The Big Yellow Asthma Trigger

Vol. 15 •Issue 7 • Page 46
The Big Yellow Asthma Trigger

School bus fumes are especially dangerous for children with asthma.

It’s where homework is scribbled down on the way to school. Where “Whisper Down the Lane” erupts into a storm of giggles. Where first kisses sometimes are shared — on a double-dare.

But the school bus is also where children with asthma struggle to breathe. The problem is diesel exhaust, and 90 percent of the nation’s fleet is spitting it out into the school yard and, oftentimes, right into the bus cabin.

“Kids can easily breathe in those particulate matters from diesel exhaust and trigger off pretty significant asthma exacerbations in the school setting,” said Ben Ortiz, MD, assistant professor of clinical pediatrics, Columbia University and Harlem Hospital, New York City.

The components of diesel exhaust, when combined with sunlight, react to form ground level ozone. Ten percent to 20 percent of respiratory hospital visits and admissions during the summer have been linked to ozone air pollution. Studies also have shown that exposure to smog may increase the risk of developing allergies or asthma at initial exposure.1

Children are especially susceptible to pollution because they breathe approximately 50 percent more air per pound of bodyweight than adults. And school bus fumes aren’t just toxic to the lungs, Dr. Ortiz explained. They can be absorbed through the skin and the nasal and oral mucosa, and then distributed throughout the body. Diesel emissions also have been linked to cancer and heart damage.

“Children have enough challenges during the course of the day,” said Joe Biluck, director of operations and technology, Medford School District, N.J. “They certainly don’t need to deal with the obnoxious fumes that are emitted from the buses.”

Clearing the air

Asthma Free School Zone (AFSZ) is a program that works to manage and improve air quality in the microenvironment of the school, so that children with asthma can breathe cleaner air in the bus, on the playground, and in the classroom.

Rebecca Kalin came up with the idea behind AFSZ when she visited a New York City school for a public health project and saw 11 buses lined up, one after the other, with their engines running for as long as 15 to 20 minutes. It “looked like an accident waiting to happen,” Kalin said. New York City law restricts idling to no more than three consecutive minutes.

So, in April 2003 she approached New York state Attorney General Eliot Spitzer about the idling problem. Spitzer brought lawsuits against nine New York City bus companies, representing 75 percent of New York City’s school bus fleet, and by September 2005 all nine had reached agreements to reduce diesel air pollution from idling in the metropolitan area.

The agreements include a requirement that bus drivers receive training about the effects of idling on air and health, and about the existence of the New York City anti-idling law. Together, these agreements will reduce air pollution each year by approximately 32,000 pounds of nitrogen oxides and 800 pounds of particulate matter, as well as save more than 179,000 gallons of diesel fuel.

Meanwhile, AFSZ has reinforced Spitzer’s tough stance on idling by providing direct environmental health education for schools and communities. AFSZ members train parents and school staff in advocacy and speak with the community through venues like precinct community meetings, libraries, health centers, and senior centers.

“Our goal is really to raise awareness about the link between environment and health, particularly respiratory health,” Kalin said. “Why aren’t we protecting the school zone the same way we protect hospital zones?” Hospitals zones contain vulnerable individuals, she said, but so do school zones.

Idling attitudes

Idling affects air quality not only on the playground and inside the bus, but also in the classroom, especially in urban schools that don’t have air conditioning. Kalin recalled speaking with teachers in the hallway who would suddenly look at their watches and say, “Oh my god, I’ve gotta run! I’ve gotta run!”

Then they would dash to their classroom and slam all the windows shut because the school buses were coming. “We can’t have the school buses come and idle with the windows open,” the teachers told her. “Our children will fall asleep, and we’ll lose two or three to the nurse’s office.”

Getting bus drivers to stop idling is one of the simplest ways to reduce particulate matter emissions. An estimated one gallon of gas is saved for every hour of no idling, so it’s a cost-saving solution.

Bus drivers’ attitudes about idling, however, aren’t always on par with the community’s goals. “They don’t read the journal on respiratory health,” said Ellen Tohn, senior adviser to the New England Asthma Regional Council, Dorchester, Mass. “No one talks to them about respiratory health. Yet drivers are at the greatest risk because they’re in the bus all the time.”

In New York City, signs that say “No Idling: Asthma Free School Zone, program in effect” are displayed in school zones. Kalin hopes the signs not only signal that asthma is a community concern, but also help empower citizens to speak up.

“It’s like the pooper-scooper law,” Kalin said. “Who enforces it? Nobody but the citizens. If I walk my dog and don’t pick up after him, I’m going to get a lot of really ugly glares from people, and I’m going to pick it up.”

While community conscience is an important factor in changing bus drivers’ habits, education is the most effective way to influence their attitudes. As soon as they learn how vulnerable the children are to fumes, Kalin said, most of them start turning off their engines.


Old-school attitudes can be adjusted, and so can old school buses. The latter, however, is a bigger problem with a bigger price tag.

New federal emissions regulations will go into effect in 2007, reducing allowed particle levels to 80 percent of today’s levels. However, these regulations won’t affect school buses built before 2007.

In addition, buses built before the Clean Air Act of 1990, which comprise approximately one-third of the nation’s fleet, are allowed to emit at least six times more toxic soot and twice the nitrogen oxides that a modern bus can.

When purchasing new buses isn’t an option, the older buses can be retrofitted with devices that reduce pollution or use cleaner fuel.

A diesel oxidation catalyst can be fitted on any bus, and it runs on diesel fuel. This device uses a chemical process to break down pollution into less harmful components. It can reduce particulate matter by 20 percent, hydrocarbons by 50 percent, and carbon monoxide by 40 percent.

A more expensive option is a diesel particulate matter filter. It’s a ceramic device that collects particulate matter in the exhaust stream. It uses ultra-low sulfur diesel (ULSD), which has been impractical for most school districts in the past because ULSD isn’t available everywhere. But the filter and ULSD combined can reduce particulate matter, hydrocarbon, and carbon monoxide emissions by 60 percent to 90 percent. Plus, ULSD will be available nationwide in October.


ULSD isn’t the only alternative diesel fuel available for buses. The Medford, N.J., school district implemented a biodiesel school bus program in 1997, operating half of their bus fleet on petroleum diesel and half on a blend of 20 percent biodiesel and 80 percent petroleum diesel (B20). The B20 reduced particulate matter emissions by 50 percent to 60 percent and provided a more cost-effective solution for maintenance. (Buses running on B20 were found to run two cents per mile cheaper than those running on petroleum diesel.)

“When you look at the broad spectrum of economics, the environmental impact to the developing lungs of the 3,500 kids we transport, and energy security, biodiesel was far and away the better solution for us,” Biluck said.

It’s also a better solution for other areas of New Jersey. Due to the success of Medford’s program, the state of New Jersey created a biodiesel rebate program for public entities such as school districts and fire departments.

Switching to B20 has had a direct effect on the children. “We transport a number of children with respiratory ailments, and we don’t see the normal struggling that these kids went through before,” he said. “Especially in the winter months when the buses never shut off — that’s when you typically see a fair amount of respiratory problems.”

Even stubborn drivers have changed their attitudes after seeing the positive effects of biodiesel. One of the Medford district drivers was less-than-enamored about the change to the soybean-based fuel, Biluck recalled.

But after driving the bus on B20 for six months, she went back to Biluck and said, “You know, I have to apologize. I’ve been noticing that in the winter months when I load and offload the kids, these kids aren’t struggling to breathe as much as they were in the past. Something is making a change, and the only thing that’s different is the biodiesel.”

Clinicians’ role

Avoidance of triggers such as diesel exhaust is still No. 1 when it comes to preventing asthma exacerbations, Dr. Ortiz said. Respiratory care clinicians should educate school-age asthma patients and their parents about these strategies.

For instance, children with asthma should sit in the front of the bus, away from the tailpipe, where fumes may be leaking through the emergency exit or the windows.

Studies have shown that exhaust levels are higher inside a moving bus when the windows are closed, so students with asthma should request that the windows be open en route when weather permits. However, if the school bus is idling, the windows should be closed to prevent a build-up of exhaust in the interior of the bus.

Physicians can remind their young patients not to congregate with friends around the back of the bus and to spend as little time as possible near the bus during loading and off-loading. Some children with asthma may need to find alternative transportation if riding the bus continues to hinder their health.

Respiratory clinicians also can play a role in stepping up public awareness, said Lucy Edmondson, senior transportation policy analyst, Environmental Protection Agency New England, Boston. “If pulmonologists are doing outreach and are working with school districts, they could promote the idea of adding advanced pollution controls to school buses,” she said, “and EPA would certainly be willing to work with those folks.”


1.Riedl M, Diaz-Sanchez D. Biology of diesel exhaust effects on respiratory function. J Allergy Clin Immunol. 2005;115(2):221-8.

Lauren Constance Everingham is editorial assistant of ADVANCE. She can be reached at [email protected].