Heated tobacco product aerosol emission compared to cigarette smoke: A scoping review

Heated tobacco products (HTPs) are promoted as reduced-risk alternatives to combustible tobacco cigarettes (TCs), yet toxicant exposure reduction and associated health benefits remain uncertain. We evaluated preclinical and interventional clinical studies comparing HTPs with TCs, focusing on aerosol composition, toxicological exposure, and harm biomarkers. A systematic PubMed search identified 1105 peer-reviewed articles published between January 2017 and October 2024. Studies were screened using validated MeSH terms and commercial brand names. Forty-three articles met inclusion criteria, reporting standardized aerosol characterization, in vivo or in vitro toxicology, or biomarker assessments. Data were extracted by independent reviewers. Clinical studies were categorized by exposure duration (acute, short, medium, or long-term). HTP aerosols contained up to 95 % lower levels of regulated toxicants and exhibited substantially reduced mutagenic, toxic, genotoxic, carcinogenic, and proinflammatory activities (85-95 % reduction) compared with TC smoke. Among 24 interventional clinical studies, 20 reported 40-97 % reductions in toxicant biomarkers of exposure (BoE)-including tobacco-specific nitrosamines, carboxyhemoglobin, volatile organic compounds, and mutagenic metabolites-among smokers who switched completely to HTPs. These reductions were observed from minutes to 24 months and occurred largely independently of systemic nicotine concentrations. Four independent studies reported no significant improvement or detected adverse effects. International health authorities acknowledge that HTP aerosols contain carcinogenic and mutagenic constituents, albeit at substantially lower concentrations than TC smoke, suggesting a potential-though unconfirmed-risk reduction. Overall, HTP users experience lower toxicant exposure than TC smokers; however, additional independent, long-term investigations are required to determine the actual health impact of sustained HTP use.