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A review of chlorinated paraffin contamination in Arctic ecosystemsKatrin Vorkampa,*, Jennifer Balmerb,1, Hayley Hungc, Robert J. Letcherd,Frank F. Rigete,faAarhus University, Department of Environmental Science, Arctic Research Centre, Roskilde, DenmarkbArctic Monitoring and Assessment Programme, Tromsø, NorwaycEnvironment and Climate Change Canada, Air Quality Processes Research Section, Toronto, CanadadEcotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University, Ottawa,CanadaeAarhus University, Department of Bioscience, Arctic Research Centre, Roskilde, DenmarkfGreenland Institute of Natural Resources, Nuuk, Greenlandarticle infoArticle history:Received 1 December 2018Received in revised form31 May 2019Accepted 2 June 2019Keywords:BioaccumulationBiomagnificationLong-range transportMCCPsPersistent organic pollutantsSCCPsabstractChlorinated paraffins (CPs) present a complex mixture of congeners which are often analysed andassessed as short-, medium- and long-chain CPs, i.e.SSCCP (C10eC13),SMCCP (C14eC17) andSLCCP(C18). Their complexity makes the chemical analysis challenging, in particular in terms of accuratequantification, but promising developments involving ultra-high resolution mass spectrometry havebeen presented lately. Most Arctic data exist for SCCPs, while LCCPs have not yet been studied in theArctic.SSCCP concentrations in Arctic air often exceeded those ofSMCCP, usually with a predominanceof the most volatile C10congeners, and of banned persistent organic pollutants (POPs), such as poly-chlorinated biphenyls (PCBs). The presence of SCCPs and MCCPs in Arctic air, as well as in the Antarcticand in the remote regions of the Tibetan plateau, provides evidence of their long-range transportincluding sufficient environmental persistence to reach the Arctic. Arctic vegetation accumulated SCCPspartly from air and partly through root uptake from soil, with consequences for the SCCP profile found inArctic plants. No results have yet been reported for CPs in terrestrial Arctic animals. Results for fresh-water sediment andfish confirmed the long-range transport of SCCPs and MCCPs and documented theirbioaccumulation. Where additional PCB data were available,SPCB was usually higher thanSSCCP infreshwaterfish. Both SCCPs and MCCPs were widely present in marine Arctic biota (e.g. mussels,fish,seabirds, seals, whales, polar bears). In mussels and Atlantic cod,SMCCP concentrations exceeded thoseofSSCCP, while this was less clear for other marine species. Marine mammals and the long-livedGreenland shark roughly hadSSCCP concentrations of 100e500 ng/g lipid weight, often dominated byC11congeners. Biomagnification appeared to be more pronounced forSSCCP than forSMCCP, but morestudies will be needed. IncreasingSSCCP concentrations were observed in Arctic air and sediment overtime, but not in beluga monitored since the 1980s. For both SCCPs and MCCPs, increasing concentrationsover time have been shown in blue mussels and Atlantic cod at some, but not all stations. Indicationsexist of local sources of SCCPs in the Arctic, including Arctic settlements and research stations. In studiesinvolving multiple locations, a general decrease of SCCP concentrations with increasing latitude or dis-tance from point sources was observed as well as relatively more MCCPs at locations closer to potentialCP sources. Monitoring of SCCPs and MCCPs has been initiated in some Arctic regions and will beimportant to assess the effect of recent regulations of SCCPs and the use of potential replacementchemicals.Copyright©2019, KeAi Communications Co., Ltd. Production and hosting by Elsevier B.V. on behalf ofKeAi Communications Co., Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).1. IntroductionChlorinated paraffins (CPs) are complex mixtures of syntheticchlorinated n-alkanes of varying chain length, degree of*Corresponding author. Frederiksborgvej 399, 4000 Roskilde, Denmark.E-mail address:kvo@envs.au.dk(K. Vorkamp).Peer review under responsibility of KeAi Communications Co., Ltd.1Present address: The Citadel, Department of Biology, Charleston, SC, USA.Contents lists available atScienceDirectEmerging Contaminantsjournal homepage:http://www.keaipublishing.com/en/journals/emerging-contaminants/https://doi.org/10.1016/j.emcon.2019.06.0012405-6650/Copyright©2019, KeAi Communications Co., Ltd. Production and hosting by Elsevier B.V. on behalf of KeAi Communications Co., Ltd. This is an open access articleunder the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Emerging Contaminants 5 (2019) 219e231
chlorination and chlorine bonding position. Short-chain chlori-nated paraffins (SCCPs), medium-chain chlorinated paraffins(MCCPs) and long-chain chlorinated paraffins (LCCPs) are definedas molecules with a chain-length of 10e13, 14e17 and18 carbonatoms, respectively. Commercial formulations can be mixtures ofthese three groups [1]. CPs can also be sub-divided by chlorinecontent, for example the commercial products CP-42 and CP-52indicate chlorine percentages of 42 and 52%, respectively [2].SCCPs are mainly used in metalworking applications and leatherprocessing, asflame retardants and in sealants, rubbers, textiles,paints and coatings [3]. MCCPs and LCCPs are used as plasticizers inflexible polyvinylchloride (PVC) and as industrial metalworkingfluids. CPs have been produced since the 1930s: Solely produced inthe USA in quantities of 20,000e35,000 tons/year until the 1970s,the production increased to about 300,000 tons/year in the USA,Japan and Europe in the 1990s and further to about one million tonsin China in 2009 [2,4e6]. The main mixtures produced were CP-42,CP-52 and CP-70, with CP-52 accounting for>80% of total SCCPproduction in China between 2008 and 2012 [7,8]. A recent emis-sion inventory estimated the CP release to the atmosphere in Chinaat about 1000e1500 tons/year of which the use as additives inmetalcuttingfluids and the production of CPs each account for400e600 tons/year [8]. As of 2015, CPs were also still produced inRussia, India, Japan and Brazil [5]. The SCCP fraction of the totalproduction of CPs has decreased since the 1970s [6].Physical-chemical properties of individual chloroalkanesdepend on their molecular structure. As a chemical group, CPshave physical-chemical properties similar to legacy persistentorganic pollutants (POPs), i.e. low water solubility, semi-volatilityand a logarithmic octanol-water partition coefficient (KOW) above3[9]. LogKOWvalues were found to increase with increasing car-bon chain length, from 3.82 to 7.75 for individual C10to C18con-geners and to 11.3 for a polychlorinated C28mixture [9]. TheInternational Agency for Research on Cancer (IARC) classified CPswith an average carbon chain length of 12 and an average chlorinecontent of approximately 60% as possibly carcinogenic to humans(class 2A) [10].SCCPs are included in several regulatory frameworks, includingthe Toxic Release Inventory of the United States EnvironmentalProtection Agency, the list of Priority Toxic Substances of the Ca-nadian Environmental Protection Act [4] and the list of Substancesof Very High Concern of the European Chemicals Agency [11]. In2012, the European Union (EU) banned the production and use ofSCCPs above a threshold of 1% by weight, except for their use asfireretardants in rubbers of conveyor belts in the mining industry andin dam sealants [12]. SCCPs are recognized as POPs by the UNECEConvention on Long-Range Transboundary Air Pollution [13]. Theywere added to Annex A (elimination) of the Stockholm Conventionon POPs in 2017, after nomination in 2006 [14]. This regulationrefers to SCCPs (C10eC13) with>48% chlorine and includes ninespecific exemptions, such as the use of SCCPs in the rubber andleather industry, as lubricant additives, in waterproofing andfireresistant paints and in metal processing [14].The POP classification according to the Stockholm Convention isbased on an evaluation of persistence, bioaccumulation, long-rangetransport and toxicity [15]. Data from the Arctic documentingpersistence, long-range transport and, depending on the studydesign, bioaccumulation, have an indicator function in these eval-uation processes. Furthermore, they contribute to elucidate theenvironmental fate of less-studied substances. The objective of thisreview was thus to present and discuss thefindings for CPs in theArctic including the information currently available on MCCPs andLCCPs. As the quantitative determination of CPs is challenging andmight hamper data comparability among studies [16], a brief dis-cussion of analytical methods is included.2. Analytical chemistryThe challenges in the analysis of CPs have been subject of severalreviews generally highlighting the critical issues of interferencesand of quantification standards that do not match the compositionof the samples [17e20]. CP quantifications have often beendescribed as semi-quantitative [19]. Six laboratories participatingin an interlaboratory comparison reportedSSCCP concentrationsbetween 8.5 and 3200 mg/l for a soil extract, leading to theconclusion that the comparability of results was at least question-able [21].The complexity of the CP mixtures has traditionally been tar-geted by gas chromatography (GC) with high resolution massspectrometry (HRMS) whose maximized specificity can reduceinterferences from other POPs or other CPs [22]. Many of thestudies addressing CPs in the Arctic used magnetic sector in-struments in electron capture negative ionization (ECNI) mode,which, however, were not widely available in environmental lab-oratories [23]. Low resolution mass spectrometry (LRMS) in-struments are more commonly available and were appliedincreasingly for CP analysis, often including attempts to counter-balance the risk of interferences due to reduced specificity byrigorous clean-up [22]. In an assessment of method limitations,Reth and Oehme [24] pinpointed specific SCCP and MCCP conge-ners that could interfere with each other. Another issue was thestrong response factor dependence on the chlorine content [25].Even small changes in the calculated chlorine content of a samplecould have a strong influence on the response factor and thecalculated concentration [16]. This leads to a lack of robustness, adrawback in the monitoring of a variety of Arctic samples. Theauthors concluded that while other quality assurance parameterslike blanks, reproducibility and precision were acceptable, accuracywas the main challenge in the LRMS approach [16].Another approach to the analysis of CPs is the dechlorinationwith subsequent carbon skeleton analysis by GC withflame ion-isation detection (FID) or LRMS [26e28]. Although the instrumentresponse does not depend on chlorination level, the degree ofchlorination will still have to be estimated for mass conversions ofthe detected alkanes to CPs. However, the method distinguishesmore clearly between SCCPs and MCCPs, based on the retentiontimes of the different alkanes [28]. Two-dimensional GCxGC withelectron capture detection (ECD) has also been applied to CPs andgiven promising results although the data processing was timeconsuming and complete separation of SCCPs and MCCPs could notbe achieved [29,30].In the last few years, the CP analysis has advanced, possiblyaccelerated by the circumstances that CPs have been addressed byseveral regulatory bodies and related monitoring programmes[14,31] and by the availability of ultra-HRMS instruments. A newtechnique using direct injections into an atmospheric pressureionization source (negative ion mode) (APCI) followed by quadru-pole time offlight (qToF)-HRMS and targeting SCCPs, MCCPs andLCCPs, has given promising results [32,33]. The APCI-qToF-HRMSapproach is combined with mathematical deconvolution algo-rithms reconstructing the CP pattern in the sample. Another HRMStechnique recently applied to CP analysis is GC-ECNI-Orbitrap-HRMS, providing high sensitivity and selectivity [34]. However,some of the quantification issues remain as long as no congener-specific standards are available. Due to the lower volatility of theLCCPs, their determination will require high temperature columnsin GC-based approaches [19].As a consequence of the challenges associated with the correctquantification of CPs in environmental samples CP concentrationsmay have a higher uncertainty than concentrations of other POPsreported from the Arctic. Furthermore, the high interlaboratoryK. Vorkamp et al. / Emerging Contaminants 5 (2019) 219e231220
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