92 Towards an understanding of the relative toxicity of nanoparticles from different transport sources

Abstract In recent decades, increasing attention has been directed toward the smallest fraction of airborne particulate matter—ultrafine particles (UFPs, <100 nm, also referred to as nanoparticles)—due to their potential health risks. The extent to which nanoparticles from different sources vary in toxicity remains insufficiently understood. Within the EU-funded project nPETS (Nanoparticle Emissions from the Transport Sector: Health and Policy Impacts), we investigated the toxicity of nanoparticles generated across various transport-related environments. These included laboratory-generated particles from rail systems and brake/clutch wear, as well as ambient nanoparticles collected from diverse European sites: a road tunnel, subway, harbour, and airport. For selected sources, we compared the toxicity of nanoparticles with that of larger particles (PM2.5 or micron-sized), performed air–liquid interface (ALI) exposures, and in certain scenarios, modelled long-term pulmonary deposition using the Multiple-Path Particle Dosimetry Model. Toxicity assessments using A549 cells and differentiated THP-1 cells focused on cytotoxicity, DNA damage, and inflammatory responses (IL-8, IL-6, TNFα, IL-1β secretion). Our findings showed that both nano- and micron-sized particles from the road tunnel and subway in Stockholm induced DNA strand breaks and inflammatory cytokine release. Overall, the collected particles exhibited low cytotoxicity but high variability in inflammatory potential. Nanoparticles from the harbour and airport (Barcelona), for example, displayed pronounced inflammatory activity. Variations in endotoxin content complicate interpretation of the role of chemical composition in the observed effects. We are currently developing a “toxicity score” framework to support future regulatory and mitigation strategies.