Public Health Consequences of E-Cigarettes (2018) / Chapter Skim
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10 Cancers
10 Cancers
Pages 381-404
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From page 381... ...
. The cancer risk associated with the use of electronic cigarettes hypothetically would be expected to be less than combustible tobacco cigarettes based on the rationale that e-cigarettes include nicotine from tobacco -- but not all the other tobacco constituents -- and would therefore result in a reduced burden of carcinogens delivered to the user.
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From page 382... ...
. (Comparisons of combustible tobacco smoke and e-cigarette aerosols are described in more detail in Chapter 18 on Harm Reduction.)
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From page 383... ...
OPTIMAL STUDY DESIGN The strongest evidence to characterize the potential association between e-cigarette use and the risk of human cancer will be methodologically rigorous epidemiological studies with human cancer as the outcome. Importantly, many e-cigarette users will be current or former combustible tobacco cigarette smokers, especially in the near term, and the effects of current and former smoking will be a challenging confounder to account
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From page 384... ...
The results do not provide any indication for cancer risk reduction from sole use of e-cigarettes. These data are extremely limited by sample size and are of low quality; for example, the cancer data are presumably self-reported and not pathologically confirmed, the sample size is very small to assess the endpoint of any cancer and precludes assessment of specific malignancies, and there is no consideration of complete combustible tobacco cigarette smoking history or potential confounding factors.
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From page 385... ...
The results were also presented for the measure of total micronuclei/1,000 cells; compared with non-smokers of combustible tobacco cigarettes and e-cigarettes, e-cigarette users had mean levels that were 133 percent higher and combustible tobacco cigarette smokers had mean levels that were 633 percent greater. The pattern of associations for both micronuclei measures presented were thus consistent in showing that the average micronuclei burden was elevated in e-cigarette users relative to that in never smokers, and was elevated fourfold or more in combustible tobacco cigarette smokers compared with e-cigarette users.
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From page 386... ...
The patient was then able to successfully quit smoking by using e-cigarettes. Even though the patient still used e-cigarettes after he stopped smoking combustible tobacco cigarettes, 6 months after quitting the latter, all the patient's markers of inflammation were significantly reduced, including leucocytes, lymphocytes, neutrophils, and C-reactive protein (Farsalinos and Romagna, 2013)
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From page 387... ...
These case reports raise interesting questions and einforce r the long-term need for carefully designed epidemiological studies of e-cigarette use in relation to cancer risk that include appropriate comparisons based on jointly considering the use of combustible tobacco cigarettes and e-cigarettes. IN VIVO ANIMAL STUDIES The literature search identified no in vivo animal studies focused on the potential carcinogenic actions of long-term e-cigarette use (Dodmane et al., 2014; Haussmann and Fariss, 2016; Toth, 1982; Waldum et al., 1996)
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From page 388... ...
, were used. Combustible tobacco cigarettes (Kentucky reference 3R4F, 1R5F, and Marlboro Gold)
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From page 389... ...
was observed for all e-liquids. 0–20 mg/ml and for combustible tobacco cigarettes, 0–0.5 mg/ml.
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. reference combustible tobacco cigarettes (3R4F)
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. Combustible tobacco 3R4F 0 cigarette smoke aerosols 3.1 ± 0.3 were genotoxic at a 3.1-µg/ 5.4 ± 1.8 cm2 dose and cytotoxic at 10.5 ± 1.2 26.9 µg/cm2.
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From page 392... ...
There was a strong inverse correlation between the FRAP activity in lung tissue and 8-OHdG levels (r = 0.845, n = 5) , further supporting the conclusion that e-cigarette aerosols increase oxidative stress in the lung.
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From page 393... ...
. Relevance of DNA-Damage/Mutagenicity Studies and the Presence of DNA-Reactive Chemicals in E-Cigarette Aerosols to Potential Human Cancer Risk from E-Cigarette Use As discussed above, some of the in vitro studies have found evidence that chemical constituents of e-cigarette aerosols are capable of reacting with DNA and in some instances inducing mutations in vitro and following in vivo exposure (Canistro et al., 2017)
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From page 394... ...
, Goniewicz (2014) measured the levels of formaldehyde and other carbonyl compounds in e-cigarettes and compared them with the levels present in combustible tobacco cigarettes.
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From page 395... ...
from combustible tobacco products. Thus, although there is substantial evidence that these DNA-reactive and potentially mutagenic compounds are formed and present in e-cigarette aerosols, the relatively low levels of exposure, coupled with the relatively low carcinogenic potential of these compounds, suggest that cancer risk from long-term use of e-cigarettes, if any, is likely to be very low, when compared with that from combustible tobacco cigarettes.
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From page 396... ...
396 TABLE 10-3 Formaldehyde and Acrolein Levels Generated from Five E-Cigarette Devices at Different Power Levels Units Adjusted to µg/15 Puffs Device 1 Device 2 Device 3 Device 4 Device 5 Power Level Form.
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From page 397... ...
For example, among smokers the overall contribution of nicotine exposure from NRT can only be expected to be a very small fraction of a smoker's overall nicotine exposure because it will be greatly outweighed by the nicotine exposure from years of smoking combustible tobacco cigarettes. Continued greater use of NRT usually occurs in more addicted smokers who have a more difficult time quitting (Alberg et al., 2005)
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From page 398... ...
Nicotine itself, as used in nicotine replacement therapies, is challenging to study in relation to cancer risk in epidemiological studies; the one high-quality study to evaluate the potential carcinogenicity of nicotine in NRT, the Lung Health Study, yielded null findings (see Murray et al., 2009, above)
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From page 399... ...
evaluated whether nicotine administration could enhance the development of NNK-initiated lung tumors in A/J mice. They found that nicotine alone, administered at a daily dose of 0.15 mg/mouse for 46 weeks did not increase lung tumor multiplicity.
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From page 400... ...
For lung cancer, the younger the age of initiation of combustible tobacco cigarette smoking, the greater the risk of developing lung cancer in adulthood even after adjusting for lifetime combustible tobacco cigarette smoke exposure dose (HHS, 2014)
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From page 401... ...
Finding: There are no available epidemiological studies on the potential association between e-cigarette use and cancer in humans to make any conclusions. This holds true for comparisons of e-cigarette use compared with combustible tobacco cigarettes and e-cigarette use compared with no use of tobacco products.
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From page 402... ...
2012. Acute effects of electronic and tobacco cigarette smoking on complete blood count.
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From page 403... ...
2006. The health consequences of involuntary exposure to tobacco smoke: A report of the Sur geon General.
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From page 404... ...
2014. Comparative in vitro toxicity profile of electronic and tobacco cigarettes, smokeless tobacco and nicotine replacement therapy products: E-liquids, extracts and collected aerosols.
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