There is much interest in comparing the types and amounts of chemicals in e-cigarette aerosols to smoke from conventional cigarettes. Lower amounts of some toxic chemicals may imply a lower risk compared to smoking. While there may be health benefits for people who smoke who completely switch to e-cigarettes, many people who vape have never smoked, or use both products (i.e. dual use, see Sections 18.3.1.2 and 18.7.6).
Most of the chemicals with toxicity concerns in e-cigarettes are present at considerably lower levels than in cigarettes. But this does not mean that e-cigarette use can be assumed to be harmless as the effects of long-term exposure to the chemicals found in e-cigarettes, even at low doses, are unknown. Further, dual use of both products may further increase health risks beyond use of either product alone.1-3
E-cigarette aerosols contain considerably lower amounts of harmful and toxic chemicals compared to conventional cigarette aerosols. An extensive study from 2021 tested carbonyl compounds (including aldehydes such as acetaldehyde and formaldehyde, Section 12.4.3.2) and polycyclic aromatic hydrocarbons (PAHs, Section 12.4.3.6) levels in e-cigarette compared to conventional cigarette and heated tobacco products aerosols. Among the 19 carbonyl compounds tested, 17 were lowest in e-cigarette aerosols. Among the 22 PAHs that were detected, 21 were lowest in e-cigarette aerosols compared to conventional cigarette and heated tobacco products. When comparing average levels of all the compounds in each class, e-cigarettes had a 99% reduction per puff of carbonyl compounds compared to conventional cigarettes, and a 98% reduction per puff of PAHs, many of which are known causes of cancer.4 This study used three different types of e-cigarettes in these comparisons. However, there is a great variety of e-cigarettes and of the ways that they are used, such as differing power settings, as described below in Section 18.5.6. More extensive studies are necessary to comprehensively compare e-cigarette aerosols to conventional cigarettes that take into account the variety of products and modes of use.
There have only been a few studies that directly compares the levels of toxic metals found in e-cigarette aerosols to conventional cigarettes (see Section 12.4.3.10). One study found relatively high levels of the metals chromium, nickel cadmium lead and the metalloid arsenic5 in e-cigarette emissions compared to what has been found in the past in cigarette emissions.6 Studies of metals in human samples, such as urine and blood, have mostly found similar, if not higher, amounts of metals in samples from e-cigarette users compared to conventional cigarettes.7 Numerous metals present in e-liquids and/or e-cigarette aerosols have associated health concerns, as detailed in Table 18.5.1 in Section 18.5.4.
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References
1. Mukerjee R, Hirschtick JL, Arciniega LZ, Xie Y, Barnes GD, et al. ENDS, cigarettes, and respiratory illness: longitudinal associations among U.S. Youth. American Journal of Preventive Medicine, 2024; 66(5):789-96. Available from: https://www.ncbi.nlm.nih.gov/pubmed/38081374
2. Kim CY, Paek YJ, Seo HG, Cheong YS, Lee CM, et al. Dual use of electronic and conventional cigarettes is associated with higher cardiovascular risk factors in Korean men. Scientific Reports, 2020; 10(1):5612. Available from: https://www.ncbi.nlm.nih.gov/pubmed/32221375
3. Wang Y, Sung HY, Lea Watkins S, Lightwood J, Yao T, et al. The association of current exclusive e-cigarette use and dual use of e-cigarettes and cigarettes with psychological distress among U.S. adults. Preventive Medicine Reports, 2023; 36:102425. Available from: https://www.ncbi.nlm.nih.gov/pubmed/37810268
4. Dusautoir R, Zarcone G, Verriele M, Garcon G, Fronval I, et al. Comparison of the chemical composition of aerosols from heated tobacco products, electronic cigarettes and tobacco cigarettes and their toxic impacts on the human bronchial epithelial BEAS-2B cells. Journal of Hazardous Materials, 2021; 401:123417. Available from: https://www.ncbi.nlm.nih.gov/pubmed/32763707
5. Salazar MR, Saini L, Nguyen TB, Pinkerton KE, Madl AK, et al. Elevated toxic element emissions from popular disposable e‑cigarettes: sources, life cycle, and health risks. ACS Central Science, 2025; 11(8):1345-54. Available from: https://www.ncbi.nlm.nih.gov/pubmed/40893954
6. Pappas RS, Fresquez MR, Martone N, and Watson CH. Toxic metal concentrations in mainstream smoke from cigarettes available in the USA. Journal of Analytical Toxicology, 2014; 38(4):204-11. Available from: https://www.ncbi.nlm.nih.gov/pubmed/24535337
7. Zhao D, Aravindakshan A, Hilpert M, Olmedo P, Rule AM, et al. Metal/metalloid levels in electronic cigarette liquids, aerosols, and human biosamples: A systematic review. Environmental Health Perspectives, 2020; 128(3):36001. Available from: https://www.ncbi.nlm.nih.gov/pubmed/32186411