Investigating the OECD database of per- and polyfluoroalkyl substances – chemical variation and applicability of current fate models
Ioana C. Chelcea A , Lutz Ahrens B , Stefan Örn C , Daniel Mucs D and Patrik L. Andersson
A E
+ Author Affiliations
- Author Affiliations
A Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
B Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07 Uppsala, Sweden.
C Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences (SLU), SE-750 07 Uppsala, Sweden.
D RISE SP – Chemical and Pharmaceutical Safety, Forskargatan 20, 151 36 Södertälje, Sweden.
E Corresponding author. Email: patrik.andersson@umu.se
Environmental Chemistry 17(7) 498-508 https://doi.org/10.1071/EN19296
Submitted: 8 November 2019 Accepted: 3 February 2020 Published: 23 April 2020
Journal Compilation © CSIRO 2020 Open Access CC BY-NC-ND
Environmental context. A diverse range of materials contain organofluorine chemicals, some of which are hazardous and widely distributed in the environment. We investigated an inventory of over 4700 organofluorine compounds, characterised their chemical diversity and selected representatives for future testing to fill knowledge gaps about their environmental fate and effects. Fate and property models were examined and concluded to be valid for only a fraction of studied organofluorines.
Abstract. Many per- and polyfluoroalkyl substances (PFASs) have been identified in the environment, and some have been shown to be extremely persistent and even toxic, thus raising concerns about their effects on human health and the environment. Despite this, little is known about most PFASs. In this study, the comprehensive database of over 4700 PFAS entries recently compiled by the OECD was curated and the chemical variation was analysed in detail. The analysis revealed 3363 individual PFASs with a huge variation in chemical functionalities and a wide range of mixtures and polymers. A hierarchical clustering methodology was employed on the curated database, which resulted in 12 groups, where only half were populated by well-studied compounds thus indicating the large knowledge gaps. We selected both a theoretical and a procurable training set that covered a substantial part of the chemical domain based on these clusters. Several computational models to predict physicochemical and environmental fate related properties were assessed, which indicated their lack of applicability for PFASs and the urgent need for experimental data for training and validating these models. Our findings indicate reasonable predictions of the octanol-water partition coefficient for a small chemical domain of PFASs but large data gaps and uncertainties for water solubility, bioconcentration factor, and acid dissociation factor predictions. Improved computational tools are necessary for assessing risks of PFASs and for including suggested training set compounds in future testing of both physicochemical and effect-related data. This should provide a solid basis for better chemical understanding and future model development purposes.
References
Agency for Toxic Substances and Disease Registry (ATSDR) (2018). ATSDR – Toxicological Profile: Perfluoroalkyls. Available at https://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=1117&tid=237 [verified 19 March 2019]Ahrens L, Bundschuh M (2014). Fate and effects of poly- and perfluoroalkyl substances in the aquatic environment: A review. Environmental Toxicology and Chemistry 33, 1921–1929.
| Fate and effects of poly- and perfluoroalkyl substances in the aquatic environment: A reviewCrossref | GoogleScholarGoogle Scholar | 24924660PubMed |
Ahrens L, Shoeib M, Harner T, Lee SC, Guo R, Reiner EJ (2011). Wastewater Treatment Plant and Landfills as Sources of Polyfluoroalkyl Compounds to the Atmosphere. Environmental Science & Technology 45, 8098–8105.
| Wastewater Treatment Plant and Landfills as Sources of Polyfluoroalkyl Compounds to the AtmosphereCrossref | GoogleScholarGoogle Scholar |
Arp HPH, Niederer C, Goss K-U (2006). Predicting the partitioning behavior of various highly fluorinated compounds. Environmental Science & Technology 40, 7298–7304.
| Predicting the partitioning behavior of various highly fluorinated compoundsCrossref | GoogleScholarGoogle Scholar |
Balaban AT (1979). Chemical graphs. Theoretica Chimica Acta 53, 355–375.
| Chemical graphsCrossref | GoogleScholarGoogle Scholar |
Blaine AC, Rich CD, Sedlacko EM, Hundal LS, Kumar K, Lau C, Mills MA, Harris KM, Higgins CP (2014). Perfluoroalkyl Acid Distribution in Various Plant Compartments of Edible Crops Grown in Biosolids-Amended soils. Environmental Science & Technology 48, 7858–7865.
| Perfluoroalkyl Acid Distribution in Various Plant Compartments of Edible Crops Grown in Biosolids-Amended soilsCrossref | GoogleScholarGoogle Scholar |
Brown TN, Wania F (2008). Screening Chemicals for the Potential to be Persistent Organic Pollutants: A Case Study of Arctic Contaminants. Environmental Science & Technology 42, 5202–5209.
| Screening Chemicals for the Potential to be Persistent Organic Pollutants: A Case Study of Arctic ContaminantsCrossref | GoogleScholarGoogle Scholar |
Buck RC, Franklin J, Berger U, Conder JM, Cousins IT, de Voogt P, Jensen AA, Kannan K, Mabury SA, van Leeuwen SP (2011). Perfluoroalkyl and polyfluoroalkyl substances in the environment: Terminology, classification, and origins. Integrated Environmental Assessment and Management 7, 513–541.
| Perfluoroalkyl and polyfluoroalkyl substances in the environment: Terminology, classification, and originsCrossref | GoogleScholarGoogle Scholar | 21793199PubMed |
Burns DC, Ellis DA, Li H, McMurdo CJ, Webster E (2008). Experimental pKa Determination for Perfluorooctanoic Acid (PFOA) and the Potential Impact of pKa Concentration Dependence on Laboratory-Measured Partitioning Phenomena and Environmental Modeling. Environmental Science & Technology 42, 9283–9288.
| Experimental pKa Determination for Perfluorooctanoic Acid (PFOA) and the Potential Impact of pKa Concentration Dependence on Laboratory-Measured Partitioning Phenomena and Environmental ModelingCrossref | GoogleScholarGoogle Scholar |
Caliński T, Harabasz J (1974). A dendrite method for cluster analysis. Communications in Statistics 3, 1–27.
| A dendrite method for cluster analysisCrossref | GoogleScholarGoogle Scholar |
Campos Pereira H, Ullberg M, Kleja DB, Gustafsson JP, Ahrens L (2018). Sorption of perfluoroalkyl substances (PFASs) to an organic soil horizon – Effect of cation composition and pH. Chemosphere 207, 183–191.
| Sorption of perfluoroalkyl substances (PFASs) to an organic soil horizon – Effect of cation composition and pHCrossref | GoogleScholarGoogle Scholar | 29793030PubMed |
Carmosini N, Lee LS (2008). Partitioning of fluorotelomer alcohols to octanol and different sources of dissolved organic carbon. Environmental Science & Technology 42, 6559–6565.
| Partitioning of fluorotelomer alcohols to octanol and different sources of dissolved organic carbonCrossref | GoogleScholarGoogle Scholar |
CAS (2019). SciFinder. Available at https://scifinder.cas.org/scifinder/login?TYPE=33554433&REALMOID=06-b7b15cf0-642b-1005-963a-830c809fff21&GUID=&SMAUTHREASON=0&METHOD=GET&SMAGENTNAME=-SM-8iKaCGmTCGHP7yOOI24GDUsJNzy%2bOcz79s1IdZR3o%2fpMdGZxHUbYH371HFTEMp2Z&TARGET=-SM-http%3a%2f%2fscifinder%2ecas%2eorg%3a443%2fscifinder%2f [verified 19 March 2019].
ChemAxon (2018). Applicability Domain assessment-pka, logD: Support Portal. Available at https://chemaxon.freshdesk.com/support/solutions/articles/43000569185-applicability-domain-assessment-pka-logd [verified 2 April 2020].
ChemAxon (2019a). Software solutions and services for chemistry & biology. Available at https://chemaxon.com/ [verified 14 January 2019].
ChemAxon (2019b). Jchem for Office. Available at https://chemaxon.com/products/jchem-for-office [verified 29 October 2019].
Chemical Computing Group (2019). Molecular Operating Environment (MOE). Available at https://www.chemcomp.com/Products.htm [verified 19 March 2019].
ChemSpider 2018. ChemSpider. Available at http://www.chemspider.com/ [verified 19 March 2019].
Dalahmeh S, Tirgani S, Komakech AJ, Niwagaba CB, Ahrens L (2018). Per- and polyfluoroalkyl substances (PFASs) in water, soil and plants in wetlands and agricultural areas in Kampala, Uganda. The Science of the Total Environment 631–632, 660–667.
| Per- and polyfluoroalkyl substances (PFASs) in water, soil and plants in wetlands and agricultural areas in Kampala, UgandaCrossref | GoogleScholarGoogle Scholar | 29539594PubMed |
de Voogt P, Zurano L, Serne P, Haftka J (2012). Experimental hydrophobicity parameters of perfluorinated alkylated substances from reversed-phase high-performance liquid chromatography. Environmental Chemistry 9, 564–570.
| Experimental hydrophobicity parameters of perfluorinated alkylated substances from reversed-phase high-performance liquid chromatographyCrossref | GoogleScholarGoogle Scholar |
Ding G, Peijnenburg WJGM (2013). Physicochemical Properties and Aquatic Toxicity of Poly- and Perfluorinated Compounds. Critical Reviews in Environmental Science and Technology 43, 598–678.
| Physicochemical Properties and Aquatic Toxicity of Poly- and Perfluorinated CompoundsCrossref | GoogleScholarGoogle Scholar |
Downs GM, Barnard JM (2002). Clustering methods and their uses in computational chemistry. Reviews in Computational Chemistry 18, 1–40.
| Clustering methods and their uses in computational chemistryCrossref | GoogleScholarGoogle Scholar |
Dürig W, Tröger R, Andersson PL, Rybacka A, Fischer S, Wiberg K, Ahrens L (2019). Development of a suspect screening prioritization tool for organic compounds in water and biota. Chemosphere 222, 904–912.
| Development of a suspect screening prioritization tool for organic compounds in water and biotaCrossref | GoogleScholarGoogle Scholar |
Ellis DA, Martin JW, De Silva AO, Mabury SA, Hurley MD, Sulbaek Andersen MP, Wallington TJ (2004). Degradation of Fluorotelomer Alcohols: A Likely Atmospheric Source of Perfluorinated Carboxylic Acids. Environmental Science & Technology 38, 3316–3321.
| Degradation of Fluorotelomer Alcohols: A Likely Atmospheric Source of Perfluorinated Carboxylic AcidsCrossref | GoogleScholarGoogle Scholar |
EPAM Systems (2019). Indigo Toolkit. Available at http://lifescience.opensource.epam.com/indigo/ [verified 14 January 2019].
European Chemicals Agency (ECHA) (2019). Candidate list of substances of very high concern for authorisation. Available at https://echa.europa.eu/candidate-list-table [verified 28 October 2019].
European Food Safety Authority (EFSA) (2018). Contaminants update: first of two opinions on PFAS in food. Available at https://www.efsa.europa.eu/en/press/news/181213 [verified 25 April 2019].
Fourches D, Muratov E, Tropsha A (2010). Trust, but verify: On the importance of chemical structure curation in cheminformatics and QSAR modeling research. Journal of Chemical Information and Modeling 50, 1189–1204.
| Trust, but verify: On the importance of chemical structure curation in cheminformatics and QSAR modeling researchCrossref | GoogleScholarGoogle Scholar | 20572635PubMed |
Gewurtz SB, Backus SM, De Silva AO, Ahrens L, Armellin A, Evans M, Fraser S, Gledhill M, Guerra P, Harner T, Helm PA, Hung H, Khera N, Kim MG, King M, Lee SC, Letcher RJ, Martin P, Marvin C, McGoldrick DJ, Myers AL, Pelletier M, Pomeroy J, Reiner EJ, Rondeau M, Sauve M-C, Sekela M, Shoeib M, Smith DW, Smyth SA, Struger J, Spry D, Syrgiannis J, Waltho J (2013). Perfluoroalkyl acids in the Canadian environment: Multi-media assessment of current status and trends. Environment International 59, 183–200.
| Perfluoroalkyl acids in the Canadian environment: Multi-media assessment of current status and trendsCrossref | GoogleScholarGoogle Scholar | 23831544PubMed |
Giesy JP, Naile JE, Khim JS, Jones PD, Newsted JL (2010). Aquatic toxicology of perfluorinated chemicals. Reviews of Environmental Contamination and Toxicology 202, 1–52.
| Aquatic toxicology of perfluorinated chemicalsCrossref | GoogleScholarGoogle Scholar | 19898760PubMed |
Gobelius L, Lewis J, Ahrens L (2017). Plant Uptake of Per- and Polyfluoroalkyl Substances at a Contaminated Fire Training Facility to Evaluate the Phytoremediation Potential of Various Plant Species. Environmental Science & Technology 51, 12602–12610.
| Plant Uptake of Per- and Polyfluoroalkyl Substances at a Contaminated Fire Training Facility to Evaluate the Phytoremediation Potential of Various Plant SpeciesCrossref | GoogleScholarGoogle Scholar |
Gobelius L, Hedlund J, Dürig W, Tröger R, Lilja K, Wiberg K, Ahrens L (2018). Per- and Polyfluoroalkyl Substances in Swedish Groundwater and Surface Water: Implications for Environmental Quality Standards and Drinking Water Guidelines. Environmental Science & Technology 52, 4340–4349.
| Per- and Polyfluoroalkyl Substances in Swedish Groundwater and Surface Water: Implications for Environmental Quality Standards and Drinking Water GuidelinesCrossref | GoogleScholarGoogle Scholar |
Gomis MI, Wang Z, Scheringer M, Cousins IT (2015). A modeling assessment of the physicochemical properties and environmental fate of emerging and novel per- and polyfluoroalkyl substances. The Science of the Total Environment 505, 981–991.
| A modeling assessment of the physicochemical properties and environmental fate of emerging and novel per- and polyfluoroalkyl substancesCrossref | GoogleScholarGoogle Scholar | 25461098PubMed |
Hall LH, Kier LB (1991). The molecular connectivity chi indexes and kappa shape indexes in structure-property modeling. In ‘Reviews in computational chemistry’. (Eds KB Lipkowitz, DB Boyd) pp. 367–422. (John Wiley & Sons, Ltd: Hoboken, NJ)
Higgins CP, Luthy RG (2006). Sorption of Perfluorinated Surfactants on Sediments. Environmental Science & Technology 40, 7251–7256.
| Sorption of Perfluorinated Surfactants on SedimentsCrossref | GoogleScholarGoogle Scholar |
Inoue Y, Hashizume N, Yakata N, Murakami H, Suzuki Y, Kikushima E, Otsuka M (2012). Unique Physicochemical Properties of Perfluorinated Compounds and Their Bioconcentration in Common Carp Cyprinus carpio L. Archives of Environmental Contamination and Toxicology 62, 672–680.
| Unique Physicochemical Properties of Perfluorinated Compounds and Their Bioconcentration in Common Carp Cyprinus carpio LCrossref | GoogleScholarGoogle Scholar | 22127646PubMed |
Jahnke A, Ahrens L, Ebinghaus R, Temme C (2007). Urban versus Remote Air Concentrations of Fluorotelomer Alcohols and Other Polyfluorinated Alkyl Substances in Germany. Environmental Science & Technology 41, 745–752.
| Urban versus Remote Air Concentrations of Fluorotelomer Alcohols and Other Polyfluorinated Alkyl Substances in GermanyCrossref | GoogleScholarGoogle Scholar |
Jones PD, Hu W, Coen WD, Newsted JL, Giesy JP (2003). Binding of perfluorinated fatty acids to serum proteins. Environmental Toxicology and Chemistry 22, 2639–2649.
| Binding of perfluorinated fatty acids to serum proteinsCrossref | GoogleScholarGoogle Scholar | 14587903PubMed |
Jonsson P, Wohlin C (2004). An evaluation of k-nearest neighbour imputation using Likert data. In ‘10th International symposium on software metrics, 2004. Proceedings’. pp. 108–118. (IEEE: Chicago, IL)
KEMI (2019). Swedish Chemicals Agency. Available at https://www.kemi.se/ [verified 15 January 2019].
Kjølholt J, Jensen AA, Warming M (2015). Short-chain polyfluoroalkyl substances. A literature review of information on human health effects and environmental fate and effect aspects of short-chain PFAS (No. Environmental project No. 1707, 2015). The Danish Environmental Protection Agency.
KNIME (2019a). End to end data science. Available at https://www.knime.com/ [verified 14 January 2019].
KNIME (2019b). OpenBabel. https://nodepit.com/node/org.knime.ext.chem.openbabel.BabelFactory [verified 19 March 2019].
KNIME (2019c). GroupBy. Available at https://nodepit.com/node/org.knime.base.node.preproc.groupby.GroupByNodeFactory [verified 19 March 2019].
Lee H, D’eon J, Mabury SA (2010). Biodegradation of Polyfluoroalkyl Phosphates as a Source of Perfluorinated Acids to the Environment. Environmental Science & Technology 44, 3305–3310.
| Biodegradation of Polyfluoroalkyl Phosphates as a Source of Perfluorinated Acids to the EnvironmentCrossref | GoogleScholarGoogle Scholar |
Lei YD, Wania F, Mathers D, Mabury SA (2004). Determination of Vapor Pressures, Octanol−Air, and Water−Air Partition Coefficients for Polyfluorinated Sulfonamide, Sulfonamidoethanols, and Telomer Alcohols. Journal of Chemical & Engineering Data 49, 1013–1022.
| Determination of Vapor Pressures, Octanol−Air, and Water−Air Partition Coefficients for Polyfluorinated Sulfonamide, Sulfonamidoethanols, and Telomer AlcoholsCrossref | GoogleScholarGoogle Scholar |
Liu J, Lee LS (2007). Effect of Fluorotelomer Alcohol Chain Length on Aqueous Solubility and Sorption by Soils. Environmental Science & Technology 41, 5357–5362.
| Effect of Fluorotelomer Alcohol Chain Length on Aqueous Solubility and Sorption by SoilsCrossref | GoogleScholarGoogle Scholar |
Liu J, Mejia Avendaño S (2013). Microbial degradation of polyfluoroalkyl chemicals in the environment: A review. Environment International 61, 98–114.
| Microbial degradation of polyfluoroalkyl chemicals in the environment: A reviewCrossref | GoogleScholarGoogle Scholar | 24126208PubMed |
López-Fontán JL, Sarmiento F, Schulz PC (2005). The aggregation of sodium perfluorooctanoate in water. Colloid & Polymer Science 283, 862–871.
| The aggregation of sodium perfluorooctanoate in waterCrossref | GoogleScholarGoogle Scholar |
Martin JW, Mabury SA, Solomon KR, Muir DCG (2003). Bioconcentration and tissue distribution of perfluorinated acids in rainbow trout (Oncorhynchus mykiss). Environmental Toxicology and Chemistry 22, 196–204.
| Bioconcentration and tissue distribution of perfluorinated acids in rainbow trout (Oncorhynchus mykiss)Crossref | GoogleScholarGoogle Scholar | 12503765PubMed |
Mejia-Avendaño S, Munoz G, Vo Duy S, Desrosiers M, Benoît P, Sauvé S, Liu J (2017). Novel Fluoroalkylated Surfactants in Soils Following Firefighting Foam Deployment During the Lac-Mégantic Railway Accident. Environmental Science & Technology 51, 8313–8323.
| Novel Fluoroalkylated Surfactants in Soils Following Firefighting Foam Deployment During the Lac-Mégantic Railway AccidentCrossref | GoogleScholarGoogle Scholar |
Moroi Y, Yano H, Shibata O, Yonemitsu T (2001). Determination of Acidity Constants of Perfluoroalkanoic Acids. Bulletin of the Chemical Society of Japan 74, 667–672.
| Determination of Acidity Constants of Perfluoroalkanoic AcidsCrossref | GoogleScholarGoogle Scholar |
Munoz G, Labadie P, Botta F, Lestremau F, Lopez B, Geneste E, Pardon P, Dévier M-H, Budzinski H (2017). Occurrence survey and spatial distribution of perfluoroalkyl and polyfluoroalkyl surfactants in groundwater, surface water, and sediments from tropical environments. The Science of the Total Environment 607–608, 243–252.
| Occurrence survey and spatial distribution of perfluoroalkyl and polyfluoroalkyl surfactants in groundwater, surface water, and sediments from tropical environmentsCrossref | GoogleScholarGoogle Scholar | 28692894PubMed |
National Cancer Institute (2019). NCI/CADD Chemical Identifier Resolver. Available at https://cactus.nci.nih.gov/chemical/structure [verified 14 January 2019].
National Center for Biotechnology Information (2019). PubChem. Available at https://pubchem.ncbi.nlm.nih.gov/ [verified 26 April 2019].
OECD (2018a). Towards a new comprehensive global database of per- and polyfluoroalkyl substances (PFASs). Organisation for Economic Co-operation and Development (OECD).
OECD (2018b). Towards a new comprehensive global database of per- and polyfluoroalkyl substances (PFASs): summary report on updating the OECD 2007 list of per- and polyfluoroalkyl substances (PFASs) (No. JT03431231), series on risk management no. 39. Organisation for Economic Co-operation and Development (OECD).
Pan Y, Zhang H, Cui Q, Sheng N, Yeung LWY, Sun Y, Guo Y, Dai J (2018). Worldwide Distribution of Novel Perfluoroether Carboxylic and Sulfonic Acids in Surface Water. Environmental Science & Technology 52, 7621–7629.
| Worldwide Distribution of Novel Perfluoroether Carboxylic and Sulfonic Acids in Surface WaterCrossref | GoogleScholarGoogle Scholar |
Patlewicz G, Richard AM, Williams AJ, Grulke CM, Sams R, Lambert J, Noyes PD, DeVito MJ, Hines RN, Strynar M, Guiseppi-Elie A, Thomas RS (2019). A Chemical Category-Based Prioritization Approach for Selecting 75 Per- and Polyfluoroalkyl Substances (PFAS) for Tiered Toxicity and Toxicokinetic Testing. Environmental Health Perspectives 127, 014501
| A Chemical Category-Based Prioritization Approach for Selecting 75 Per- and Polyfluoroalkyl Substances (PFAS) for Tiered Toxicity and Toxicokinetic TestingCrossref | GoogleScholarGoogle Scholar | 30632786PubMed |
Paul AG, Jones KC, Sweetman AJ (2009). A First Global Production, Emission, And Environmental Inventory For Perfluorooctane Sulfonate. Environmental Science & Technology 43, 386–392.
| A First Global Production, Emission, And Environmental Inventory For Perfluorooctane SulfonateCrossref | GoogleScholarGoogle Scholar |
Pizzo F, Lombardo A, Brandt M, Manganaro A, Benfenati E (2016). A new integrated in silico strategy for the assessment and prioritization of persistence of chemicals under REACH. Environment International 88, 250–260.
| A new integrated in silico strategy for the assessment and prioritization of persistence of chemicals under REACHCrossref | GoogleScholarGoogle Scholar | 26773396PubMed |
Plassmann MM, Berger U (2013). Perfluoroalkyl carboxylic acids with up to 22 carbon atoms in snow and soil samples from a ski area. Chemosphere 91, 832–837.
| Perfluoroalkyl carboxylic acids with up to 22 carbon atoms in snow and soil samples from a ski areaCrossref | GoogleScholarGoogle Scholar | 23466094PubMed |
Posner S, Roos S, Brunn Poulsen P, Jörundsdottir HO, Gunnlaugsdottir H, Trier X, Astrup Jensen A, Katsogiannis AA, Herzke D, Bonefeld-Jörgensen EC, Jönsson C, Pedersen GA, Ghisari M, Jensen S (2013). Per- and polyfluorinated substances in the Nordic Countries: Use, occurence and toxicology (No. TemaNord 2013: 542). Nordic Council of Ministers.
QSAR Toolbox Coordination Group (2019). QSAR Toolbox. Available at https://qsartoolbox.org/ [verified 11 October 2019].
Rännar S, Andersson PL (2010). A Novel Approach Using Hierarchical Clustering To Select Industrial Chemicals for Environmental Impact Assessment. Journal of Chemical Information and Modeling 50, 30–36.
| A Novel Approach Using Hierarchical Clustering To Select Industrial Chemicals for Environmental Impact AssessmentCrossref | GoogleScholarGoogle Scholar | 20050708PubMed |
Rayne S, Forest K (2009). Perfluoroalkyl sulfonic and carboxylic acids: A critical review of physicochemical properties, levels and patterns in waters and wastewaters, and treatment methods. Journal of Environmental Science and Health. Part A, Toxic/Hazardous Substances & Environmental Engineering 44, 1145–1199.
| Perfluoroalkyl sulfonic and carboxylic acids: A critical review of physicochemical properties, levels and patterns in waters and wastewaters, and treatment methodsCrossref | GoogleScholarGoogle Scholar |
Schlechtriem DC, Nendza DM, Hahn DS, Zwintscher A, Schüürmann DG, Kühne DR (2014). Contribution of non-lipid based processes to the bioaccumulation of chemicals. Report No. UBA-FB 00. 92 pp.
Stenberg M, Linusson A, Tysklind M, Andersson PL (2009). A multivariate chemical map of industrial chemicals – Assessment of various protocols for identification of chemicals of potential concern. Chemosphere 76, 878–884.
| A multivariate chemical map of industrial chemicals – Assessment of various protocols for identification of chemicals of potential concernCrossref | GoogleScholarGoogle Scholar | 19515399PubMed |
Stockholm Convention (2019). Stockholm Convention. Available at http://www.pops.int/Home/tabid/2121/Default.aspx [verified 30 January 2020].
Trier X, Lunderberg D (2015). S9 | PFASTRIER | PFAS Suspect List: fluorinated substances. https://doi.org/10.5281/zenodo.3542121
Tropsha A (2010). Best Practices for QSAR Model Development, Validation, and Exploitation. Molecular Informatics 29, 476–488.
| Best Practices for QSAR Model Development, Validation, and ExploitationCrossref | GoogleScholarGoogle Scholar | 27463326PubMed |
US EPA (2015). EPI SuiteTM - Estimation Program Interface v4.11. Available at https://www.epa.gov/tsca-screening-tools/download-epi-suitetm-estimation-program-interface-v411 [verified 14 January 2019].
VEGA HUB (2019). VEGA HUB. Available at https://www.vegahub.eu/ [verified 19 March 2019].
Vierke L, Berger U, Cousins IT (2013). Estimation of the Acid Dissociation Constant of Perfluoroalkyl Carboxylic Acids through an Experimental Investigation of their Water-to-Air Transport. Environmental Science & Technology 47, 11032–11039.
| Estimation of the Acid Dissociation Constant of Perfluoroalkyl Carboxylic Acids through an Experimental Investigation of their Water-to-Air TransportCrossref | GoogleScholarGoogle Scholar |
Wang Z, MacLeod M, Cousins IT, Scheringer M, Hungerbühler K (2011). Using COSMOtherm to predict physicochemical properties of poly- and perfluorinated alkyl substances (PFASs). Environmental Chemistry 8, 389–398.
| Using COSMOtherm to predict physicochemical properties of poly- and perfluorinated alkyl substances (PFASs)Crossref | GoogleScholarGoogle Scholar |
Wang Z, DeWitt JC, Higgins CP, Cousins IT (2017). A Never-Ending Story of Per- and Polyfluoroalkyl Substances (PFASs)?. Environmental Science & Technology 51, 2508–2518.
| A Never-Ending Story of Per- and Polyfluoroalkyl Substances (PFASs)?Crossref | GoogleScholarGoogle Scholar |
Xiang Q, Shan G, Wu W, Jin H, Zhu L (2018). Measuring log Kow coefficients of neutral species of perfluoroalkyl carboxylic acids using reversed-phase high-performance liquid chromatography. Environmental Pollution 242, 1283–1290.
| Measuring log Kow coefficients of neutral species of perfluoroalkyl carboxylic acids using reversed-phase high-performance liquid chromatographyCrossref | GoogleScholarGoogle Scholar | 30121482PubMed |
Xiao F, Golovko SA, Golovko MY (2017). Identification of novel non-ionic, cationic, zwitterionic, and anionic polyfluoroalkyl substances using UPLC–TOF–MSE high-resolution parent ion search. Analytica Chimica Acta 988, 41–49.
| Identification of novel non-ionic, cationic, zwitterionic, and anionic polyfluoroalkyl substances using UPLC–TOF–MSE high-resolution parent ion searchCrossref | GoogleScholarGoogle Scholar | 28916102PubMed |
Yim O, Ramdeen KT (2015). Hierarchical Cluster Analysis: Comparison of Three Linkage Measures and Application to Psychological Data. The Quantitative Methods for Psychology 11, 8–21.
| Hierarchical Cluster Analysis: Comparison of Three Linkage Measures and Application to Psychological DataCrossref | GoogleScholarGoogle Scholar |
