Characterisation of mainstream and passive vapours emitted by selected electronic cigarettes

Electronic cigarettes have achieved growing popularity since their introduction onto the European market. They are promoted by manufacturers as healthier alternatives to tobacco cigarettes, however debate among scientists and public health experts about their possible impact on health and indoor air quality means further research into the product is required to ensure decisions of policymakers, health care providers and consumers are based on sound science. This study investigated and characterised the impact of ‘vaping’ (using electronic cigarettes) on indoor environments under controlled conditions using a 30 m3 emission chamber. The study determined the composition of e-cigarette mainstream vapour in terms of propylene glycol, glycerol, carbonyls and nicotine emissions using a smoking machine with adapted smoking parameters. Two different base recipes for refill liquids, with three different amounts of nicotine each, were tested using two models of e-cigarettes. Refill liquids were analysed on their content of propylene glycol, glycerol, nicotine and qualitatively on their principal flavourings. Possible health effects of e-cigarette use are not discussed in this work. Electronic cigarettes tested in this study proved to be sources for propylene glycol, glycerol, nicotine, carbonyls and aerosol particulates. The extent of exposure differs significantly for active and passive ‘vapers’ (users of electronic cigarettes). Extrapolating from the average amounts of propylene glycol and glycerol condensed on the smoking machine filter pad to the resulting lung-concentration, estimated lung concentrations of 160 and 220 mg m−3 for propylene glycol and glycerol were obtained, respectively. Vaping refill liquids with nicotine concentrations of 9 mg mL−1 led to vapour condensate nicotine amounts comparable to those of low-nicotine regular cigarettes (0.15–0.2 mg). In chamber studies, peak concentrations of 2200 μg m−3 for propylene glycol, 136 μg m−3 for glycerol and 0.6 μg m−3 for nicotine were reached. Carbonyls were not detected above the detection limits in chamber studies. Particles in the size range of 20 nm to 300 nm constantly increased during vaping activity and reached final peak concentrations of 7 × 106 particles L−1. Moreover, the tested products showed design flaws such as leakages from the cartridge reservoirs. Possible long term effects of e-cigarettes on health are not yet known. E-cigarettes, the impact of vaping on health and the composition of refill liquids require therefore further research into the product characteristics. The consumers would benefit from harmonised quality and safety improvements of e-cigarettes and refill liquids.

Published: 13 October 2014

Positive:

Link to publication: http://www.sciencedirect.com/science/article/pii/S1438463914000972

Authors

Otmar Geiss
Ivana Bianchi
Francisco Barahona
Josefa Barrero-Moreno


Summary

Electronic cigarettes (e-cigarettes) have become increasingly popular since their introduction onto the European market in 2005. Use in Great Britain, for example, more than doubled from 2.7% of vapers in 2010 to 6.7% in 2012 (Dockrell et al., 2013).

They are frequently advertised by manufacturers as a healthier alternative to tobacco cigarettes (Ayers et al., 2011) and a smoking cessation tool, and have become a popular substitute for traditional tobacco because of indoor smoking restrictions on traditional tobacco cigarettes (Etter and Bullen, 2011).

Uncertainties about their impact on health and indoor air quality have caused debate among scientists and public health experts. Concerns most frequently relate to product safety in terms of product design, exposure to toxic products, potential for abuse (including dual use with tobacco products), use by young people and effectiveness in helping smokers to quit smoking tobacco cigarettes (Noel et al., 2011).

Although some studies have indicated that they are less harmful than smoking regular tobacco cigarettes (Caponetto et al., 2013 and Wagener et al., 2012), e-cigarettes and refill liquids nonetheless require further research into the detail and composition of the products, as will be required under the newly revised Tobacco Product Directive (2014/40/EU), to ensure that the decisions of policymakers, health care providers and consumers are based on sound science (Etter et al., 2011).

Only a few studies have reported on the impact of e-cigarette vaping on indoor air quality (passive vaping).Schripp et al. (2013) found that volatile organic compounds (VOCs) and ultrafine particles (UFP) were released from an e-cigarette while actively vaping in an 8 m3 emission chamber. Schober et al. (2014)reported on VOC, particle and polycyclic aromatic hydrocarbons (PAHs), carbonyls and metals releases into a real office environment. This study also monitored the effect of vaping on FeNO release and the urinary metabolite profile. McAuley et al. (2012) compared the effects of e-cigarettes vapour and cigarette smoke on indoor quality. In this study, vapours were generated using a smoking machine and were collected in a sampling bag for analysis. Fuoco et al. (2014) analysed e-cigarette generated aerosols in terms of particle number concentrations and size distribution.

Other studies have focused on safety and quality aspects of refill liquids. They reported inconsistent levels of nicotine (Goniewicz et al., 2013) and nicotine impurities (Trehy et al., 2011, Etter et al., 2013 and Hutzler et al., 2014) among batches/brands. Williams et al. (2013) described the possibility of metals, or chemicals from plastics in the delivery system, leaching into the vapour before inhalation. Behar et al. (2014)identified toxicants in cinnamon-flavoured e-cigarette refill liquids.

This study proposes a systematic approach to characterise e-cigarette emissions under controlled conditions using a smoking machine with adapted smoking parameters for the generation of vapours from well characterised refill-liquids. The impact of vaping on the indoor environment was investigated introducing the generated vapours into a 30 m3 walk-in emission chamber operated under defined conditions (temperature, relative humidity and ventilation rate). The composition of e-cigarette mainstream vapours in terms of propylene glycol, glycerol, low molecular carbonyls and nicotine emissions was determined applying an adapted standardised smoking protocol for regular cigarettes. Two models of e-cigarettes were used in this study, differing primarily by the way in which refill liquids are evaporated. In order to cover the widest range possible, two very different base recipes for the refill liquid, each with three different amounts of nicotine, were used for the emission testing. Possible health effects of e-cigarette use are not discussed in this work.


Conclusion

Electronic cigarettes tested in this study proved to be sources of propylene glycol, glycerol, nicotine, carbonyls and aerosol particulates. The extent to which people could be passively exposed to these depends on the ventilation rate, room size, indoor climate, room equipment and number of e-cigarettes in use. In addition to exposure to toxicants, consideration must also be given to the generally perceived air quality in microenvironments where vaping is permitted (independently of its toxicity). Sensory assessment of the acceptability of air quality or odour intensity by a human panel could answer this question and should be further explored.

In addition to considering exposure to second-hand vapour, this study shows that active vapers inhale relatively high concentrations of propylene glycol, glycerol, aerosol particulates and certain carbonyls. This exposure might require further toxicological evaluation.

Possible long term effects of e-cigarettes health are not yet known. E-cigarettes, the impact of vaping on health and the composition of refill liquids require therefore further research into the product characteristics. For the benefit of consumers, quality and safety requirements of e-cigarettes and refill liquids should be harmonised.


Full text

Full text in .pdf format: Full text