| Abstract
| - There is growing evidence that fine airborne particulatescould play the most important role in determining healtheffects. The aim of this work was to investigate thenumberconcentration and size distributions of particulates intheexhausts of diesel vehicles (mainly buses) of differentagesand make, operating under different loads. Particle-sizing instruments used were the Scanning Mobility ParticleSizer (SMPS) and Aerodynamic Particle Sizer (APS).The average particle number concentration of theexhaustswas in the range (0.7−3.9) × 107cm-3 in the SMPSrange (0.0075−0.304 μm) and (0.3−32) × 103cm-3 in theAPS range (0.5−30 μm). In most cases, particlenumberconcentrations increased with the increased power outputfrom the engine and, in both SMPS and APS ranges,varied significantly within each group of vehicles, butthedifferences between the groups were small. Forindividualvehicles, there was no relation between emissions in thesmaller and larger particle ranges. Emissioncharacteristicsdid not appear to be correlated with engine model orage. The implications of these findings to particleemissiontesting and control as well as to exposure and riskanalysis are discussed.
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