Soil to tobacco component transfer factors for natural radionuclides 40K, 226Ra, and 232Th and the risk assessment of tobacco leaf in smoking

Abstract

This study determined the activity concentrations and corresponding transfer factors (TF) of ⁴⁰K, ²²⁶Ra, and ²³²Th 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⁻¹ (dry weight) for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively. The average activity concentrations of ⁴⁰K, ²²⁶Ra, and ²³²Th were 447, 5.41 and 5.69 Bq/kg-dw for the root, 670, 9.64 and 7.61 Bq kg-dw⁻¹ for the stem, and 793, 6.79 and 6.15 Bq kg-dw⁻¹ for the leaf, respectively. The TF values were 0.42–1.42, 0.10–0.49 and 0.06–0.23 for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively. The stem and leaf ⁴⁰K TF values were significantly higher than the root values. The stem ²²⁶Ra TF values were significantly higher than the root values. The ²²⁶Ra and ²³²Th 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⁻¹ (average 0.60 mSv y⁻¹). The Excess Lifetime Cancer Risk (ELCR) caused by smoking was an average of 2.39 × 10⁻³.