Brake wear particle emissions: a review

Abstract

Traffic-related sources have been recognized as a significant contributor of particulate matter particularly within major cities. Exhaust and non-exhaust traffic-related sources are estimated to contribute almost equally to traffic-related PM10 emissions. Non-exhaust particles can be generated either from non-exhaust sources such as brake, tyre, clutch and road surface wear or already exist in the form of deposited material at the roadside and become resuspended due to traffic-induced turbulence. Among non-exhaust sources, brake wear can be a significant particulate matter (PM) contributor, particularly within areas with high traffic density and braking frequency. Studies mention that in urban environments, brake wear can contribute up to 55 % by mass to total non-exhaust traffic-related PM10 emissions and up to 21 % by mass to total traffic-related PM10 emissions, while in freeways, this contribution is lower due to lower braking frequency. As exhaust emissions control become stricter, relative contributions of non-exhaust sources—and therefore brake wear—to traffic-related emissions will become more significant and will raise discussions on possible regulatory needs. The aim of the present literature review study is to present the state-of-the-art of the different aspects regarding PM resulting from brake wear and provide all the necessary information in terms of importance, physicochemical characteristics, emission factors and possible health effects.

Characterization of leaf-level particulate matter for an industrial city using electron microscopy and X-ray microanalysis

“…The main traffic-related marker evidenced by the EDX analysis, and confirmed by the PCA in this study is Cu, which is reportedly generated by mechanical abrasion of car components, particularly tyre wear breakdown (Pant and Harrison, 2013) or brake wear (Grigoratos and Martini, 2015). The high Cu concentration found at the site close to both the factory and street (CFS) can be due to the presence of a busy road with a little slope in the proximity of a roundabout.…”

“…Several sampling and analysis methodologies have evaluated the quality of urban PM for a range of environments, including traffic (Pant and Harrison, 2013;Grigoratos and Martini, 2015), indoor metro stations (Lu et al, 2015;Querol et al, 2012), industries (Deshmukh et al, 2012), and the wider suburbs (Blanco et al, 2003). Human health is shown to be affected more by enhanced exposure levels to cumulative PM (mainly associated with pulmonary diseases) or their chemical composition (Donaldson and Seaton, 2012;Warheit et al, 2007) than by single events of acute pollutant concentration (Kariisa et al, 2014).…”

Contact Pressure and Sliding Velocity Maps of the Friction, Wear and Emission from a Low-Metallic/Cast-Iron Disc Brake Contact Pair

“…Resuspension of particles into the air is also considered a source of non-exhaust emission. PM10 from disc brakes could contribute up to 50 % of the total nonexhaust emissions from road transport in the EU [4], [5]. Since PM10 emissions have adverse health effects [5], the EU has defined European Emission Standards [7] which describe the acceptable limits for exhaust emissions of new vehicles sold in the EU.…”

Characterization and preliminary risk assessment of road dust collected in Venice airport (Italy)

“…Sb and Cu are tracer of brake pads wear (Hulskotte et al, 2007;Varrica et al, 2013;Grigoratos and Martini, 2015;Valotto et al, 2015;Valotto et al, 2017b), while Ni, Cr, and Mo in addition to Fe and C are typical steel constituent (Tomita and Okabayashi, 1985). Because the brake discs are made of steel, and Mg and Co were identified in brake dust (Grigoratos and Martini, 2015) we suggest as representative pollutant source of PC3 the "brake wear". Indeed, samples characterized by higher scores are both fractions of #2 and #14 which were collected at the end of two down ramps where brakes are typically most stressed.…”

“…Road traffic is an important source of atmospheric particulate matter in urban and industrialized areas (e.g., Thorpe and Harrison, 2008;Wik and Dave, 2009;Franco et al, 2013;Kumar et al, 2013;Pant and Harrison, 2013;Amato et al, 2014;Grigoratos and Martini, 2015;Suvarapu and Baek, 2016;Timmers and Achten, 2016). It includes exhaust and non-exhaust emissions.…”