Pb-210: A Predictive Biomarker of Retrospective Cigarette Smoke Exposure

Although cigarette smoking continues to occur worldwide, there are few methods available to assess a person's retrospective exposure to mainstream smoke. The tobacco of cigarettes contains trace quantities of radioactive Pb-210 and Po-210, which are volatilized and inhaled when a cigarette is smoked. It was hypothesized that urinary Pb-210 and Po-210 activity concentrations could be used as biomarkers of exposure to mainstream tobacco smoke. Human subjects (n = 250) were recruited from Beijing, China, and reported their smoking habits. Each subject provided a 24-hour urine sample, which was assayed for its Pb-210 and Po-210 activity concentrations. Although the urinary Po-210 activity from smoking was very low compared with background levels, the urinary Pb-210 activity correlated with the number of cigarettes smoked per day (CPD; rho = 0.38, P < 0.001) and the urinary cotinine concentration (rho = 0.52, P < 0.001). In a linear regression model, a 1-unit increase in CPD was associated with an increase of 0.13 mBq in urinary Pb-210 activity. In a logistic regression model, a 1-unit increase in urinary Pb-210 activity was associated with an estimated 25% increase in the odds of being a smoker. These data were modeled using the respiratory, gastrointestinal, and biokinetic models of the International Commission on Radiological Protection. When the final model was applied for a long-term smoker (20 CPD) that suddenly quits, the predicted urinary activity decreased to 50% of the steady-state activity in about 90 days. Based on this half-time estimate and the regression results, urinary Pb-210 can be used to assess the probability of having smoked in the past months. Cancer Epidemiol Biomarkers Prev; 19(2); 338-50. (C) 2010 AACR.OncologyPublic, Environmental & Occupational HealthSCI(E)2ARTICLE2338-3501