The Chemistry of Vaping Products and Cigarettes: A Comprehensive Review

Nick Tsintolas

Abstract: The recent popularization of ecigarette products as a safer alternative to smoking has prompted extensive scientific research into the kinds and extent of chemicals it produces in comparison to a traditional cigarette. This article serves as a review of the current knowledge surrounding the chemistry of vape and cigarette emissions and as a call for further research.

Introduction to Vapes and Cigarettes:

E-cigarettes, or vapes, have entered the mainstream and revolutionized the “smoking” experience. An understanding of these products is essential when discussing the chemicals they give off. Vapes work by heating a liquid cartridge containing nicotine and other chemicals, aerosolizing the mixture.1 See Figure 1below:

Figure 1: A breakdown of the components of a traditional e- cigarette. Note the heating coil, nicotine cartridge, and vaporizing chamber as the producers of theaerosolized mixture.2

These chemicals, called “base compounds,” include propylene glycol and vegetable glycerin, which initially on their own are not dangerous. When heated, they become the toxic chemicals acrolein, formaldehyde, and acid aldehyde.3 When analyzing the chemicals produced by vapes, it is important to consider their origin. Many vaping injuries and illnesses result from the use of devices tampered with in the black market or modified by their users. This is especially pertinent to vapes containing THC, the active ingredient in marijuana. These alterations worsen the effect of vapes and can confound proper experimentation into their chemical production.4

For cigarettes, the tobacco and other chemicals follow a combustion reaction.1 While there is a difference in how smokers and vapers are exposed to these harmful chemicals and the extent of the exposure, a vast majority of the chemicals are the same.3 The primary chemical both products contain is nicotine, an addictive substance that causes stress with withdrawal and brings a sense of relaxation with use.5 Nicotine can also raise blood pressure, increase adrenaline levels, and increase the risk for a heart attack.4

Vaping can cause seizures and serious lung damage after just a year of use. The chemicals in e-cigarettes can also hamper brain development in children. The documented illnesses and conditions associated with smoking are lung cancer, breast cancer, shortness of breath, and heart disease, all of which develop after years of exposure to these chemicals.5

Discussion of Scientific Research:

Initial studies into the chemical output of ecigarettes by the FDA revealed a toxic compound in antifreeze and carcinogenic tobacco-related compounds present in ecigarettes advertised as “tobacco free”. Significant levels of other carcinogens like formaldehyde and benzene were detected in these vaping products. Levels of acrolein, a chemical known to damage DNA, increased in the saliva of five adults after a 15-minute vaping session. Acrolein’s DNA alteration potential establishes it as an additional carcinogen present in vapes.5 Juul, a popular e-cigarette manufacturer, has made natural

nicotine more neutral and thus less irritating to the throat, and as a result has increased the nicotine content in their products, which exacerbates its addictivequalities.3

Following these initial discoveries about the chemicals in vapes and cigarettes, research teams in 2016 including Jennifer Margham, et al and in 2020 including James Nichol, et al studied the chemical composition of e-cigarettes and published their findings in Chemical Research in Toxicology. The team including Nichol, et al, advanced the work of Margham, et al and included many of the same researchers.6

Margham, et al used the Ky3R4F Kentucky Reference Cigarette as the cigarette reference and the Vype ePen as the e-cigarette reference, both of which are legitimate, untampered products. A smoking machine was used to simulate use.6 Figure 2: A smoking machine similar to the one used in the study.The barrel, pictured here, is attached to a ventilator that breathes in and out, simulating taking a puff from a cigarette or vape.7 The vape puff rate and volume were standardized throughout the study. The Vype ePen provides 200 puffs before itruns

out of liquid, so the experimenters recorded results in increments of 100 puffs. Likewise, the cigarette puff rate and volume in the study were also standardized; the Ky3R4F cigarette lasts between 10-15 puffs, so researchers recorded emissions on a percigarette basis. Researchers also measured relevant chemical levels in their laboratory air as a control. All samples were analyzed for their chemical emissions.6

Many of the chemical emissions in the study were in trace quantities below the limit of detection (LOD) and/or the limit of quantification (LOQ). With the goal of obtaining a percentage difference between the ePen and Ky3R4F emissions, researchers used Equation (1) to obtain an emission value when one product’s data was less than the LOD:

)&*+)%&' ("#$& (1) !"#!$#"%&' ("#$& =

2

In order to report levels greater than the LOD but less than the LOQ, (when data is detectable but not fully useful) researchers used Equation (2):

(2) !"#!$#"%&' ("#$& = )&*+)%&' , . + ( )&*+)%&' , -/ − )&*+)%&' , . )

2

Vape and cigarette levels below both the LOD and LOQ, were omitted from percentage difference calculations.6

Table 1 summarizes the e-cigarette emission levels of the chemicals discussed earlier in this article review in comparison to cigarette emissions. These are only a handful of the over 150 toxicantsanalyzed.6

Compound

Formaldehyde Acetaldehyde Acrolein Glycerol Propylene Glycol Nicotine Acetone

Table1:ResultsfromMargham, et al.6 Emission Results

98.6-99.9% less emissions in vapes; for vape emissions, half were from air, half were from ePen 98.6-99.9% less emissions in vapes; for vape emissions, half were from in air, half were from ePen 98.6-99.9% less emissions in vapes; all emissions exclusively from ePen Higher emission levels than cigarettes due to its role in heating the liquid Higher emission levels than cigarettes due to its role in heating the liquid 97% less emissions than cigarettes 98.6-99.9% less emissions in vapes; for vapes, more present in air than from ePen

Compound

Formaldehyde Acetaldehyde Acrolein Glycerol Propylene Glycol Nicotine Acetone

Table 2: Results from Nichols, et al.3 Emission Results

Less emissions in vapes; a non-significant difference was detected between IS1.0(TT) and ePen levels Less emissions in vapes; levels no hirer from IS1.0(TT) than from the air Less emissions in vapes; levels no hirer from IS1.0(TT) than from the air Higher emission levels from IS1.0(TT) than cigarettes and ePen, used in the liquid heating process Higher emission levels from IS1.0(TT) than cigarettes and ePen, used in the liquid heating process 97% less emissions than cigarettes; similar emissions between IS1.0(TT) and ePen Less emissions in vapes (Further details not extensively reported)

Overall, the ePen was shown to have fewer chemical emissions in its aerosol than cigarettes, with, on average, between 82-99% lower per-puff emission level than the traditional cigarette. The authors of this article suggested their findings support the claim that e-cigarettes are a “less harmful alternative” to traditional cigarettes, but they remained cautious of the impact of these toxicants, even at decreased levels.6

They used the 1RgF Kentucky Reference Cigarette as the cigarette reference, IS1.0(TT) as an e- cigarette reference, previous data on the Vype ePen, and a control of laboratory air. A smoking machine was also used to simulate use. Similar procedures as the previous study were used for emission analysis. Table 2 summarizes the findings of Nichol, etal.3

In general, Nichol, et al concurred with the previous study to show that e-cigarettes had significantly lower toxicant levels than cigarettes. These researchers cite the need to test the toxicology of the chemicals at the levels they are found in e-cigarette aerosols.3

Conclusions and Further Research:

While extensive research has identified the similarities between of the chemicals produces by vapes and cigarettes, this knowledge is not exhaustive. Given that cancers take years to develop and vaping products are new to the market, decades must pass to allow the longterm studies required to fully understand the effects of vaping to be conducted. More research is necessary to confirm and supplement what is known about the chemistry of vaping and cigarettes, especially its impact on the body.

1 Rodriguez, Carmen Heredia. "Cigarettes Vs. Vaping: That's the 'Wrong Comparison,' Says Inhalation Researcher." Kaiser Health News, Kaiser Family Foundation, 4 Nov. 2019, khn.org/news/cigarettes-vs-vaping-thatsthe-wrong-comparison-says-inhalation-researcher/. Accessed 3 May 2020. 2 HowStuffWorks.Com. “Electronic Cigarette.” HowStuffWorks, 2011, https://science.howstuffworks.com/innovation/everyday-innovations/electronic-cigarette1.htm 3 Margham, Jennifer, et al. "Chemical Composition of Aerosol from an E-Cigarette: A Quantitative Comparison with Cigarette Smoke." Chemical Research in Toxicology, vol. 29, no. 10, 18 Sept. 2016, pp. 1662-78. ACS Publications, https://pubs.acs.org/doi/10.1021/acs.chemrestox.6b00188. Accessed 3 May 2020. 4 Blaha, Michael Joseph, M.D., M.P.H., editor. "5 Vaping Facts You Need to Know." Johns Hopkins Medicine: Health, Johns Hopkins University, www.hopkinsmedicine.org/health/wellness-and-prevention/5-truths-you-need-to-knowabout-vaping. Accessed 3 May 2020. 5Gottschalk, Laura, et al. "Is Vaping Safer than Smoking Cigarettes?" Edited by Dr. Diana Zuckerman and other senior staff. National Center for Health Research, 2020, www.center4research.org/vaping-safer-smoking-cigarettes-2/. Accessed 3 May 2020. 6 Nichol, James, et al. "Comprehensive Chemical Characterization of the Aerosol Emissions of a Vaping Product Based on a New Technology." Chemical Research in Toxicology, vol. 33, no. 3, 3 Mar. 2020, pp. 789-99. ACS Publications, pubs.acs.org/doi/10.1021/acs.chemrestox.9b00442. Accessed 3 May 2020. 7 HarvardUniversity.“Smokingmachine.”TheHarvardGazette,TheHarvard Gazette, https://news.harvard.edu/gazette/story/2016/11/creating-a-smokingmachine/