A new study now shows directly that personal exposure of particles is linked to asthma symptoms. Children carried pollution monitors in their backpacks on the way to school where PM2.5 ranged from 20 to 50 micrograms per cubic meter. Although only around 10 percent of the total mass of particles was diesel soot, it was this that was most closely linked to the children’s asthma. This nicely complements results of our study in Munich in 1989/1990 which was the first survey indirectly linking car exhaust and airway symptoms in children. Mechanisms how this happens are not very well known – for a discussion of the biphasic response see our paper of a mouse model, yea, yea.