Radiation hazards and transfer factors of radionuclides from soil to plant and cancer risk at Al-Taji city-Iraq

The concentrations of natural radionuclides in various common plant species grown in the city of Al-Taji in the capital, Baghdad, were examined using NaI (Tl) gamma spectroscopy. The measurements were made on three parts of each plant sample which included roots, stalk, and leaves in addition to soil. The assessing of transport factors shows the K-40 transfer coefficients were lower than those values mentioned in other previous studies. The mean concentrations of specific activity for U-238, Th-232 and K-40 in the basil plant were 4.455±2.944, 18.774±14.998 and 123.767±23.047 Bq/kg respectively. For celery it was 3.904±3.326 Bq/kg, 32.899±6.739 Bq/kg, 85.032±35.650 Bq/kg. As for mint, it was 2.233±4.337 Bq/kg, 25.354±8.696 Bq/kg and 92.115±33.070 Bq/kg. The results showed that the concentration of uranium, thorium and cesium did not exceed the permissible limit. Potassium concentrations will not exceed the internationally permitted level in all parts of plants under study. The radium equivalent activity was 70.527 Bq/kg less than 370 Bq/kg recommended by UNSCEAR. The maximum absorbed dose rate in soil samples was 58.205 nGy/h, which is less than 84 nGy/h. Whereas the average annual effective dose equivalent in soil samples was 285.535 mSv/y which are less than the 290 mSv/y recommended by UNSCEAR, Respectively. The maximum hazard risk index was 0.214 in soil samples and is less than ≤1 recommended by UNSCEAR. The lifetime cancer risk (ECLR) ranged from 142.620×10⁻³ to 999.372×10⁻³. This value is above the global average of 0.29×10⁻³ and 1.16×10⁻³ reported by UNSCEAR. The lifetime cancer risk is a function of environmental geology and the K-40 soil transfer factor to the plant is very high compared to other radionuclides in the samples. Therefore, there is a risk from its management.