1. Nanoparticles from Road Vehicle Exhaust. An Artifact or a Reality? Background Current emission standards for motor vehicles are mass based. Properties such as number and size as well composition are not measured on legislative basis due to the complexity of the matter and uncertainties inherent to the characterization procedures. However, in considering the next steps, regulators are posing the question what property of the emitted aerosol is responsible for the toxic effects and, therefore, whether another metric would be necessary to regulate.

2. Nanoparticles from Road Vehicle Exhaust. An Artifact or a Reality? Key Questions:  What is the relationship between chemical composition and size of the particles and health effects?  Are nanoparticles emitted from motor vehicles an issue? To what extent they contribute to the atmospheric nuclei mode?  Which are the appropriate laboratory sampling/measurement methods for precise characterization?  Which is the most appropriate representation of the transportation sector to the ambient PM concentrations? Are emission factors the most appropriate tool? How can we predict the future based on today’s knowledge?  What kind of investigations are needed to understand better the processes responsible for dispersion of PM in the urban atmosphere?

3. Panel Contributions  Diane Hall, BP/Concawe, UK 'Nanoparticles from road vehicle exhaust: an artefact or a reality?‘  David Kittelson, University of Minnesota, USA ‘Vehicle generated nanoparticles are not an artifact’  Jorma Keskinen, Tampere University of Technology, Finland ‘Occurrence and fate of traffic generated nanoparticles in (urban) atmosphere’  Urban Wass, Volvo Technology, Sweden ‘Nuclei or accumulation mode - which particles are most significant from a health point of view?’  Les White, LWAssociates, UK ‘Particulates: Where is the current policy emphasis in the EU?’