Cigarette Smokers Versus Cannabis Smokers Versus Co-users of Cigarettes and Cannabis: A Pilot Study Examining Exposure to Toxicants

Introduction: Studies suggest tobacco and cannabis co-users may experience greater toxicant exposure than exclusive cigarette (ET) smokers. No study has systematically tested differences in toxicant exposure among co-users, exclusive cannabis (ECa) smokers, and ET smokers. Aims and Methods: Adult daily cigarette smokers and/or weekly cannabis smokers completed two laboratory visits. Co-users (n = 19) tested positive for urinary 11-nor-9-carboxy-Lambda(9)-tetrahydro-cannabinol (THCCOOH), self-reported cannabis use >= 1 per week, and smoked >= 5 cigarettes per day (CPD). ET smokers (n = 18) denied past month cannabis use, tested negative for urinary THCCOOH and smoked =5 CPD. ECa smokers (n = 16) tested positive for urinary THCCOOH, self-reported cannabis use =1 per week, and denied past month tobacco use (NicAlert <3). Self-reported tobacco and cannabis use were collected at both visits. First morning urinary tobacco and combustion-related biomarkers of exposure were compared following a cannabis or tobacco smoking session (visit 2). Results: Co-users and ET smokers had higher levels of exhaled carbon monoxide, total nicotine equivalents, metabolites of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNAL), and all four measured mercapturic acids (measures of volatile organic compounds) than ECa smokers (ps < .005). ET smokers (geometric mean = 7220.2 pmol/mg) had higher levels of 2-hydroxypropylmercapturic acid than co-users (geometric mean = 5348.7 adjusted p =.009). Phenanthrene tetraol did not differ by group (p > .05). Conclusions: Co-users and ET smokers demonstrated comparable levels of biomarkers of exposure to harmful constituents despite smoking similar amounts of tobacco. ECa smokers demonstrated lower levels of toxicant exposure for most biomarkers.