A report on the health risks to children from the diesel exhaust from school buses is being received skeptically by school transportation experts.
Nearly 90 percent of the nation’s 454,000 school buses have diesel engines, says the study released this month by the Union of Concerned Scientists. The Cambridge, Mass.-based group advocates the adoption of alternatives to the use of fossil fuels.
The report, “Pollution Report Card: Grading America’s School Bus Fleets,” is available from the Union of Concerned Scientists. An executive summary is also available. (Both requires Adobe’s Acrobat Reader.)
Drawing on national and state data, the study found that more than one-third of those buses were manufactured before 1991, which means they were built before more-stringent emissions standards were put in place. Such older buses, the report says, can “release at least six times more toxic soot and nearly three times more smog-forming nitrogen oxides than today’s models.”
Moreover, “buses degrade over time” and produce dirtier emissions, said Patricia Monahan, the author of the study and a senior analyst for the group.
The report also graded the 50 states and the District of Columbia based on estimates of the emissions from their “average” school buses. The states given a D, the lowest mark awarded, were California and Washington.
The states given a B were Alabama, Delaware, Maryland, Massachusetts, Missouri, and Pennsylvania. The District of Columbia received the same mark. No state received an A.
‘Missing the Bigger Picture’
But several school officials criticized the report for ignoring the emissions from the nation’s vast diesel-powered trucking industry.
“What about commercial buses, transit buses, motor coaches, tractor semis, large single-unit trucks?” said Charles Gauthier, the executive director of the National Association of State Directors of Pupil Transportation Services, based in Dover, Del. “Just to raise the public’s fears [by] only looking at school buses to me is missing the bigger picture here.”
Ms. Monahan acknowledged that school buses make up only a “very small portion” of diesel vehicles. But she said school buses are “pervasive” in areas frequented by children, and that one small study found that diesel fumes become concentrated inside school buses.
A study by the Fairfax County, Va., schools, which operates 1,460 diesel-powered buses, reached the opposite conclusion, said Linda Farbri, the transportation director of the 165,000-student district. Last year, the district in suburban Washington tested 12 of its buses, of different makes, models, sizes, ages, and engine types. Onboard diesel exhaust was “below the limits of detection,” Ms. Farbri said.
Still, U.S. Environmental Protection Agency rules adopted last year require, starting in 2007, that all new diesel vehicles meet sharply higher standards for emissions.
