Assessment of Age-Dependent Effective Dose and Toxicity Risks Due To Ingestion of 226RA and 228RA in River Water Samples in a Part of Bitumen Belt, Ondo State. Nigeria

Exposure to naturally occurring radioactive chemical elements in food and water is attracting the attention of many researchers in recent times because of its deleterious health effects. In this study, the activity concentrations of natural radionuclides in some river waters in southwestern Nigeria were measured using high-purity germanium (HPGe) detector. They ranged from 0.12 to 2.31, 0.17 to 2.85, and 7.86 to 65.51 Bql-1 for 226Ra, 228Ra, and 40K respectively. Mean of the total annual effective dose were 9.86, 2.46, 1.71, 2.43, 5.74, and 0.99 mSvy-1 for age groups ≤1y, 1-2y, 2-7y, 7-12y, 12-17y, and >17y respectively. Estimated mass concentration of 226Ra and 228Ra in the samples ranged from 3.29x10-6 to 59.71x10-6 µgl-1 with a mean of 35.04x10-6 µgl-1 and 1.69x10-8 to 28.30x10-8 µgl-1 with a mean of 14.30x10-8 µgl-1 respectively. Mortality and morbidity risks ranged from 0.04x10-3 to 0.77x10-3 with a mean of 0.42x10-3 and 0.04x10-3 to 0.80x10-3 with a mean of 0.44x10-3 respectively for 226Ra while they ranged from 0.11x10-3 to 1.89x10-3 with a mean of 0.96x10-3 and 0.16x10-3 to 2.66x10-3 with a mean of 1.38x10-3 respectively for 228Ra. Lifetime average daily dose (LADD) of 226Ra and 228Ra ranged from 9.39x10-14 µgkg-1d-1 to 181.01x10-14 µgkg-1d-1 with a mean of 100.06x10-14 µgkg-1d-1 and 4.82x10-16 µgkg-1d-1 to 80.70x10-16 µgkg-1d-1 with a mean of 40.90x10-16 µgkg-1d-1 respectively. The hazard quotient (HQ) for 226Ra and 228Ra ranged from 8.38x10-14 to 161.61x10-14 with a mean of 89.33x10-14 and 4.30x10-16 to 70.09x10-16 with a mean of 36.50x10-16 respectively. Radiological hazard indicator of radium is of concern in these river water samples.