Levels and toxicological effects of heavy and trace metals in cigarette sidestream smoke particulates

[[abstract]]Introduction: Heavy and trace metals present in tobacco are discharged as part of tobacco smoke during smoking. It has long been known that excessive exposure to heavy and trace metals is harmful to health. However, metals are one of the most understudied groups of substances in environmental tobacco smoke, the most common indoor air pollutant encountered by nonsmokers. Objective: Our previous study has demonstrated that cigarette sidestream smoke particulates (CSSP) possess toxicological properties relevant to carcinogenicity and oxidative stress. In this study, we further determine whether the toxicological effects of CSSP are attributed to metals. Materials and methods: The metal content of CSSP isolated from a popular Taiwanese brand of cigarettes is determined by ICP-mass. The carcinogenic risk is estimated according to inhalation unit risk. In addition, the capacities of CSSP and the reconstituted metal mixture in cytotoxicity, ROS formation, and AhR-Nrf2 activation are compared. Results: 15 metals are detected in CSSP. Carcinogenic As, Cd, Cr, and Ni are among them. The estimated total carcinogenic risk from inhalation of these carcinogenic metals is 10 × 10−6 for one cigarette in a 60-m3 room. However, the reconstituted metal mixture are not responsible for oxidative stress detected with CSSP. Conclusion: Although oxidative stress is an important mechanism underlying the carcinogenicity of environmental tobacco smoke, metals present in the particulate phase of sidestream smoke do not contribute to oxidant/antioxidant imbalance