Bioaccumulation and effects of per- and polyfluoroalkyl substances in bivalves: A review

Per- and polyfluoroalkyl substances (PFAS) are a large group of anthropogenic chemicals. Due to their chemical properties, they are used heavily in commercial goods. However, these same properties that make them highly favorable for manufacturing make them extremely mobile, persistent, and resistant to breakdown in the aquatic environment. While PFAS research has historically focused on model organisms, understanding the effects of PFAS on nonmodel aquatic organisms is critical to best protect vulnerable species. Bivalves are aquatic organisms that provide many commercial and ecological benefits. It is essential to assess the effects of PFAS on bivalves to evaluate their potential as bioindicators in PFAS-contaminated areas as well as to preserve the ecosystem services that they provide. The objective of the current review is to examine the impacts observed in bivalves exposed to PFAS, as well as to determine gaps in knowledge and provide recommendations for future studies. Studies have shown that the structure of PFAS can significantly alter their bioaccumulation potential, oftentimes with longer chain lengths yielding higher bioaccumulation factors. While overt toxicity is observed in bivalve larvae and embryos, most effects associated with PFAS exposure are sublethal, ranging from oxidative stress to immunotoxicity, genotoxicity, and alterations to lipid and carbohydrate metabolism and xenobiotic metabolism. With >9,000 PFAS, effects do differ among them as a result of the structure-function relationship, in addition to the different effects seen across bivalve species, highlighting the need to assess multiple PFAS as well as bivalves to best determine the potential effects of exposure. This is apparent in the need for mixture studies in addition to singular PFAS exposures, as aquatic systems are not closed systems. All this to say, this review highlights the current knowledge on the bioaccumulation and toxicity of PFAS in bivalve species.