A surprising fraction of the exhaust from school buses ends up back inside the bus. That’s according to a study led by Julian Marshall, a Ph.D. student in the Energy and Resources Group at the University of California at Berkeley. He says the impact of a single bus is much greater on its passengers than on the passers-by. The research looks at how pollution children take up from the brief rides to school each morning. This Science Update looks at the research, which leads to the findings presented and offers links to other sources for further inquiry.