Heavy metal contamination, risk assessment, and source apportionment of roadside dust in a rapidly urbanizing tropical city: Implications for developing urban environments.

This study assessed contamination levels in roadside dust across different land use types in a rapidly urbanizing tropical city in Southeast Asia, using inductively coupled plasma - mass spectrometry (ICP-MS). A total of 22 elements were analyzed from commercial, residential, industrial, institutional, and agricultural areas, followed by ecological and human health risk assessment. Results showed high concentrations of Fe, Al, Ti, and Cr, with Fe being the most abundant, reflecting the geogenic composition of roadside dust. Industrial land use exhibited the highest average concentrations of geogenic and trace metals; however, based on potentially toxic metals, it posed low ecological risk despite these elevated concentrations. Moreover, both commercial and residential areas showed signs of Pb and Hg contamination and ecological risk, with the highest risk index observed in the commercial area (236.46). Furthermore, based on health risk assessment, ingestion was the dominant exposure pathway, followed by dermal contact and inhalation. The average daily dose (ADD) was consistently higher in children than in adults, indicating greater potential exposure among children. Among heavy metals analyzed, Pb contributed the highest exposure dose, whereas Cd and Hg contributed substantially lower doses. Multivariate analyses (PCA and CCA) identified significant sources of dust contamination from natural sources and anthropogenic activities, including urban development, vehicle emissions, and their components. This indicates that roadside dust is an effective environmental indicator for assessing heavy metal contamination and associated ecological and human health risks in rapidly urbanizing cities.