A STUDY ON THE RADIATION DOSE DUE TO DISSOLVED 222RN IN WATER SAMPLES OF MANDYA CITY, KARNATAKA, INDIA.

Measurement of dissolved radon concentrations in the water samples collected from selected borewells (depth ~300 ft), wells (depth ~25 ft) and overhead tanks (height ~30 ft) of Mandya city, Karnataka, India, has been carried out by using Emanometry method. The radon concentrations in the waters of borewell, well and overhead tank ranges from 1.5 ± 0.1 to 102.8 ± 5.1, 1.3 ± 0.1 to 3.8 ± 0.4 and 2.5 ± 0.2 to 9.7 ± 1.1 Bq l-1 with the mean values of 16.8, 2.5 and 6.2 Bq l-1, respectively. Majority of borewell water samples showed higher concentrations of dissolved 222Rn compared to waters of well and overhead tank. The overall mean value of dissolved radon concentration of 12.2 Bq l-1 is found to be close to the maximum contaminant level of 11 Bq l-1 suggested by US Environment Protection Agency. The physicochemical parameters like pH, TDS and conductivity were also measured, and dependence of dissolved 222Rn on these parameters has been studied. Using the mean value of dissolved radon concentration, a new attempt has been made to compute the doses imparted to different organs and tissues of the human body. Dosimetric calculations showed that stomach and small intestine receive greater doses due to dissolved radon compared to other organs.

Radiological and chemical toxicity due to ingestion of uranium through drinking water in the environment of Bangalore, India.

Groundwater samples collected from 96 bore wells in the study area (city of Bangalore) were analysed for concentration of natural uranium using laser-induced fluorimetry. The risk to the population of the region associated with radiological and chemical toxicity of uranium due to its ingestion through drinking water over a lifetime was estimated. The concentration of uranium was found to be in the range 0.136 to 2027.5 µg L(-1) with an average value of 92.42 µg L(-1). In the present study, about 61% of the samples show concentrations of uranium within the safe limit of 30 µg L(-1) as set by the world health organisation. The radiological risk estimated as lifetime cancer risk is in the range 4.3 × 10(-7) to 6.4 × 10(-3) with an average of 2.9 × 10(-4). The chemical toxicity risk measured as lifetime average daily dose is found to range from 0.005 to 75.42 µg kg(-1) d(-1). The reference dose estimated as 1.12 µg kg(-1) d(-1) was used to assess the chemical toxicity. The results indicate that the chemical toxicity due to ingestion of uranium through drinking water is of more concern than the radiological toxicity. The present study, being the first of its kind in this region, will augment the database of uranium in groundwater.

Indoor radon concentration and its possible dependence on ventilation rate and flooring type.

The results of radon concentration measurements carried out in dwellings with natural ventilation for 1 y in Bangalore are reported. Measurements, covering three sessions of the day (morning, afternoon, night) were performed two times in a month for 1 y at a fixed place of each dwelling at a height of 1 m above the ground surface in selected dwellings. The low-level radon detection system (LLRDS), an active method, was used for the estimation of radon concentration. The measurements were aimed to understand the diurnal variation and the effect of ventilation rate and flooring type on indoor radon concentration. The geometric mean (± geometric standard deviation) of indoor radon concentration from about 500 measurements carried out in 20 dwellings is found to be 25.4 ± 1.54 Bq m⁻³. The morning, afternoon and night averages were found to be 42.6 ± 2.05, 15.3 ± 2.18 and 28.5 ± 2.2 Bq m⁻³, respectively. The approximate natural ventilation rates of the dwellings were calculated using the PHPAIDA--the on-line natural ventilation, mixed mode and air infiltration rate calculation algorithm and their effects on indoor radon concentrations were studied. The inhalation dose and the lung cancer risk due to indoor radon exposure were found to be 0.66 mSv y⁻¹ and 11.9 per 106 persons, respectively. The gamma exposure rate was also measured in all the dwellings and its correlation with the inhalation dose rate was studied.

Variations of radon and thoron concentrations in different types of dwellings in Mysore city, India.

(222)Rn and (220)Rn, the immediate decay products of radium isotopes, are causative agents of lung cancer. (222)Rn and (220)Rn concentrations in houses with different floorings, roofs and walls and in different rooms of houses have been measured in Mysore city, Karnataka state, India, using solid-state nuclear track detectors. The radon and thoron concentrations in dwellings with granite floorings are found to be higher compared with other types. A correlation between the indoor radon concentration and dose in air from terrestrial gamma radiation is observed.

Radon daughters' concentration in air and exposure of joggers at the university campus of Bangalore, India.

The concentration of radon daughters in outdoor air was measured continuously from January 2006 to December 2006 near the Department of Physics, Bangalore University campus, Bangalore. The concentration was measured by collecting air samples at a height of 1 m above the ground level on a glass micro fibre filter paper with a known air flow rate. The results show that the radon progeny concentration exhibits distinct seasonal and diurnal variations that are predominantly caused by changes in the temperature gradient at the soil-atmosphere interface. The concentration was found to be high from 20.00 to 8.00 hrs, when the turbulence mixing was minimum and low during the rest of the time. In terms of the monthly concentration, January was found to be the highest with September/August being the lowest. The diurnal variations in the concentrations of radon progeny were found to exhibit positive correlation with the relative humidity and anti-correlation with the atmospheric temperature. From the measured concentration, an attempt was made to establish the annual effective dose to the general public of the region and was found to be 0.085 mSv/a. In addition, an attempt was also made for the first time to study the variation of inhalation dose with respect to the physical activity levels. Results show that in the light of both the effect of chemical pollutants and radiation dose due to inhalation of radon daughters, evening jogging is advisable.

Concentrations of 226Ra, 232Th, and 40K in the soils of Bangalore region, India.

Several soil samples of Bangalore region were analyzed for the concentrations of Ra, Th, and K by gamma ray spectrometry. The concentration of Ra varied in the range 7.7-111.6 Bq kg with a mean value of 26.2 Bq kg, Th in the range 16.7-98.7 Bq kg with a mean of 53.1 Bq kg, and that of K in the range 151.8-1424.2 Bq kg with a mean of 635.1 Bq kg. The external gamma absorbed dose rates in air were also measured using a portable environmental radiation dosimeter, and the gamma dose rates were found to vary in the range 61.4-201.7 nGy h with a mean of 117.2 nGy h. These results along with the results of estimation of radium equivalent activity (Raeq), absorbed dose rate (D), annual effective dose rate, external hazard index (Hex), internal hazard index (Hin), and representative level index (Igamma) are presented in this paper. The results are also compared with the literature values reported for other regions of India as well as worldwide average values and discussed.