Meta-Analysis on the Health Effects of Primary and Secondary Exposure to Electronic Cigarette Vapor.
Cigarette smoking is a global health hazard. The current primary and secondary tobacco smoker death toll is approximately 6 million per year (WHO, 2015). Moreover, smoking is one of the leading causes of cancer, asthma, cardiovascular diseases and addiction (Health and Services, 2014). Passive smoking or second-hand smoking, which is caused by the inhalation of sidestream vapor from the cigarette and/or mainstream vapor exhaled by the cigarette user, may lead to severe health conditions in the secondary smoker (Cao et al., 2015). Even though, there are regulations restricting the smoking indoors or at public places, passive smoking remains a global health concern, as it causes approximately 600,000 deaths per year (Oberg et al., 2011, Arora and Kumar, 2011).
Electronic cigarettes (e-cigarettes or e-cig) were introduced mainly for mitigation or cessation of tobacco smoking, as well as to reduce passive smoking (Bullen, 2014). E-cigs are „recreational nicotine devices‟ which are designed to mimic the „act of smoking‟ (vaping) (Cahn and Siegel, 2011a). Apart from the primary health consequences caused by nicotine and toxic byproducts of vaping, the continuous act of smoking may lead to addiction. Increasing rate of adolescent addiction to vaping and subsequent chronic smoking has also been a great concern (Fillon, 2015b, Klein, 2015).
While the global health consequences of tobacco smoking are well established and being addressed, the studies of e-cigarette vaping are rather controversial and inconclusive. Therefore, there is an urgent need for critical evaluation of primary and secondary health hazards and addictive effects of vaping.
Primary smoking health consequences: In contradiction to the popular claim that e-cigs are healthier alternatives for tobacco smoking and an effective smoking cessation approach (Adkison et al., 2013, Goniewicz et al., 2013), studies have reported higher levels of toxic chemicals, carcinogens, nicotine by-products in e-cig vapors, which may lead to primary health hazards (Farsalinos et al., 2015a, Etter, 2009, Cavico et al., 2014).
Secondary smoking health consequences: Many of the promoting studies of e-cigs have implied that no toxic vapor is produced from them (Long, 2014, Tayyarah and Long, 2014). However, recent reports suggest that e-cigs do produce both sidestream and mainstream toxic vapors that may cause severe health consequences in bystanders, especially vulnerable populations such as pregnant women and children (Protano et al., 2015, Ballbe et al., 2014).
E-cigarette nicotine addiction: There is an alarming rise in news on e-cig addiction in nonsmokers, especially young adolescents and school children. This addiction has been attributed to the misleading commercials from e-cigarette companies (Dufort and Owila, 2014). Regulations are in place to ban or control selling e-cigarettes to minors to avoid addiction in adolescents and school children (Tremblay et al., 2015, Kmietowicz, 2014).
Knowledge gap: Currently available information of e-cigarette safety, their efficacy as a tobacco cessation approach, and primary and secondary harmful health hazards are mostly inaccurate, inconsistent or controversial (Peralta and Guntur, 2014, Drummond and Upson, 2014). Albeit the lower toxin levels found in e-cigs as opposed to tobacco cigarettes, a growing body of literature provides evidence of carcinogens, additives and flavors in e-cigs. However, another set of reports contradict these studies implying the e-cigs are indeed user- and environment-friendly. 3 Therefore, there exists a knowledge gap regarding critical evaluation of these studies to assess the real-time health effects of vaping.
There are highly controversial studies performed on the health hazards of e-cigs. Yet the effects of e-cigs on this „cycle of primary and secondary health hazards and addiction‟ have not be systematically reviewed before. Due to the controversial nature of the reported health hazards of e-cigs, the community may continue using e-cigs while the rate of new users increases rapidly. Therefore, a comparative and systematic evaluation of the primary, secondary and addictive effects of e-cigarettes is essential.
1.4 Research Questions
Three research question have been chosen to be addressed based on the literature survey conducted above. The questions are as follows;
1.5 Hypothesis
The mainstream vapor inhaled into the primary smoker leads to health effects such as cancer, asthma, heart diseases and dental/oral conditions. Long-term usage of e-cigarettes by primary smokers lead to nicotine addiction. Both sidestream vapor released from the e-cigarette 4 and mainstream vapor exhaled by e-cigarette user are inhaled by the bystander (secondary smoker) and this passive smoking cause health conditions as well as addiction. Therefore, I hypothesize that there is a „health effects cycle‟ of electronic cigarettes (Figure 1. 1).