Multi analytical characterization of brake dust before and after the interaction with simulated biofluids

Car brakes are a significant source of particulate matter, which can be internalized and pose risks to human health. Some of these particles are primarily composed of Fe and heavy metals and have the potential to interact with the human brain, as well as other tissues and organs with potentially detrimental effects. As the automotive industry transitions to hybrid and electric vehicles, it is essential to assess whether these newer vehicle types generate fewer particles and how these particles may interact with human biology compared to those released by traditional combustion vehicles. This study aims to characterize the brake dust produced by different types of vehicles, such as combustion and hybrid cars, using a multi-analytical approach, including techniques such as PXRD, SEM-EDX and TEM. A dissolution test was also conducted to evaluate the release of Fe in an environment simulating bodily fluids. The results of this study provided a detailed characterization of the particulate matter emitted from brakes, focusing on both the morphology and the chemical composition of the particles in their original state and after the interaction with a simulated biofluid. The use of various techniques allowed for a comprehensive analysis of the microscale and nanoscale differences between the particles such as the presence of aggregations, the valence state, the amorphization and crystallinity degree, the surface physical state and the chemistry. Notably, the study identified chemical reactions, such as iron oxidation, which could have important implications for human health, particularly concerning neurotoxicity. These findings offer valuable insights into the understanding of the interactions and mechanisms that stand behind the health risk posed by automotive brake dust, contributing to the broader understanding of the neurotoxic potential of particulate matter. The study also highlights the importance of tracking and quantifying non-exhaust emissions, which constitute a significant portion of urban pollution, in environmental regulations. This work supports the development of improved legislations to address the release of inorganic particulate matter, including heavy metals and ferromagnetic particles, from vehicle emissions.