Lung alveolar cell reactivity to organic fractions extracted from air particulate matter collected in an African megacity.

Airborne particulate matter (PM) exposure is strongly associated with adverse respiratory and cardiovascular outcomes. In rapidly urbanising cities such as Luanda, where no air quality monitoring exists, assessing the biological effects of PM10 is critical to guide public health strategies and legislation. This study investigated the organic composition and cytotoxicity mechanisms of PM10 collected near a busy road in central Luanda from June to November 2023. Chemical analysis identified polycyclic aromatic hydrocarbons (PAHs), quinones, saccharides (e.g., levoglucosan), hydroxy acids, and dicarboxylic acids, with temporal patterns reflecting alternating contributions from traffic emissions, biomass burning, and secondary organic aerosol formation. A549 alveolar basal epithelial adenocarcinoma cells exposed to PM10 organic extracts showed a dose- and time-dependent response, with viability reduced to ∼50% after 72 h for the most toxic samples, which were richer in hydroxy and dicarboxylic acids. Flow cytometry confirmed cell cycle disruption, particularly S-phase arrest at low exposure concentrations after 72 h, indicating impaired proliferation and DNA synthesis. Reactive oxygen species (ROS) formation increased significantly upon exposure, especially in late-campaign samples enriched in PAHs and quinones. Correlation analysis linked quinones with ROS formation, while aliphatic alcohols and organic acids (hydroxy and dicarboxylic) were positively associated with G0/G1 and negatively associated with the S and G2 phases. No compound class correlated directly with viability. These findings indicate that Luanda PM10 contains biologically active organics capable of inducing oxidative stress, cell cycle disruption, and reduced metabolic activity. Broader chemical characterisation and multi-site sampling are needed to refine health risk estimates and support evidence-based regulation.