E-CIGARETTES may be carcinogenic, with evidence linking vaping to DNA damage, inflammation, and cancer-related biomarkers.
A qualitative risk assessment has concluded that nicotine-based e-cigarettes are likely to be carcinogenic to humans who use them, with an indeterminate future burden of oral cancer and lung cancer. While direct epidemiological evidence of cancer causation remains limited because e-cigarettes have only been widely used for around two decades, the assessment draws together human biomarker data, animal studies, laboratory analyses, and mechanistic evidence to evaluate carcinogenic potential.
The review found that biomarkers of exposure and harm increasingly point toward tumorigenic pathways. Vape-derived metabolites were associated with DNA damage attributable to carcinogens including nicotine-derived nitrosamines, volatile organic compounds, flavor-derived agents, and certain metals. Additional biomarkers indicated oxidative stress, epigenetic change, and inflammation in oral and respiratory tissues, often compared with cigarette smoking.
Mechanistic Evidence Supports Carcinogenicity
Laboratory and animal findings strengthened concern around e-cigarettes cancer risk. Rodent bioassays included inhalation exposure of mice to e-cigarette aerosol, with lung adenocarcinomas reported in 22.5% of exposed animals. Mechanistic data were evaluated against key characteristics of carcinogens, implicating a complex aerosol mixture that may act through genotoxic and non-genotoxic processes.
The review also noted that conclusions across published reviews have shifted between 2017 and 2025, moving from calls for more evidence toward explicit concern about e-cigarette carcinogenicity. Human studies remain limited, but the available evidence includes oral cancer case reports, biomarker studies using high cotinine levels, and signals of DNA damage and inflammatory effects relevant to cancer development.
A companion commentary drew a historical parallel with tobacco, emphasizing that smoking was once given the benefit of doubt while evidence accumulated slowly over decades. The authors argued that the same delay should not be repeated for e-cigarettes, particularly given emerging evidence around dual tobacco and e-cigarette use and the known challenge of quantifying cancer risk in young e-cigarette-only cohorts.
For clinicians, the findings support a precautionary approach. E-cigarettes should not be positioned as a risk-free smoking alternative, especially when dual use may persist. The current evidence does not yet quantify cancer burden, but it does indicate biologically plausible pathways linking vaping with oral and lung cancer risk.
Reference
Stewart BW et al. The carcinogenicity of e-cigarettes: a qualitative risk assessment. Carcinogenesis. 2026;47(1):bgag015.
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