Polycyclic Aromatic Compounds Identified in Thirdhand Smoke Contaminated House Dust

摘要

Thirdhand smoke (THS) is the residue of tobacco smoke that remains in house dust and on surfaces, and can be re-emitted into air and further react in the indoor environment to create additional compounds. THS-contaminated house dust poses a special risk to children due to their hand-to-mouth behaviors, as well as their vulnerable stage of development. Chemicals already characterized in THS-contaminated house dust include nicotine, tobacco-specific nitrosamines, and polycyclic aromatic hydrocarbons (PAHs). Here we report on the concentrations of a suite of non-traditionally measured polycyclic aromatic compounds (PACs), including oxygenated-PAHs and methyl-PAHs, which may be more toxic than parent PAHs. House dust samples were collected using the HVS3 cyclone vacuum from homes of smokers (n=30) and nonsmokers (n=9) in San Diego, CA, USA, and characterized for a variety of PACs by GCxGC/ToF-MS. Multiple PACs were elevated in dust samples from smokers' as compared to nonsmokers' homes. Of particular note was the detection of 1,2,naphthoquinone (1,2NQ), which was the most highly abundant oxy-PAH, and was elevated in smokers' homes relative to nonsmokers' (median 7822 ng/m2 vs. 4111 ng/m2), though this difference was not significant. 1,2NQ levels were significantly correlated with nicotine measured in the same samples (rho = 0.0374, p=0.027), suggesting that this compound may be associated with THS. 1,2 NQ is directly mutagenic and has not been reported before in house dust to our knowledge, though it has been reported in tobacco smoke, PM2.5 air pollution and diesel exhaust. Results indicate that measurement of traditional 16 EPA PAHs may underestimate toxic compounds in house dust, and that thirdhand smoke in house dust may be a source of elevated levels of certain toxic PACs. The compound 1,2 NQ and other PACs in house dust may pose a risk to children and policies should be strengthened to prevent THS exposure in homes.