Etemadi A, et al. - Researchers analyzed variations in carcinogen exposure across 165 participants of Golestan Cohort Study from northeastern Iran, including 60 never-users of any tobacco, 35 exclusive cigarette, 40 exclusive (78% daily) waterpipe, and 30 exclusive smokeless tobacco (nass) users. Baseline urine samples were analyzed to measure concentrations of 39 biomarkers of exposure. The highest concentrations of tobacco alkaloids were detected in nass users. Compared with never-tobacco users and nass users, both cigarette and waterpipe smokers had higher polycyclic aromatic hydrocarbon (PAH) and volatile organic compound (VOC) biomarkers, which highly correlated with nicotine dose. Compared with all other groups, higher PAH biomarkers of phenanthrene and pyrene and two VOC metabolites (phenylmercapturic acid and phenylglyoxylic acid) were detected in waterpipe smokers. Comparable PAH biomarkers were noted among Golestan never tobacco users vs those in US cigarette smokers. Overall, two patterns of exposure biomarkers were defined that allowed discrimination of the use of the combustible products (cigarettes and waterpipe) from the smokeless product. High levels of PAH metabolites in the Golestan Cohort were attributed to environmental exposure from non-tobacco sources.