How Healthy Is the Air on the Yellow School Bus?

August 10, 2011 | Written By:

by Austin Sears, HSC intern


When I was little, riding the bus was one of my absolute favorite things about going to school. I grew up in a suburb of Chicago, so school buses were extremely common in our community. In the United States, 24 million children ride school buses daily. On average these children spend an hour and a half on the bus on a given day. School buses are a great resource for families that do not live within walking distance of their schools. 

School buses provide students and their families with a great transportation option, but they also emit a large amount of air pollutants. One thing that many people often don’t know is that the pollutants can be present in the cabin of the bus, sometimes at much higher levels than in the air outside. This is an issue that we have talked about before, but I read a recent study that detailed the performance of retrofit systems, something that I will get to a little later. The biggest question here, though, is how does this happen?

Pollutants enter the cabin in a few different ways. When the bus is idling, particularly when doors and windows are open and the buses are lined up waiting for children to board, the wind carries harmful pollutants into the bus. Cracks or faulty seals on windows, doors and other parts of the bus also allow particles to enter the cabin both when the bus is both idling and in motion. If the bus does not have any form of filtration system installed, the soot is then easily carried into the cabin. There are ultrafine particles that are present in the exhaust that are particularly harmful because they easily penetrate lung tissues and enter the circulatory system. Children are especially vulnerable, as they take  more breaths per minute than adults and because their respiratory systems are not fully developed. Children are also exposed to these pollutants for seven and a half hours a week, for the entirety of the school year. 

So what can be done about this? While there is no perfect solution to this problem, here are a few things that can be done to clean up the air in and around buses: 

  • Retrofitting buses by installing a Diesel Particulate Filter (DPF) to the exhaust pipe can limit the amount of particulate matter being released by the bus. This is the most effective method of filtering the exhaust, as this filter captures 90 percent of the soot emitted. 
  • Another type of retrofitting is to install a Closed Crankcase Ventilation Filter (CCVF), which prevents emissions from the engine compartment from entering the bus through cracks and openings in windows and doors. The two filtration systems are most effective when used in conjunction with one another, though it is possible to retrofit a bus with only one of the options. 
  • Limiting the amount of idling done near schools by both buses and other vehicles by vehicles close to parked buses, especially when buses have windows and doors open. By turning off the vehicle completely, the driver saves gasoline while also limiting the amount of pollutants being released into the air.

Now that you have all of this information, what can you do with it? There are some things that you can do in your own communities to reduce the amount of particulate matter children breathe on a regular basis:

  • Encourage parents, students, teachers, and community members to install no idling signs in and around schools to cut down on the amount of harmful emissions in the vicinity of the school. 
  • Encourage schools or school districts to apply for both state and federal no-match funds that could be used to purchase the filtration systems needed to limit the amount of pollutants entering the bus cabin and the ambient air around the bus. 
  • Bring up the issues at parent/teacher conferences, to principals or superintendents, or to the PTA. Let others know that there is money available to make this happen at little to no cost for the school. 

If you are in Illinois, we have connections to a number of organizations that are working on this issue. Check out the Campaign to Clean Up Diesel Pollution, a coalition of more than 80 organizations, including Healthy Schools Campaign, led by the Respiratory Health Association of Metropolitan Chicago and Citizen Action/Illinois. If you have any questions about air quality or the clean diesel campaign, you can contact Jonathan Doster at Citizen Action/Illinois.

On a national scale, numerous groups are working diligently to spread the word about the air quality in and around school buses. For instance, the EPA has a Clean School bus Program, the Clean Air Campaign backs a No-Idling Program, and the Union of Concerned Scientists has conducted extensive research about the buses being used in all 50 states. There are also regional efforts in New Jersey, New Hampshire, Cleveland, Southwestern Ohio, New York City, and Georgia, to name a few.

But these organizations cannot do all of the work by themselves — they need your help! Is there a clean diesel, retrofit, or no idling initiative in your city or state? Have you helped implement any of these programs in your area? Tell us in the comments section of this post. We'd love to hear about efforts in your area!

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