Estimation of indoor and outdoor effective doses and lifetime cancer risk from gamma dose rates along the coastal regions of Kollam district, Kerala

摘要

The exposure of human beings to ionizing radiation from natural sources is a continuously inescapable feature of life on earth. Direct measurement of absorbed dose rates in air has been carried out in many countries of the world during the last few decades. Such investigations are useful for the assessment of public dose rates. Indoor and outdoor gamma dose rates were evaluated along the coastal regions of Kollam district, Kerala, through direct measurement using portable gamma dosimeter, and analysis of soil sample for activity of ~(238)U, ~(232)Th, and ~(40)K concentration was carried out using gamma spectroscopy. Indoor and outdoor exposure rates, the annual effective dose (AED), and lifetime cancer risk of residents along the coastal regions of Kollam district, Kerala, were evaluated. The reduction coefficients were also calculated for the region. The mean indoor effective dose due to background gamma along the coastal region of Neendakara panchayath was found to be 7.56 mSvy~(-1) which is larger as compared with the worldwide average of the AED of 0.48 mSv y~(-1) and the outdoor mean effective dose of 4.83 mSvy~(-1). Estimated excess lifetime cancer risk (ELCR) from indoor AED equivalent ranges from 22.56 to 26.46 × 10~(-3) and ELCR from outdoor ranges from 14.95 to 16.65 × 10~(-3). Excess average lifetime cancer risk estimate from all the values is found to be 20.56 × 10~(-3), which is larger compared with the resulting worldwide average 0.25 × 10~(-3).