School Buses

For many people, memories of school include riding a yellow bus each day or taking one on field trips. Concerns of air pollution inside and outside of the cabin from the bus's diesel engine were probably not even given a thought.

In recent years, however, several studies have indicated that the pollution emitted from diesel school buses can pose a grave threat to school children, bus drivers and school staff. At times, dirty soot levels inside a school bus can be ten times higher than the outside air, increasing children's and staff's exposure to harmful pollutants.

"In Illinois, at least 70 percent of the 18,500 school buses in service today are powered by diesel fuel."
Illinois Environmental Protection Agency


Health effects

The exhaust from diesel buses contains more than 40 toxic air contaminants, carcinogens, ozone smog-forming compounds and fine particulate matter ("soot"). Exposure to fine particles is known to cause asthma attacks, heart attacks, lung cancer, strokes and even premature death.

In Illinois alone, it is estimated that diesel exhaust triggers more than 20,000 asthma attacks, causes more than 690 heart attacks and leads to approximately 570 premature deaths each year. Although diesel pollution is unhealthy for everyone, children, seniors, occupational workers and people who live with lung disease are especially at risk.

Children at risk

Although diesel exhaust is unhealthy for everyone, children are particularly vulnerable to the harmful impacts of diesel pollution because:

  • Their lungs are still developing.
  • They are more active than adults and therefore breathe more rapidly.
  • They have more lung surface area compared to their body weight and therefore, pound-for-pound, inhale more air and pollution than adults.
  • Their essential defense mechanisms have not yet fully developed, which also increases their susceptibility to the harmful effects of pollution.


Today, the federal government requires all newly manufactured school diesel buses (model 2007 and later) to be equipped with pollution controls called diesel particulate filters, which can eliminate up to 90 percent of diesel soot from a tailpipe. These same pollution controls are commercially available and should be also installed on older dirty diesel school buses. To view a list of resources for clean school buses, click here.

In addition to installing these controls, schools can clean up their diesel school bus fleet by:

  • Installing Closed-Crankcase Filtration Devices. These can help eliminate diesel exhaust emitted directly from the engine compartment.
  • Installing anti-idling technology. Using automatic idling controls, such as auxiliary power units, engine stop/start technologies, and direct-fired heaters can reduce pollution and save fuel.
  • Implementing diesel no idling policies. These policies help schools reduce diesel pollution by curbing unnecessary idling. Visit US EPA Clean School Bus Resources.


Current regulations

  • Illinois Diesel No Idling Law. Illinois has a state law that bans excessive idling from diesel school buses and other diesel vehicles in the Chicago metropolitan area and St. Louis Metro East area. For more details about the state law, click here.
  • Chicago Idling Ordinance. Chicago requires large diesel vehicles operating in the city to follow even more stringent idling restrictions. For more details about the ordinance, click here.

How you can help

  • Sign up for E-Advocacy to learn more about our ongoing advocacy efforts and how you can help improve the lung health of your community.

For more information, visit the Air Quality Library.