clark-county-school-district-busesBy Catherine Colbert

When David Kilbourne picked up his 8-year-old son from Lake Travis Elementary in spring 2007, he noticed smoke billowing from idling buses parked in queue behind the school. The exhaust fumes his son was breathing each day as he waited to be picked up, he says, were contributing to his son’s migraine headaches. “My son is the quarterback for his youth football team,” said Kilbourne. “Because there’s only one quarterback, when he gets these headaches, it affects the team.”

Kilbourne remembers noticing the bus exhaust during the school’s bus safety week. “They were talking about how buses are safe when it comes to traffic accidents,” he said, “but there’s more to a bus’s safety than traffic accidents, like having air that’s safe to breathe.”

The coincidence spurred Kilbourne to take action. Not only did he write several letters to his local newspaper, but Kilbourne approached the head of his district’s transportation department to discuss air quality in and around its buses. After he spoke to Rick Walterscheid, the transportation director at the Lake Travis Independent School District, the school system put a no-idling policy into effect.

Walterscheid didn’t stop there, either. Later that year the 79th Texas Legislature adopted House Bill 3469, which established and authorized the formation of the Texas Commission on Environmental Quality (TCEQ) to administer a statewide clean school bus program.

With the goal of reducing diesel exhaust emissions, TCEQ offers grants to all Texas public school districts and charter schools that operate at least one diesel-fueled school bus. The TCEQ’s grants offset the cost of school district’s sometimes daunting costs to retrofit school buses, as well as other projects that reduce emissions of diesel exhaust.

Lake Travis ISD, located in a Hill Country suburb of Austin, Texas, was among more than 50 Texas school districts that were eligible for TCEQ’s funding in 2007. That year, Walterscheid’s district applied for and received more than $80,000 in grant money to retrofit a portion of its fleet of buses.

Walterscheid, who manages a fleet of 76 buses that shuttle about 2,500 students each day, said the district’s students are all breathing a little easier these days with help from the TCEQ and its grant program.

“Looking back, the process wasn’t that difficult,” he says, explaining that the district put diesel particulate filters on nine of its buses last year, resulting in “a 90% improvement (in emissions).”

Lake Travis ISD is certainly among the trend setters; one of several districts nationwide that have made firm commitments to clean the air its students and others breathe. This growing national trend includes school districts adopting no-idling policies and those moving to alternative fuels as well.

Nationally, several large city school systems have retrofitted many of their school buses to reduce harmful emissions, according to the Environmental Defense Fund, which is leading a campaign to clean up school buses nationwide.

The non-profit environmental group reports that the entire fleet of New York City’s 4,070 large buses is scheduled to be retrofitted by 2008; Atlanta has installed passive filters on 353 long school buses and Boston has retrofitted 328 school buses.

Environmental Defense points to the NYC plan and Texas’ program, which is better funded than many, as model projects. Parents and educators can get up to speed on the basic steps to take at ED’s Four Steps to Cleaner Buses.


In recent years, several environmental groups have documented that exhaust from diesel-fueled buses make the safe ride to school a truly unhealthy one. Diesel exhaust comprises a cauldron of cancer-causing agents: particulate matter (or soot), smog-forming nitrogen oxides, and a complex mixture of gases. Studies have found that those gases don’t stay outside the bus, either, but permeate the interior.

This “indoor pollution” problem has wide implications: An estimated 24 million children get to class by riding school buses in the United States.

In Texas, with some 1.3 million children hopping on its more than 36,000 buses each school day, the pollution problem for the children is compounded by their sometimes lengthy commutes.

Many school buses in Texas haven’t been making the grade. More than a third of the school buses in the state are more than 10 years old. Not only do these older buses emit more pollution than newer models but they expose children unnecessarily to diesel exhaust, which has been found to make breathing even harder for children with asthma and other respiratory problems.

“Mr. Kilbourne raised my awareness of how we can affect a student,” said Walterscheid. “Talking to him brought to the forefront the issues that we needed to address and made the decision to apply for retrofit funding with the TCEQ that much easier.” <!–nextpage–>

“The school buses we run are the only mode of transportation for many students whose parents both work,” says Walterschied. “So, some parents don’t have a choice of whether or not to put their children on the bus. We are here to serve and we have the duty to improve the situation that students have to be in.”

A handful of organizations fund the effort of retrofitting school buses to make the drive to and from school healthier for children. The TCEQ is the primary organization that heads up bus retrofitting in Texas. The Texas Parent Teachers Association, through its Supplemental Environment Program, helps fund retrofitting, as well, but at a lesser extent.

The Texas Emissions Reduction Plan (TERP) has set aside money for retrofitting expenses, but the organization is primarily focused on funding replacement of school buses, which can cost up to $85,000 apiece.

“It’s ideal for school districts to ask for and get as many new buses as they can,” says Hazel Barbour, program manager for Clean School Bus Program of Central Texas, which is run through a partnership with Clean Air Force and the Capital Area Council of Governments. Barbour’s program assists several Texas counties, including Travis, Williamson, Hayes, Caldwell, Bastrop, and others. As part of her role with the Clean School Bus Program she assists districts in filling out the necessary forms to apply for retrofitting grants and getting the necessary bids for the work to be done.

Retrofitting work is bid on and performed by contractors approved by the U.S. Environmental Protection Agency and the California Air Resources Board, which together ensure that retrofitters meet certain standards.

Four retrofitting options have been approved for funding through the TCEQ. These include:

  • Diesel particulate filters, which can cost from $6,500 to $8,250, are ceramic devices that collect particulate matter in the exhaust system and require a high temperature to break down the matter in the exhaust system. These filters must be used in conjunction with ultra-low sulfur diesel (ULSD) fuel. The combination of particulate filters and ULSD fuel can reduce emissions of particulates, organic compounds, and carbon monoxide in the exhaust gases by 60 to 90 percent. They work best on engines built after 1994.
  • Closed crankcase filtration systems, allow a diesel engine’s crankcase to be closed and use an air filter to trap blow-by aerosols consisting mainly of oil droplets with some carbon and traces of “wear debris” and all particles that are smaller than 10 micrometers in diameter. These particles are considered “inhalable”, because they are small enough to pass into the lower airways. Blow-by gas emissions can be as much as 25 percent of the total emissions from a diesel engine. The filtration efficiency of crankcase filters averages between 80 and 97 percent, but the crankcase filter must be changed at every lube oil change or every 500 hours of operation. Crankcase filters are inexpensive and are best used in conjunction with some type of filtration system in the exhaust stream. These systems may be more effective at reducing children’s in-cabin exposures to pollutants than control systems fitted into the exhaust systems alone. The devices are reimbursed at $800 per bus.
  • Diesel oxidation catalysts, which cost from $600 to $1,500, chemically break down pollutants in the exhaust stream to reduce particulate matter in emissions. Diesel oxidation catalysts can reduce emissions of particulates by 20 to 40 percent, hydrocarbons by 50 percent and carbon monoxide by 40 percent and can be used with regular diesel fuel.
  • Partial flow-through filters comprise a fitting on tailpipes that uses a two-stage filter to accumulate and reduce particulate matter emissions by 70 to 75 percent. This type of retrofit can also reduce total vehicle emissions by up to 80 percent when paired with a closed crankcase filtration system. It is designed to be maintenance-free and can be used with ultra-low sulfur diesel (ULSD) fuel. This type of retrofit costs $5,000 to $6,000.

Costs for retrofitting can be daunting for school districts without the help. However, emissions from school buses drop by as much as 90% when engines and exhaust systems are retrofitted. <!–nextpage–>

The U.S. Environmental Protection Agency maintains a list of vendors who sell retrofit devices. Companies the likes of Caterpillar, Clean Diesel Technologies, and PUREM North America supply school districts with diesel particulate filters, for example.

In Texas, about $8 million worth of grant money is available for the 2008 application period, according to TCEQ officials. Districts have through November 14 to apply and until March 31, 2009 to complete retrofits. School districts can make as many grant requests as they like up to $250,000 per grant request. For more info see the TCEQ FAQ.

Walterscheid’s Lake Travis Independent School District applied for $99,700 in ’08 grant money to retrofit 20 of its buses with partial flow-through filters. When this next retrofitting is completed, Lake Travis will boast 29 retrofitted buses district-wide that will exceed state and federal requirements for environmental standards.

“When this grant funding was announced, there was hesitance with the technology,” said Walterscheid. “We had concerns that the engine wouldn’t get hot enough to burn diesel particulates, so we’ve put those (retrofitted) buses on our longer routes.”


A study conducted jointly by the Environmental Defense, The Clean Air Task Force, and The Conroe Independent School District at The Woodlands, north of Houston, in Texas shines some light on the real culprits of the diesel exhaust systems.

Published in March 2007, Measuring Pollution Levels Inside Texas School Buses points to the bus’s tailpipe and open crankcase as the primary sources of air pollution. (See also this page on the study’s findings.)

The bus’s crankcase is located a few feet from the bus’s front door and vents to the air. When the door opens and closes, exhaust re-enters the vehicle during the course of a daily route.

“Several studies show that air pollution levels inside the school buses can be up to five times greater than levels outside the bus,” the report states.

Children, particularly those with asthma or respiratory problems, are at a greater risk because they breathe more rapidly than adults, they inhale more pollutants per pound of body weight, and their bodies aren’t equipped with a strong defense system. Even if for short periods of time, exposure to diesel exhaust pollution is linked to dizziness, coughing, chronic bronchitis, and increased incidence and severity of asthma attacks.

According to The Burden of Asthma in Texas report, published in May 2007 by the Texas Department of State Health Services and the Asthma Coalition of Texas, “asthma remains one of the most prevalent chronic diseases and growing health concerns in Texas and is one of the most frequent reasons for hospital admissions among children.”

Reports estimate that some 390,000 to as many as 600,000 children in Texas have asthma. (For more info, see this Burden of Asthma in Texas report.)

Multiply that across the nation, and it is easy to understand why there’s a growing trend across the U.S. to retrofit buses to clean up emissions and also to use alternative, cleaner-burning forms of fuel.

Many U.S. schools have transitioned to other forms of less-polluting fuels for their bus fleets. Compressed natural gas (CNG) is used widely in Europe and South America and in the US, this fossil fuel substitute for gasoline and diesel is becoming more widely available, particularly in California, where it’s used to power city and county bus fleets, and now school buses.

Biodiesel, mostly a plant-based fuel, also is growing in popularity. According to the July-August 2007 issue of The Futurist magazine, biodiesel should experience explosive growth within the next 10 years because it can be used in diesel engines without any modifications to the engine: “More than 80% of all commercial trucks and city buses run on diesel gas. This suggests a huge potential market for biodiesel in the U.S.”

The Clark County school district in Nevada has been making inroads into clean-burning buses for several years. The fifth-largest school district in the nation., it serves the cities of Las Vegas, Henderson, North Las Vegas, Boulder City, and Mesquite, and is believed to have the largest fleet of school buses fueled by biodiesel.

The district fuels its buses with recycled cooking oil, sourced from area restaurants. And since Las Vegas is a popular tourist town that never sleeps, the area generates six gallons of oil per resident each year – twice the national average. This clean fleet of school buses saves the environment from untold carbon emissions, according to the Las Vegas Regional Clean Cities Coalition, leaving only a whiff of fumes whose worst offense would be to cause hunger pangs.

Yes, the buses in Clark County smell like french fries.