title: Vehicle engines produce exhaust nanoparticles even when not fueled.
abstract: Vehicle engines produce submicrometer exhaust particles affecting air quality, especially in urban environments. In on-road exhaust studies with a heavy duty diesel vehicle and in laboratory studies with two gasoline-fueled passenger cars, we found that as much as 20-30% of the number of exhaust particles larger than 3 nm may be formed during engine braking conditions-that is, during decelerations and downhill driving while the engine is not fueled. Particles appeared at size ranges extending even below 7 nm and at high number concentrations. Their small size and nonvolatility, coupled with the observation that these particles contain lube-oil-derived metals zinc, phosphorus, and calcium, are suggestive of health risks at least similar to those of exhaust particles observed before. The particles' characteristics indicate that their emissions can be reduced using exhaust after-treatment devices, although these devices have not been mandated for all relevant vehicle types. Altogether, our findings enhance the understanding of the formation vehicle emissions and allow for improved protection of human health in proximity to traffic.
authors.affiliation: Aerosol Physics Laboratory, Department of Physics, Tampere University of Technology , P.O. Box 599, Tampere FIN-33720, Finland.
authors.forename: Topi
authors.initials: T
authors.lastname: Rönkkö
authors.forename: Liisa
authors.initials: L
authors.lastname: Pirjola
authors.forename: Leonidas
authors.initials: L
authors.lastname: Ntziachristos
authors.forename: Juha
authors.initials: J
authors.lastname: Heikkilä
authors.forename: Panu
authors.initials: P
authors.lastname: Karjalainen
authors.forename: Risto
authors.initials: R
authors.lastname: Hillamo
authors.forename: Jorma
authors.initials: J
authors.lastname: Keskinen
mesh_terms: D001334:Automobile Driving; D005742:Gasoline / Q000032:analysis*; D018986:Motor Vehicles; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D013052:Spectrometry, X-Ray Emission; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D005742:Gasoline; D001335:Vehicle Emissions