Q&A:

6.1 Do e-cigarette vapours pose the same risks to bystanders and family members as second-hand smoke from cigarettes?

No, far from it. Overall: bystanders are exposed to far lower levels of toxicants and for much less time. Three things are very different and toxic exposure to bystanders depends on all three:

1. The quantity emitted. Most of the inhaled vapour is absorbed by the user and only a small fraction is exhaled (15% or less, depending on the constituent).  In contrast, about four times as much environmental tobacco smoke comes directly from the burning tip of the cigarette than is exhaled by the smoker. There is no equivalent of this “sidestream smoke” for vaping.
2. The toxicity of the emissions. Tobacco smoke contains hundreds of toxic products of combustion that are either not present or present at very low levels in vapour aerosol. Vapour emissions do not have toxicants present at levels that pose a material risk to health. Exposure to nicotine, itself relatively benign, is unlikely to reach a level of pharmacological or clinical relevance.
3. The time that the emissions remain in the atmosphere. Environmental tobacco smoke persists for far longer in the environment (about 20-40 minutes per exhalation). The vapour aerosol droplets evaporate in less than a minute and the gas phase disperses in less than 2 minutes.

Many studies have misunderstood the risks; it is not sufficient to detect agents in the indoor air to declare a risk, the risk depends on exposure. It is possible to compare exposures with second-hand tobacco smoke or by reference to an indoor air quality standard – for example, standards set in workplaces for occupational exposure.

[With thanks to Roberto Sussman]

Further reading

• Avino et al. Second-hand Aerosol From Tobacco and Electronic Cigarettes: Evaluation of the Smoker Emission Rates and Doses and Lung Cancer Risk of Passive Smokers and Vapers. 2018 [link]  “…excess life cancer risk (ELCR) for second-hand smokers was five orders of magnitude larger than for second-hand vapers.“
• O’Connell G et al. An Assessment of Indoor Air Quality before, during and after Unrestricted Use of E-Cigarettes in a Small Room, setting Int. J. Environ. Res. Public Health 2015. [link] “In this study, the data suggest that any additional chemicals present in indoor air from the exhaled e-cigarette aerosol, are unlikely to present an air quality issue to bystanders at the levels measured when compared to the regulatory standards that are used for workplaces or general indoor air quality.” [note: tobacco industry study].
• Fernández E et al. Particulate Matter from Electronic Cigarettes and Conventional Cigarettes: a Systematic Review and Observational Study, Current Environmental Health Reports., 2015. [link] “We have found similar concentrations of PM2.5 in the smoke-free homes and in the e-cigarette user homes, both under 10 μg/m3, which is the threshold concentration for long-term exposures established in the Air Quality Guidelines of the World Health Organization [13]. This is in contrast to the PM2.5 concentrations in the conventional cigarette user’s home, which were 58 times higher than in the e-cigarette user home.” Despite these encouraging findings, the authors tried to put a negative spin on the paper. They were called out by Mike Siegel: New Article Demonstrates Severe Bias by Anti-Tobacco Researchers in the Communication of Scientific Results about E-Cigarettes

6.2 Should vaping be banned by law in public places and workplaces?

No. There is a (contested) case to ban indoor smoking as there is science showing that second-hand cigarette smoke exposure is harmful to bystanders. However, e-cigarette vapour is quite different chemically and physically. The evidence suggests vaping creates exposures far below thresholds that would be allowed for occupational health limits, for example. The force of law should be reserved for protecting people from material harm caused by others. Vaping may still be disagreeable to some people, but it is primarily a matter of etiquette and respect for the preferences of others. E-cigarette policy should be decided, therefore, by the owners and managers of premises (hotels, bars, restaurants, shops, transportation, offices, public buildings etc). The hospitality industry may be more open to vaping and to welcome vapers, but public buildings will be most likely to prohibit it. The point is that owners and managers should be able to make the decisions that are right for them and their clientele.