A change to ultralow- sulfur fuel reduced a marker for inflammation in children’s lungs by 16 percent for all children riding the bus and by 20-31 percent for asthmatics. Researchers followed 275 elementary children on school buses before and after cleaner fuels and technologies were used on the buses. On average, children in the districts missed an average of 3.1 school days over a nine month period. When riding a bus that used ULSD, there was an 8 percent lower risk of being absent. For those riding a bus with a diesel oxidation catalyst there was a 6 percent reduction in absenteeism. The researchers extrapolated a 14 million day reduction in absenteeism nationally if all buses were fitted with similar pollution controls.