Abstract
With the rapid increase in electronic cigarette (e-cig) users worldwide, secondhand exposure to e-cig aerosols has become a serious public health concern. We summarize the evidence on the effects of e-cigs on indoor air quality, chemical compositions of mainstream and secondhand e-cig aerosols, and associated respiratory and cardiovascular effects. The use of e-cigs in indoor environments leads to high levels of fine and ultrafine particles similar to tobacco cigarettes (t-cigs). Concentrations of chemical compounds in e-cig aerosols are generally lower than those in t-cig smoke, but a substantial amount of vaporized propylene glycol, vegetable glycerin, nicotine, and toxic substances, such as aldehydes and heavy metals, has been reported. Exposures to mainstream e-cig aerosols have biologic effects but only limited evidence shows adverse respiratory and cardiovascular effects in humans. Long-term studies are needed to better understand the dosimetry and health effects of exposures to secondhand e-cig aerosols.
Highlights
An electronic cigarette (e-cig) is a battery-powered nicotine delivery system widely used as an alternative to tobacco cigarettes (t-cigs)
To provide a better understanding of the public health risks associated with secondhand exposures to e-cig aerosols, we summarize here the evidence for the impacts of e-cigs on indoor air quality and human health
We reviewed articles published in English and listed on PubMed and the Web of Science before April 2019 that investigated either particulate matter (PM) or chemical compositions in e-cig aerosols, as well as associated health effects
Summary
An electronic cigarette (e-cig) is a battery-powered nicotine delivery system widely used as an alternative to tobacco cigarettes (t-cigs). In the United States, the total number of current e-cig users in middle schools and high schools increased from 0.3 million in 2011 to 3.6 million in 2018 [23]. For t-cigs, the combustion of tobacco leaves releases nicotine and substantial amounts of toxic by-products. Because e-cigs are easy to use, have appealing flavors, and are perceived risk-free [12, 20], they are becoming the most popular tobacco product among adolescents. The newly introduced pod-based e-cigs (e.g., JUUL), which use nicotine salts, offer a wide range of flavors, and have a sleek design, are even more attractive to adolescents than are regular tank-based e-cigs [20, 48, 57, 87]. The impacts of e-cigs on population health remain largely unknown; with increasing evidence on their biological effects from in vitro and in vivo studies [107], the safety of e-cigs has become a serious public health concern
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