The researchers analyzed urine and saliva samples for biomarkers of nicotine: tobacco-specific N-nitrosamines (TSNAs), including the established carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1 butanol, or NNAL, and a number of different metabolites of volatile organic compounds (VOCs). Both TSNAs and VOCs are well-known to contribute to cigarette-related carcinogenic risk. “The NRT-only and e-cigarette–only users had markedly lower NNAL levels than combustible cigarette–only, dual combustible cigarette–NRT, and dual combustible cigarette–e-cigarette users (P < 0.001).” Dr Shahab and colleagues report. Indeed, former smokers who only used e-cigarette had 97% lower NNAL levels compared with NNAL levels detected in smokers. “Results followed a similar, albeit less pronounced, pattern for the other TSNAs measured,” they add.