Maternal Offloading of Per- and Polyfluoroalkyl Substances to Eggs by Lake Michigan Salmonids

Per- and polyfluoroalkyl substances (PFAS) distribute and bioaccumulate within aquatic organisms and food webs. Many PFAS are proteinophilic compounds that display higher concentrations in the blood, liver, and kidney of vertebrates than in muscle. Several studies have shown that birds and mammals exhibit maternal offloading of PFAS to offspring through transport to the placenta, milk, and egg deposition, but no study to date has observed maternal offloading in fish. We analyzed PFAS concentrations in muscle tissue and eggs with targeted LC-MS/MS for sexually mature Lake Michigan salmonids including Chinook salmon, coho salmon, and steelhead trout. In eggs, 83% of measured total PFAS concentrations were perfluoroalkane sulfonic acids (PFSAs) compared to only 23% in female muscle and 55% in male muscle. Higher detection frequencies and concentrations for perfluorooctane sulfonic acid (PFOS) were observed in eggs compared to muscle tissue, consistent with maternal offloading of PFOS to eggs. In contrast, maternal offloading of perfluorooctanoic acid (PFOA) was not observed. We conclude that salmonids can bioaccumulate and offload PFAS to embryos, which has implications for embryo health, egg predation by fish and wildlife, and ultimately human exposure.