Monte Carlo simulation of the health risk from exposure to rn-222 in groundwater sources in the Nasarawa local government area of Nasarawa state, North-central Nigeria

Abstract

Aim: This study assesses 222Rn concentrations in groundwater sources within Nasarawa Local Government Area and evaluates the Excessive Lifetime Cancer Risk (ELCR) associated with their consumption. Methods: Groundwater samples were collected from multiple locations and analyzed using a RAD-7 electronic radon detector with RAD–H2O accessories. 222Rn concentrations were estimated using both a conventional formula and a Monte Carlo simulation performed over 10,000 iterations. These simulations were conducted using the Oracle Crystal Ball Software. ELCR values were validated against the 5th, 50th, and 95th percentiles of the resulting probability distribution. Results: The mean 222Rn concentration was 2,201 Bq/m³, which significantly exceeded the World Health Organization (WHO) recommended limit of 300 Bq/m³. The annual effective dose due to ingestion (AEDing) also surpassed the 0.1 mSv/yr threshold set by the European Union and the WHO, while the total annual effective dose from ingestion and inhalation exceeded the 1 mSv/yr maximum contamination limit. The highest ELCR value (2.97 ± 0.35) was recorded in Usha, likely due to the alaskite- and clay-rich geology of the region. All the ELCR values exceeded the recommended limit of 0.003875 set by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Conclusions: These findings highlight a significant potential public health risk from 222Rn-contaminated groundwater, especially if consumed without pre-treatment. The implementation of intervention and remediation strategies is strongly recommended to reduce exposure, even though no radiological health effects have been reported in the region to date.