Analysis and human levels of persistent perfluorinated chemicals
Abstract: An extensive use of perfluorinated chemicals (PFCs) in the last 50 years has resulted in a worldwide spread of these persistent chemicals. Human populations are subjected to a large number of PFCs in ways that are not yet fully explained. The aims of this thesis are to develop and assure the quality of analytical methods in order to collect information on human levels and to facilitate the assessment of human exposure of PFCs.Solid-phase extraction (SPE) methods for human blood and milk using two sorbents, octadecyl (C18) and a weak anion exchange polymer (WAX), were developed. Perfluorinated alkyl sulfonates (PFSAs) and perfluorinated alkyl carboxylic acids (PFCAs) with carbon chain lengths between four and fourteen together with perfluorooctane sulfonamide (PFOSA) could be extracted from human matrices. These extraction procedures enable selective and sensitive analysis of PFCs in human matrices using single quadrupole mass spectrometry (SQMS). The accuracy and reliability of the methods are discussed in the context of intralaboratory as well as interlaboratory quality assurance. Further improvements of the analysis are discussed including the evaluation of ultra performance liquid chromatography (UPLC).Human whole blood, plasma and serum from Sweden, Australia and the United Kingdom have been analysed. The blood matrix selection in the assessment and comparisons of human exposure to PFCs is crucial. Human plasma contains a high percentage of PFSAs and PFCAs. On the contrary, only about 20% of the total PFOSA content is present in plasma after removal of the red blood cells. Up to eleven persistent PFCs are detected in human blood, with detection levels between 0.1-0.5 ng/mL. A gender difference with higher serum levels for males is apparent. An age trend was observed for perfluorooctane sulfonate (PFOS) levels in serum from Australia. The levels found in Australian serum indicate that emissions from the PFC production facilities are of less importance for human exposure.Matched human milk and serum samples from Sweden show that milk levels of PFCs are about 1% of the maternal serum level. Up to five persistent PFCs are found in human milk from Sweden, with detection limits between 0.005-0.1 ng/mL, and the levels in Swedish pooled milk samples have remained constant between 1996 and 2004. A linear relationship between the maternal serum level and milk level was seen for PFOS and its shorter homologue perfluorohexane sulfonate (PFHxS). The daily intake of PFOS for a nursing infant in Sweden is estimated to be 121 ng/day if the maternal serum level is 20 ng/mL. Lactation is therefore a major exposure source for breast-fed infants.Monomethyl- and dimethyl-branched isomers of PFOS could be separated in human blood using high performance liquid chromatography (HPLC). Human plasma contains a smaller percentage of the linear PFOS compared to commercially available PFOS standard materials, which indicate isomer specific uptake and/or elimination. A difference in the isomer composition is also seen between the countries studied. Human blood from the UK and Australia have significantly lower amount of linear PFOS (59-60%) compared to Swedish blood (68%). This geographical variation suggests different human exposure sources and pathways.
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