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

Abstract

This pioneering study represents a comprehensive comparative analysis of naturally occurring radioactive materials (NORMs: 226Ra (≈238U),232Th, 40K) on the roadside dust samples collected from a coastal city (Khulna) and a highly urban megacity (Dhaka), Bangladesh. The corresponding radioactivity was calculated based on Instrumental Neutron Activation Analysis of elemental abundances (uranium [U], thorium [Th], and potassium [K]). Averagen=30 radioactivity levels of 226Ra (≈238U), 232Th, and 40K in the road dust of Khulna city were 46.82 ± 24, 74.79 ± 25, and 541.14 ± 160.8, whereas in Dhaka city, they were 84.4 ± 13, 126 ± 11, and 549 ± 48 (Bq.kg-1), respectively. Khulna city had 1.3, 2.5, and 1.4 times greater 226Ra (≈238U), 232Th, and 40K radioactivity than the global average values, respectively. For Dhaka city, the following values were 2.42, 4.2, and 1.4 times elevated. The levels of radioactivity in Dhaka city are significantly higher than those in Khulna city; however, both cities have exceeded the world average values. The mechanisms for the enrichment and dispersion of NORMs from their fundamental source (surface soil) were studied, considering waterlogging, relative solubility-controlled leaching and translocation, climate conditions, and aerodynamic fractionations (dry and wet air deposition). The computation of standard radiological indices indicates risks to human health. Respiratory harm can be inflicted by α-particles originating from the radioactive decay products of 232Th and 238U. In addition to public awareness, policymakers should prioritize limiting the evolution of dust particles to mitigate the associated health risks.