Age-Stratified Spatial Radiological Risk Assessment of 226Ra 232Th and 40K in Water Surrounding the Geita Gold Mine in Tanzania

Long-term ingestion of water contaminated with naturally occurring radioactive material (NORM) may pose health risks. Water around the Geita Gold Mine in Tanzania was assessed by high-purity germanium gamma spectrometry to quantify the activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K, and computed age-stratified ingestion doses and risk indices were determined. The average activity concentrations were 57 mBq L^-1 for ²²⁶Ra and 5026 mBq L^-1 for ⁴⁰K, while the activity concentrations of ²³²Th were below the detection limit in all samples. The estimated adult fatal cancer risk ranged from 0.9 × 10^-6 to 3.1 × 10^-6 (mean 2.0 × 10^-6). The excess lifetime hereditary effect ranged from 2.0 × 10^-6 to 7.3 × 10^-6 for males (average 4.5 × 10^-6 ± 1.5 × 10^-6) and 2.1 × 10^-6 to 7.7 × 10^-6 for females (average 4.8 × 10^-6 ± 1.6 × 10^-6). One-way ANOVA and Pearson correlations indicated significant spatial variation in activities and indices across sites and age groups. Under current conditions, waters appear to be radiologically safe. However, mine-adjacent hotspots warrant targeted surveillance. The obtained results provide a baseline for sound monitoring approaches at the Geita Gold Mine and other mines showing similar activity profiles.