Abstract
The average annual effective dose equivalent and the collective effective dose equivalent have been determined from measurements of the concentrations of 40K, 238U and 232Th in top soil in and around the city of Lagos using in situ ? spectrometry. The average outdoor absorbed dose rate was (0.041 ± 0.012) µGy.h-1 resulting in an annual average effective dose equivalent of 50 µSv.y-1. The collective effective dose equivalent to the population in the city is 2.84 x 102 man.Sv.y-1.