Relationship of Human Toenail Nicotine, Cotinine, and 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanol to Levels of These Biomarkers in Plasma and Urine

Recently, we developed sensitive and quantitative methods for analysis of the biomarkers of tobacco smoke exposure nicotine, cotinine, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in human toenails. In this study, we further evaluated the newly developed toenail biomarkers by investigating their relationship to demographic factors, reported exposure, plasma nicotine, cotinine, and trans -3′-hydroxycotinine, and urinary NNAL. Toenails of 105 smokers, mean age 38.9 years (range, 19-68), were analyzed. Fifty-five (53.4%) were male, with approximately equal numbers of Whites and African-Americans. The average number of cigarettes smoked per day was 18 (range, 5-50). There was no effect of age or gender on the toenail biomarkers. Toenail NNAL was higher in White than in African-American participants ( P = 0.019). Toenail nicotine and toenail cotinine correlated significantly with cigarettes smoked per day ( r = 0.24; P = 0.015 and r = 0.26; P = 0.009, respectively). Toenail nicotine correlated with plasma nicotine ( r = 0.39; P < 0.001); toenail cotinine correlated with plasma cotinine ( r = 0.45; P < 0.001) and plasma trans -3′-hydroxycotinine ( r = 0.30; P = 0.008); and toenail NNAL correlated with urine NNAL ( r = 0.53; P = 0.005). The results of this study provide essential validation data for the use of toenail biomarkers in investigations of the role of chronic tobacco smoke exposure in human cancer. (Cancer Epidemiol Biomarkers Prev 2007;16(7):1382–6)