LAUSR

Abstract The aim of this study is to determine the indoor radon concentration and to evaluate the annual effective dose received by the inhabitants in Dammam, Al-Khobar, and compare it with new premises built at university of dammam. The research has been carried out by using active detection method; Electronic Radon Detector (RAD-7) a solid state α-detector with its special accessories. The indoor radon concentration measured varies from 10.2 Bqm−3 to 25.8 Bqm−3 with an average value of 18.8 Bqm−3 and 19.7 Bqm−3 to 23.5 Bqm−3 with an average value of 21.7 Bqm−3, in Dammam and Al-khobar dwellings, respectively. In university of dammam the radon concentration varies from 7.4 Bqm−3 to 15.8 Bqm−3 with an average value of 9.02 Bqm−3. The values of annual effective doses were found to be 0.47mSv/y, 0.55mSv/y, and 0.23mSv/y, in Dammam, Al-khobar and university new premises, respectively. The average radon concentration in the old dwellings was two times compared to that in the new premises and it was 25.4 Bqm−3 lower than the world average value of 40 Bqm−3 reported by the UNSCEAR. The annual effective doses in the old dwellings was found to be (0.55mSv/y) two times the doses received at the new premises, and below the world wide average of 1.15mSv/y reported by ICRP (2010) . The indoor radon concentration in the study region is safe as far as health hazard is concerned.