Radon levels and lifetime cancer risk from ingestion and inhalation of well water samples in Akoko South West, Ondo State, Nigeria

Abstract

Due to increased population, urbanisation, and climatic change, the overexploitation and over-reliance on groundwater sources- wells and boreholes have surfaced. Groundwater is understood as harmless and safe, yet it often contains natural radioactivity. The health risks posed by the ingestion and inhalation of radon-222 from the well water in Akoko South-West Local Government Area of Ondo State, Nigeria, were assessed in this study. A liquid scintillation counter was used to analyse ten water samples from wells for radon concentration. The average radon concentration was 23.29 Bq/L, ranging between 10.30 and 41.89 Bq/L. Roughly 90% of the samples recorded concentrations greater than the United States Environmental Protection Agency’s 11.1 Bq/L maximum contaminant level. The ingestion of annual effective dose was determined between 0.0018 and 0.0073mSv/y with a mean of 0.0041mSv/y while the inhalation dose ranged between 0.0260 and 0.1056mSv/y with a mean of 0.0587mSv/y. According to the assessment, 80% of estimated dose values were below the reference level specified by the World Health Organization (WHO) of 0.1 mSv/y. Cancer risk during a lifetime varies from 0.10 ×10-3 to 0.40 ×10-3 with a mean of 0.22 ×10-3. As much as about 30% of the estimated values are above the reference level of 0.29 ×10-3.  In general, radon concentrations sampled in wells have exceeded the USEPA comparison level; however, the estimated radiation doses have been measured within permissible levels. Consequently, it is recommended to routinely monitor radon concentration in groundwater, which will help manage radiologic risk and safeguard public health.