Experimental assessment of ambient gamma dose equivalent rates measured outdoors in the Republic of Benin from 2019 to 2020

Natural background radiation, consisting of cosmic, terrestrial, and skyshine components, varies significantly due to environmental and geological factors. This study assessed outdoor gamma radiation levels across medical imaging centers in Benin, providing the first national-scale data on natural background radiation. Measurements were conducted using a radiameter, with georeferenced data mapped to the geological background of Benin. The results revealed an annual mean dose of 0.68 mSv, slightly below the international guideline of 0.9 mSv. However, significantly higher doses were recorded in the Borgou (1.93 mSv) and the Collines (1.37 mSv) regions, where granite rock formations rich in radionuclides such as ⁴⁰ K and uranium decay chains are prevalent. Statistical analysis confirmed a strong correlation between elevated radiation levels and granite-rich areas. These findings highlight the uneven distribution of natural radiation across Benin, influenced more by geological features than by altitude. While the study provides valuable baseline data, it was limited to external gamma radiation and did not account for radon exposure, indoor environments, or outdoor occupancy factors. Future studies should address these gaps, including a more extensive sampling strategy and assessments of internal exposures, to better understand the public health implications. This research lays the foundation for epidemiological studies and informs regulatory efforts to ensure radiological safety in Benin.