Radiological impact of presence of radon, thoron and their progeny in the environment of LPG bottling plant

Complete text of publication follows. The problem of radon, a ubiquitously present radioactive gas, is an important global problem of radiation hygiene concerning the world population. Measurement of radon, thoron and their progeny is important because the radiation dose to human population due to inhalation of radon and its progeny contribute more than 50% of the dose from all sources of radiation, both naturally occurring and man-made (UNSCEAR, 2000). The estimated level of health risk associated with average indoor radon levels is much higher than those due to other environmental carcinogen (Nazaroff and Nero, 1988). Recently, a pooled analysis of seven case control studies showed a positive correlation between residential exposure to radon and lung cancer (Krewski et al., 2005). The U.S. Environmental Protection Agency (EPA) currently recommends that all levels beneath the third floor be tested for radon (USEPA, 2005). In this light, tracking indoor radon concentration is thus fundamental from health and hygiene point of view. In the present work, the inhalation dose rates, annual effective dose and the lifetime fatality risk to the workers in the LPG bottling plant due to exposure from the mixed field of radon and thoron were measured. The measurements have been carried out by using tracks etch technique using solid state nuclear track detectors (SSNTDs) has been used. It is one of the most widely used techniques for radon measurement. The radon and thoron concentration and the inhalation dose were found to vary from 7.78±2.02 Bq/m3 to 59.01±5.57 Bq/m3, 1.16±0.28 Bq/m3 to 65.08±5.09 Bq/m3, and 0.23 mSv/y to 2.29 mSv/y respectively. The concentration of radon daughters was found to vary from 0.84 mWL to 6.38 mWL, the concentration of thoron daughters was found to vary from 0.03 mWL to 1.76 mWL, the annual exposure due to radon and thoron daughters, collectively, was found to vary from 0.036 WLM to 0.273 WLM, the life time fatality risk was found to vary from 0.11 x 10-4 to 0.82 x 10-4 and the annual effective dose from radon and thoron (PAEC) was found to vary from 0.14 mSv/y to 1.06 mSv/y. The measurements indicated moderate to high levels of radon/thoron concentrations at different locations in the environment of the LPG bottling plant. At certain locations, the inhalation dose is almost 100% was more than that the Global average value (1mSv). However the dose levels observed in the environment of the LPG bottling plant were marginally below the ICRP recommendations (20mSv) for workers. In the light of these findings, the LPG bottling plants may affect doses from external irradiation and the inhalation of radon decay products is significant from health point of view.