Overlooked Highly Volatile Persistent Organic Pollutants in the Atmosphere

InfoMetricsFiguresRef. Environmental Science & TechnologyASAPArticle This publication is free to access through this site. Learn More CiteCitationCitation and abstractCitation and referencesMore citation options ShareShare onFacebookX (Twitter)WeChatLinkedInRedditEmailJump toExpandCollapse ViewpointJuly 29, 2024Overlooked Highly Volatile Persistent Organic Pollutants in the AtmosphereClick to copy article linkArticle link copied!Shizhen ZhaoShizhen ZhaoState Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, ChinaGuangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou 510640, ChinaMore by Shizhen Zhaohttps://orcid.org/0000-0003-1534-9283Kevin C. JonesKevin C. JonesLancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, U.K.More by Kevin C. Joneshttps://orcid.org/0000-0001-7108-9776Roland WeberRoland WeberPOPs Environmental Consulting, 73527 Schwäbisch Gmünd, GermanyMore by Roland Weberhttps://orcid.org/0000-0002-3626-0707Yuwei XiaoYuwei XiaoState Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, ChinaUniversity of Chinese Academy of Sciences, Beijing 100049, ChinaMore by Yuwei XiaoGan Zhang*Gan ZhangState Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, ChinaGuangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou 510640, China*[email protected]More by Gan ZhangView Biographyhttps://orcid.org/0000-0002-9010-8140Open PDFEnvironmental Science & TechnologyCite this: Environ. Sci. Technol. 2024, XXXX, XXX, XXX-XXXClick to copy citationCitation copied!https://pubs.acs.org/doi/10.1021/acs.est.4c02731https://doi.org/10.1021/acs.est.4c02731Published July 29, 2024 Publication History Received 18 March 2024Published online 29 July 2024article-commentary© 2024 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissionsThis publication is licensed for personal use by The American Chemical Society. ACS Publications© 2024 American Chemical SocietySubjectswhat are subjectsArticle subjects are automatically applied from the ACS Subject Taxonomy and describe the scientific concepts and themes of the article.Atmospheric chemistryComputer simulationsOrganic compoundsThermodynamic propertiesVolatile organic compoundsThe atmosphere plays an important role in the cycling of persistent organic pollutants (POPs) in the Earth surface system. It is also an ideal monitoring matrix as it provides essential information about the distribution, sources, and transmission of POPs, to support the risk assessments and the evaluation of the effectiveness of the management policies for POPs. While many POPs in the atmosphere are considered "semivolatile", implying dynamic partitioning between the gas and particle phases and having the tendency for temperature-driven air–surface exchanges, some emerging organic pollutants or POPs that are newly listed in the Stockholm Convention that occur in the atmosphere either are highly volatile (cf. VOCs) or have low or extremely low volatility. Currently, highly volatile POPs (HV-POPs), which predominantly occur in the gas phase, have not been studied well in POP research.In atmospheric chemistry, volatile components are classified on a continuum from extremely low-volatility organic compounds (ELVOCs), low-volatility organic compounds (LVOCs) to semivolatile organic compounds (SVOCs), intermediate-volatility organic compounds (IVOCs), and volatile organic compounds (VOCs). (1) For POPs, their volatilities actually cover a wide range from ELVOCs to VOCs, currently without finer operational boundaries being adopted by the scientific community. This vague boundary impedes a thorough comprehension of the atmospheric fate of POPs and their associated health risks. It also results in a disconnect between POPs and secondary organic aerosols (SOA), to which the hydrophilic oxidized products of POPs could contribute. Therefore, we propose to incorporate HV-POPs into the realm of atmospheric chemistry, with a specific subdivision to delineate their volatility.In Figure 1, a chromatogram map shows chromatographic peaks of several POPs overlaid with homologues of normal alkanes, based on real laboratory data. For instance, the effective saturation concentration (C*) within the range of IVOCs is determined to be from 300 to 3 × 106 μg/m3, with a saturation vapor pressure at 298 K ranging from 0.01 to 10 Pa, corresponding to the saturation vapor pressures of C12–C20 n-alkanes. The POPs that fall within the volatility range from IVOCs to VOCs are defined as HV-POPs. This includes hexachlorobutadiene (HCBD), pentachlorobenzene (PeCB), and hexachlorobenzene (HCB), along with emerging contaminants such as volatile methylsiloxanes (VMSs) and fluorotelomer alcohols (FTOHs). In addition to the identified compounds in Figure 1, ultra-short-chain per- and polyfluoroalkyl substances (PFASs), such as trifluoroacetic acid (TFA) and its ester derivatives, and very short-chain chlorinated paraffins (vSCCPs, C6–C9), could also be HV-POPs. It is noteworthy that many "traditional" legacy POPs such as α-hexachlorocyclohexane (α-HCH) and "light" congeners of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polychlorinated naphthalenes (PCNs) are also found in the band of HV-POPs. Compared to that on legacy POPs, research on HV-POPs in the atmosphere is currently scarce and dispersed.Figure 1Figure 1. Chromatogram map overlaid by typical persistent organic pollutants (POPs) and C6–C30 n-alkanes using a CP-Sil 8 CB GC column (50 m × 0.25 mm × 0.12 μm).High Resolution ImageDownload MS PowerPoint SlideHV-POPs can be sampled from air using active and passive methodologies. The active air samplers include low- or high-volume samplers with filters and cartridges and denuder samplers. The former is easy to deploy, while the denuder sampler is more efficient at trapping the gas phase of HV-POPs, reducing sampling artifacts. The passive air sampler (PAS) is easy to prepare and deploy, requiring no electricity, making it preferable for remote regions and surveys at multiple sites. Strong absorbents such as XAD, Tenax resins, and activated carbon are usually employed to capture VOCs. The PAS using XAD sorbent-impregnated polyurethane foam (PUF) sampler (SIP-PAS) has been adapted for sampling HV-POPs. However, it is reported that there is a breakthrough of HCBD from PUF plugs, which are widely used to capture SVOC-POPs, leading to an underestimation of HCBD in Arctic air. (2) Specific quality control and quality assurance (QA/QC) practices are needed for target HV-POPs throughout the laboratory procedures to ensure reliable recoveries. Air sampling of HV-POPs is easily normalized with established standard operating protocols, making monitoring data from various laboratories more comparable.Several HV-POPs have served as vital raw materials and solvents for the chemical industry, with widespread applications, large production, and significant volumes of disposed waste. We give examples in China. First, chlorobenzenes (CBs) are used extensively in pesticide and dye manufacturing and in the electronics industry as raw materials and additives. More than half of the global production and consumption of CBs occurs in China. Second, HCBD is used as a chemical solvent, a heat transfer agent, and a hydraulic system liquid and can be unintentionally emitted from chlorinated solvent production (e.g., chloromethane and perchloroethylene). Nearly 1000 t of HCBD emissions was estimated for 2016 in China. Third, methylsiloxanes, essential in organic synthesis, are predominantly manufactured in China, with a global annual production of 8–10 million t. (3)Because of their high volatility and large production and consumption volumes, HV-POPs can occur in the atmosphere at high levels relative to other POPs and are likely to be transported to remote places such as the Arctic. Our recent analysis of HV-POPs in urban air samples from Guangzhou, China, revealed concentrations of HCBD and VMSs in the range of nanograms to micrograms per cubic meter. This is similar to or higher than the values of polycyclic aromatic hydrocarbons (PAHs), a well-known group of air toxics. HCBD concentrations in areas surrounding perchloroethylene production could range from micrograms to milligrams per cubic meter, exceeding its occupational exposure limit of 210 μg/m3. (4) Abundant evidence shows that HCBD, HCB, and α-HCH are widespread in the Arctic.Their high volatility enables HV-POPs to reside in the atmosphere for a long time, favoring their reactions with free radicals. This can lead to their mineralization and transformation into hydrophilic oxidized products, which can be removed by atmospheric deposition. For example, there is potential for HCB to be transformed into more water-soluble pentachlorophenol (PCP) and for FTOH to perfluorooctanoic acid (PFOA). For VMSs at higher concentrations in indoor air, the continuously produced silanol products may participate in the formation of SOA. Modelers may treat HV-POPs as "long-life" gases, disregarding their exchange in multiple media. Observation-based inverse models can be applied to estimate their primary emissions, thereby supporting chemicals management and policy making.Inhalation may be the key pathway for HV-POPs to enter wildlife and human food chains. Most HV-POPs exhibit a low KOW (<105) and a high KOA (>106), making them prone to bioaccumulate in respiring animals, including humans. (5) HCBD can form toxic metabolites in the human body, and the U.S. Environmental Protection Agency classifies it as a potential human carcinogen (Group C). PeCB, HCB, PFASs and their precursors, are widely detected in human breast milk and serum and are capable of accumulating in the human placenta.Future research may benefit from integrating the concept of HV-POPs into the regulatory frameworks of the Stockholm Convention. Robust global collaboration is essential for standardized monitoring, observation-based inverse modeling, mitigation strategies in the technosphere, and direct and indirect atmospheric transport studies at regional and global scales.Author InformationClick to copy section linkSection link copied!Corresponding AuthorGan Zhang - State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou 510640, China; https://orcid.org/0000-0002-9010-8140; Email: [email protected]AuthorsShizhen Zhao - State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou 510640, China; https://orcid.org/0000-0003-1534-9283Kevin C. Jones - Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, U.K.; https://orcid.org/0000-0001-7108-9776Roland Weber - POPs Environmental Consulting, 73527 Schwäbisch Gmünd, Germany; https://orcid.org/0000-0002-3626-0707Yuwei Xiao - State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100049, ChinaNotesThe authors declare no competing financial interest.BiographyClick to copy section linkSection link copied!Gan ZhangHigh Resolution ImageDownload MS PowerPoint SlideGan Zhang is a distinguished research professor in organic geochemistry. He obtained his B.S. (1983) and M.S. (1987) from Nanjing University and his Ph.D. (1995) from the University of Chinese Academy of Sciences. Since 1999, he has been a full professor at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. He has served as the director of the State Key Laboratory of Organic Geochemistry (SKLOG) since 2016. His research encompasses a wide spectrum of topics, including the environmental fate of persistent organic pollutants (POPs), carbon dynamics in the earth surface systems, natural abundance compound-specific radiocarbon analysis (CSRA), and astro-organic geochemistry. He has published more than 500 research papers in peer-reviewed journals, with citations of >26 000 times and an h-index of 83 (Web of Science).AcknowledgmentsClick to copy section linkSection link copied!This work is supported by the National Natural Science Foundation of China (42107120), the Guangdong Major Project of Basic and Applied Basic Research (2023B0303000007), the Alliance of International Science Organizations (ANSO-CR-KP-2021-05), the Guangdong Basic and Applied Basic Research Foundation (2023B1515020067), and the Youth Innovation Promotion Association of CAS (2022359).ReferencesClick to copy section linkSection link copied! This article references 5 other publications. 1Chang, X.; Zhao, B.; Zheng, H.; Wang, S.; Cai, S.; Guo, F.; Gui, P.; Huang, G.; Wu, D.; Han, L.; Xing, J.; Man, H.; Hu, R.; Liang, C.; Xu, Q.; Qiu, X.; Ding, D.; Liu, K.; Han, R.; Robinson, A. L.; Donahue, N. M. Full-volatility emission framework corrects missing and underestimated secondary organic aerosol sources. One Earth 2022, 5 (4), 403– 412, DOI: 10.1016/j.oneear.2022.03.015 Google ScholarThere is no corresponding record for this reference.2Balmer, J. E.; Hung, H.; Vorkamp, K.; Letcher, R. J.; Muir, D. C. G. Hexachlorobutadiene (HCBD) contamination in the Arctic environment: A review. Emerging Contaminants 2019, 5, 116– 122, DOI: 10.1016/j.emcon.2019.03.002 Google ScholarThere is no corresponding record for this reference.3Mojsiewicz-Pieńkowska, K.; Krenczkowska, D. Evolution of consciousness of exposure to siloxanes─review of publications. Chemosphere 2018, 191, 204– 217, DOI: 10.1016/j.chemosphere.2017.10.045 Google Scholar3Evolution of consciousness of exposure to siloxanes-review of publicationsMojsiewicz-Pienkowska, Krystyna; Krenczkowska, DominikaChemosphere (2018), 191 (), 204-217CODEN: CMSHAF; ISSN:0045-6535. (Elsevier Ltd.) The purpose of this description is to review scientific literature from 1944 to 2017 as a source of information on the reasons for the increased interest in siloxanes (silicones). Not only the research area, but first, the changes in the tendency of research aims are important issues in the evaluation. On the one hand, the authors emphasize the unique properties of linear and cyclic siloxanes, providing many examples of beneficial applications, and on the other hand, there are some warnings of overcoming of the safety barrier of their presence in human environment. Analyzing the results from the SCOPUS database, it can be argued that the increased interest of scientists and government agencies particularly relates to the anal. of siloxanes in biol. and environmental samples. This is caused not only by the widespread use of various siloxanes in the pharmaceutical, medical, cosmetic and food industries, but also by the direct contact of these compds. with tissues, as well as an increased access to knowledge and modern research tools that have developed the awareness of hazards. The development of research methods enables not only const. monitoring of progressively lower siloxanes concns. in various samples, but because of the specificity of these methods, it also enables an identification of specific siloxane compds. and evaluation of their effects on humans and environment. This paper discusses the issues of the evolution of consciousness of exposure to siloxanes due to their increased synthesis and widespread use in many areas of human life, which contributes to environmental pollution. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1Oqt7zJ&md5=7edb7cbfc5be05d59e53b804ef27d2754Kong, Q.; Wang, Y.; Yang, X. A Review on Hexachloro-1,3-butadiene (HCBD): Sources, Occurrence, Toxicity and Transformation. Bull. Environ. Contam. Toxicol. 2020, 104 (1), 1– 7, DOI: 10.1007/s00128-019-02744-5 Google ScholarThere is no corresponding record for this reference.5Kelly, B. C.; Ikonomou, M. G.; Blair, J. D.; Morin, A. E.; Gobas, F. Food web-specific biomagnification of persistent organic pollutants. Science 2007, 317 (5835), 236– 239, DOI: 10.1126/science.1138275 Google Scholar5Food Web-Specific Biomagnification of Persistent Organic PollutantsKelly, Barry C.; Ikonomou, Michael G.; Blair, Joel D.; Morin, Anne E.; Gobas, Frank A. P. C.Science (Washington, DC, United States) (2007), 317 (5835), 236-239CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) Substances that accumulate to hazardous levels in living organisms pose environmental and human health risks, which governments seek to reduce or eliminate. Regulatory authorities identify bioaccumulative substances as hydrophobic, fat-sol. chems. having high octanol-water partition coeffs. (KOW) (≥100,000). Here the authors show that poorly metabolizable, moderately hydrophobic substances with a KOW between 100 and 100,000, which do not biomagnify (i.e., increase in chem. concn. in organisms with increasing trophic level) in aquatic food webs, can biomagnify to a high degree in food webs contg. air-breathing animals (including humans) because of their high octanol-air partition coeff. (KOA) and corresponding low rate of respiratory elimination to air. These low KOW-high KOA chems., representing a third of the org. chems. in com. use, constitute an unidentified class of potentially bioaccumulative substances that require regulatory assessment to prevent possible ecosystem and human health consequences. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXnsFaqtrs%253D&md5=d20310b2e8903d4b4944c54bf9479039Cited By Click to copy section linkSection link copied!This article has not yet been cited by other publications.Download PDFFiguresReferencesOpen PDF Get e-AlertsGet e-AlertsEnvironmental Science & TechnologyCite this: Environ. Sci. Technol. 2024, XXXX, XXX, XXX-XXXClick to copy citationCitation copied!https://doi.org/10.1021/acs.est.4c02731Published July 29, 2024 Publication History Received 18 March 2024Published online 29 July 2024© 2024 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissionsArticle Views-Altmetric-Citations-Learn about these metrics closeArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.Recommended Articles FiguresReferencesAbstractHigh Resolution ImageDownload MS PowerPoint SlideFigure 1Figure 1. Chromatogram map overlaid by typical persistent organic pollutants (POPs) and C6–C30 n-alkanes using a CP-Sil 8 CB GC column (50 m × 0.25 mm × 0.12 μm).High Resolution ImageDownload MS PowerPoint SlideGan ZhangHigh Resolution ImageDownload MS PowerPoint SlideGan Zhang is a distinguished research professor in organic geochemistry. He obtained his B.S. (1983) and M.S. (1987) from Nanjing University and his Ph.D. (1995) from the University of Chinese Academy of Sciences. Since 1999, he has been a full professor at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. He has served as the director of the State Key Laboratory of Organic Geochemistry (SKLOG) since 2016. His research encompasses a wide spectrum of topics, including the environmental fate of persistent organic pollutants (POPs), carbon dynamics in the earth surface systems, natural abundance compound-specific radiocarbon analysis (CSRA), and astro-organic geochemistry. He has published more than 500 research papers in peer-reviewed journals, with citations of >26 000 times and an h-index of 83 (Web of Science).References This article references 5 other publications. 1Chang, X.; Zhao, B.; Zheng, H.; Wang, S.; Cai, S.; Guo, F.; Gui, P.; Huang, G.; Wu, D.; Han, L.; Xing, J.; Man, H.; Hu, R.; Liang, C.; Xu, Q.; Qiu, X.; Ding, D.; Liu, K.; Han, R.; Robinson, A. L.; Donahue, N. M. Full-volatility emission framework corrects missing and underestimated secondary organic aerosol sources. One Earth 2022, 5 (4), 403– 412, DOI: 10.1016/j.oneear.2022.03.015 There is no corresponding record for this reference.2Balmer, J. E.; Hung, H.; Vorkamp, K.; Letcher, R. J.; Muir, D. C. G. Hexachlorobutadiene (HCBD) contamination in the Arctic environment: A review. Emerging Contaminants 2019, 5, 116– 122, DOI: 10.1016/j.emcon.2019.03.002 There is no corresponding record for this reference.3Mojsiewicz-Pieńkowska, K.; Krenczkowska, D. Evolution of consciousness of exposure to siloxanes─review of publications. Chemosphere 2018, 191, 204– 217, DOI: 10.1016/j.chemosphere.2017.10.045 3Evolution of consciousness of exposure to siloxanes-review of publicationsMojsiewicz-Pienkowska, Krystyna; Krenczkowska, DominikaChemosphere (2018), 191 (), 204-217CODEN: CMSHAF; ISSN:0045-6535. (Elsevier Ltd.) The purpose of this description is to review scientific literature from 1944 to 2017 as a source of information on the reasons for the increased interest in siloxanes (silicones). Not only the research area, but first, the changes in the tendency of research aims are important issues in the evaluation. On the one hand, the authors emphasize the unique properties of linear and cyclic siloxanes, providing many examples of beneficial applications, and on the other hand, there are some warnings of overcoming of the safety barrier of their presence in human environment. Analyzing the results from the SCOPUS database, it can be argued that the increased interest of scientists and government agencies particularly relates to the anal. of siloxanes in biol. and environmental samples. This is caused not only by the widespread use of various siloxanes in the pharmaceutical, medical, cosmetic and food industries, but also by the direct contact of these compds. with tissues, as well as an increased access to knowledge and modern research tools that have developed the awareness of hazards. The development of research methods enables not only const. monitoring of progressively lower siloxanes concns. in various samples, but because of the specificity of these methods, it also enables an identification of specific siloxane compds. and evaluation of their effects on humans and environment. This paper discusses the issues of the evolution of consciousness of exposure to siloxanes due to their increased synthesis and widespread use in many areas of human life, which contributes to environmental pollution. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1Oqt7zJ&md5=7edb7cbfc5be05d59e53b804ef27d2754Kong, Q.; Wang, Y.; Yang, X. A Review on Hexachloro-1,3-butadiene (HCBD): Sources, Occurrence, Toxicity and Transformation. Bull. Environ. Contam. Toxicol. 2020, 104 (1), 1– 7, DOI: 10.1007/s00128-019-02744-5 There is no corresponding record for this reference.5Kelly, B. C.; Ikonomou, M. G.; Blair, J. D.; Morin, A. E.; Gobas, F. Food web-specific biomagnification of persistent organic pollutants. Science 2007, 317 (5835), 236– 239, DOI: 10.1126/science.1138275 5Food Web-Specific Biomagnification of Persistent Organic PollutantsKelly, Barry C.; Ikonomou, Michael G.; Blair, Joel D.; Morin, Anne E.; Gobas, Frank A. P. C.Science (Washington, DC, United States) (2007), 317 (5835), 236-239CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science) Substances that accumulate to hazardous levels in living organisms pose environmental and human health risks, which governments seek to reduce or eliminate. Regulatory authorities identify bioaccumulative substances as hydrophobic, fat-sol. chems. having high octanol-water partition coeffs. (KOW) (≥100,000). Here the authors show that poorly metabolizable, moderately hydrophobic substances with a KOW between 100 and 100,000, which do not biomagnify (i.e., increase in chem. concn. in organisms with increasing trophic level) in aquatic food webs, can biomagnify to a high degree in food webs contg. air-breathing animals (including humans) because of their high octanol-air partition coeff. (KOA) and corresponding low rate of respiratory elimination to air. These low KOW-high KOA chems., representing a third of the org. chems. in com. use, constitute an unidentified class of potentially bioaccumulative substances that require regulatory assessment to prevent possible ecosystem and human health consequences. >> More from SciFinder ®https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXnsFaqtrs%253D&md5=d20310b2e8903d4b4944c54bf9479039