Abstract:
The exposure of man to naturally occurring radionuclides through food and water intake gives rise
to a dose which varies depending on the location, diet and habit of the individuals concerned. The
activity concentrations of 40K, 232Th and 238U have been measured in soils, rice and maize samples
collected from some cities in Ondo State. Activity concentration measurements were carried out
using a co ̶axial type high purity germanium (HpGe) detector. Spectral analyses were performed
using spectrometry Software (MAESTRO ̶32). Potassium ̶ 40 was found to have the highest
activity concentration in all the foodstuffs (Rice and Maize). The activity concentration of 40K,
232Th and 238U in the soil has the highest value of 533.06 ± 79.96 Bq Kg ̶1 .While the activity
concentration of 40K 232Th and 238U in the rice samples has the highest value of 46.47 ± 12.06 Bq
Kg ̶1. The 40K 232Th and 238U activity concentration for Maize has the highest value of 18.91 ±
3.36 Bq Kg ̶1. The mean absorbed dose rates due to the presence of 40K, 232Th and 238U in the soil
samples is 17.05 ± 2.65 nGy h-1. The mean annual effective doses equivalent to individuals from
the consumption of rice and Maize from Ondo state ranged from 1.33 mSv y ̶1 to 1.45 mSv y ̶1
while the mean annual effective dose equivalent in the farms due to soil radioactivity in Ondo State
is 26.08 mSv y ̶ 1. This implies that there is low exposure for either farmer or worker dealing with
transportation of soil in which phosphate fertilizers have been used and that soil could pose a
significant health hazards when used for building constructions and when it is being inhaled while
that of rice and Maize are less than the Maximum permissible dose of 2.4 mSv y ̶1 world average
recommended for the public by International Commission on Radiological Protection (ICRP
1991).
