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Cleaning Up School Buses

More than 24 million children nationwide ride a bus to and from school every day, and the majority of those buses are running on diesel. The exhaust dirties the air inside and outside of the bus. Diesel exhaust from school buses idling in line seeps into the buses through open windows and doors, exposing the children on the buses and children waiting to board. Engines are designed to vent some crankcase emissions to the air, which means the driver, and then the passengers, get hit with the pollution. Diesel exhaust can also get into school ventilation systems and through open school windows, causing poor indoor air quality.

Emissions from school buses and other sources are a health concern for everyone, but children are more susceptible to air pollution problems because they breathe 50 percent more air per pound of body weight than do adults. There is no known safe exposure to diesel exhaust. According to a study of diesel exhaust inside school buses, done by NRDC and U.C. Berkeley School of Public Health, a student sitting in the back of a school bus with the windows closed receives an average exposure to diesel exhaust that is up to 4 times greater than a child riding in a passenger car immediately ahead of the same bus.

So what’s being done to tackle the problem?

Funding provided by the Heinz Endowments and the PA DEP enabled school bus companies serving Pittsburgh Public Schools (PPS) to retrofit more than fifty buses with diesel particulate filters and closed crankcase ventilation systems, greatly reducing children’s exposure to diesel exhaust.

“Cleaner bus air in pipeline for schoolchildren,” Pittsburgh Tribune-Review, February 18, 2009.

More recently, GASP and partners conducted a survey in 2014 of local schools and found idling happening throughout the area. Mandated “No Idling” signs were absent at many locations. GASP worked with PPS to ensure signs are available for all of their schools. GASP has delivered signs to parochial, charter, and private schools in the district as well, and we have signs available if your school needs or wants one.

GASP also worked to pressure PPS to have their contractors modernize their bus fleets, by having PPS require that the buses serving their children are updated with new engines or be retrofit with pollution control devices. Read about the success that this effort has led to, as well as remaining challenges, in our blog post here.

If you see idling for more than 5 minutes per 60 minute period (15 minutes if students are on board), please talk to your school personnel. Contact GASP to discuss idling at your school or to request free “No Idling” signs, by emailing

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Group Against Smog and Pollution