Bioaccumulation and effects of per- and polyfluoroalkyl substances (PFAS) 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 non-model 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 preserving the ecosystem services they provide. The overall objective of the current review is to is to further examine the impacts observed in bivalves exposed to PFAS as well as determining gaps in knowledge and providing recommendations for future studies. Studies have shown that PFAS structure can significantly alter the bioaccumulation potential of PFAS 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 in bivalves is sublethal with effects ranging from oxidative stress, immunotoxicity, genotoxicity, and alterations to lipid and carbohydrate metabolism and xenobiotic metabolism. With over 9,000 PFAS, effects do differ between PFAS as a result of the structure-function relationship in addition to different effects seen across bivalve species, further 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.