Soil to tobacco component transfer factors for natural radionuclides K, Ra, and Th and the risk assessment of tobacco leaf in smoking.

This study determined the activity concentrations and corresponding transfer factors (TF) of K, Ra, and Th in three tobacco components (root, stem, and leaf). The radiation hazard index parameters were assessed for the tobacco leaf. The activity concentrations in the soil were 589-762, 32-43, and 49-59 Bq kg-dw (dry weight) for K, Ra, and Th, respectively. The average activity concentrations of K, Ra, and Th were 447, 5.41 and 5.69 Bq/kg-dw for the root, 670, 9.64 and 7.61 Bq kg-dw for the stem, and 793, 6.79 and 6.15 Bq kg-dw for the leaf, respectively. The TF values were 0.42-1.42, 0.10-0.49 and 0.06-0.23 for K, Ra, and Th, respectively. The stem and leaf K TF values were significantly higher than the root values. The stem Ra TF values were significantly higher than the root values. The Ra and Th activity concentrations and TFs of tobacco components had a significant positive correlation. Based on the activity concentrations of the tobacco leaves, the annual inhalation effective dose to the lungs for an adult smoker was 0.32-0.81 mSv y (average 0.60 mSv y). The Excess Lifetime Cancer Risk (ELCR) caused by smoking was an average of 2.39 × 10.