Radiological exposure evaluation along the beaches of Limbe—Cameroon: experimental and monte Carlo-based organ dose evaluation from natural radionuclides

Abstract

This study evaluated natural radioactivity levels and associated radiation doses from beach sands from Limbe, Cameroon, to assess potential public exposure. Sand samples from Batoké, Down Beach, and Limbola, along Cameroon’s Atlantic coast, were analysed using high-resolution gamma spectrometry with a Broad Energy Germanium (BEGe) detector to determine the activity concentrations of naturally occurring radionuclides (²³⁸U, ²³⁵U, ²²⁶Ra, ²³²Th, and ⁴⁰ K). Measured values were found within global average levels. Radiological hazard parameters, including absorbed dose rate (54.29 nGy/h), annual effective dose (66.59 µSv/yr), radium equivalent activity (119.37 Bq/kg), and external hazard index (0.32), were all below international safety limits, indicating negligible radiological risk for individuals spending time at various beaches. Monte Carlo (MC) simulations using the Particle and Heavy Ions Transport code System were used to estimate organ-specific doses for adult male and female anatomies from measured radionuclide concentrations. The obtained results indicate the highest exposure in the lower extremities due to proximity to ground radiation, with significant sex-based differences, with testes receiving up to 223.26 µSv/year versus 166.03 µSv/year for ovaries. Separate occupancy factors were applied for frequent beach workers and occasional visitors. Cancer risk assessment showed a low but non-trivial lifetime risk, especially with prolonged exposure. MC-derived dose estimates, reflecting anatomical realism and posture, provide a robust basis for radiological health risk projections. Overall, results indicate negligible radiological risk for typical beach use, while providing detailed organ dose data for different exposure groups. These findings establish a baseline for future monitoring and potential risk mapping of coastal radiation exposure in the region.