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Introduction Smoking exposes people to high levels of Tobacco-Specific Nitrosamines (TSNAs), which include potent carcinogens. We systematically reviewed TSNA exposure between people smoking, vaping, and doing neither. Aims and Methods Databases were searched between August 2017–March 2022, using vaping-related terms. Peer-reviewed articles reporting TSNA metabolites (NNAL, NNN, NAB, and NAT) levels in bio-samples among adults exclusively vaping, exclusively smoking, or doing neither were included. Where possible, meta-analyses were conducted. Results Of 12 781 identified studies, 22 were included. TSNA levels fell substantially when people who smoke switched to vaping in longitudinal studies and were lower among people who vaped compared to smoked in cross-sectional studies. Levels of TSNAs were similar when comparing people who switched from smoking to vaping, to those who switched to no use of nicotine products, in longitudinal studies. Levels were higher among people who vaped compared to people who neither vaped nor smoked in cross-sectional studies. When comparing people who vaped to smoked: pooled urinary NNAL was 79% lower across three randomized controlled trials and 96% lower across three cross-sectional studies; pooled NAB was 87% lower and NAT 94% lower in two cross-sectional studies. When comparing people who neither vaped nor smoked to people who vaped, pooled urinary NNAL was 80%, NAB 26%, and NAT 27% lower in two cross-sectional studies. Other longitudinal data, and NNN levels could not be pooled. Conclusions Exposure to all TSNAs was lower among people who vaped compared to people who smoked. Levels were higher among people who vaped compared to people who neither vaped nor smoked. Implications As well as TSNAs, there are many other toxicant exposures from smoking and vaping that can increase the risk of disease. However, it is likely that the reduced exposure to TSNAs from vaping relative to smoking reduces the risk to health of those who use vaping products to quit smoking. Future high-quality research, with robust definitions of exclusive vaping and smoking, and accounting for TSNAs half-lives, is needed to fully assess exposure to TSNAs among people who vape. [ABSTRACT FROM AUTHOR]

Background: Tobacco industry (TI) companies have entered the UK e-cigarette ("vaping") market in recent years. However, their motives and ambitions are unclear. This study explored how popular TI vaping products are and who uses them, and how they differ from independent products.Methods: Secondary analysis of data from a longitudinal web-based survey of smokers, ex-smokers, and vapers (n = 3883) in the UK in 2019. The main study sample consisted of daily and nondaily vapers, who were current or ex-cigarette smokers, and had stated the brand of their preferred e-cigarette device (n = 1202). Proportions using TI and independent brands were calculated and regression analysis assessed associations with sociodemographic and smoking/vaping characteristics between vapers of TI and independent products. Chi-square tests were used to analyze differences between TI and independent products.Results: Overall, 53.4% used TI products. A university education (67.6%; adjOR = 1.54; 95% CI, 1.140-2.088), nondaily vaping (68.2%; adjOR = 1.39; CI, 1.029-1.880), and cigarette dependence (moderate, strong and very strong urges to smoke) were associated with using TI vaping brands. TI products used were less likely to be refillable ("open") than independent brands (60.9% vs. 18.3%, chi-square = 228.98, p < .001), more likely to use nicotine salts (16.7% vs. 8.6%, chi-square = 25.04, p < .001) and tobacco flavors (23.8% vs. 17.9%, chi-square = 12.65, p < .001).Conclusion: TI vaping products were popular in the UK, associations with product and user characteristics suggest that TI products may be less conducive to smoking cessation, although the findings were not always consistent.Implications: Consequences of regulations need to be carefully considered to ensure that independent producers are not more negatively impacted than tobacco industry producers, and to avoid reducing utility of products for smoking cessation. [ABSTRACT FROM AUTHOR]