Comparison of environmental radioactivity in road dust between a city and a megacity: geo-environmental evaluation, health risks, and potential remediation.

This study presents a comprehensive comparative analysis of naturally occurring radioactive materials (NORMs)—specifically radium-226 (^226Ra, approximately uranium-238), thorium-232 (^232Th), and potassium-40 (^40K)—in roadside dust samples from Khulna, a coastal city, and Dhaka, a highly urbanized megacity in Bangladesh. Using Instrumental Neutron Activation Analysis, the research found that both cities exhibit radioactivity levels significantly exceeding global averages, with Dhaka showing notably higher concentrations than Khulna. The study explores the geochemical fractionation and environmental dispersion mechanisms of these radionuclides, linking their presence to natural soil composition and anthropogenic activities such as construction and traffic. Radiological risk assessments indicate potential health hazards, particularly from inhalation of alpha particles emitted by decay products of ^232Th and ^238U, with excess lifetime cancer risk values surpassing recommended safety limits in both cities. The authors recommend active and passive mitigation strategies, including dust control measures and public awareness, to reduce exposure and support sustainable urban health goals.