Skin dose estimation of Multani Mitti (Fuller's earth) using Geant4 Monte Carlo simulations

This study is aimed to estimate the skin dose due to presence of natural radionuclides in the Multani Mitti (MM, fuller's earth). The activity concentration of natural radionuclides is measured by using Canberra's HPGe detector model GC3020. The average activity concentration levels of 238U, 232Th and 40K are found to be 47, 71 and 748 Bq kg−1 respectively which are higher than corresponding world's median values 30, 35 and 400 Bq kg−1 as reported in Unscear 2000. Geant4 MC simulation is used to estimate skin doses arising due to application of MM on the skin. The decay chains for 238U and 232Th are simulated using Radioactive Decay Module (RDM) available in the Geant4, which automatically accounts for the all members of the decay chain and all types of radioactive emissions. The skin dose conversion factors for natural radionuclides in MM for 238U,232Th and 40K are found to be 0.5, 0.5 and 330 mGy MBq−1 hr−1. The main contribution to skin dose comes from 40K. The radiological health risks to miners and workers are evaluated by measuring radium equivalent activity, radiation hazard indices, annual absorbed dose rate, annual gonadal effective dose equivalent and annual effective dose equivalent. The values of annual absorbed dose rate, gonadal dose and annual effective dose equivalent are found higher than world's median values in the soil. Therefore, miners and workers dealing with MM are vulnerable to potential negative health effects of radiation exposure.