We characterize nicotine exposure in the U.S. population by measuring urinary nicotine and its major (cotinine, trans-3′-hydroxycotinine) and minor (nicotine 1′-oxide, cotinine N-oxide, and 1-(3-pyridyl)-1-butanol-4-carboxylic acid, nornicotine) metabolites in participants from the 2015–2016 National Health and Nutrition Examination Survey. This is one of the first U.S. population-based urinary nicotine biomarker reports using the derived total nicotine equivalents (i.e., TNEs) to characterize exposure. Serum cotinine data is used to stratify tobacco non-users with no detectable serum cotinine (−sCOT), non-users with detectable serum cotinine (+sCOT), and individuals who use tobacco (users). The molar concentration sum of cotinine and trans-3′-hydroxycotinine was calculated to derive the TNE2 for non-users. Additionally, for users, the molar concentration sum of nicotine and TNE2 was calculated to derive the TNE3, and the molar concentration sum of the minor metabolites and TNE3 was calculated to derive the TNE7. Sample-weighted summary statistics are reported. We also generated multiple linear regression models to analyze the association between biomarker concentrations and tobacco use status, after adjusting for select demographic factors. We found TNE7 is positively correlated with TNE3 and TNE2 (r = 0.99 and 0.98, respectively), and TNE3 is positively correlated with TNE2 (r = 0.98). The mean TNE2 concentration was elevated for the +sCOT compared with the −sCOT group (0.0143 [0.0120, 0.0172] µmol/g creatinine and 0.00188 [0.00172, 0.00205] µmol/g creatinine, respectively), and highest among users (33.5 [29.6, 37.9] µmol/g creatinine). Non-daily tobacco use was associated with 50% lower TNE7 concentrations (p < 0.0001) compared with daily use. In this report, we show tobacco use frequency and passive exposure to nicotine are important sources of nicotine exposure. Furthermore, this report provides more information on non-users than a serum biomarker report, which underscores the value of urinary nicotine biomarkers in extending the range of trace-level exposures that can be characterized. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Hair nicotine and cotinine have been proposed as longer-term markers of exposure to secondhand smoke. In this study, we evaluated the rate and extent of nicotine and cotinine deposition into beard hair among six male nonsmokers following a single exposure to 4 mg of nicotine in Nicorette((R)) (nicotine polacrilex) gum. We collected beard hair samples daily for 12 days following exposure and urine samples for 6 days after exposure. Using liquid chromatographic-tandem mass spectrometric analysis, we found that both nicotine and cotinine could be detected in beard samples within 24 h of the exposure and reached a maximum of about 71 pg nicotine and 47 pg cotinine/mg hair, respectively, within 1-2 days, followed by a gradual decline. Compared to beard hair concentrations, nicotine, cotinine, and hydroxycotinine were excreted in urine at much higher levels and also peaked on the day after exposure (mean +/- SD urine cotinine = 300 +/- 183 ng/mL). Our results confirmed that both nicotine and cotinine can be measured in beard hair samples following a single dose of nicotine. However, both the time-course and extent of deposition of these analytes in beard hair in this study differed from the results reported previously from a similar evaluation.