Gamma radiation and indoor radon concentrations in the western and southwestern regions of Saudi Arabia

The exposure of the population to natural gamma radiation in air and to indoor radon gas was investigated in Makkah, AlBaha, Assir, Jazan and Najran regions in the western and southwestern of Saudi Arabia. The survey was performed by using LiF:Mg,Cu,P thermoluminescence dosimeters (TLDs) for indoor and outdoor absorbed dose rates in air measurements in 885 locations, and a passive integrating ionizing system, equipped with an E-Perm Electret ion chamber, for radon concentration measurements in a total of 1119 dwellings. The ambient indoor rates vary from 54 to 191 nSv h−1, while it is in the range of 42–112 nSv h−1 for the outdoor. The indoor and outdoor rates of the directional dose equivalent ranged from 56 to 185 nSv h−1 and from 43 to 135 nSv h−1, respectively. Makkah region showed the highest mean indoor ambient and directional rates, whereas Assir region showed the highest mean outdoor rates. The indoor and outdoor gamma dose rates were significantly correlated. On the other hand, the indoor radon concentrations ranged from 11 to 137 Bq m−3 with an overall mean of 32 Bq m−3 for all investigated houses. The overall annual mean effective dose rate from radon and its decay progenies was estimated to be 0.76 mSv y−1, which yields an excess lifetime cancer risk of around 2.3 × 10−3