Radiometric analysis of Radon-222 concentration in water sources used for domestic purposes in Nasarawa Metropolis, Nasarawa State, Nigeria

Abstract

This study investigates the concentration of Rn-222 in domestic water sources within Nasarawa metropolis, Nasarawa State, Nigeria. With the aim of accessing the potential health concerns related to radon accumulation.  A total of thirty water samples comprising ten each from wells, boreholes, and streams were collected and analyzed using a liquid scintillation counter (Tri-Carb LSA 1000). Key parameters evaluated include Rn-222 activity concentration, annual effective dose from ingestion and inhalation, dose contributions to the stomach and lungs, and the excess lifetime cancer risk. Measured Rn-222 levels ranged from 0.06 to 18.50 counts per minute (cpm), with a background radiation count of 63.83 cpm attributed to environmental and non-sample sources. Radon activity concentrations spanned from 3.14 × 100 to 1.15 × 103 Bq/L, with an average of 4.17 × 101 Bq/L which substantially exceed the World Health Organization (WHO) recommended safety threshold of 100 Bq/L for drinking water. The mean annual effective dose from ingestion (3.05 × 10⁻³ mSv/y) remained below the International Commission on Radiological Protection (ICRP) public exposure limit of 1 mSv/y. However, the mean dose to the stomach was 3.65 × 10⁻⁴ mSv/y, indicating minor but quantifiable internal exposure. Notably, the average annual effective dose from inhalation was 18.4 mSv/y, significantly surpassing the ICRP guideline, thus raising potential health concerns, particularly in enclosed, poorly ventilated settings where radon may accumulate. The study therefore recommends continuous monitoring of domestic water sources and improved ventilation practices to minimize radon-related health risks.