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18.5.3 Chemical “ingredients” in e-liquids
Foreword

Relevant news and research: Chemical “ingredients” in e-liquids

Carrico, M. A., Imran, R., Gaitan, N., Lipato, T., Breland, A. and Cobb, C. O. (2026). Acute effects of electronic nicotine delivery system liquid nicotine form and sweet enhancer among people who use inhaled tobacco products. Exp Clin Psychopharmacol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/42060406


Evans, H. L. (2026). Smokeless in Theory: Scrutinizing the Evidence Before the Mandate Arrives. J Am Coll Surg. Available from: https://www.ncbi.nlm.nih.gov/pubmed/42047377


Fei, T., Li, J., Wu, B., Yu, J., Cui, P., Sha, Y., Cheng, Q., Chen, M., Fang, Y. and Yang, J. (2026). Analysis of the effect of glycerol addition and heating temperature on the puff-by-puff release of volatile organic compounds from heated tobacco products. Anal Methods, 16, 3364-3373. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41958360


Guo, X., Isenor, B. H., Wong, K., Davis, J., Chan, A. and Zhao, R. (2026). Tobacco-specific alkaloid (TSA) formation in aged e-cigarette juices: mechanistic insights into hydroxyl radical-initiated nicotine oxidation. Environ Sci Process Impacts. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41968989


McGrath, J., Royle, O., Thorpe, A., McCauley, J. I., Ueland, M., Kabakova, I., Chen, H., Clases, D., Oliver, B. G. and Bordin, D. M. (2026). Analytical investigation of metal distribution from e-cigarette aerosols to lung deposition using multi-platform mass spectrometry. Anal Bioanal Chem. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41991746


Block, A. C., Martin, C. D., Leigh, N. J., Page, M. K., Kaiser, L. M., Nardotto, G. H. B., Rosario, S. R., Felicione, N. J., O'Connor, R. J., Goniewicz, M. L. and Quisenberry, A. J. (2026). Effects of nicotine form and tobacco flavor on pharmacokinetics, subjective effects, and behavioral indicators of abuse liability of e-cigarettes. Nicotine Tob Res. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41863629


Han, S., Cui, L., Fang, Q., Li, X., Fu, Y., Feng, P., Tian, Y., Song, Z., Wang, H., Chen, H. and Hou, H. (2026). From liquid to aerosol: an innovative HPLC method sheds light on nicotine salt dynamics of e-cigarettes. Anal Bioanal Chem. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41776043


Lawson, D. and Coulson, J. (2026). Influence of e-Liquid pH on Heavy Metal Emissions in Open-System Electronic Cigarette Aerosols and Associated Health Risks. Nicotine Tob Res. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41894250


Sharrod-Cole, H., Danks, J., Holdcroft, C., Patel, R. and Starbrook, L. (2026). Illicit substances in school-confiscated vapes: Lessons from a laboratory-driven public health pilot. Public Health Pract (Oxf), 100770. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41883357


Shin, H. S., Pyo, H., Oh, Y., Choi, K. Y., Vu, T. H. V. and Park, D. (2026). Solvent and Phthalate Impurities of Health Concern in Tobacco-Derived and Synthetic Nicotine. Chem Res Toxicol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41906762


Shin, H. S., Van Vu, T. H., Choi, K. Y., Oh, Y., Pyo, H. and Park, D. (2026). Comprehensive Detection of Unintentional Hazardous Substances in e-Cigarette Liquids. Nicotine Tob Res. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41804785


Turner, A., Scott, J. W. and Dabrowski, M. C. (2026). Aluminium, copper, nickel, lead and zinc in e-liquids from contemporary disposable vapes. Environ Monit Assess, 4. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41872591


Wang, Z., Cui, H., Tuo, S., Du, W. and Wang, Z. (2026). Enhanced solution absorption of free-base over protonated nicotine in aerosols. Sci Rep. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41792211


Bagdas, D., Kebede, N., Sedaille, J., Eid, T., Erythropel, H. C., Zimmerman, J. B. and Addy, N. A. (2026). Effects of commercial unflavored and vanilla-flavored e-liquids on nicotine intake and withdrawal. bioRxiv. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41648260


Block, A. C., Smith, D. M. and Goniewicz, M. L. (2026). Vaping Delta(9)-tetrahydrocannabinol (Delta(9)-THC) in liquid forms: pharmacokinetics, pharmacodynamics, and regulatory implications. Expert Rev Clin Pharmacol, 1-16. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41664603


Fazeli, E., Martinez, B., Son, Y. and Khlystov, A. (2026). Flavoring Compound Chemical Class and Vaping Conditions Determine Toxic Carbonyl Emissions from E-Cigarettes. Chem Res Toxicol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41649144


Tetteh-Quarshie, S., Mensah, E. N., Booker, D. M. and Henderson, B. J. (2026). Flavorants enhance nicotine vapor self-administration in diet-induced obese female mice. J Pharmacol Exp Ther, 3, 103819. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41719691


Thong, C. Z. Y., Ng, I. K. S., Teo, K. S. H., Wong, C. S. W., Goh, W. G. W., Low, L., van der Eijk, Y. and See, K. C. (2026). The 'K-Podemic': a narrative review on drug-laced vaping for frontline clinicians. Singapore Med J. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41626923


Valenzuela, E. F., Almeida, R. S. S., Simoes, I. F., Goncalves Miranda, A., Ramos, M. O., Maciel, R., Rosa, F. W. and de Freitas Santos Junior, A. (2026). Electronic Smoking Devices Among University Students: Usage Patterns and Chemical Composition of Inhaled Substances. Anal Sci Adv, 1, e70059. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41676014


Wong, M., Martinez, T., Hua, M., Hendricks, N. G. and Talbot, P. (2026). Unraveling the Toxicological Effects of Hydroxyacetone horizontal line A Reaction Product in Electronic Cigarette Aerosols. Chem Res Toxicol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41650339


Woo, W., Tran, L. N., Tian, L., Canchola, A. and Lin, Y. H. (2026). Dynamic Chemistry and Toxicity of E-Cigarette Aerosols and Their Product Waste. Chem Res Toxicol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41678326


Harvanko, A. M., Ruzycki, C. A., McDonald, J., Claus, E. D., Schroeder, M. and Ramoa, C. (2026). E-liquid flavor alters nicotine exposure, puff topography, and subjective effects under ad libitum use conditions. Addict Behav Rep, 100665. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41574226


Lee, J. and Su, W. C. (2026). A New Aerosol Respiratory Deposition Approach: Health Risks of Metals in Aerosols from Electronic Nicotine Delivery Systems and Heated Tobacco Products. J Aerosol Sci. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41531470


Smethells, J. R., Wilde, S., Muelken, P., Harris, A. C. and LeSage, M. G. (2026). beta-Nicotyrine and e-cigarette abuse liability II: Behavioral economic demand and intracranial self-stimulation in rats. Drug Alcohol Depend, 113025. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41520411


Martinez, B., Son, Y. and Khlystov, A. (2025). Evaluation of carbonyl collection methods in electronic cigarette aerosols. Front Chem, 1694858. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41384229


Taylor, E., Robson, D., Brose, L. S., Hammond, D., Reid, J. L., Block, A. C., Goniewicz, M. L., Nikolaidou, M. and McNeill, A. (2025). Nicotine and tobacco-specific nitrosamine exposure among youth in England who smoke cigarettes and/or vape. Tob Control. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41344996


Tkach, V. V., Morozova, T. V., Gaivao, I., Martins-Bessa, A., Ivanushko, Y. G., Martins, J. and Barros, A. N. (2025). Sweeteners in E-Cigarettes: A Minireview of Flavoring and Biological Action. J Xenobiot, 6. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41440756


Alam El Din, S. M., Iyengar, S., Aherrera, A. D., Quarles, C. D., Jr., Mihalic, J., Bressler, J. and Rule, A. M. (2025). Detection of Metal-Containing Particles in FDA-Authorized and New Disposable Electronic Cigarette Aerosols. Environ Sci Technol, 46, 24707-24716. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41247037


Chattopadhyay, S., Malayil, L. and Sapkota, A. R. (2025). Viable, Multi-Drug-Resistant Bacteria Recovered from E-Liquids Used with Commercial Electronic Cigarettes. Int J Environ Res Public Health, 11. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41302671


Harrington, T., Ferketich, A. K., Lu, B., Wagner, D. D. and Roberts, M. E. (2025). Prospective associations between nicotine type and the continuation of youth e-cigarette use. BMC Public Health, 1, 4158. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41299554


Oh, S. G. and Kim, Y. H. (2025). Aerosol PG/VG mass ratio-based regulatory indicators for electronic cigarette device oversight: Linking heating temperature to harmful carbonyl formation in aerosols. J Hazard Mater, 140578. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41297268


Smethells, J. R., Wilde, S., Muelken, P., Vigliaturo, J., Raleigh, M. D., Pravetoni, M., Kellar, K. J., Olson, T., LeSage, M. G. and Harris, A. C. (2025). beta-Nicotyrine and e-cigarette abuse liability I: Pharmacodynamics and interaction with pharmacokinetics and discriminative stimulus effects of nicotine in rats. Drug Alcohol Depend, 112949. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41176900


Taffe, M. A., Coons, T. R., Doran, T. A., Grant, Y. and Vandewater, S. A. (2025). 6-Methyl nicotine and nicotine have similar thermoregulatory and reinforcing effects in middle aged female rats with a history of nicotine vapor self-administration. Pharmacol Biochem Behav, 174132. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41242637


Jefferis, T., Sengupta, M., Bui, A., Dawkins, C., Griffin, K., Strongin, R. M. and Sayes, C. M. (2025). Production of 3-Cyanopyridine upon Vaping Nicotinamide and Evaluation of the Toxicological Effects of Individual and Combined Exposures via Isobologram-Based Analysis. Chem Res Toxicol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41150859


Loedige, K. M. and Khokhar, J. Y. (2025). Impact of flavorants on nicotine vapor self-administration in adolescent mice: Cherry on top?. J Pharmacol Exp Ther, 10, 103700. Available from: https://www.ncbi.nlm.nih.gov/pubmed/41045825


Olmedo, P. and Gil, F. (2025). Modern Disposable E‑Cigarettes: Small in Size but Big in Toxic Metals. ACS Cent Sci, 8, 1272-1274. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40904750


Wong, M., Martinez, T., Hua, M., Hendricks, N. and Talbot, P. (2025). Unraveling the Toxicological Effects of Hydroxyacetone - A Reaction Product in Electronic Cigarette Aerosols. bioRxiv. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40950067


Moisi, R., Comanescu, M. A. and Medvedovici, A. V. (2025). Reversed-Phase (RP) and Hydrophilic Interaction (HILIC) Separation Mechanisms for the Assay of Nicotine and E-Cigarette Liquids. Molecules, 16. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40871595


Piechowski, J. M. and Bagatto, B. (2025). A simple, cost-effective, method for creating electronic cigarette vapor condensate. Biol Methods Protoc, 1, bpaf055. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40799310


Pourchez, J., Mercier, C. and Forest, V. (2025). The rise of nicotine analogues in vaping products. Lancet Respir Med. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40845865


Barroso, C. N. F., Melo, L. M. A., Aranha, L. M. S., Pereira, T. F. L., Souza, K. A. O., Costa, J. L., Arantes, L. C., Marton, M., Vojs, M. and Dos Santos, W. T. P. (2025). A novel electrochemical method for detecting synthetic cannabinoids in e-cigarette and biological samples using a lab-made electrode. Talanta, Pt A, 128574. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40682941


Keyser, B. M., Leverette, R., McRae, R., Wertman, J., Shutsky, T., Jordan, K. G., Szeliga, K. and Makena, P. (2025). In vitro toxicological evaluation of nicotine concentration and flavor variants of Vuse Alto ENDS. Food Chem Toxicol, 115640. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40659112


Lin, W., Hill, T., 3rd, Stroup, A. M., Sarles, S. E., Ogura, T., Augustine, F., O'Sullivan, S., Rahman, I., Robinson, R., Jabba, S. V., Nuss, C. and Hensel, E. (2025). Chemosensory Tobacco Product Toxicology Part 1: Sensory Mechanisms. Toxicol Sci. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40708233


Lin, W., Hill, T., 3rd, Stroup, A. M., Sarles, S. E., Ogura, T., Augustine, F., O'Sullivan, S., Rahman, I., Robinson, R., Jabba, S. V., Nuss, C. and Hensel, E. (2025). Chemosensory Tobacco Product Toxicology Part 2: Toxicological Testing, Assays, and State of the Science. Toxicol Sci. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40705669


Pennington, C. and Aldave, S. H. (2025). Disposable electronic cigarettes: Chemical composition in new and used devices. J Chromatogr A, 466178. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40614579


Robertson, N. E., Hunsaker, H. C., Yamamoto, M., Cheung, K., Poulin, B. A. and Nguyen, T. B. (2025). E‑Liquid and Aerosol Characterization of Popular Disposable E‑Cigarettes. ACS Omega, 27, 29615-29627. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40687050


Sanchez, L. M., Bae, D., Cho, J., Harlow, A. F., Kirkpatrick, M. G., Schuler, L. A., Miech, R. A., Dai, H. D., Sussman, S. Y., Han, D. H., Meza, L. and Leventhal, A. M. (2025). Awareness and Use of Vaping Products With a Nicotine Analogue Among Adolescents and Young Adults. Pediatrics, 2. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40588286


Sussman, R. A., Gomez-Ruiz, H. and Farsalinos, K. (2025). Comment on Svarch-Perez et al. Methods for a Non-Targeted Qualitative Analysis and Quantification of Benzene, Toluene, and Xylenes by Gas Chromatography-Mass Spectrometry of E-Liquids and Aerosols in Commercially Available Electronic Cigarettes in Mexico. Int. J. Environ. Res. Public Health 2024, 21, 1308. Int J Environ Res Public Health, 7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40724116


Svarch-Perez, A., Paz-Gonzalez, M. V., Ruiz-Juarez, C., Olvera-Chacon, J. C., Larios-Solis, A., Castro-Gaytan, S., Aldeco-Perez, E. and Alcocer-Varela, J. C. (2025). Reply to Sussman et al. Comment on "Svarch-Perez et al. Methods for a Non-Targeted Qualitative Analysis and Quantification of Benzene, Toluene, and Xylenes by Gas Chromatography-Mass Spectrometry of E-Liquids and Aerosols in Commercially Available Electronic Cigarettes in Mexico. Int. J. Environ. Res. Public Health 2024, 21, 1308". Int J Environ Res Public Health, 7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40724117


Yuan, S., Sun, S., Qin, R. and Li, P. (2025). Monitoring the nicotine delivery stability in electronic cigarettes based on in-situ AS/SRD/FOS technology. Anal Chim Acta, 344244. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40610138


Zhang, X., Li, Y., Liu, J., Pan, Z., Chen, Y., Wang, M., Dai, Y., Zhao, K., Gu, J., Zhang, H., Zhang, S., Wurita, A. and Hasegawa, K. (2025). Identification of two novel imidazole-derived GABA agonists butomidate and tf-etomidate in e-cigarette liquids. Forensic Toxicol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40643820


Erythropel, H. C., Jabba, S. V., Mellinghoff, R. A., Garcia-Gallet, V., Silinski, P., Zimmerman, J. B. and Jordt, S. E. (2025). Prevalence of Artificial Sweetener Neotame in US-Marketed Disposable E-Cigarettes. JAMA. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40455485


Li, W., Davis, D. R., Wu, R., Gueorguieva, R., Green, B. G. and Krishnan-Sarin, S. (2025). The effect of "ice" components in sweet-flavored nicotine-containing e-liquids among young adult e-cigarette users. Exp Clin Psychopharmacol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40489161


Piechowski, J. M. and Bagatto, B. (2025). Qualitative chemical analysis of cinnamon flavored e-cigarette vapor to identify compounds of interest that may affect cardiovascular function. MicroPubl Biol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40463482


Comite? National Contre le Tabagisme (2025). The CNCT alerts on the use of a new addictive molecule used by the tobacco industry: 6-methyl-nicotine. . Available from: https://cnct.fr/wp-content/uploads/2025/05/Press-release-WNTD-1.pdf


GŽnŽration Sans Tabac (2025). The CNCT warns of 6-methyl-nicotine: a new addictive threat in vaping products and oral pouches. . Available from: https://www.generationsanstabac.org/en/actualites/le-cnct-alerte-sur-la-6-methyl-nicotine-une-nouvelle-menace-addictive-dans-les-produits-de-vapotage-et-sachets-oraux/


Maeder, S. and Jeannet, C. (2025). A Comparative Assessment of the FDA List of 93 HPHCs in Aerosol Generated by Tobacco Heating System 2.2 versus 3R4F Reference Cigarette Smoke. Chem Res Toxicol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40396687


Pawaskar, K., Scott, S. M., Engel, S., Mulloy, S. M. and Lee, A. M. (2025). Flavor compounds found in electronic cigarette liquids differentially enhance voluntary nicotine consumption and preference in mice. Nicotine Tob Res. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40378181


Omaiye, E. and Talbot, P. (2025). Quantification of 16 Metals in Fluids and Aerosols from Ultrasonic Pod-Style Cigarettes and Comparison to Electronic Cigarettes. Environ Health Perspect. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40207990


Page, M. K., Merzianu, A. D., Leigh, N. J. and Goniewicz, M. L. (2025). Stability of Flavoring Chemicals in e-Cigarette Liquids: A Naturalistic Product Aging Study over 24 months. ACS Omega, 15, 15706-15715. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40290923


Toledo, E. F. V., Simoes, I. F., Farias, M. T., Minho, L. A. C., Conceicao, J. L., Santos, W., Mesquita, P. R. R. and Junior, A. F. S. (2025). A Comprehensive Review of the Harmful Compounds in Electronic Cigarettes. Toxics, 4. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40278584


Erythropel, H. C., Jabba, S. V., Mellinghoff, R. A., Garcia-Gallet, V., Silinski, P., Zimmerman, J. B. and Jordt, S. E. (2025). Prevalence of Potent Artificial Sweetener Neotame in Popular US-Marketed Disposable Electronic Cigarettes. Res Sq. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40060039


Sniadach, J., Kicman, A., Michalska-Falkowska, A., Jonczyk, K. and Waszkiewicz, N. (2025). Changes in Concentration of Selected Biomarkers of Exposure in Users of Classic Cigarettes, E-Cigarettes, and Heated Tobacco Products-A Narrative Review. Int J Mol Sci, 5. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40076424


Klupinski, T. P., Adetona, A., Ivanov, A., Richardson, A., Strozier, E. D., Aume, L. L. S., Karam, H., Makselan, S. D., McCauley, M., Mullins, L., Stiffler, B., Lucas, E. A. and Kim, H. (2025). Chemical Constituents and Particle Size Distribution of Mainstream Emission from Electronic Waterpipe. Nicotine Tob Res. Available from: https://www.ncbi.nlm.nih.gov/pubmed/39887006


Kubica, P., Majchrzak, T. and Vakh, C. (2025). Unveiling per- and polyfluoroalkyl substances contamination in e-cigarette refill liquids: A comprehensive analytical assessment. Sci Total Environ, 178297. Available from: https://www.ncbi.nlm.nih.gov/pubmed/39765165


Dai, W., Shi, J., Carreno, J., Kleinman, M. T., Herman, D. A., Arechavala, R. J., Renusch, S., Hasen, I., Ting, A. and Kloner, R. A. (2024). Impact of electronic cigarette vaping on the cardiovascular function in young and old rats. Sci Rep, 1, 30420. Available from: https://www.ncbi.nlm.nih.gov/pubmed/39639066


Harris, T. (2024). Physical and Chemical Characterization of Aerosols Produced from Commercial Nicotine Salt-Based E-Liquids. Chem Res Toxicol. Available from: https://www.ncbi.nlm.nih.gov/pubmed/39654291


Earlier news and research

For news items and research on this topic earlier than 2025, click here.

Intro
Chapter 2