The genotoxicity of mainstream and sidestream marijuana and tobacco smoke condensates.

While the prevalence of tobacco use has decreased in Canada over the past decade, that of marijuana use has increased, particularly among youth. However, the risks of adverse health effects from marijuana smoke exposure, specifically as compared to tobacco, are currently not well understood. The objectives of this study were to evaluate the relative ability of matched marijuana and tobacco condensates to induce (geno)toxic responses in three in vitro test systems. This study provides comparative data for matched sidestream and mainstream condensates, as well as condensates prepared under both a standard and an extreme smoking regime designed to mimic marijuana smoking habits. The results indicate that tobacco and marijuana smoke differ substantially in terms of their cytotoxicity, Salmonella mutagenicity, and ability to induce chromosomal damage (i.e., micronucleus formation). Specifically, the marijuana condensates were all found to be more cytotoxic and more mutagenic in the presence of S9 than the matched tobacco condensates. In contrast, the tobacco condensates appeared to induce cytogenetic damage in a concentration-dependent manner, whereas the matched marijuana condensates did not. In addition, when corrected for total particulate matter yield, little difference was observed in the mutagenic activity of samples smoked under the extreme vs the standard regime for both tobacco and marijuana condensates.