Background This study examined whether thirdhand smoke (THS) persists in smokers’ homes after they move out and nonsmokers move in, and whether new nonsmoking residents are exposed to THS in these homes. Methods Homes of 100 smokers and 50 nonsmokers were visited before the residents moved out. Dust, surfaces, and air and participants’ fingers were measured for nicotine and children’s urine samples were analyzed for cotinine. The new residents who moved into these homes were recruited if they were nonsmokers. Dust, surfaces, and air, and new residents’ fingers were examined for nicotine in 25 former smoker and 16 former nonsmoker homes. A urine sample was collected from the youngest resident. Results Smoker homes’ dust, surface, and air nicotine decreased after the change of occupancy (p<.001); yet dust and surfaces showed higher contamination levels in former smoker homes than former nonsmoker homes (p<.05). Nonsmoking participants’ finger nicotine was higher in former smoker homes compared to former nonsmoker homes (p<.05). Finger nicotine levels among nonsmokers living in former smoker homes were significantly correlated with dust and surface nicotine and urine cotinine. Conclusions These findings indicate that THS accumulates in smokers’ homes and persists when smokers move out even after homes remain vacant for two months and are cleaned and prepared for new residents. When nonsmokers move into homes formerly occupied by smokers, they encounter indoor environments with THS polluted surfaces and dust. Results suggest that nonsmokers living in former smoker homes are exposed to THS in dust and on surfaces.

To obtain information on the concentration and spectrum of bile acids in human cecal content, samples were obtained from 19 persons who had died an unnatural death from causes such as trauma, homicide, suicide, or drug overdose. Bile acid concentration was measured via an enzymatic assay for 3alpha-hydroxy bile acids; bile acid classes were determined by electrospray ionization mass spectrometry and individual bile acids by gas chromatography mass spectrometry and liquid chromatography mass spectrometry. The 3alpha-hydroxy bile acid concentration (mumol bile acid/ml cecal content) was 0.4 +/- 0.2 mM (mean +/- SD); the total 3-hydroxy bile acid concentration was 0.6 +/- 0.3 mM. The aqueous concentration of bile acids (supernatant after centrifugation) was identical, indicating that most bile acids were in solution. By liquid chromatography mass spectrometry, bile acids were mostly in unconjugated form (90 +/- 9%, mean +/- SD); sulfated, nonamidated bile acids were 7 +/- 5%, and nonsulfated amidated bile acids (glycine or taurine conjugates) were 3 +/- 7%. By gas chromatography mass spectrometry, 10 bile acids were identified: deoxycholic (34 +/- 16%), lithocholic (26 +/- 10%), and ursodeoxycholic (6 +/- 9), as well as their primary bile acid precursors cholic (6 +/- 9%) and chenodeoxycholic acid (7 +/- 8%). In addition, 3beta-hydroxy derivatives of some or all of these bile acids were present and averaged 27 +/- 18% of total bile acids, indicating that 3beta-hydroxy bile acids are normal constituents of cecal content. In the human cecum, deconjugation and dehydroxylation of bile acids are nearly complete, resulting in most bile acids being in unconjugated form at submicellar and subsecretory concentrations.

Homes of smokers remained polluted with THS for up to 6 months after cessation. Residents continued to be exposed to THS toxicants that accumulated in settled house dust and on surfaces before smoking cessation. Further research is needed to better understand the consequences of continued THS exposure after cessation and the efforts necessary to remove THS.

Partial smoking bans in hotels do not protect non-smoking guests from exposure to tobacco smoke and tobacco-specific carcinogens. Non-smokers are advised to stay in hotels with complete smoking bans. Existing policies exempting hotels from complete smoking bans are ineffective.

Environmental tobacco smoke is a major contributor to indoor air pollution. Dust and surfaces may remain contaminated long after active smoking has ceased (called 'thirdhand' smoke). Polycyclic aromatic hydrocarbons (PAHs) are known carcinogenic components of tobacco smoke found in settled house dust (SHD). We investigated whether tobacco smoke is a source of PAHs in SHD. House dust was collected from 132 homes in urban areas of Southern California. Total PAHs were significantly higher in smoker homes than nonsmoker homes (by concentration: 990 ng/g vs 756 ng/g, p = 0.025; by loading: 1650 ng/m(2) vs 796 ng/m(2), p = 0.012). We also found significant linear correlations between nicotine and total PAH levels in SHD (concentration, R(2) = 0.105; loading, R(2) = 0.385). Dust collected per square meter (g/m(2)) was significantly greater in smoker homes and might dilute PAH concentration in SHD inconsistently. Therefore, dust PAH loading (ng PAH/m(2)) is a better indicator of PAH content in SHD. House dust PAH loadings in the bedroom and living room in the same home were significantly correlated (R(2) = 0.468, p < 0.001) suggesting PAHs are distributed by tobacco smoke throughout a home. In conclusion, tobacco smoke is a source of PAHs in SHD, and tobacco smoke generated PAHs are a component of thirdhand smoke.