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Historical human exposure to perfluoroalkyl acids in the United States and Australia reconstructed from biomonitoring data using population-based pharmacokinetic modelling
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS) and perfluorohexane sulfononic acid (PFHxS) have been found in human serum worldwide. Since the beginning of the 21st century, a downward trend in the human body burden, especially for PFOS and PFOA, has been observed while there is no clear trend in wildlife. The inconsistency between the concentration decline in human serum and in wildlife could be indicative of a historical exposure pathway for humans linked to consumer products that has been reduced or eliminated.  In this study, we investigate the past human exposure trends in two different regions, USA and Australia, by reconstructing the historical intake from cross-sectional biomonitoring data of PFOS and PFOA using a population-based pharmacokinetic model. For PFOS in the USA , the reconstructed daily intake peaked at 4.5 ng/kg-bw/day between 1988 and 1999; and in Australia it was 4.0 ng/kg-bw/day between 1984 and 1996. For PFOA in USA and Australia, the peak reconstructed daily intake was 1.1 ng/kg-bw/day in 1995 and 3.6 ng/kg-bw/day in 1992, respectively, and started to decline in 2000 and 1995, respectively. The model could not be satisfactorily fitted to the biomonitoring data for PFHxS within reasonable boundaries for its intrinsic elimination half-life, and thus reconstructing intakes of PFHxS was not possible.  Our results indicate that humans experienced similar exposure levels and trends to PFOS and PFOA in the USA and Australia.  Our findings support the hypothesis that near-field consumer product exposure pathways were likely dominant prior the phase-out in industrialized countries. The intrinsic elimination half-life, which represents elimination processes that are common for all humans, and elimination processes unique to women (i.e., menstruation, cord-blood transfer and breast feeding) were also investigated. The intrinsic elimination half-lives for PFOS and PFOA derived from model fitting for men were 4.9 and 2.4 years, respectively, for the USA, and 3.8 and 2 years respectively for Australia. The elimination half-lives in women were up to 15% lower for PFOS and up to 12% lower for PFOA. =Our results show that menstruation is a depuration pathway for PFOA for women, similarly but to a lesser extent compared to previous reports for PFOS.  However menstruation, cord-blood transfer and breast feeding together do not fully explain the apparently more rapid elimination of PFOA and PFOS by women compared to men.

Keyword [en]
PFOS, PFOA, PFHxS, Human exposure, population, Australia, USA, pharmacokinetic model
National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-141081OAI: oai:DiVA.org:su-141081DiVA: diva2:1085752
Available from: 2017-03-30 Created: 2017-03-30 Last updated: 2017-03-31Bibliographically approved
In thesis
1. From emission sources to human tissues: modelling the exposure to per- and polyfluoroalkyl substances
Open this publication in new window or tab >>From emission sources to human tissues: modelling the exposure to per- and polyfluoroalkyl substances
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Produced since the 1950’s, per- and polyfluoroalkyl (PFASs) substances are persistent, bioaccumulative and toxic compounds that are ubiquitous in the environment. Being proteinophilic with a tendency to partition to protein-rich tissues, PFASs have been found in human serum worldwide and in wildlife with a predominance of long-chain perfluoroalkyl carboxilic acids (C7-C14 PFCAs) and perfluoroalkyl sulfonic acids (C6-C9 PFSAs). Due to rising concern regarding their hazardous properties, several regulatory actions and voluntary industrial phase-outs have been conducted since early 2000s, shifting the production towards other fluorinated alternatives. This thesis explores the human exposure to long-chain PFASs and their alternatives using different modelling methods and aims to 1) link comprehensively the past and current industrial production with the human body burden and 2) assess the potential hazardous properties of legacy PFASs replacements, on which information is very limited. In Paper I, the historical daily intakes in Australia and USA were reconstructed from cross-sectional biomonitoring data of perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) andperfluorohexanesulfonic acid (PFHxS). The results indicate that humans experienced similar exposure levels and trends to PFOS and PFOA in both regions, suggesting a common historical exposure possibly dominated by consumer products. The model could not be fitted to PFHxS concentration in serum. In Paper II, the relative contribution of indirect (i.e. subsequent metabolism of precursors into legacy PFASs) versus direct exposure was evaluated on occupationally exposed ski wax technicians. The indirect exposure contributed by up to 45% to the total body burden of PFOA. In Paper III, the physicochemical properties, the persistence and the long-range transport of fluorinated alternatives were predicted using different in silico tools. Findings suggest that fluorinated alternatives are likely similar to their predecessors, in terms of physicochemical properties and environmental fate. Finally, Paper IV compares the toxic potency of PFOS, PFOA and their alternatives as a function of external and internal dose. While alternatives are less potent than their predecessors when considering the administered dose, they become similarly potent when the assessment is based on levels in the target tissue. This thesis demonstrates that pharmacokinetic models are effective tools to comprehensively reconnect the body burden to the exposure of phased-out chemicals. More importantly, the studies on fluorinated alternatives raise the necessity to provide more information and data on the potential hazard of these novel and emerging products.

Place, publisher, year, edition, pages
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University, 2017. 42 p.
Keyword
PFAAs, PFOA, PFOS, fluorinated alternatives, human exposure, pharmacokinetic modelling, hazard assessment
National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
urn:nbn:se:su:diva-141034 (URN)978-91-7649-712-8 (ISBN)978-91-7649-713-5 (ISBN)
Public defence
2017-05-12, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.

Available from: 2017-04-19 Created: 2017-03-29 Last updated: 2017-04-03Bibliographically approved

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