Assessment of Radon-222, Radium-226 Concentrations and Potential Risk to Artisanal Miners Around Ririwai Tin Mine Kano State, North Western Nigeria

Abstract

Mining and mineral processing in Nigeria generate substantial economic benefits through employment and wealth creation, yet they also present significant environmental and public health challenges due to exposure to naturally occurring radioactive materials (NORMs). This study evaluated the radiological hazards associated with artisanal tin mining in Ririwai, Kano State, by analyzing Radon-222 (²²²Rn) and Radium-226 (²²⁶Ra) concentrations in soil samples using RAD7 and NaI(Tl) gamma spectrometry. Results showed elevated ²²²Rn levels with a mean concentration of 412.2±11.46 Bq·m⁻³ (range: 234-782 Bq·m⁻³), significantly higher than global background levels. The radon exhalation rate averaged 17.175±5.87 Bq·m⁻²·h⁻¹, while ²²⁶Ra activity concentrations ranged from 4.36-107.30 Bq·kg⁻¹ (mean: 51.017±5.87 Bq·kg⁻¹). The calculated annual effective dose of 3.21 mSv·yr⁻¹ exceeded both the global average (2.4 mSv·yr⁻¹) and the ICRP recommended limit of 1 mSv·yr⁻¹ for public exposure. Radiological risk assessment revealed concerning values, including a fatality risk of 1.7×10⁻⁴ and lifetime fatality risk of 10.2×10⁻³, which are substantially higher than the USEPA's negligible risk range (1×10⁻⁶-1×10⁻⁴). Similarly, severe hereditary effects (6.4×10⁻⁵) and lifetime hereditary risks (3.84×10⁻³) were significantly elevated. These findings demonstrate that artisanal miners and nearby communities face substantial radiation exposure that could lead to increased cancer incidence and other health effects. The study underscores the urgent need for regulatory interventions, including radiation monitoring programs, improved mining practices, and public awareness campaigns to mitigate these environmental health risks while maintaining the economic benefits of small-scale mining operations in Nigeria.