Supportive evidence is provided by the work of von Uexküllet al. (2005), who investigated the chemical composition of both brake lining materials and emitted brake dusts from a range of commercial, heavy-goods vehicles, and trailers, using a combination of X-ray fluorescence (XRF) and inductively-coupled plasma atomic emission spectroscopy (ICP-AES) analytical techniques. Their findings indicated significant differences in the chemical composition of the emitted brake dusts relative to the bulk lining materials. Ni and Cu were found in much greater concentrations in the emitted dust relative to the bulk lining material. Kennedy and Gadd (2003) presented evidence to suggest that brake dust is enriched in Cr, Cu, Fe, and tin (Sn) compared to parent brake linings. During the braking process wear of the brake discs/drums, which are commonly made of steel or alloys, may occur. A thin layer of wear debris, called a transfer film, may form at the frictional interface between lining and disc/drum. Transfer films contain a range of elements and compounds derived from the numerous additives that are used in brake system components. Whilst a portion of the brake wear material may be emitted to the atmosphere very quickly, some remains locked up in the transfer film for a time before being ejected from the brake system (Blau and Meyer, 2003). Oxide coatings