ABSTRACT
In the estimation of the effective dose to the public, outdoor and indoor occupancy factors have been an important parameter. These factors vary, depending on the prevailing environmental condition in a particular location. The factors have been estimated for the rural and urban areas in Nigeria. An outdoor factor of 0.3 and 0.22 have been estimated for rural and urban dwellers, respectively. The rural outdoor factor is 50% above the value recommended as the world average by the UNSCEAR. The urban outdoor factor is 10% higher than this value. The total outdoor gamma dose rate in the air due to (40)K, (238)U and (232)Th in the soil for some rural population in the southern part of Nigeria is 29.50 +/- 3.80 nGy h(-1) and the average outdoor effective dose has been estimated to be 54.28 +/- 6.95 microSv y(-1) using the present occupancy factor.
