Viewpoint: Here’s the wacky formula used by Environmental Working Group to stoke unwarranted fears about safe chemicals – Genetic Literacy Project

The EWG study, published in Environmental Research, is a model. Rather than actually measure serum levels of PFOs, the group merely measured the quantity of PFOs in a fish multiplied by the number of fish eaten in a week and calculated a serum level. All models simplify reality by making assumptions; the fidelity of those assumptions to the real world measures how well the model mirrors reality. Let’s look at some of EWG’s assumptions.The Dose Makes the PoisonThe pharmacokinetics of PFOs in humans remains, at best, unsettled science. The EWG study admits that “no direct measurements of PFOS absorption through the gastrointestinal tract have been conducted in humans”The EWG model, based on a chain of events, predicted that as more fresh-water fish was eaten, the serum level of PFOs would rise. There are two key assumptions in that chain that are PFOS is removed through cookingthe PFO concentration in fresh-water fish is consistent and knownThe assumption that no PFOS are removed through cooking is wrong. As a study in Food Science and Nutrition reports, how fish is prepared does make a difference: Washing removed 74% of PFOs, while cooking provided other reductions — “grilling (91%), steaming (75%), frying (58%), and braising (47%) comparing to uncooked sample.”Yet the EWG authors claim,“The calculations within the present study…assume that cooking does not materially impact PFAS and that 100% of the PFAS measured in fillets will result in exposure and subsequently impact serum levels. This could potentially overestimate exposure” [emphasis added]They “knew“ this because the citation within the study suggests cooking seafood reduces PFAs by 29% based on a meta-analysis.In calculating our exposure of PFOs, the EWG needed to know the potential amount of PFOs contained in fresh-water fish. They made use of two EPA assessments, the National Rivers and Streams Assessment (NRSA) done every five years, and the 2015 Great Lakes Human Health Fish Fillet Tissue Study. There was a wide range of values in those datasets, as EWG writes,“Across both U.S. EPA’s datasets, the lowest total PFAS was 425 ng/kg and the highest was 286,767 ng/kg. The mean total PFAS was 20,870 ng/kg and the median was 11,880 ng/kg. … fish sampling from the Great Lakes Human Health Fish Fillet Tissue Study found overall higher levels of PFOS and total sum of detected perfluorinated compounds compared to the National Rivers and Streams Assessment.”
— Read on

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