{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,19]],"date-time":"2026-10-19T23:15:37Z","timestamp":1792451737794,"version":"4.5.0"},"reference-count":63,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2021,1,6]],"date-time":"2021-01-06T00:00:00Z","timestamp":1609891200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["P30ES000002"],"award-info":[{"award-number":["P30ES000002"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJERPH"],"abstract":"<jats:p>Up to 95% of the liquid volume in an e-cigarette consists of propylene glycol. Previous research has shown that propylene glycol can generate diacetyl and formaldehyde when heated. New research shows that propylene glycol can also generate methylglyoxal, an alpha di-carbonyl compound recently shown to cause epithelial necrosis at even lower concentrations than diacetyl, the flavoring chemical associated with bronchiolitis obliterans (\u201cPopcorn Lung\u201d). We analyzed chemical emissions from 13 JUUL pod flavors. Diacetyl and methylglyoxal was detected in 100% of samples with median concentration (range) of 20 \u00b5g\/m3 (less than limit of quantification: 54 \u00b5g\/m3) and 4219 \u00b5g\/m3 (677\u201315,342 \u00b5g\/m3), respectively. We also detected acetaldehyde (median concentration: 341 \u00b5g\/m3) and propionaldehyde (median concentration: 87 \u00b5g\/m3) in all samples. The recent evidence that methylglyoxal is more cytotoxic to airway epithelial cells than diacetyl makes this an urgent public health concern. Current smokers considering e-cigarettes as a smoking cessation tool, and never users, who may be under the impression that e-cigarettes are harmless, need information on emissions and potential risks to make informed decisions.<\/jats:p>","DOI":"10.3390\/ijerph18020385","type":"journal-article","created":{"date-parts":[[2021,1,6]],"date-time":"2021-01-06T09:15:16Z","timestamp":1609924516000},"page":"385","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":40,"title":["An Unrecognized Hazard in E-Cigarette Vapor: Preliminary Quantification of Methylglyoxal Formation from Propylene Glycol in E-Cigarettes"],"prefix":"10.3390","volume":"18","author":[{"given":"Parham","family":"Azimi","sequence":"first","affiliation":[{"name":"Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zahra","family":"Keshavarz","sequence":"additional","affiliation":[{"name":"Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marianne","family":"Lahaie Luna","sequence":"additional","affiliation":[{"name":"Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA"},{"name":"Occupational &amp; Environmental Health Division, Dalla Lana School of Public Health, University of Toronto, Toronto, ON M5T 3M7, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7098-0954","authenticated-orcid":false,"given":"Jose Guillermo","family":"Cedeno Laurent","sequence":"additional","affiliation":[{"name":"Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jose","family":"Vallarino","sequence":"additional","affiliation":[{"name":"Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0301-0242","authenticated-orcid":false,"given":"David C.","family":"Christiani","sequence":"additional","affiliation":[{"name":"Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joseph G.","family":"Allen","sequence":"additional","affiliation":[{"name":"Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"CDCMMWR (2017). QuickStats: Percentage of Adults Who Ever Used an E-cigarette and Percentage Who Currently Use E-cigarettes, by Age Group\u2014National Health Interview Survey, United States, 2016. MMWR Morb. Mortal. Wkly. Rep., 66.","DOI":"10.15585\/mmwr.mm6633a6"},{"key":"ref_2","unstructured":"US Food and Drug Administration (2019). Youth Tobacco Use: Results from the National Youth Tobacco Survey, FDA."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"472","DOI":"10.1016\/j.amepre.2010.12.006","article-title":"Electronic Cigarettes as a Smoking-Cessation Tool: Results from an Online Survey","volume":"40","author":"Siegel","year":"2011","journal-title":"Am. J. Prev. Med."},{"key":"ref_4","unstructured":"(2021, January 05). JUUL Market Share in 2019. Available online: https:\/\/blog.technavio.com\/blog\/juul-market-share-dominating-e-cigarettes-market."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Burstyn, I. (2014). Peering through the mist: Systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks. BMC Public Health, 14.","DOI":"10.1186\/1471-2458-14-18"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1016\/j.microc.2018.10.019","article-title":"The effect of varying battery voltage output on the emission rate of carbonyls released from e-cigarette smoke","volume":"145","author":"Qu","year":"2019","journal-title":"Microchem. J."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"73","DOI":"10.18001\/TRS.4.3.6","article-title":"Can Established Vapers Distinguish Different PG:VG Ratios? A Pilot Study","volume":"4","author":"Schneller","year":"2018","journal-title":"Tob. Regul. Sci."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"678","DOI":"10.1136\/tobaccocontrol-2018-054616","article-title":"Characteristics and toxicant emissions of JUUL electronic cigarettes","volume":"28","author":"Talih","year":"2019","journal-title":"Tob. Control"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"392","DOI":"10.1056\/NEJMc1413069","article-title":"Hidden Formaldehyde in E-Cigarette Aerosols","volume":"372","author":"Jensen","year":"2015","journal-title":"N. Engl. J. Med."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"13080","DOI":"10.1021\/acs.est.6b05145","article-title":"Flavoring Compounds Dominate Toxic Aldehyde Production during E-Cigarette Vaping","volume":"50","author":"Khlystov","year":"2016","journal-title":"Environ. Sci. Technol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"10806","DOI":"10.1021\/acs.est.7b02205","article-title":"Flavoring Chemicals and Aldehydes in E-Cigarette Emissions","volume":"51","author":"Klager","year":"2017","journal-title":"Environ. Sci. Technol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1207","DOI":"10.1021\/acsomega.6b00489","article-title":"Aldehyde Detection in Electronic Cigarette Aerosols","volume":"2","author":"Ogunwale","year":"2017","journal-title":"ACS Omega"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"110727","DOI":"10.1016\/j.fct.2019.110727","article-title":"Acetoin is a precursor to diacetyl in e-cigarette liquids","volume":"133","author":"Vas","year":"2019","journal-title":"Food Chem. Toxicol."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Allaman, I., B\u00e9langer, M., and Magistretti, P.J. (2015). Methylglyoxal, the dark side of glycolysis. Front. Neurosci., 9.","DOI":"10.3389\/fnins.2015.00023"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"11192","DOI":"10.3390\/ijerph111111192","article-title":"Carbonyl Compounds Generated from Electronic Cigarettes","volume":"11","author":"Bekki","year":"2014","journal-title":"Int. J. Environ. Res. Public Health"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1219","DOI":"10.2116\/analsci.29.1219","article-title":"Determination of Carbonyl Compounds Generated from the E-cigarette Using Coupled Silica Cartridges Impregnated with Hydroquinone and 2,4-Dinitrophenylhydrazine, Followed by High-Performance Liquid Chromatography","volume":"29","author":"Uchiyama","year":"2013","journal-title":"Anal. Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"791","DOI":"10.2116\/bunsekikagaku.60.791","article-title":"Determination of carbonyl compounds generated from the electronic cigarette using coupled silica cartridges impregnated with hydroquinone and 2,4-dinitrophenylhydrazine","volume":"60","author":"Ohta","year":"2011","journal-title":"Bunseki Kagaku"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"549","DOI":"10.2116\/analsci.32.549","article-title":"Determination of Chemical Compounds Generated from Second-generation E-cigarettes Using a Sorbent Cartridge Followed by a Two-step Elution Method","volume":"32","author":"Uchiyama","year":"2016","journal-title":"Anal. Sci."},{"key":"ref_19","unstructured":"(2019, December 23). American Chemical Society E-cigarettes Can Damage DNA. Available online: https:\/\/www.sciencedaily.com\/releases\/2018\/08\/180820085208.htm."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1006\/taap.2002.9525","article-title":"Necrosis of nasal and airway epithelium in rats inhaling vapors of artificial butter flavoring","volume":"185","author":"Hubbs","year":"2002","journal-title":"Toxicol. Appl. Pharmacol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"169","DOI":"10.1093\/toxsci\/kfn016","article-title":"Respiratory Toxicity of Diacetyl in C57Bl\/6 Mice","volume":"103","author":"Morgan","year":"2008","journal-title":"Toxicol. Sci."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"498","DOI":"10.1164\/rccm.200611-1620OC","article-title":"Bronchiolitis Obliterans Syndrome in Chemical Workers Producing Diacetyl for Food Flavorings","volume":"176","author":"Rooyackers","year":"2007","journal-title":"Am. J. Respir. Crit. Care Med."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"481","DOI":"10.1007\/s00420-008-0354-9","article-title":"No acute effects of an exposure to 50 ppm acetaldehyde on the upper airways","volume":"82","author":"Muttray","year":"2009","journal-title":"Int. Arch. Occup. Environ. Health"},{"key":"ref_24","first-page":"262","article-title":"Further studies on sensory response to certain industrial solvent vapors","volume":"28","author":"Silverman","year":"1946","journal-title":"J. Ind. Hyg. Toxicol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1908","DOI":"10.1001\/jama.1957.02980330010003","article-title":"Effect of possible smog irritants on human subjects","volume":"165","author":"Sim","year":"1957","journal-title":"J. Am. Med. Assoc."},{"key":"ref_26","unstructured":"US Department of Health and Human Services (1993). Registry of Toxic Effects of Chemical Substances (RTECS, Online Database), National Toxicology Information Program, National Library of Medicine."},{"key":"ref_27","unstructured":"US Department of Health and Human Services (1993). Hazardous Substances Data Bank (HSDB, Online Database), National Toxicology Information Program, National Library of Medicine."},{"key":"ref_28","unstructured":"Hiraki, B., Misra, M., and Cook, D. (2019). HPHC Analysis of Seven Flavors of a Temperature-Regulated Nicotine Salt Pod System, JUUL Labs, Inc."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"733","DOI":"10.1289\/ehp.1510185","article-title":"Flavoring Chemicals in E-Cigarettes: Diacetyl, 2,3-Pentanedione, and Acetoin in a Sample of 51 Products, Including Fruit-, Candy-, and Cocktail-Flavored E-Cigarettes","volume":"124","author":"Mallory","year":"2016","journal-title":"Environ. Health Perspect."},{"key":"ref_30","first-page":"1","article-title":"Determination of carbonyl compounds in drinking water by pentafluorobenzylhydroxylamine derivatization and capillary gas chromatography with electron capture detection","volume":"1","author":"Munch","year":"1998","journal-title":"US EPA Method 556"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"75","DOI":"10.1016\/S0021-9673(98)00188-5","article-title":"Determination of carbonyl compounds in water by derivatization\u2013solid-phase microextraction and gas chromatographic analysis","volume":"809","author":"Bao","year":"1998","journal-title":"J. Chromatogr. A"},{"key":"ref_32","first-page":"86","article-title":"Analysis of Selected Carbonyl Compounds in Tobacco Samples by Using Pentafluorobenzylhydroxylamine Derivatization and Gas Chromatography-Mass Spectrometry","volume":"26","author":"Bao","year":"2014","journal-title":"Beitr. Tab. Int. Contrib. Tob. Res."},{"key":"ref_33","unstructured":"Health Canada (1999). Determination of \u201ctar\u201d, Nicotine and Carbon Monoxide in Mainstream Tobacco Smoke, Health Canada."},{"key":"ref_34","unstructured":"Baylor, K., Morison, G., and Taylor, D.R. (2014). Laboratory Data Review for the Non-Chemist, United States Environmental Protection Agency Region 9."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1136\/tc.2009.035279","article-title":"Electronic nicotine delivery systems: Emerging science foundation for policy","volume":"19","author":"Henningfield","year":"2010","journal-title":"Tob. Control"},{"key":"ref_36","first-page":"4375","article-title":"Second safety report on the Ruyan\u00ae e-cigarette","volume":"27","author":"Laugesen","year":"2008","journal-title":"Cell"},{"key":"ref_37","first-page":"36","article-title":"E-cigarette: Primi dati e possibili prospettive","volume":"2\u20133","author":"Tinghino","year":"2009","journal-title":"Tabaccologia"},{"key":"ref_38","unstructured":"Laugesen, M. (2008). Safety Report on the Ruyan E-Cigarette Cartridge and Inhaled Aerosol, Health New Zealand Ltd."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Cobb, N.K., Byron, M.J., Abrams, D.B., and Shields, P.G. (2010). Novel Nicotine Delivery Systems and Public Health: The Rise of the \u201cE-Cigarette\u201d, American Public Health Association.","DOI":"10.2105\/AJPH.2010.199281"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"330","DOI":"10.1056\/NEJMoa020300","article-title":"Clinical Bronchiolitis Obliterans in Workers at a Microwave-Popcorn Plant","volume":"347","author":"Kreiss","year":"2002","journal-title":"N. Engl. J. Med."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"330","DOI":"10.1177\/0192623307312694","article-title":"Respiratory toxicologic pathology of inhaled diacetyl in Sprague-Dawley rats","volume":"36","author":"Hubbs","year":"2008","journal-title":"Toxicol. Pathol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"373","DOI":"10.1016\/j.fct.2013.08.053","article-title":"Evaluation of the hypersensitivity potential of alternative butter flavorings","volume":"62","author":"Anderson","year":"2013","journal-title":"Food Chem. Toxicol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"829","DOI":"10.1016\/j.ajpath.2012.05.021","article-title":"Respiratory and olfactory cytotoxicity of inhaled 2, 3-pentanedione in Sprague-Dawley rats","volume":"181","author":"Hubbs","year":"2012","journal-title":"Am. J. Pathol."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"1662","DOI":"10.1021\/acs.chemrestox.6b00188","article-title":"Chemical composition of aerosol from an e-cigarette: A quantitative comparison with cigarette smoke","volume":"29","author":"Margham","year":"2016","journal-title":"Chem. Res. Toxicol."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"168","DOI":"10.1093\/ntr\/ntu176","article-title":"Evaluation of Electronic Cigarette Liquids and Aerosol for the Presence of Selected Inhalation Toxins","volume":"17","author":"Farsalinos","year":"2015","journal-title":"Nicotine Tob. Res."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"e10","DOI":"10.1136\/tobaccocontrol-2014-052175","article-title":"Flavour chemicals in electronic cigarette fluids","volume":"25","author":"Tierney","year":"2016","journal-title":"Tob. Control"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"4796","DOI":"10.3390\/ijerph120504796","article-title":"Toxicity assessment of refill liquids for electronic cigarettes","volume":"12","author":"Varlet","year":"2015","journal-title":"Int. J. Environ. Res. Public Health"},{"key":"ref_48","unstructured":"U.S. Department of Health & Human Services (2016). Criteria for A Recommended Standard: Occupational Exposure to Diacetyl and 2,3-Pentanedione, U.S. Department of Health & Human Services."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"122","DOI":"10.1179\/oeh.2011.17.2.122","article-title":"A Proposal for a Safe Exposure Level for Diacetyl","volume":"17","author":"Egilman","year":"2011","journal-title":"Int. J. Occup. Environ. Health"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"520","DOI":"10.1016\/j.jaap.2018.07.019","article-title":"Surface chemistry of electronic cigarette electrical heating coils: Effects of metal type on propylene glycol thermal decomposition","volume":"134","author":"Saliba","year":"2018","journal-title":"J. Anal. Appl. Pyrolysis"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"1012","DOI":"10.1177\/0192623319879906","article-title":"Flavorings-Related Lung Disease: A Brief Review and New Mechanistic Data","volume":"47","author":"Hubbs","year":"2019","journal-title":"Toxicol. Pathol."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"1485","DOI":"10.1007\/s00125-014-3243-7","article-title":"Methylglyoxal impairs endothelial insulin sensitivity both in vitro and in vivo","volume":"57","author":"Nigro","year":"2014","journal-title":"Diabetologia"},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Nigro, C., Leone, A., Raciti, G., Longo, M., Mirra, P., Formisano, P., Beguinot, F., and Miele, C. (2017). Methylglyoxal-glyoxalase 1 balance: The root of vascular damage. Int. J. Mol. Sci., 18.","DOI":"10.3390\/ijms18010188"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"4466","DOI":"10.1002\/jcp.26352","article-title":"Electronic cigarette: A recent update of its toxic effects on humans","volume":"233","author":"Huang","year":"2018","journal-title":"J. Cell. Physiol."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"2226","DOI":"10.1016\/j.clinph.2015.02.058","article-title":"Upregulation of axonal HCN current by methylglyoxal: Potential association with diabetic polyneuropathy","volume":"126","author":"Shimatani","year":"2015","journal-title":"Clin. Neurophysiol."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"5432","DOI":"10.1093\/nar\/gkq306","article-title":"Imidazopurinones are markers of physiological genomic damage linked to DNA instability and glyoxalase 1-associated tumour multidrug resistance","volume":"38","author":"Thornalley","year":"2010","journal-title":"Nucleic Acids Res."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"28291","DOI":"10.1074\/jbc.M111.328674","article-title":"Methylglyoxal activates nociceptors through transient receptor potential channel A1 (TRPA1) a possible mechanism of metabolic neuropathies","volume":"287","author":"Eberhardt","year":"2012","journal-title":"J. Biol. Chem."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1136\/tobaccocontrol-2012-050859","article-title":"Levels of selected carcinogens and toxicants in vapour from electronic cigarettes","volume":"23","author":"Goniewicz","year":"2014","journal-title":"Tob. Control"},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1016\/j.mrfmmm.2008.11.008","article-title":"Relationship between DNA lesions, DNA repair and chromosomal damage induced by acetaldehyde","volume":"662","author":"Mechilli","year":"2009","journal-title":"Mutat. Res."},{"key":"ref_60","unstructured":"U.S. Environmental Protection Agency (2008). Toxicological Review of Propionaldehyde (CAS No. 123-38-6), U.S. Environmental Protection Agency."},{"key":"ref_61","unstructured":"CORESTA, E., and Force, C.T (2015). Routine analytical machine for e-cigarette aerosol generation and collection\u2013definitions and standard conditions. Paris CORESTA, 1, 1\u20136. Available online: https:\/\/www.coresta.org\/sites\/default\/files\/technical_documents\/main\/CRM_81.pdf."},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"30","DOI":"10.18001\/TRS.6.1.4","article-title":"JUUL and Combusted Cigarettes Comparably Impair Endothelial Function","volume":"6","author":"Rao","year":"2020","journal-title":"Tob. Regul. Sci."},{"key":"ref_63","doi-asserted-by":"crossref","unstructured":"Omaiye, E.E., McWhirter, K.J., Luo, W., Pankow, J.F., and Talbot, P. (2018). Toxicity of JUUL Fluids and Aerosols Correlates Strongly with Nicotine and Some Flavor Chemical Concentrations. bioRxiv, 490607.","DOI":"10.1101\/490607"}],"container-title":["International Journal of Environmental Research and Public Health"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1660-4601\/18\/2\/385\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T05:07:45Z","timestamp":1760159265000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1660-4601\/18\/2\/385"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,1,6]]},"references-count":63,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2021,1]]}},"alternative-id":["ijerph18020385"],"URL":"https:\/\/doi.org\/10.3390\/ijerph18020385","relation":{},"ISSN":["1660-4601"],"issn-type":[{"value":"1660-4601","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,1,6]]}}}