Abstract
Geology of parent rock controls strongly the soil properties which in turn effect the generation and transportation of radon from its point of production to the surface of earth's crust. Indoor radon concentrations mainly depend upon uranium and thorium content beneath the earth surface and diffusion of radon from rock and soil fractures, stoma and fissures. This paper presents the results of a survey of indoor radon concentrations in Neelum Valley District. CR-39 detectors were installed in 210 houses covering the entire study area. The detectors were retrieved after exposing to indoor radon for a period of 90 days and then etched in 6 M NaOH at 80 degrees C for 16 h. The observed track densities were converted into the indoor radon concentrations using calibration factor of 2.7 tracks cm(-2).h(-1) per kBq.m(-3). Mean annual effective doses were calculated for each measured value of radon concentration using UNSCEAR 2000 model. Effects of geology, fissures, crevice and cracks on radon levels have also been discussed. Results obtained from this study have been compared with radon concentration action levels given by the World Health Organisation and US Environmental Protection Agency and UK Health Protection Agency.