Sooty Air in School Buses: How Risky?

The results of a limited new study measuring the air that children breathe inside school buses are troubling enough to merit a much broader look.

Research by scientists at UC Berkeley and two environmental advocacy groups found that the air inside the big yellow buses can contain up to 8.5 times more diesel exhaust than the air around them. If true, these levels greatly exceed federal emissions limits set to protect communities and should cause real concern: Soot is known to be carcinogenic, and the microscopic particles emitted by diesel engines can exacerbate or even cause asthma and allergies, rapidly growing health problems for children nationwide, especially in urban areas.

Closing the bus windows, according to the study, only worsens the problem, doubling soot concentrations inside. Leaks in the floorboards apparently allow exhaust fumes to seep in.

The study, however, has serious limitations. The researchers studied only four buses, all in the Los Angeles school district. Diesel engine manufacturers claim that the results are at odds with similar analyses of the air inside truck cabs. Clearly, more study is needed--and quickly.

The California Air Resources Board acted in December to cut diesel emissions, approving $50 million to replace 375 school buses with alternative-fuel vehicles and to fit 1,875 old, dirty diesel buses with soot-trapping filters. That still leaves some 21,000 buses statewide, most running on diesel fuel, that aren’t likely to be replaced or retrofitted soon.

The air board’s research screening committee, meeting Friday, is poised to approve a more comprehensive study of school bus emissions. We need a much better understanding of whether children are at risk.