A new look at inhalable metalliferous airborne particles on rail subway platforms.
Nomenclature / Abbreviations BoBo: In this axle arrangement, all two-axle bogies are driving Bo2: In this axle arrangement, one two-axle bogie is driving while the other is trailing DMA: First driving motor car in an electric multiple unit DMB: Last/second driving motor car in an electric multiple unit EDX: Energy-dispersive X-ray spectroscopy EC: European commission FESEM: Field emission scanning electron microscope IARC: International agency for research on cancer ICP-MS: Inductive coupled plasma mass spectrometry NRMM: Non-road mobile machinery PM: Particulate matter (,) RZS: Compact brake calliper unit for wheel-mounted brake disc (from Knorr-Bremse) SMPS: Scanning mobility particle sizer UIC: International union of Railways OPC: Ordinary Portland cement Abstract Inhalable airborne particles have inverse health affect. In railways, mechanical brakes, the wheel–rail contact, current collectors, ballast, sleepers, and masonry structures yield particulate matter. Field tests examined a Swedish track using a train instrumented with particle measurement devices, brake pad temperature sensors, and speed and brake sensors. The main objective of this field test was to study the characteristics of particles generated from disc brakes on a running train with an on-board measuring setup. Two airborne particle sampling points were designated, one near a pad–rotor disc brake contact and a second under the frame, not near a mechanical brake or the wheel–rail contact; the numbers and size distributions of the particles detected were registered and evaluated under various conditions (e.g. activating/deactivating electrical brakes or negotiating curves). During braking, three speed/temperature-dependent particle peaks were identified in the fine region, representing particles 280 nm, 350 nm, and 600 nm in diameter. In the coarse region, a peak was discerned for particles 3–6 µm in diameter. Effects of brake pad temperature on particle size distribution were also investigated. Results indicate that the 280 nm peak increased with increasing temperature, and that electrical braking significantly reduced airborne particle numbers. FESEM images captured particles sizing down to 50 nm. The ICP-MS results indicated that Fe, Cu, Zn, Al, Ca, and Mg were the main elements constituting the particles.