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A modeling assessment of the physicochemical properties and environmental fate of emerging and novel per- and polyfluoroalkyl substances
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).ORCID iD: 0000-0002-7035-8660
2015 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 505, 981-991 p.Article in journal (Refereed) Published
Abstract [en]

Long-chain perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonic acids (PFSAs) are persistent, bioaccumulative, and toxic contaminants that are globally present in the environment, wildlife and humans. Phase-out actions and use restrictions to reduce the environmental release of long-chain PFCAs, PFSAs and their precursors have been taken since 2000. In particular, long-chain poly- and perfluoroalkyl substances (PFASs) are being replaced with shorter-chain homologues or other fluorinated or non-fluorinated alternatives. A key question is: are these alternatives, particularly the structurally similar fluorinated alternatives, less hazardous to humans and the environment than the substances they replace? Several fluorinated alternatives including perfluoroether carboxylic acids (PFECAs) and perfluoroether sulfonic adds (PFESAs) have beet recently identified. However, the scarcity of experimental data prevents hazard and risk assessments for these substances. In this study, we use state-of-the-art in silico tools to estimate key properties of these newly identified fluorinated alternatives. [i] COSMOtherm and SPARC ate used to estimate physicochemical properties. The US EPA EPISuite software package is used to predict degradation half-lives in air, water and soil. [ii] In combination with estimated chemical properties, a fugacity-based multimedia mass-balance unit-world model the OECD Overall Persistence (Pov) and Long-Range Transport Potential (LRTP) Screening Tool is used to assess the likely environmental fate of these alternatives. Even though the fluorinated alternatives contain some structural differences, their physicochemical properties are not significantly different from those of their predecessors. Furthermore, most of the alternatives are estimated to be similarly persistent and mobile in the environment as the long-chain PFASs. The models therefore predict that the fluorinated alternatives will become globally distributed in the environment similar to their predecessors. Although such in silico methods are coupled with uncertainties, this preliminary assessment provides enough cause for concern to warrant experimental work to better determine the properties of these fluorinated alternatives.

Place, publisher, year, edition, pages
2015. Vol. 505, 981-991 p.
Keyword [en]
Hazard assessment, Environmental fate, Fluorinated alternative, In silico tool, PFOS, PFOA
National Category
Earth and Related Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-114232DOI: 10.1016/j.scitotenv.2014.10.062ISI: 000347654900096PubMedID: 25461098OAI: oai:DiVA.org:su-114232DiVA: diva2:796937
Note

AuthorCount:4;

Available from: 2015-03-20 Created: 2015-02-25 Last updated: 2017-12-04Bibliographically 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: 2017-11-29Bibliographically approved

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