Assessment of excess lifetime cancer risk and radioactive heat production from waste dumpsites in three cities in Southwestern Nigeria

Radiation exposures at various dumpsites around three cities located in southwest Nigeria were assessed by gamma ray spectroscopy using a highly shielded Canberra NaI (Tl) detector. The average activity concentrations obtained for 40K were 535 ± 65, 430 ± 78, 471 ± 72 and 410 ± 29, 270 ± 84, 371 ± 27 Bq kg−1; the mean concentrations of 226Ra were 66 ± 4, 47 ± 3, 11 ± 1 and 57 ± 10, 49 ± 13, 59 ± 17 Bq kg−1; while the mean concentrations of 232Th were 55 ± 19, 29 ± 8, 13 ± 2 and 29 ± 3, 21 ± 5, 41 ± 12 Bq kg−1 for designated and undesignated sites in Abeokuta, Akure and Osogbo respectively. The highest mean absorbed dose rate obtained was 86 ± 17 nGy h−1. The total excess lifetime cancer risk ranged from 1.28 to 3.22 × 10−3 which is relatively higher than the world average.