Pollution associated to road traffic and its combustion processes are considerably discussed in recent years. Nowadays, attention is also paid to the non-combustion processes, such as braking. During braking nonairborne and airborne fraction is released into the environment. Manufacturers try to use materials with low environmental risks, but during braking new compounds can be created, due to the high temperatures and pressures. Both fractions as well contain considerable amounts of nano-sized particles which may consequently enter the water environment and may pose risk to the living organisms. However, there are no standardized and unified procedures which could be used for the brake wear debris toxicity assessment.Aim of the study was the evaluation of the acute aquatic toxicity of the airborne brake wear debris and the most commonly used binders (phenolic resins) in the friction composites for brake linings. Brake wear debris from low-metallic brake pads was collected after standard dynamometer test from pocket filter and characterized by Raman microspectroscopy and scanning electron microscopy. Phenolic resin as binder is material with the highest volume in the formulation of the friction composite and contains Hexamethylenetetramine (HMTA) which can be decomposed at the ammonia and formaldehyde in high temperatures. Three commercially available phenolic resins were tested in the initial state and as well after thermal treatment (160 °C), which simulate process of manufacturing. Scanning electron microscopy and Fourier-transform infrared spectroscopy were used for characterization of phenolic resins. EC50 toxicity parameter for freshwater green algae detection organism Raphidocelis subcapitata was evaluated for all tested materials.Keywords: Acute aquatic toxicity, airborne brake wear debris, friction composite, phenolic resin, Raphidocelis subcapitata
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