PM₁₀-bound elements in Luanda's urban atmosphere: Concentrations, sources, and their environmental and health impacts

An unprecedented study was carried out in the megacity of Luanda, Angola, involving daily sampling of particulate matter (PM₁₀) from June to November 2023. The analysis was focused on the detection of 56 metal(loid)s and complemented by the application of several contamination and health risk indices. PM₁₀ levels ranged from 23.6 to 108 μg/m³, averaging 59.3 μg/m³, exceeding WHO's 24-h guideline on 83% of days. In addition to crustal elements, the most abundant constituents were Zn (159 ng/m³), Ba (43.2 ng/m³), Pb (17.8 ng/m³), Cu (10.5 ng/m³), Sr (7.0 ng/m³), Ni (4.5 ng/m³), Sb (3.7 ng/m³) and Cr (3.5 ng/m³). Mineral dust, primarily from unpaved roads and local soils, accounted for 31 wt% of PM₁₀, while sea salt contributed 6%. Geochemical markers (e.g., Ce-La-V relationships) suggest that vanadium originates predominantly from upper crust weathering. Elemental ratios such as Fe/Cu, Cu/Sb, and Zn/Sb indicate significant contributions from traffic-related emissions (e.g., brake and tyre wear) and industrial sources. Sulphur, an important PM₁₀ component, likely stems from fossil fuel combustion and petroleum refining. Luanda experiences severe air pollution, with high inputs from Sb, Cd, Zn, and other elements linked to traffic, industrial emissions, and biomass burning. The extremely high ecological risk (RI = 4360 ± 2440) highlights critical contamination, driven primarily by Cd and Sb, while the Nemerow risk index (1990 ± 1530) underscores urgent public health concerns. Non-cancer hazard indices (HI) exceeded safe thresholds for children (2.29) and adults (2.18), with Fe, Mn, Be, Pb, Ni, Co, and Sb identified as key contributors. Carcinogenic risks from PM₁₀ inhalation (2.34 × 10^-3 for children and 1.36 × 10^-3 for adults) also exceeded acceptable levels, emphasising the need for targeted pollution mitigation strategies.