A new study by Environmental Working Group (EWG), scientists find that consumption of just a single serving of freshwater fish per year could be equal to a month of drinking water laced with the “forever chemical” PFOS, or perfluorooctanesulfonic acid, at high levels that may be harmful.

Researchers calculated that eating one fish in a year equated to ingesting water with PFOS at 48 parts per trillion, or ppt, for one month.

The study bolsters EWG’s long-running calls for strict regulation of PFOS and the other toxic “forever chemicals” known as PFAS, or per- and polyfluoroalkyl substances,

in addition to more tests of food such as fish, since diet is thought to be a major source of PFAS exposure for Americans.

The findings are a particular issue for communities with environmental justice concerns, whose survival often depends on eating freshwater fish they’ve caught.

EWG found the median amounts of PFAS in freshwater fish were an astounding 280 times greater than forever chemicals detected in some commercially caught and sold fish.