Urinary cyanoethyl mercapturic acid, a biomarker of the smoke toxicant acrylonitrile, clearly distinguishes smokers from non-smokers.

INTRODUCTION: Cyanoethyl mercapturic acid (CEMA) is a urinary metabolite of acrylonitrile, a toxicant found in substantial quantities in cigarette smoke, but not in non-combusted products such as e-cigarettes or smokeless tobacco and rarely in the diet or in the general human environment. Thus, we hypothesized that CEMA is an excellent biomarker of combusted tobacco product use. METHODS: We tested this hypothesis by analyzing CEMA in the urine of 1259 cigarette smokers (urinary cotinine ≥ 25 ng/ml) and 1191 non-smokers. The analyses of CEMA and cotinine were performed by validated liquid chromatography-tandem mass spectrometry methods. Logistic regression was fit for log-transformed CEMA to construct the ROC curve. RESULTS: We found that a CEMA cut point of 27 pmol/ml urine differentiated cigarette smokers from non-smokers with sensitivity and specificity >99%. Use of different cotinine cut points to define smokers (10-30 ng/ml) had little effect on the results. CONCLUSIONS: CEMA is a highly reliable urinary biomarker to identify users of combusted tobacco products such as cigarettes as opposed to users of non-combusted products, medicinal nicotine, or non-users of tobacco products. IMPLICATIONS: CEMA can be used to distinguish users of combusted tobacco products from non-combusted products such as e-cigarettes, smokeless tobacco, and medicinal nicotine. Levels of CEMA in the urine of people who use these non-combusted products are extremely low, in contrast to cotinine.