Pollution Report Card

The report evaluates the emissions of US school bus fleets, finding that the vast majority rely on high-polluting diesel engines that pose significant health risks to children. It advocates for a transition to cleaner alternatives, specifically natural gas, and calls for federal and state funding to replace aging fleets.

• Diesel fuel powers nearly 90 percent of the 454,000 school buses in the United States, and its exhaust is linked to cancer, premature death, and respiratory ailments like asthma.
• Older school buses are significantly more polluting than newer models; those built before 1990 and 1991 can release at least six times more toxic soot and nearly three times more smog-forming nitrogen oxides.
• Natural gas school buses are the cleanest commercially available option, emitting 90 percent less toxic soot than new diesel buses and over 98 percent less than older diesel models.
• In a state-by-state grading of pollution performance, no state received an 'A' grade, and only six states and the District of Columbia were ranked 'ahead of the curve'.
• California and Washington received the lowest overall grades ('D's) for pollution performance, with California maintaining a high percentage of buses built before 1977.
• States with the best pollution performance, such as Delaware and Maryland, have implemented policies that require the retirement of buses after 12 or 14 years and provide funding for replacements.
• While diesel emission control technologies like particulate traps and selective catalytic reduction show potential to reduce pollutants by 90 percent or more, they are often new, under development, or unproven in real-world conditions.
• The report identifies a critical need for an in-use inspection and maintenance program because heavy-duty engines are not tested for real-world emissions, and actual pollution levels may be two to six times higher than certification standards indicate.
• The Union of Concerned Scientists recommends a national school bus replacement program with strict pollution limits, supported by federal and state grants to remove the financial trade-off between educational expenses and cleaner buses.

APA

MONAHAN, P. (2002). Pollution Report Card. Union of Concerned Scientists. https://www.ucs.org/sites/default/files/2019-09/acffjputs.pdf

Chicago

MONAHAN, PATRICIA. Pollution Report Card. Union of Concerned Scientists, 2002. https://www.ucs.org/sites/default/files/2019-09/acffjputs.pdf.

Wikipedia

{{cite report |last1=MONAHAN |first1=PATRICIA |title=Pollution Report Card |publisher=Union of Concerned Scientists |date=February 2002 |url=https://www.ucs.org/sites/default/files/2019-09/acffjputs.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{monahan2002pollution, author = {MONAHAN, PATRICIA}, title = {{Pollution Report Card}}, institution = {Union of Concerned Scientists}, year = {2002}, month = feb, url = {https://www.ucs.org/sites/default/files/2019-09/acffjputs.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }