Human exposure to perfluoroalkyl acids

Sammanfattning: Perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonic acids (PFSAs) are persistent organic contaminants which have been globally measured in human serum samples at low μg L-1 concentrations. One hypothesis, the so-called "indirect hypothesis", postulates that exposure to precursor compounds is responsible for the presence of PFCAs and PFSAs in human serum. The main purpose of this thesis was to test an alternative hypothesis that direct intake of PFCAs and PFSAs via the diet is the dominant ongoing pathway of exposure. Exposure modeling results in paper I and II demonstrate that dietary intake is the major exposure pathway of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), while known precursors account for only a few percent of the total exposure. To address the uncertainties related to dietary intake pathways, highly sensitive analytical methods for a range of PFCAs and PFSAs are developed, validated and applied in paper III and IV. By the development of a novel analytical technique in paper III, detection limits in the pg g-1 range are achieved for a wide range of analytes in different food categories. Analysis of a large set of food basket samples from the Swedish market in paper IV shows that the concentrations in many dietary samples are lower than those used to estimate exposure to PFOA and PFOS in paper I and II. However, an updated dietary intake estimate in paper IV supports the conclusion of paper I and II that dietary intake is the major ongoing human exposure pathway for the general population. Pharmacokinetic modeling undertaken in paper II was reevaluated in this thesis and back-calculated daily intakes from serum concentrations of PFOA and PFOS are shown to be in agreement with the estimated dietary intakes from paper IV. However, due to uncertainties and simplifying assumptions in the pharmacokinetic model, it is possible that there are additional pathways of human exposure contributing to human serum levels.