Assessment of background radiation and frequency of micronuclei formation in two selected populations in Sri Lanka.

Abstract

This study assessed background radiation and frequency of micronuclei formation in persons living in Norochcholai and Ragama. Ninety-six healthy individuals (20-59 years of age) from both sexes were selected for the study, comprising 50 from Norochcholai (area closest to the power plant) and 46 from Ragama (control). Ten milliliters of venous blood was drawn and the cytokinesis—block micronuclei assay was performed. Thousand binucleate cells were assessed; the median spontaneous micronuclei formation was estimated. Background radiation was measured using an Automess dose rate meter 6150AD. There was no significant difference in the median micronuclei (MN) frequency between the two sexes (p= 0.538) and the two study areas (p=0.539). There was no correlation between background radiation and MN frequency. Fifty-four water samples (26 from Norochcholai and 28 from Ragama) were analyzed by gamma spectrometry and radioactivity was not detected in any of the water samples. Fifty-one soil samples (25 from Norochcholai and 26 from Ragama) were analyzed by gamma spectrometry. The median radioactivity concentration (IQ range) of 232 Th, 40 K, 226Ra and 210Pb in Norochcholai were 50.0Bqkg-l (31.3-91.2), 99Bqkg-1 (84.0-111.3), 22Bqkg-l (14.3-40.3Bqkg-l) and 27Bqkg-l (23-44Bqkg-l) respectively; in Ragama, the median radioactivity concentrations (IQ range) of were significantly higher in Norochcholai than that of Ragama area exceþt for 40K.The gamma ray absorbed dose rates in soil samples of Norochcholai varied between 32.1 nGyh-l and 81.1 nGyh-l with an average of 51.2nGy h-l which is lower than the global average of 57 nGyh-l; in Ragama, this varied between 27.8-40. lnGyh-1. The mean Raeq of Norochcholai was 149.7 Bqkg-l. A radium equivalent activity above 370, the limit set by the Nuclear Energy Agency group of experts as safe to be used in building materials, was observed in 2 soil samples from Norochcholai. All the soil samples from Ragama had a Raeq below 370Bq/kg. The median Raeq was 73.7 Bq/kg. The median annual effective dose in Norochcholai was 0.062 mSv.y-l and in Ragama it was 0.040mSvy-l. They were within the safe limit of ImSv/y. Hex of all the samples were below I. Thus the soil from both the study areas are safe for human health. Pb were 38.4Bq/kg (26.4-52.1), 100.7Bq/kg (93.1-163.9), 11.7Bq/kg (10.1-16.3) and 25.9 Bq/kg (19.8-47.5) respectively. 232Th activity concentration in both were higher than the world average. Activity concentrations of all the radionuclides. The results of this study can be used as baseline data to monitor exposure to radiation in the selected population in the future. This is important for monitoring radiation hazards and will be useful in case of a nuclear accident. KEYWORDS: Background radiation, micronuclei, Nuclear accident, baseline data, gamma spectrometry