Metabolites of a tobacco-specific lung carcinogen in nonsmoking women exposed to environmental tobacco smoke

Background: Environmental tobacco smoke (ETS) is associated with lung cancer in nonsmokers. Most epidemiologic studies find a higher risk for lung cancer in nonsmoking women married to smokers than in those married to nonsmokers. We measured metabolites of a tobacco-specific lung carcinogen in urine from healthy, nonsmoking women exposed to ETS. Methods: We recruited women and their partners through advertisements. Couples completed questionnaires on smoking history and demographics, and both partners provided 100 mL of urine; 23 women had male partners who smoked in the home (i.e., exposed women), and 22 women had male partners who did not smoke (i.e., unexposed women). Urine samples were analyzed for nicotine, for cotinine, for 4-(methylnitrosamino)-1- (3-pyridyl)-1-butanol (NNAL) and its glucuronide (NNAL-Gluc), as well as for creatinine. NNAL and NNAL-Gluc are metabolites of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Unpaired Student's t tests were conducted on log-transformed values. All statistical tests are two-sided. Results: Urinary levels of nicotine, cotinine, NNAL, and NNAL-Gluc were statistically significantly higher in exposed women than in unexposed women. Geometric means for these compounds in exposed versus unexposed women, respectively, were as follows: nicotine, 0.050 nmol/mg of creatinine (95% confidence interval [CI] = 0.033 to 0.076) versus 0.008 nmol/mg of creatinine (95% CI = 0.004 to 0.014); cotinine, 0.037 nmol/mg of creatinine (95% CI = 0.022 to 0.061) versus 0.007 nmol/mg of creatinine (95% CI = 0.004 to 0.011); NNAL, 0.013 pmol/mg of creatinine (95% CI = 0.007 to 0.024) versus 0.004 pmol/mg of creatinine (95% CI = 0.002 to 0.007); and NNAL-Gluc, 0.027 pmol/mg of creatinine (95% CI = 0.016 to 0.045) versus 0.004 pmol/mg of creatinine (95% CI = 0.003 to 0.006). Conclusions: Nonsmoking women exposed to ETS take up and metabolize the tobacco-specific lung carcinogen NNK, which could increase their risk of lung cancer. Within couples, the NNAL plus NNAL-Gluc level in exposed women compared with that of their smoking partners averaged 5.6%. Notably, epidemiologic studies have estimated the excess risk for lung cancer in nonsmoking women exposed to ETS as 1%-2% of that in smokers.