210Po and 210Pb activity in Chinese cigarettes

The radon decay products lead-210 ((210)Pb) and polonium-210 ((210)Po) are known components of tobacco. China is the world's largest producer and consumer of cigarettes, yet no comprehensive published reports of the (210)Pb and (210)Po activity concentrations in Chinese cigarettes are available. Twelve brands of cigarettes that were commonly smoked within a group of 184 Chinese smokers were selected for (210)Pb and (210)Po activity analysis. For each brand, the tobacco from two cigarettes was isolated, dried, weighed, spiked with a (209)Po tracer for yield, and digested with concentrated HNO3, followed by HCl. The polonium in each digested solution was spontaneously deposited onto a nickel disc. The polonium activity was then counted using alpha spectroscopy. The mean (range) (210)Po activity for all brands was 23 (18-29) mBq cig(-1). The state of radioactive equilibrium between (210)Po and (210)Pb in each cigarette was verified in three brands of cigarettes. Cigarettes from two brands were smoked on a machine in order to estimate the fraction of (210)Pb and (210)Po inhaled. An average of 8% of the (210)Pb and 13% of the (210)Po in the tobacco of the cigarettes was transferred to the mainstream smoke. It is thus estimated that a person smoking 20 of these cigarettes per day in China would inhale a mean (range) of 37 (29-46) mBq d(-1) of (210)Pb and 60 (47-75) mBq d(-1) of (210)Po. Cigarette smoking in China may therefore be a large source of a person's daily intake of (210)Pb and (210)Po.