Natural radioactivity in farm soils and major food crops grown in Ayetoro, Ogun State, Southwestern Nigeria

Radioactivity data in food and farm soil in sedimentary rocky areas like Ayetoro, Nigeria, are scarce. Maize, cassava and the underneath soil samples were collected from Ayetoro. The 40K, 226Ra and 232Th activity concentrations in the samples were measured with a gamma ray spectrometer. The soil-to-food crop transfer factors, ingestion effective dose rates due to the crops and the outdoor effective dose rates due to soils were evaluated. The mean 40K, 226Ra and 232Th activity concentrations in maize were 160.3 ± 66.5 Bqkg−1, 18.1 ± 7.1 Bqkg−1 and 15.0 ± 8.0 Bqkg−1 respectively and the soils were 671.5 ± 352.9 Bqkg−1, 66.8 ± 25.3 Bqkg−1 and 62.1 ± 27.9 Bqkg−1 for 40K, 226Ra and 232Th respectively. The mean activity concentrations in cassava were 294.6 ± 137.2 Bqkg−1, 28.6 ± 14.9 Bqkg−1 and 18.2 ± 13.0 Bqkg−1 for 40K, 226Ra and 232Th respectively and the soils were 679.5 ± 281.1 Bqkg−1, 66.8 ± 32.7 Bqkg−1 and 49.7 ± 46.9 Bqkg−1 for 40K, 226Ra and 232Th respectively. The results indicated that the activity concentrations, ingestion effective dose and outdoor effective dose are low and no serious radiological health impact is expected.