School Bus Pollution Report Card 2006

The 2006 School Bus Pollution Report Card by the Union of Concerned Scientists finds that U.S. school buses are among the oldest vehicles on the road, with an average age of nine years, and emit nearly twice as much soot per mile as tractor-trailer trucks. The report grades states on tailpipe soot emissions, smog-forming pollution, and the success of their cleanup programs. While some states like California and Washington have made significant strides in reducing soot through retrofits and cleaner fuels, national soot pollution from school buses has only decreased by more than two percent. The document highlights the vulnerability of children to diesel exhaust, which is linked to asthma and lung growth deficits, and argues that substantial federal and state investment is needed for bus replacement and the installation of particulate traps.

• U.S. school buses are among the oldest vehicles in operation, with an average age of nine years; 37 percent of the fleet was built more than 10 years ago.
• The average school bus emits nearly twice as much soot per mile as a tractor-trailer truck (big rig).
• Pollution levels vary significantly by state; the dirtiest fleets in South Carolina and South Dakota emit nearly three times more soot than the cleanest fleet in Delaware.
• National efforts to reduce school bus soot through retrofits and cleaner fuels have achieved a reduction of more than two percent, with California and Washington leading the country.
• Children are more vulnerable to air pollution than adults due to physiological differences and higher breathing rates, with diesel exhaust linked to lung growth deficits and asthma.
• Pollution can concentrate inside school buses, with some studies showing fine particle concentrations 5 to 15 times higher than ambient air.
• Leaky crankcases are identified as a major source of onboard fine particulate pollution, and closed crankcase filtration controls can be effective in reducing this exposure.
• Replacing all school buses built before 1994 with new low-emission models would cost approximately $13.4 billion, while retrofitting those built after 1993 with particulate traps and crankcase filtration would cost about $2.6 billion.
• Compressed natural gas (CNG) is the cleanest commercially available fuel option, reducing soot by over 90 percent compared to a 2005 conventional diesel bus.
• The EPA's Clean School Bus USA program has a limited budget, ranging between $5 million and $7.5 million annually since 2003, which is insufficient to meet the goal of retrofitting or replacing all buses by 2010.

APA

Monahan, P. (2006). School Bus Pollution Report Card 2006. Union of Concerned Scientists. https://www.ucs.org/sites/default/files/2019-10/pollution-report-card-2006-1.pdf

Chicago

Monahan, Patricia. School Bus Pollution Report Card 2006. Union of Concerned Scientists, 2006. https://www.ucs.org/sites/default/files/2019-10/pollution-report-card-2006-1.pdf.

Wikipedia

{{cite report |last1=Monahan |first1=Patricia |title=School Bus Pollution Report Card 2006 |publisher=Union of Concerned Scientists |date=May 2006 |url=https://www.ucs.org/sites/default/files/2019-10/pollution-report-card-2006-1.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{monahan2006school, author = {Monahan, Patricia}, title = {{School Bus Pollution Report Card 2006}}, institution = {Union of Concerned Scientists}, year = {2006}, month = may, url = {https://www.ucs.org/sites/default/files/2019-10/pollution-report-card-2006-1.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }