Magnetic differentiation and quantification of airborne particulate matter from vehicular brake systems

Exposure to particulate air pollution poses a threat to pulmonary, cardiovascular and neurological health, being associated significantly with increased morbidity and premature mortality worldwide. Ultrafine, metal-rich particles (UFPs; 0.600 µm and decreased to 2 – 15 wt.% for particles 99% of particle number concentration). Moreover, even larger fractions (e.g. ~2.5 µm) are dominated by agglomerated UFPs ~10 – 50 nm in size, as demonstrated by electron microscopy. Overall, my thesis demonstrates that vehicle brake systems are one of the major sources of Fe-bearing UFPs in urban environments. Such UFPs (especially Fe2+-bearing magnetite, often co-associated with other potentially toxic metals and organic species) might pose a particular threat to neuronal and cardiovascular health. The observed abundance of magnetite in the ultrafine size fraction of brake-wear PM (estimated to be ~7.6 wt.% of PM < 200 nm) might be especially hazardous to the human brain, where ultrafine magnetite particles have been reported to have a causal link with neurodegeneration and Alzheimer’s disease (through generation of excess oxidative stress). Prospectively, given the potential risk to human health, the high concentrations of magnetite, specifically, in brake-wear PM might need to be reduced in order to mitigate such risk, especially for vulnerable population groups