Diesel particle filter regeneration: Impact on the physicochemical composition and toxicity of diesel exhaust emissions

This study investigated the impact of Diesel Particulate Filter (DPF) regeneration on the composition and toxicity of exhaust emissions from a Euro 6d diesel passenger vehicle. Multiple real-world-simulated driving cycles were performed under two DPF conditions: normal operation and active regeneration. Exhaust emissions were characterized in real time for gaseous and particulate pollutants, while the nanoparticle fraction of the particulate mass was chemically analyzed for its organic and inorganic components. The toxicological effects of DPF regeneration were evaluated using an in vitro Air-Liquid Interface (ALI) exposure system with human lung cells. The results indicate that DPF regeneration accounted for more than 95 % of total particle number emissions, while significant amounts of carbon monoxide and methane were emitted as well. Exposures in the absence of particles led to similar reductions in cell viability and inflammatory responses, regardless of the DPF condition. In contrast, when particles were present, the cellular response became significantly stronger, indicating that the increased toxicity is primarily driven by the particulate fraction. Chemical analyses of nanoparticle mass revealed higher concentrations of water-soluble elements and oxygenated polycyclic aromatic hydrocarbons during regeneration. Overall, DPF regeneration transiently but substantially alters emission characteristics and significantly increases their toxicological potential.