{"id":23441,"date":"2021-06-30T11:53:44","date_gmt":"2021-06-30T09:53:44","guid":{"rendered":"https:\/\/www.cara.eu\/?p=23441"},"modified":"2021-06-30T11:53:46","modified_gmt":"2021-06-30T09:53:46","slug":"brake-particles","status":"publish","type":"post","link":"https:\/\/www.cara.eu\/en\/brake-particles\/","title":{"rendered":"Brake particles"},"content":{"rendered":"
\n\tRoad traffic is a major source of particulate emissions that pose a significant risk to human health and the environment. Despite efforts by governments and scientists to reduce tailpipe emissions, the contribution of non-exhaust emissions has increased and become dominant in recent years. \r\n\r\n <\/p>\n<\/div>\n\n
Road traffic is a major source of particulate matter emissions that pose a significant risk to human health and the environment. It is one of the priority areas for action to improve air quality, and is now the focus of public and scientific attention and the centre of the environmental debate. Over the last twenty years, the issue of reducing exhaust emissions has been brought to the forefront of the international and particularly European scene (introduction of Euro standards, particulate filters, SCR systems to reduce NOx, etc.). Nevertheless, in view of the efforts made to reduce tailpipe emissions, the contribution of non-exhaust emissions has increased and has become predominant in recent years. These non-exhaust emissions are mainly due to brake wear and to particles emitted when tyres come into contact with the road. By 2030, they are expected to increase by 53.5% worldwide, according to the OECD (Organisation for Economic Co-operation and Development). Moreover, epidemiological studies show that the toxicological impact of these particles is far from negligible.<\/p>\n<\/div>\n\n
Among non-exhaust emissions, brake particles are predominant, especially in urban areas and near high-traffic roads. Indeed, the wear process that takes place during the contact between the brake pads and the brake disc is responsible for significant emissions of fine and ultrafine particles. They represent up to 55% of PM10 emissions from non-exhaust sources and up to 20% of total PM2.5 emissions from road traffic. These emissions are still poorly known and quantified because of their variability, as many parameters influence their characteristics, such as the diversity of vehicles and brake pads, road characteristics, driving style, etc. They are also poorly studied because the methods used to characterise them are complex. Measurements at the source of brake particles show that their concentration increases significantly with vehicle speed, weight and braking frequency. Indeed, the more the braking system is used, the more the friction of the contact zone on the disc increases. This friction will generate, on the one hand, coarse particles due to mechanical abrasion and, on the other hand, ultrafine particles (with a diameter of less than 100 nanometers) emitted by thermal degradation of the brake pad materials in the event of overheating. Recent studies have confirmed that increasing the temperature of brakes, up to a certain threshold, favours the formation of nanoparticles. Thus, this temperature represents an important issue to be taken into account for the reduction of brake emissions.<\/p>\n<\/div>\n\n
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