Sudhir Mittal

Human exposure to indoor radon, thoron, and their progenies has become a serious problem throughout the world. In the current research, assessment of indoor radon and thoron and their effect on human beings have been analyzed from 200 various locations (five samples from each location) of Jodhpur, Jhunjhunu, Bikaner, and Nagaur districts of Northern Rajasthan, India made with the help of RAD7 technique. The radon and thoron levels inside the houses of indoor air vary from 10.75 to 90 Bq m−3 and 18.65 to 210 Bq m−3, respectively. The calculated values of all dwellings of indoor radon concentration are lower than the action limit provided by the International Commission on Radiological Protection (ICRP). The results calculated from absorbed dose rate to lungs, equivalent dose to lungs, effective dose to specific parts of lungs tracheobronchial, pulmonary + pulmonary lymph region, overall lung dose due to 222Rn and 220Rn exposure, annual effective dose, excess life time cancer risk (ELCR), and lung cancer cases per year per million people (LCC) due to radon and thoron level and their risk due to exposure are also discussed. In this study, we also examined the risk effect due to radon and thoron correlated with building material and ventilation conditions.

In the present study, soil samples collected from 40 different locations of Jodhpur, Nagaur, Bikaner and Jhunjhunu districts of northern Rajasthan, India has been analyzed for ²²⁶Ra, ²³²Th and ⁴⁰K using gamma ray spectroscopy. The measured activity concentration ranges from 14 ± 8 to 37 ± 9 Bq kg⁻¹, 42 ± 10 to 84 ± 11 Bq kg^−1.and 304 ± 125 to 734 ± 141 Bq kg⁻¹ with the mean value of 24 ± 10 Bq kg⁻¹, 55 ± 11 Bq kg⁻¹ and 549 ± 145 Bq kg⁻¹ for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. The radium equivalent activity (Ra_eq) of all the soil samples ranges from 119 to 209 Bq kg⁻¹ with an average value of 146 Bq kg⁻¹, which is lower than the safe limit 370 Bq kg⁻¹ set by the Organization for Economic Cooperation and Development. The total absorbed dose and annual effective dose of all the investigated samples has also been explored in the present manuscript. The corresponding values of external and internal hazard index of all the soil samples ranges from 0.31 to 0.58 and 0.35 to 0.68 with the average value of 0.39 and 0.46, respectively. It was observed that the soil of Jodhpur, Nagaur, Bikaner and Jhunjhunu districts is suitable for construction purpose without posing any health hazard.

In the present study, analysis of 238U concentration in 40 drinking water samples collected from different locations of Jodhpur, Nagaur, Bikaner and Jhunjhunu districts of Rajasthan, India has been carried out by using high resolution inductively coupled plasma mass spectroscopy (HR-ICP-MS) technique. The water samples were taken from hand pumps and tube wells having depths ranging from 50 to 800 feet. The measured uranium concentration lies in the range from 0.89 to 166.89 μg l^-1 with the mean value of 31.72 μg l^-1. The measured uranium content in twelve water samples was found to be higher than the safe limit of 30 μg l^-1 as recommended by World Health Organization (WHO, 2011) and US Environmental Protection Agency (USEPA, 2011). Radiological risk calculated in the form of annual effective dose estimated from annual uranium intake ranges from 0.66 to 138.63 μSv y^-1 with the mean value of 26.28 μSv y^-1. The annual effective dose in two drinking water samples was found to be greater than WHO (2004) recommended level of 100 μSv y^-1. Chemical risk calculated in the form of lifetime average daily dose (LAAD) estimated from the water samples varies from 0.02 to 4.57 μg kg^-1 d^-1 with the mean value of 0.87 μg kg^-1 d^-1. The lifetime average daily dose (LAAD) of ten drinking water samples was found to be greater than WHO (2011) recommended level of 1 μg kg^-1 d^-1. The corresponding values of hazard quotient of 48% water samples were found to be greater than unity.A good positive correlation of uranium concentration with total dissolved solids (TDS) and conductance has been observed. However no correlation of uranium concentration with pH was observed. The results revels that uranium concentration in drinking water samples of the study area can cause radiological and chemical threat to the inhabitants.

The annual variation in radon and thoron concentrations in different seasons has been revealed for 40 different locations of Jodhpur, Nagaur, Bikaner and Jhunjhunu districts of Northern Rajasthan by using pinhole dosimeter, and the results have been compared with ventilation conditions and building materials. The indoor radon concentration was observed to vary from 109 ± 17 to 334 ± 13 Bq m⁻³, 63 ± 17 to 255 ± 21 Bq m⁻³, 45 ± 11 to 128 ± 19 Bq m⁻³and 74 ± 9 to 300 ± 21 Bq m⁻³and thoron concentration varies from 26 ± 15 to 418 ± 21 Bq m⁻³, 3 ± 2 to 134 ± 33 Bq m⁻³, 12 ± 6 to 140 ± 19 Bq m⁻³and 6 ± 4 to 408 ± 29 Bq m⁻³for winter, spring, summer and autumn seasons, respectively. In winter season, indoor radon concentration of about 50% dwellings was observed to be within or higher than the action level as recommended by International Commission of Radiation Protection. However, in summer the action level is lower than the action limit. The exposure of human beings to indoor radon and thoron and the associated risk has also been examined. The total annual mean effective dose due to indoor radon and thoron in Northern Rajasthan are less than or close to the action level 3–10 mSv y⁻¹as recommended by International Commission of Radiation Protection.