On-site ALI versus submerged culture: Chemical and toxicological investigation of brake wear sub-micrometric particles

Poor air quality is a significant risk to human health and the environment, with a direct correlation to respiratory diseases and premature death. Ultra fine particles (UFPs) in the atmosphere are particularly hazardous. This study evaluates the toxicological response of epithelial cells (A549) and macrophages (dTHP-1) to particulate matter (PM) emissions from car brake wear, under both submerged and Air-Liquid Interface (ALI) conditions. Toxicity was assessed using cell viability (Resazurin assay) and cytokine assays. Emissions were collected using a dynamometric bench simulating driving and braking conditions. Under ALI, freshly emitted particles were directly deposited onto cells, while in submerged conditions, particles were collected on filters and then deposited onto cells. M1a and M1b materials were tested, both materials are falling into category of ECE R90 Low Metallic pads. M1a showed slight toxicity under ALI and significant immune response in submerged conditions, while M1b showed no toxicity in either condition.