Abstract
Thirdhand smoke (THS) is the residual tobacco smoke after extinguishing a cigarette. Some constituents of the tobacco smoke may stay in the air after extinguish, but most of them will be adsorbed onto the surfaces such as wallpapers, clothes. The adsorbed components will be gradually re-emitted into the atmosphere for a long period of time, and could be taken up by a human body. In our daily life, THS can be noticed through malodor or color changes of the wallpaper of a smoking room. However, THS has been recognized as a new type of passive smoking issue since Winckoff et al. published a paper on THS in 2009. In 2010, Sleiman et al. reported the de novo formation of tobacco-specific nitrosamines (TSNAs), known as carcinogens, and their findings have boomed the research on THS. In this article we aimed to overview the current state of the THS research activities from the viewpoints of the characteristics, chemistry, field surveys, toxicity, health effects, and exposure assessments of THS. THS is characterized by the four "R"s, namely, Remain, Reaction, Re-emit, and Re-suspended. THS remains in the environment for a long period, and be aged, and the chemical composition of THS is different from that of ETS, and THS contains some compounds specific to THS, due to the chemical reactions during the aging. Field surveys of THS have been conducted by the direct air measurements, wiping the surfaces, analysis of dust-adsorbed compounds. The higher concentrations of nicotine and detection of TSNAs have been reported for the smoking environments. Exposures to the THS extract induced various kinds of DNA damages. The metabolic or immunity systems were affected by the THS extract exposure to test animals. Exposure assessments suggest the THS exposures to infants will be more serious than to adults. More studies should be necessary on the health effects by the THS exposures as well as malfodor of THS as a new type of passive smoking issue.
