Characterisation of particle emissions from the driving car fleet and the contribution to ambient and indoor particle concentrations

The population is mainly exposed to high air pollution concentrations in the urban environment, where motor vehicle emissions constitute the main source of fine and ultrafine particles. These particles can penetrate deep into the respiratory system, and studies indicate that the smaller the particle, the larger the health impacts. The chemical composition, surface reactivity and physical properties are also important. However, the knowledge about chemical and physical properties of particles and the temporal and spatial variability of the smallest particles is still very limited. The present study summarises the first results of a larger project with the aims to improve the knowledge. The concentration and the emissions of ultrafine particles from petrol and diesel vehicles, respectively, have been quantified using Scanning Mobility Particle Sizer of ultrafine particles in the size range 6-700 nm and routine monitoring data from urban streets and urban background in Denmark. The quantification was carried out using receptor modelling. The number size distributions of petrol and diesel emissions showed a maximum at 20-30 nm and non-traffic at approximate to 100 nm. The contribution of ultrafine particles from diesel vehicles is dominating in streets. The same technique has been applied on PM10, and approximate to 50% contribution from non-traffic. The technique has also been introduced in relation to elemental and organic carbon, and the first data showed strong correlation between traffic pollution and elemental carbon. The outdoor air quality has a significant effect on indoor pollution levels, and we spend most of the time indoors. Knowledge about the influence of ambient air pollution on the concentrations in the indoor environment is therefore crucial for assessment of human health effects of traffic pollution. The results of our studies will be included in air quality models for calculation of human exposure. Preliminary results from our first campaign showed, that the deposition rate of particles in the apartment is negligible in the particle size range 100-500 nm. In the size range below 100 nm the deposition rate increases with decreasing particle diameter to a value of approximately 1 h(-1) at 10 mn. The penetration efficiency shows a maximum of 60% at 100 nm. More detailed studies of exchange of particles in outdoor/indoor air and the transformation are planned to take place during three next campaigns. (C) 2003 Elsevier Science Ltd. All rights reserved.