title: The policy relevance of wear emissions from road transport, now and in the future--an international workshop report and consensus statement.
abstract: Road transport emissions are a major contributor to ambient particulate matter concentrations and have been associated with adverse health effects. Therefore, these emissions are targeted through increasingly stringent European emission standards. These policies succeed in reducing exhaust emissions, but do not address "nonexhaust" emissions from brake wear, tire wear, road wear and suspension in air of road dust. Is this a problem? To what extent do nonexhaust emissions contribute to ambient concentrations of PM10 or PM2.5? In the near future, wear emissions may dominate the remaining traffic-related PM10 emissions in Europe, mostly due to the steep decrease in PM exhaust emissions. This underlines the need to determine the relevance of the wear emissions as a contribution to the existing ambient PM concentrations, and the need to assess the health risks related to wear particles, which has not yet received much attention. During a workshop in 2011, available knowledge was reported and evaluated so as to draw conclusions on the relevance of traffic-related wear emissions for air quality policy development. On the basis of available evidence, which is briefly presented in this paper it was concluded that nonexhaust emissions and in particular suspension in air of road dust are major contributors to exceedances at street locations of the PM10 air quality standards in various European cities. Furthermore, wear-related PM emissions that contain high concentrations of metals may (despite their limited contribution to the mass of nonexhaust emissions) cause significant health risks for the population, especially those living near intensely trafficked locations. To quantify the existing health risks, targeted research is required on wear emissions, their dispersion in urban areas, population exposure, and its effects on health. Such information will be crucial for environmental policymakers as an input for discussions on the need to develop control strategies.
  
  
  CONCLUSIONS
  Road transport particulate matter (PM) emissions are associated with adverse health effects. Stringent policies succeed in reducing the exhaust PM emissions, but do not address "nonexhaust" emissions from brake wear, tire wear, road wear, and suspension in air of road dust. In the near future the nonexhaust emissions will dominate the road transport PM emissions. Based on the limited available evidence, it is argued that dedicated research is required on nonexhaust emissions and dispersion to urban areas from both an air quality and a public health perspective. The implicated message to regulators and policy makers is that road transport emissions continue to be an issue for health and air quality, despite the encouraging rapid decrease of tailpipe exhaust emissions.
authors.affiliation: Department of Climate, Air and Sustainability, Netherlands Organisation for Applied Scientific Research, TNO, Utrecht, The Netherlands. hugo.deniervandergon@tno.nl
authors.forename: Hugo A C Denier
authors.initials: HA
authors.lastname: van der Gon
authors.forename: Miriam E
authors.initials: ME
authors.lastname: Gerlofs-Nijland
authors.forename: Robert
authors.initials: R
authors.lastname: Gehrig
authors.forename: Mats
authors.initials: M
authors.lastname: Gustafsson
authors.forename: Nicole
authors.initials: N
authors.lastname: Janssen
authors.forename: Roy M
authors.initials: RM
authors.lastname: Harrison
authors.forename: Jan
authors.initials: J
authors.lastname: Hulskotte
authors.forename: Christer
authors.initials: C
authors.lastname: Johansson
authors.forename: Magdalena
authors.initials: M
authors.lastname: Jozwicka
authors.forename: Menno
authors.initials: M
authors.lastname: Keuken
authors.forename: Klaas
authors.initials: K
authors.lastname: Krijgsheld
authors.forename: Leonidas
authors.initials: L
authors.lastname: Ntziachristos
authors.forename: Michael
authors.initials: M
authors.lastname: Riediker
authors.forename: Flemming R
authors.initials: FR
authors.lastname: Cassee
mesh_terms: D000397:Air Pollution / Q000009:adverse effects; D004391:Dust; D004781:Environmental Exposure / Q000009:adverse effects; D058735:Environmental Policy; D015386:Hazardous Substances / Q000009:adverse effects; D018570:Risk Assessment; D014186:Transportation; D001335:Vehicle Emissions
chemical_list: D004391:Dust; D015386:Hazardous Substances; D001335:Vehicle Emissions