Effects of hibernation on the bioaccumulation and tissue distribution of per- and polyfluoroalkyl substances in frogs (Rana tigrina cantor) via skin exposure

We investigated the bioaccumulation, tissue distribution, maternal transfer and effects of hibernation of per- and polyfluoroalkyl substances (PFASs) in frogs via skin exposure. Relationships between toxicokinetic parameters, such as assimilation efficiencies and depuration rate constants of PFASs, and carbon chain length were revealed, indicating a high bioaccumulation potential for PFASs with longer carbon chains. Eggs were the main site for the deposition of perfluoroalkyl sulfonic acids (PFSAs) and C9 − C16 perfluoroalkyl carboxylic acids (PFCAs), whereas the carcass was the primary organ for C4 − C8 PFCAs. More than 80 % of the total body burden of some PFASs was maternally transported to the eggs. Hibernation inhibited the development of eggs in frogs, reduced the elimination rate of PFASs and resulted in bioamplification factors (a concentration increase caused by weight loss and/or a decrease in elimination rate) of 1.79 and 2.70 for total PFSAs and PFCAs, respectively. The bioamplification of PFASs in maternal tissues or organs was mainly caused by a decreased elimination rate, whereas in eggs, it was primarily caused by weight loss. The liver tended to retain more PFASs during hibernation, which might have been related to the physiological impact of hibernation on circulation. To our knowledge, this is the first study to reveal the mechanisms responsible for PFAS bioamplification in different tissues. The results of the present study are significant for understanding the bioaccumulation and toxic effects of PFASs in oviparous animals during the hibernation of physiological processes.