Environmental occurance, human exposure, and metabolism of per- and polyfluoroalkyl substances—a review

Abstract Per- and polyfluoroalkyl substances (PFASs) are known as ‘forever chemical’, commonly used in commercial and daily-life products. Due to their special physico-chemical characteristics, PFASs have been found in various environmental matrices, and can be exposed to organisms and humans. The present review outlines the current state of knowledge on the occurrence of PFASs in the environment, human exposure routes, biomonitoring data, and metabolic mechanism. Diet is considered to be the main route of PFASs exposure, and these compounds enter the human body through accumulation in the food chain, particularly through biomagnification by aquatic organisms. Detection of different PFASs has been reported in human samples including urine, blood, serum, breast milk, hair, and nails, among which perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) and perfluorohexane sulfonic acid (PFHxS) are most frequently identified in serum and short-chain PFASs are frequently detected in urine. After entering into human body, particular biotransformation pathways of PFASs in mammals are primarily through hydroxylation, carboxylation, and enzymatic conversion. PFASs can affect metabolism by increasing inflammation, peroxisome proliferator-activated receptor (PPAR) signaling. Long-chain PFASs may cause stronger immunosuppressive effects and higher bioaccumulation potential than short-chain PFASs. PFASs and their metabolites induce similar or even more toxic effects by activating the same signaling associated with endogenous metabolism, thereby affecting lipid metabolism and leading to metabolic disorders and related diseases. This review may contribute to the human exposure risk of PFASs, especially from the respective of human exposure level and metabolic transformation.