS sources like military bases across the country that have been contaminated by use of PFAS containing foams for fire-training and fire-fighting activities.