12 - Human dietary exposure to per- and poly-fluoroalkyl substances (PFASs)

Abstract

Per- and polyfluoroalkyl substances (PFASs) are a class of emerging contaminants with numerous industrial and commercial applications. Within this class the best studied substances are the perfluoroalkane sulfonates (PFSAs) and perfluoroalkyl carboxylates (PFCAs). PFSAs and PFCAs have been detected in human serum samples from all around the world and are ubiquitous in the global environment and wildlife. As well as being completely resistant to environmental degradation, some PFSAs and PFCAs are bioaccumulative and potentially toxic, which raises a concern about population-wide exposure to this group of substances. Dietary intake has been suggested as a major pathway of human exposure to the two most widely studied substances among PFSAs and PFCAs, namely perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). However, the difficulties associated with the analysis of PFSAs, PFCAs and related PFASs at ultra-trace levels in food samples have hampered the understanding of human exposure. Recent advances in analytical chemistry have dramatically improved the ability to measure these substances and other PFASs in food matrices, and method detection limits down to low picogram per gram food can now be reached. Worldwide interlaboratory studies also indicate that the accuracy and precision of analytical methods have significantly improved over the last decade. These modern methods have been applied to quantify human dietary exposure to PFCAs and PFSAs in several European countries. Overall, the exposure to PFOS and PFOA from diet is typically a factor of 6 to 10 higher than the exposure from other known exposure pathways for the general adult population of Western countries. Furthermore, application of toxicokinetic models indicates that present day serum concentrations of PFOS and PFOA can largely be explained by the estimated dietary exposures. Despite the recent advances in analytical techniques, the sources of food contamination are not very well characterized. It has been demonstrated that bioaccumulation and biomagnification in aquatic food webs is a primary transfer mechanism for PFOS and several long-chain perfluoroalkyl carboxylic acids to the human diet. However, more research is needed to understand the accumulation of PFASs in terrestrial food webs and the transfer of a range of PFASs from food-contact materials.