Setting the radiological baseline: measuring natural radioactivity (226Ra, 232Th, 40K) in agricultural soils of Farta District, Ethiopia, and assessing potential health risks

Tracking natural radioactivity, especially from naturally occurring radioactive material (NORM), matters for public health radiation concerns. We measured agricultural soils from Ethiopia's Farta District using high-purity germanium gamma-ray spectrometry. There's something people often miss: international guidelines like 1 mSv per year or 370 Bq/kg (for radium equivalent activity, Raeq) aren't strict regulatory cutoffs, just broad screening tools. They help flag areas worth a closer look but don't mean there's a problem if background levels are naturally higher. Here's what we found: 226Ra ranged from 12 to 342 Bq/kg, 232Th from 10 to 321 Bq/kg and 40 K from 65 to 671 Bq/kg. The averages are 144 ± 83, 141 ± 81 and 340 ± 182 Bq/kg for each, in order. Average Raeq was 370 ± 200 Bq/kg, which matches the usual international screening number, although some spots went above it. Factoring in an agricultural occupancy rate of 0.4 (because farmers spend more time outdoors), the average annual effective dose (AED) hit 0.41 mSv. If you assume a more general lifestyle with less outdoor exposure (occupancy 0.2), the AED drops to 0.20 mSv. So, you can really see how behavior shapes exposure. A number of samples went above the recommended marks for the internal hazard index (H_in) and annual gonadal dose equivalent. But again, these are just screening flags; they don't mean there's an immediate health threat. This work builds a strong baseline for the region. It gives future projects like environmental monitoring, food-chain tracking, radon measurements, or health studies a solid place to start, especially in a geologically unique area like Ethiopia's Farta District.