Road dust is an important urban reservoir of potentially toxic elements (PTEs) and a relevant source of human exposure through resuspension and inhalation, particularly in large megacities. This study provides an integrated assessment of the seasonal variability, contamination levels, source identification, particle characteristics, lung bioaccessibility, and health risk of road dust in Mexico City, one of the world’s largest urban centers. A total of 74 road dust samples were collected during the dry and wet seasons, and V, Cr, Mn, Co, Ni, Cu, As, Cd, Sb, and Pb were analyzed by ICP–MS in the <20 µm fraction. Geochemical indices, spatial analysis, Pearson correlation, principal component analysis, SEM–EDS particle characterization, in vitro lung bioaccessibility (ALF), and human health risk models were applied. Sb, Cu, and Pb were identified as the most enriched elements, exceeded local background concentrations at all sampling sites. Spatial patterns revealed recurrent hotspots in the northern, northeastern, and central sectors of the city. SEM–EDS analyses showed that most particles belonged to the 2.5–5 µm equivalent-size class and included Fe-rich spherules, Pb-rich aggregates, silicate grains, and C-rich particles. Health risk assessment indicated acceptable risks for adults, whereas children exceeded the non-carcinogenic threshold (HI = 3.85–4.60) and slightly surpassed the upper acceptable carcinogenic risk level. Lung bioaccessibility results revealed low Pb solubility but high mobility of Ni and Cu, with some samples reaching complete dissolution under ALF conditions. These findings demonstrate that traffic-derived road dust represents a persistent urban exposure pathway in Mexico City and highlight the importance of integrating total concentrations, particle characteristics, and bioaccessibility data to improve environmental and health-risk assessments in urban environments.

This work reports a method for the precise and accurate determination of Pb isotope composition in soils and geological matrices by ICP-QMS. Three reference materials (AGV-2, SRM 2709 and JSO-1) were repeatedly measured, using ICP-QMS instruments in order to assess the quality of this analytical procedure. Mass discrimination was evaluated for Pb/Pb with Pb isotope reference material NIST SRM 981, and the correction applied to the above mentioned reference materials to achieve good accuracy of the analytical methodology. An internal standardization using 205Tl was employed to avoid instrumental drift. The measured isotope compositions of all analyzed reference material were comparable with the reported (JSO-1 and SRM 2709) and certified values (AGV-2). The accuracy results agreed in average within 0.002% for 207Pb/204Pb and 0.825% for 207Pb/206Pb. These data corroborate that ICP-QMS results to be reliable in terms of accuracy and precision, for the determination of the Pb isotopic compositions in soils and geological matrices. Este trabajo reporta un método para la determinación precisa y exacta la composición isotópica de Pb en matrices ambientales y geológicas mediante ICP-QMS. Se analizaron réplicas de tres materiales de referencia (AGV-2, SRM 2709 y JSO-1), por medio de ICP-QMS con el objeto de evaluar la calidad del procedimiento analítico. La discriminación de masas para Pb/Pb fue evaluado usando el material de referencia NIST 981, y esta corrección fue aplicada a los materiales de referencia antes mencionados, para obtener la exactitud del método analítico desarrollado. Se aplicó una estandarización interna con 205Tl para corregir la deriva instrumental. La composición isotópica obtenida para los materiales de referencia es comparable con los valores reportados (JSO-1 and SRM 2709) y certificados (AGV-2). Los valores de exactitud de los resultados obtenidos varían en promedio entre 0.002% para 207Pb/204Pb y 0.825% para 207Pb/206Pb. Estos resultados indican que el método ICP-QMS es confiable en términos de precisión y exactitud para la determinación de relaciones isotópicas de Pb en matrices de suelos y geológicas.