JEP  Vol.11 No.9 , September 2020
Chemical Constituents in E-Cigarette Liquids and Aerosols
Abstract: Electronic cigarettes (e-cigarettes, EC) form an aerosol from the heating element and liquid-containing cartridge. The heating element aerosolizes the refill solutions (e-liquids) when the power source of e-cigarette is pressed. E-liquids consist of combinations of propylene glycol, glycerine, nicotine and flavouring ingredients. Puffing activates the battery-operated heating element in the atomizer and will produce smoke that is similar to conventional cigarette (CC). This study evaluated the chemical composition of e-liquid and aerosol samples available in Malaysia. We analyzed the volatile organic compounds in e-liquids and the aerosols samples from EC using gas chromatography mass spectrometer. Seventy-two EC e-liquids were analyzed through different flavours from more than 60 brands. Samples consisted of 32 nicotine-free (0 mg) and 40 nicotine-containing refill solutions (3 - 12 mg). Overall, 116 compounds were identified from EC e-liquids. On the other hand, 275 compounds were identified from their resultant aerosol samples. There were 42 compounds found in both e-liquids and aerosols. Seven compounds were only found in e-liquids and 38 compounds were only found in aerosols. Propylene glycol was found in all of the e-liquid and aerosol samples. Glycerin was found in 99% of the e-liquid and 100% of aerosol samples. At least 60% of the EC e-liquids and the resultant aerosol contain piperidine, butanoic acid ethyl ester and nicotine. It was also found that at least 9 out of 35 nicotine free labeled e-liquids contain nicotine. Some of these compounds were known to be detrimental to health and were detected in aerosol although they were not present in e-liquids. While some of the compounds are flavouring ingredients, it is necessary to evaluate its long-term effects on EC users.
Cite this paper: Naeem, M. , Zain, S. , Ng, C. and Noh, M. (2020) Chemical Constituents in E-Cigarette Liquids and Aerosols. Journal of Environmental Protection, 11, 664-681. doi: 10.4236/jep.2020.119040.

[1]   Trtchounian, A., Williams, M. and Talbot, P. (2010) Conventional and Electronic Cigarettes (e-Cigarettes) Have Different Smoking Characteristics. Nicotine & Tobacco Research, 12, 905-912.

[2]   Farsalinos, K., Tsiapras, D., Kyrzopoulos, S., Savvopoulou, M., Avramidou, E. and Vasilopoulou, D. (2012) Acute Effects of Using an Electronic Nicotine-Delivery Device (e-Cigarette) on Myocardial Function: Comparison with the Effects of Regular Cigarettes. European Heart Journal, 33, 203.

[3]   Kalininskiy, A., Bach, C.T., Nacca, N.E., Ginsberg, G., Marraffa, J., Navarette, K.A., McGraw, M.D. and Croft, D.P. (2019) E-Cigarette, or Vaping, Product Use Associated Lung Injury (EVALI): Case Series and Diagnostic Approach. The Lancet Respiratory Medicine, 7, 1017-1026.

[4]   Stoebner, S., Faou, A.L., Huteau, M., Gricourt, Y. and Cuvillon, P. (2019) E-Cigarette or Vaping Product Use Associated Lung Injury (EVALI): Health Issues Going beyond Anaesthetic and Surgical Perioperative Procedures. Anaesthesia Critical Care & Pain Medicine, 38, 563-564.

[5]   Zain, S.M.S.M., Khair, S.K.J., Mohamad, N., Noh, M.F.Md. and Radhakrishnan, D.A. (2019) Nicotine Content in Electronic Cigarette Refill Solutions and Its Release in Aerosols. Journal of Environmental Protection, 10, 1317-1332.

[6]   National e-Cigarette Survey (NECS) (2016) Prevalence, Pattern and Perception Regarding e-Cigarette and Vape Use among Malaysian Adults. Institute for Public Health, Ministry of Health Malaysia, Kuala Lumpur.

[7]   Mohamed Elkalmi, R., Bhagavathul, A.S., Adamu Ya’u, A., et al. (2016) Familiarity, Perception, and Reasons for Electronic-Cigarette Experimentation among the General Public in Malaysia: Preliminary Insight. Journal of Pharmacy and Bioallied Science, 8, 240-247.

[8]   Pissinger, C. and Dossing, M. (2014) A Systematic Review of Health Effects of Electronic Cigarettes. Preventive Medicine, 69, 248-260.

[9]   Sleiman, M., Logue, J.M., Montesinos, V.N., Russell, M.L., Litter, M.I., Gundel, L.A. and Destaillats, H. (2016) Emissions from Electronic Cigarettes: Key Parameters Affecting the Release of Harmful Chemicals. Environmental Science & Technology, 50, 9644-9651.

[10]   Geiss, O., Bianchi, I., Barahona, F. and Barrero-Moreno, J. (2015) Characterization of Mainstream and Passive Vapours Emitted by Selected Electronic Cigarettes. International Journal of Hygiene and Environmental Health, 218, 169-180.

[11]   Fuoco, F.C., Buonanno, G., Stabile, L. and Vigo, P. (2014) Influential Parameters on Particle Concentration and Size Distribution in the Mainstream of e-Cigarettes. Environmental Pollution, 184, 523-529.

[12]   Schober, W., Szendrei, K., Matzen, W., Osiander-Fuchs, H., Heitmann, D., Schettgen, T., Jorres, R.A. and Fromme, H. (2014) Use of Electronic Cigarettes (e-Cigarettes) Impairs Indoor Air Quality and Increases FeNO Levels of e-Cigarette Consumers. International Journal of Hygiene and Environmental Health, 217, 628-637.

[13]   Bekki, K., Uchiyama, S., Ohta, K., Inaba, Y., Nakagome, H. and Kunugita, N. (2014) Carbonyl Compounds Generated from Electronic Cigarettes. International Journal of Environmental Research and Public Health, 11, 11192-11200.

[14]   Farsalinos, K.E., Voudris, V. and Poulas, K. (2015) E-Cigarettes Generate High Levels of Aldehydes Only in “Dry Puff” Conditions. Addiction, 110, 1352-1356.

[15]   Goniewicz, M.L., Knysak, J., Gawron, M., Kosmider, L., Sobczak, A., Kurek, J., Prokopowicz, A., Jablonska-Czapla, M., RosikDulewska, C., Havel, C., Jacob, P. and Benowitz, N. (2013) Levels of Selected Carcinogens and Toxicants in Vapour from Electronic Cigarettes. Tobacco Control, 23, 133-139.

[16]   Kosmider, L., Sobczak, A., Fik, M., Knysak, J., Zaciera, M., Kurek, J. and Goniewicz, M.L. (2014) Carbonyl Compounds in Electronic Cigarette Vapors: Effect of Nicotine Solvent and Battery Output Voltage. Nicotine & Tobacco Research, 16, 1319-1326.

[17]   Herrington, J.S. and Myers, C. (2015) Electronic Cigarette Solutions and Resultant Aerosol Profiles. Journal of Chromatography A, 1418, 192-199.

[18]   National Institute for Occupational Safety and Health (NIOSH, NIOSH): Manual of Analytical Methods. NIOSH, Cincinnati.

[19]   Cheng, T. (2014) Chemical Evaluation of Electronic Cigarettes. Tobacco Control, 23, 11-17.

[20]   Ohta, K., Uchiyama, S., Inaba, Y., et al. (2011) Determination of Carbonyl Compounds Generated from the Electronic Cigarette Using Coupled Silica Cartridges Impregnated with Hydroquinone and 2,4-Dinitrophenylhydrazine. Bunseki Kagaku, 60, 791-797.

[21]   Williams, M., Villarreal, A., Bozhilov, K., et al. (2013) Metal and Silicate Particles Including Nanoparticles Are Present in Electronic Cigarette Cartomizer Fluid and Aerosol. PLoS ONE, 8, e57987.

[22]   Burstyn, I. (2014) Peering through the Mist: Systematic Review of What the Chemistry of Contaminants in Electronic Cigarettes Tells Us about Health Risk. BMC Public Health, 14, Article No. 18.

[23]   Wieslander, G., Norback, D. and Lindgren, T. (2001) Experimental Exposure to Propylene Glycol mist in Aviation Emergency Training: Acute Ocular and Respiratory Effects. Occupational and Environmental Medicine, 58, 649-655.

[24]   Choi, H., Schmidbauer, N., Sundell, J., Hasselgren, M., Spengler, J. and Bornehag, C.G. (2010) Common Household Chemicals and the Allergy Risks in Pre-School Age Children. PLoS ONE, 5, e13423.

[25]   Grana, R., Benowitz, N. and Glantz, S.A. (2014) E-Cigarettes: Scientific Review. Circulation, 129, 1972-1986.

[26]   Kienhuis, A.S., Soeteman-Hernandez, L.G., Bos, P.M.J., Cremers, H.W.J.M., Klerx, W.N. and Talhout, R. (2015) Potential Harmful Health Effects of Inhaling Nicotine-Free Shisha-Pen Vapor: A Chemical Risk Assessment of the Main Components Propylene Glycol and Glycerol. Tobacco Induced Diseases, 13, 15.

[27]   Hutzler, C., Paschke, M., Kruschinski, S., Henkler, F., Hahn, J. and Luch, A. (2014) Chemical Hazards Present in Liquids and Vapors of Electronic Cigarettes. Archives of Toxicology, 8, 1295-1308.

[28]   Hess, R., Bartels, M.J. and Pottenger, L.H. (2004) Ethylene Glycol: An Estimate of Tolerable Levels of Exposure Based on a Review of Animal and Human Data. Archives of Toxicology, 78, 671-680.

[29]   Hajek, P., Etter, J., Benowitz, N., Eissenberg, T. and Hayden McRobbie, H. (2014) Electronic Cigarettes: Review of Use, Content, Safety, Effects on Smokers and Potential for Harm and Benefit. Addiction, 109, 1801-1810.

[30]   Bein, K. and Leikauf, G.D. (2011) Acrolein—A Pulmonary Hazard. Molecular Nutrition & Food Research, 55, 1342-1360.

[31]   US OSHA (2007) Acetaldehyde. United States Department of Labor, Occupational Safety and Health Administration (OSHA), Washington DC.

[32]   Sutfin, E.L., McCoy, T.P., Morrell, H.E.R., Hoeppner, B.B. and Wolfson, M. (2013) Electronic Cigarette Use by College Students. Drug and Alcohol Dependence, 131, 214-221.

[33]   Kosmider, L., Kimber, C.F., Kurek, J., Corcoran, O. and Dawkins, L.E. (2017) Compensatory Puffing with Lower Nicotine Concentration e-Liquids Increases Carbonyl Exposure in e-Cigarette Aerosols. Nicotine & Tobacco Research, 20, 998-1003.

[34]   Etter, J.F., Zather, E. and Svensson, S. (2013) Analysis of Refill Liquids for Electronic Cigarettes. Addiction, 108, 1671-1679.

[35]   Kong, A.Y., Derrick, J.C., Abrantes, A.S. and Williams, R.S. (2016) What Is Included with Your Online e-Cigarette Order? An Analysis of e-Cigarette Shipping, Product and Packaging Features. Tobacco Control, 27, 699-702.

[36]   Zucchet, A. and Schmaltz, G. (2017) Electronic Cigarettes—A Review of the Physiological Health Effects. Facets, 2, 575-609.

[37]   Pagano, T., Di Francesco, A.G., Smith, S.B., George, J., Wink, G., Rahman, I., et al. (2016) Determination of Nicotine Content and Delivery in Disposable Electronic Cigarettes Available in the United States by Gas Chromatography-Mass Spectrometry. Nicotine & Tobacco Research, 18, 700-707.

[38]   Farsalinos, K.E., Kistler, K.A., Gillman, G. and Voudris, V. (2015) Evaluation of Electronic Cigarette Liquids and Aerosol for the Presence of Selected Inhalation Toxins. Nicotine & Tobacco Research, 17, 168-174.

[39]   Xue, J., Yang, S. and Seng, S. (2014) Mechanisms of Cancer Induction by Tobacco-Specific NNK and NNN. Cancers, 6, 1138-1156.

[40]   Abramovitz, A., McQueen, A., Martinez, R.E., Williams, B.J. and Sumner, W. (2015) Electronic Cigarettes: The Nicotyrine Hypothesis. Medical Hypotheses, 85, 305-310.

[41]   Etter, J.F. and Bullen, C. (2011) Electronic Cigarette: Users Profile, Utilization, Satisfaction and Perceived Efficacy. Addiction, 106, 2017-2028.

[42]   Pisinger, C., Aadahl, M., Toft, U. and Jorgensen, T. (2011) Motives to Quit Smoking and Reasons to Relapse Differ by Socioeconomic Status. Preventive Medicine, 52, 48-52.

[43]   National Center for Chronic Disease Prevention and Health Promotion (2014) Chapter 12 Smoking-Attributable Morbidity, Mortality, and Economic Costs. The Health Consequences of Smoking: 50 Years of Progress: A Report of the Surgeon General, 647-680.

[44]   Balfour, D.J. (1982) The Effects of Nicotine on Brain Neurotransmitter Systems. Pharmacology & Therapeutics, 16, 269-282.

[45]   Kilaru, S., Frangos, S.G., Chen, A.H., et al. (2001) Nicotine: A Review of Its Role in Atherosclerosis. Journal of the American College of Surgeons, 193, 538-546.

[46]   Condorelli, R.A., La, V.S., Giacone, F., Iacoviello, L., et al. (2013) In Vitro Effects of Nicotine on Sperm Motility and Bio-Functional Flow Cytometry Sperm Parameters. International Journal of Immunopathology and Pharmacology, 26, 739-746.

[47]   Leventhal, A.M., Strong, D.R., Kirkpatrick, M.G., et al. (2015) Association of Electronic Cigarette Use with Initiation of Combustible Tobacco Product Smoking in Early Adolescence. JAMA, 314, 700-707.

[48]   Tierney, P.A., Karpinski, C.D., Brown, J.E., Luo, W. and Pankow, J.F. (2016) Flavour Chemicals in Electronic Cigarette Fluids. Tobacco Control, 25, e10-e15.

[49]   Shibamoto, T. (2014) Diacetyl: Occurrence, Analysis, and Toxicity. Journal of Agricultural and Food Chemistry, 62, 4048-4053.

[50]   Sherwood, C.L. and Boitano, S. (2016) Airway Epithelial Cell Exposure to Distinct e-Cigarette Liquid Flavorings Reveals Toxicity Thresholds and Activation of CFTR by the Chocolate Flavoring 2,5-Dimethypyrazine. Respiratory Research, 17, 57.

[51]   Uchiyama, S., Ohta, K., Inaba, Y. and Kunugita, N. (2013) 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. Analytical Sciences, 29, 1219-1222.

[52]   Spencer, A. and Lauterbach, J.H. (2015) Generation of Acetaldehyde and Other Carbonyl Compounds during Vaporization of Glycerol and Propylene Glycol during Puffing of a Popular Style of e-Cigarette. 54th Meeting of the Society of Toxicology, San Diego, 22-26 March 2015, Abstract 188.

[53]   Brown, C.J. and Cheng, J.M. (2014) Electronic Cigarettes: Product Characterisation and Design Considerations. Tobacco Control, 23, ii4-ii10.

[54]   Hess, C.A., Olmedo, P., Navas-Acien, A., Goessler, W., Cohen, J.E. and Rule, A.M. (2017) E-Cigarettes as a Source of Toxic and Potentially Carcinogenic Metals. Environmental Research, 152, 221-225.

[55]   Williams, M., To, A., Bozhilov, K. and Talbot, P. (2015) Strategies to Reduce Tin and Other Metals in Electronic Cigarette Aerosol. PLoS ONE, 10, e0138933.

[56]   The National Academies of Sciences, Engineering, and Medicine (NASEM) (2018) Public Health Consequences of e-Cigarettes. The National Academies Press, Washington DC.