Indoor gamma dose rates in the high background radiation area of Abeokuta, South Western Nigeria

An indoor gamma dose rates survey was conducted in selected dwellings comprising homes and offices in Abeokuta, South Western Nigeria. Absorbed dose rates were measured using Gamma RAE II R (RAE Systems), which is a CsI-based dosimeter. Absorbed dose rates in the dwellings vary from 0.077 to 0.397 µSv/h, with an overall mean of 0.201 ± 0.074 µSv/h, which is more than twice the world population-weighted average indoor absorbed dose rate (0.084 µSv/h). Buildings made from mud bricks have higher absorbed dose rates than those made from cement-blocks, and houses built on rock outcrops have higher absorbed dose rates compared to those erected/built on soil. The calculated annual effective doses in the study area range from 0.540 to 2.782 mSv with an average value of 1.406 ± 0.521 mSv. The distributions of dose rates according to variations in the local geology and building materials were presented. This study provides data on the indoor component of the terrestrial gamma dose rates in Abeokuta, Nigeria, which is an update of the existing knowledge on the levels of the background radiation exposure in this high natural background radiation area.