LAUSR

Abstract Vaping is promoted as a healthier alternative to smoking over the recent years, and e-cigarette (EC) users are considered to affect air quality (and thus contribute to passive smoking) much less than tobacco cigarette (TC) smokers. Here we test this hypothesis, by comparing measurements of the size distributions of particles and the levels of Volatile Organic Compounds (VOCs) exhaled by both EC and TC users. A total of 26 individuals (16 EC users and 10 TC users) provided exhaled air samples that were analyzed using the same protocol. Our measurements show that the particle number concentration emitted by both EC and TC users are comparable, but the size distributions of the particles emitted by the former exhibit significantly higher variability compared to those from the latter. The burden of the VOCs was much higher in the exhaled air of TC smokers compared to that of EC users. Although some of the VOCs measured in the exhaled air of EC users were expected, as they are used directly in the e-liquids, the collected mixtures were highly variable (i.e., varying significantly from case to case) with only 8 compounds being common among all individuals participating in the study. In contrast, we identified 65 compounds among the TC smokers that were common among the participants. Toxic compounds (e.g., benzene, acetaldehyde, toluene, xylenes, styrene, phenol, naphthalene, etc.) were also present in the exhaled air of EC users. The high variabilities observed in the size distributions of the exhaled particles and the levels of VOCs from different EC users (i.e., due to different devices, operational settings and liquids) warrants for further research in order to fully understand the main- and side-stream effects of EC use in the human micro-environment. Despite that, the high particle emissions and the presence, even at trace levels, of toxic VOCs in the exhaled air of EC users that are reported in this study, suggests that ECs should not be considered as harmless substitutes of TCs.