Determination of 210Pb and 210Po in Brazilian cigarette tobacco

Cigarette smoking is one of the important pathways that could contribute to enhance the radiation dose to man, due to the relatively large concentrations of 210Pb and 210Po found in tobacco leaves. In this work, concentrations of these two radionuclides were determined in eight of the most commercialized cigarette brands produced in Brazil. The samples analyzed were bought randomly in the market. The 210 Pb was determined by counting the beta activity of the 210Bi in a gas flow proportional detector, after radiochemical separation and precipitation of the PbCrO4. The 210Po was determined by alpha spectrometry, using a surface barrier detector, after radiochemical separation and spontaneous deposition of Po in copper disk. The results showed concentrations ranging from 15,8 to 30,2 mBq per gram of dry tobacco for 210Pb and from 18,8 to 27,4 mBq per gram of dry tobacco for 210Po. Taking in account the experimental error of the measurements, radioactive equilibrium between 210Pb and 210Po is observed for all analyzed samples. This result was expected, since the delayed time from the harvest of tobacco leaves to the introduction of cigarettes in the market is enough to reach that equilibrium. Assuming a 20 cigarettes per day consumption, and a 10% of Pb and 20% of Po being inhaled by the primary smokers, it is obtained a value of yearly intake of 11,3 Bq of 210Pb and 21,2 Bq of 210Po, due to cigarette consumption. These values lead to an increment to the committed effective dose of 0,025 mSv year-1 and an increment to the probability of getting cancer of 1 x 10-6 per year. (author)