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It is our experience that many attorneys and their teams struggle to keep up with new science in a systematic and organized fashion. However, we have also encountered scientific savvy firms that are up-to-date on the science and hard at work analyzing and developing new legal strategies based on the emerging science. This latter group is best-positioned to provide their clients with the best science-based defense.

E-cigarettes are electronic nicotine delivery systems (ENDS) that deliver nicotine in an aerosolized form, and as we have discussed in a number of previous posts (see here, here, and here), the science related to e-cigarettes has literally skyrocketed over the past couple of years. This is clearly depicted in the following graphic which shows the number of publications (over 20 years) based on a keyword search using the term “e-cigarette” in the Pubmed database. Please keep in mind this is an underestimate of the actual number of publications since a more sophisticated keyword search strategy, and searches of other databases would certainly turn up additional publications.

Regarding the safety of e-cigarettes, scientists are evaluating the safety and toxicity of e-cigarettes as a whole (e.g. effects of inhaling e-cigarette aerosol, chemical analysis of aerosols to detect potentially harmful substances such as heavy metals, formaldehyde, etc.), as well as individual constituents, such as potential toxicity of e-liquids as a whole, or individual ingredients found in e-liquids (e.g. flavorings, nicotine, propylene glycol, glycerol, among many others). Another safety issue is related to the actual devices themselves, and instances of exploding e-cigarette devices have triggered numerous lawsuits which have grabbed media headlines over the past couple of years (see here for a recent one).

To provide our readers with a sense of some of the recent safety science related to e-cigarettes, we provide high-level summaries of four recent studies that evaluate the safety of e-cigarettes or their constituent ingredients.


Acute Exposure to Propylene Glycol and Glycerol Aerosol Did Not Significantly Alter Lung Function in Healthy and Asthmatic Individuals (February 2017)

Boulay et al. sought to characterize the acute effects of inhaling a mixture of propylene glycol (PG) and glycerol (Gly) aerosol on lung function in both healthy and asthmatic subjects. The study was a randomized cross-over, placebo-controlled study, and the e-liquid consisted of a mixture of 70% PG and 30% Gly (a ratio that is representative of what is used in marketed e-cigarettes). The authors stated that they wanted to create a best-case scenario on the pulmonary effects of PG and Gly, and thus excluded other e-liquid constituents (such as flavorings and nicotine). Overall, the authors report that acute exposure to PG/Gly aerosol did not appear to cause significant functional pulmonary alterations in healthy or asthmatic individuals. However, they did note that the pulmonary effects of chronic use of e-cigarettes remains to be investigated.

Study Purports to Demonstrate that Inhalation of E-Cigarette Aerosol Can Impair Lung Function in Animals (March 2017)

In a study by Larcombe et al., investigators evaluated lung function and pulmonary inflammation in mice after exposure to e-cigarette aerosol or tobacco smoke. Animals were exposed for 8 weeks to tobacco smoke, medical air (control) or one of four types of e-cigarette aerosol (these varied based on nicotine content and main excipient (propylene glycol or glycerin)). Twenty-four hours after the final exposure, the authors measured pulmonary inflammation, lung volume, lung mechanics, and responsiveness to methacholine (a measure of lung function). Overall, the authors reported that mice exposed to tobacco cigarette smoke had increased pulmonary inflammation and responsiveness to methacholine compared with air controls. Mice exposed to e-cigarette aerosol did not have increased inflammation, but did display decrements in lung function at both functional residual capacity and high transrespiratory pressures. Mice exposed to glycerin based e-cigarette aerosols were also hyper-responsive to methacholine regardless of the presence or absence of nicotine. According to the authors, the results of this study are the first to demonstrate that exposure to e-cigarette aerosol during adolescence and early adulthood is can result in significant impairments in lung function.

Study Purports that Flavorings Affect the Toxicity of E-Cigarette Aerosols  (November 2016)

Using an in vitro system, another study evaluated the potential adverse effects of flavored e-cigarette aerosol. Aerosol from e-cigarettes was generated using a smoking machine, and the authors tested different devices prefilled with liquids of different flavors (tobacco, piña colada, menthol, coffee and strawberry), nicotine carrier, variable nicotine concentrations and with modified battery output voltage. To test for potential adverse effects, human bronchial epithelial cells were exposed e-cigarette aerosol (55 puffs), tobacco smoke or air (controls). Overall, the authors found that product type, battery output voltage and flavors significantly affected toxicity of e-cigarette aerosol, with the strawberry-flavored product being the most toxic to the cells.

Flavoring Compounds Dominate Aldehyde Production during E-Cigarette Vaping (November 2016)

Citing a paucity of safety data regarding e-cigarette flavorings, Khlystov and Samburova sought to measure aldehydes produced by three popular brands of e-cigarettes with flavored and unflavored e-liquids. According to the authors, they show that in the tested e-cigarette brands, thermal decomposition of flavoring compounds dominated the formation of aldehydes during vaping. Further, the level produced exceeded occupational safety standards. Their data also suggest that production of aldehydes was found to be exponentially dependent on concentration of flavoring compounds.

As e-cigarette science continues to emerge, it has become increasingly important for key stakeholders to monitor scientific developments and how they may impact litigation risk. Maintaining an awareness of the latest scientific findings can help you assess the potential implications of new findings and reduce the risk of being ambushed by opponents.

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