Health risk of metal exposure via inhalation of cigarette sidestream smoke particulate matter.

Cigarette sidestream smoke particulate matter (CSSP) is a major source of airborne metals in the indoor environment. However, the health impacts of inhalation of CSSP-bound metals are rarely studied. In this study, we quantify the amount of 37 metals discharged through CSSP from a leading Taiwan brand of cigarette, Long Life. We also estimate cancer and non-cancer risks due to inhalation of these metals and investigate possible modes of toxic action. Long Life CSSP exhibits a distinctive carcinogenic metal profile compared with Western brands. When released to a 60-m3 poorly ventilated room, Long Life CSSP metals increase the risk for cancer by a 9.26 or 20.90 in a million chance and the hazard quotient for non-cancer toxicity by 0.496 or 0.286 per cigarette depending on risk estimation system. Cd accounts for more than 90% and 80% of cancer and non-cancer risk, respectively. Long Life CSSP also contains considerable amounts of Al, Ba, and Fe. Metals are not responsible for CSSP-induced cytotoxicity, oxidative stress, and transactivation activity of AhR, Nrf2, and ERα. However, they diminish resveratrol-activated Nrf2 activity and downstream antioxidant gene expression in low-AhR-expressing lung cells. Our results suggest that chronic exposure to Long Life CSSP elevates Cd-associated cancer and non-cancer risks. Furthermore, exposure to Long Life CSSP metals may impair Nrf2-mediated antioxidant protection.