School Bus Fumes Worst for Kids on Board

By Randy Dotinga, Forbes

FRIDAY, April 8 (HealthDay News) -- Toxic gases produced by diesel school buses are far worse for those riding inside than for passers-by, new findings suggest.

An analysis of previous research reveals that kids inside a single diesel school bus inhale as much toxic gas as all the other people who are exposed to the gases coming out the bus's tailpipe, said study co-author Julian Marshall, a graduate student at the University of California at Berkeley who researches air pollution and health. "This means that the kids are doing a lot more inhaling of pollution than you and I are," he said.

On the other hand, Marshall said, traveling by school bus is still safer than riding in a car. "I don't want parents to think the air on a bus is terrible, and therefore I should drive Johnny to school because we can't trust a school bus."

According to the Union of Concerned Scientists, most of the 442,000 school buses on American roads still use diesel fuel, although some newer buses rely on natural gas, which is considered safer. Exposure to diesel fuel exhaust has been linked to a variety of ailments, including cancer and respiratory ailments such as asthma and chronic bronchitis.

"Across the country, what we see is that children are riding in some the oldest vehicles on the road," said Patricia Monahan, a senior analyst with the advocacy organization, which is pushing for safer buses. "School buses tend to remain on the road for 20, 30 or 40 years, and a lot of them don't have to meet new pollution standards."

In 2002, researchers in Los Angeles measured the levels of pollution inside school buses and found that significant amounts were from the exhaust of the buses themselves. It's not clear how the exhaust is getting into the buses from their engines, however. "The exhaust may leave the tailpipe and circle back around the bus and through a window," Marshall said. "Another possibility is that there are cracks and leaks in the floor and exhaust manifold."

In the new study, Marshall and a colleague analyzed the data from the previous study and tried to figure out how much bus exhaust ends up in the lungs of riders and other city residents. They report their findings in the April 15 issue of Environmental Science and Technology.

The researchers estimated that the amount of diesel pollution breathed by the 40 children inside a diesel school bus is about equal to particles of the bus's exhaust that are breathed by hundreds of thousands of other people who live downwind in a typical urban area.

"The numbers were quite high and quite shocking," said Marshall, who hopes his research will make the hazards of air pollution more understandable to politicians.

What to do? The best solution is to replace diesel buses, said Monahan. But it's not easy. "Parents and school districts are in a tough spot. You don't want to trade books for buses," she said. "It's up to the state and federal government to step up to the plate and provide funding for cleaner school buses."

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