GIS-Based Spatial Assessment of Outdoor Background Ionizing Radiation and Associated Radiological Risk Indices in Major Markets of Dutsin-Ma, Katsina State, Nigeria

Abstract

Terrestrial background ionizing radiation constitutes a continuous source of human 
exposure, and elevated levels may increase long-term radiological risks in densely 
occupied environments. This study applied Geographic Information System (GIS) 
techniques to evaluate terrestrial background radiation and associated radiological 
risks in Wednesday and Old Markets, Dutsin-Ma, Katsina State, Nigeria, where 
population density and commercial activities are increasing. In-situ measurements 
were obtained at 20 systematically selected locations using a calibrated Bosean FS
5000 Geiger–Müller survey meter, while geographic coordinates were recorded with 
a handheld GPS receiver. Mean outdoor dose rates ranged from 0.09–0.19 µSv h⁻¹, 
with average values of 0.147, 0.163, and 0.155 µSv h⁻¹ for Wednesday Market, Old 
Market, and both markets combined, respectively. Corresponding absorbed dose 
rates ranged from 86.7–193.3 nGy h⁻¹ and exceeded the worldwide outdoor 
terrestrial gamma-radiation average of 59 nGy h⁻¹ at all sampled locations. These 
elevated levels may partly reflect the regional Precambrian Basement Complex 
geology. The annual effective dose equivalent ranged from 0.106–0.237 mSv y⁻¹, with 
an overall mean of 0.190 mSv y⁻¹. Excess lifetime cancer risk varied from 0.372
0.830 × 10⁻³ and averaged 0.666 × 10⁻³, exceeding the commonly adopted worldwide 
reference value of 0.29 × 10⁻³. GIS-based interpolation delineated localized 
radiation and cancer-risk hotspots within both markets. Estimated adult organ doses 
were highest for the gonads and lowest for the liver. These findings establish 
baseline geospatial radiological data for Dutsin-Ma and underscore the need for 
periodic environmental radiation monitoring and systematic risk assessment as local 
population density and commercial activities continue to increase.