Unfortunately, most buses are powered by diesel engines that actually pollute the air inside the bus. Studies show the pollution gets trapped inside the bus, where kids breathe it in.
Dr. John Balbus, EDF’s chief health scientist, answers common questions about school bus pollution and your child’s health.
Q: I don’t see billowing clouds of black smoke behind the school bus. Does that mean the bus exhaust is clean?
Unfortunately, it’s not that simple. Even clean-looking exhaust from tailpipes, and from the engine itself, can contain small particles and other toxic pollutants that can get inside the school bus, and in children’s lungs.
Q: How does diesel pollution get inside a school bus?
Diesel pollution can enter a school bus from both the tailpipe and the engine. In school buses, the engine is in the front, right near the door, so every time the door opens, engine and tailpipe exhaust get sucked inside.
Exhaust can also seep into the bus through open windows and even through the floorboards. Because of this, air quality inside the bus can be five times worse than outside air. Even if your child spends a short amount of time on a school bus, he or she may be breathing in high levels of harmful air pollutants that make up diesel exhaust.
Q: What are the pollutants in diesel exhaust?
Diesel exhaust contains more than 40 toxic substances, smog-forming emissions, particulate pollution (sometimes called “soot”), unburned hydrocarbons and other harmful byproducts — many of which are known cancer-causing agents.
Particulate pollution is a mix of soot, smoke and tiny particles formed in the atmosphere from sulfur dioxide, nitrogen oxides (also a key ingredient of smog) and ammonia. Sooty particles are most dangerous when very small as they are easily inhaled and damage lungs.
Q. How does breathing in diesel exhaust harm children?
Exposure to diesel exhaust can have serious health effects. Children can suffer worsening of asthma and other respiratory symptoms, and may be at greater risk of developing asthma, especially when exposed very early in life. One recent study suggests that diesel soot can affect children’s brain function.
Children are at particular risk compared to adults because their lungs are still developing and because they breathe in much more air for their body weight. Breathing in pollution during childhood can result in irreversible damage as children develop.
Adults are also affected by diesel exposures. In addition to worsening asthma and other lung conditions, diesel exhaust can contribute to chronic heart disease and acute heart attacks as well as lung cancer. While there are no studies showing effects on the cardiovascular system in children, exposures during childhood may have a long-term impact on the health of blood vessels and the heart.
Q. If the air inside a school bus is unhealthy, should I drive my child to school instead?
The safest way to get to school is by bus. Going in a car increases the risk of an accident or other safety hazard. Every day half a million school buses carry 24 million children to school, field trips and athletic events.
While school buses are still the safest way to transport kids, diesel buses can be cleaner and healthier. If your child’s bus is an older, more polluting model that has not been retrofitted with a filter and your child’s school is within walking distance with access to safe sidewalks and bike lanes, you might encourage your child to walk or bicycle to school. Your child will get the added benefit of healthy exercise.
Q. My child has asthma — should I be particularly worried about the diesel exhaust on school buses?
Asthma and other respiratory problems are a particular cause for concern for children who ride older, polluting school buses. If the bus is your child’s only option for getting to school, talk with school officials and the bus company providing service about cutting back the time your child spends on the bus.
For example, the route might be adjusted so your child is the last to be picked up in the morning and the first to be dropped off after school.
Or arrange alternate ways for your child to get to school, such as carpooling or walking, on some days.
Q. Would having my child wear a surgical mask help filter out dangerous pollution and soot?
No, a surgical mask will not help. Besides being difficult to fit properly, a mask will only block out large particles, and your nose and mouth do that anyway. A surgical mask cannot filter out the ultrafine particles that are the most dangerous, nor the other toxic gases and chemicals in diesel exhaust.
Q. How can I make sure the bus my child rides to school is clean?
Check with your local school district and city officials to find out the age of its bus fleets and if they have been retrofitted with a filter to trap 85 percent of soot pollutants. Unless your child’s school bus has been retrofitted or your child is riding on a brand new school bus (2007 or later model), your child is most likely breathing in unhealthy levels of pollution.
Pollution increases with the age of the school bus. For example, bus engines built before 1990 are allowed to emit 60 times more soot (particulate matter) than bus engines built in 2007. New buses meeting 2007 federal emission standards are much cleaner than older buses for both soot and nitrogen oxides emissions.
- Learn more about the best retrofit options and the pollutants they filter out.
- See also Four Steps to Cleaner Buses(www.edf. org/page.cfm?tagID=15492).
Q. What can I do to get involved and get cleaner school buses in my district?
You can start with these steps:
- Start a clean school buses campaign in your neighborhood.
- Encourage your school district officials or private school administrators, community leaders and local legislators to use cleaner buses or retrofit the older diesel buses.
- Tell your city council members, state and local legislators that you support legislation to reduce diesel pollution through anti-idling laws, retrofits and replacements.
More ways you can help.
Q. How can I convince my local school board or city officials that retrofitting or buying new buses is worth the expense?
Investing in retrofits now makes sense for the long term. The health benefits of installing a retrofit can outweigh the costs by at least 13 to 1. In other words, for every dollar spent on retrofits, the expected savings is $13 in health benefits, such as fewer emergency room visits and hospitalizations.
In addition, every dollar invested in replacing old diesel vehicles with 2007 or 2010 engine models will yield in $40 in health benefits, according to the Environmental Protection Agency.
Q. I see buses lined up and idling outside the school while waiting for children to board after school. Why don’t they just turn off their engines and how can I do to get them to stop?
Bus engines should be turned off when waiting, especially within 500 feet of a school. Often drivers leave engines idling to run the air conditioning or heaters during hot summer or cold winter months.
If this is the case, suggest that drivers make arrangements to wait inside schools between jobs. Or help find other sources of power to warm or cool the bus.
Besides polluting the air, idling buses waste about one gallon of fuel per hour of idling. With fuel prices at record highs, instituting a no-idling policy makes a lot of financial sense and is healthier for everybody.
You can work with school officials and bus drivers to take steps to minimize the effects of idling, for example:
- Line up buses diagonally rather than single file. When buses park in single file, the exhaust flows easily into other buses through open doors.
- Move the exhaust pipe to the opposite side of the bus to minimize pollution from entering the doors of adjacent waiting buses.
Q. Where can I get more information about school bus pollution?
See the Environmental Defense Fund web site www.CleanBuses.org.