Dangers of Diesel PoweredSchool Buses
by Jane Dale Owen
The daily routine of your child’s bus ride to school may prove to be hazardous to their health. The National Resource Defense Council (NRDC) reports that children who ride a diesel bus to school may be exposed to more than four times the amount of toxic diesel exhaust that would be inhaled by a passenger of a car driving directly in front of it. Exposure to diesel exhaust may result in lung damage, respiratory problems, allergies, exacerbation of asthma, emphysema, bronchitis and, in cases of long term exposure, increased lung cancer risk.
More than 24 million children in the United States take the bus to and from school every day. This equates to about 10 billion rides annually. The bus-commuting child spends about 180 hours on a bus each year. These exposures may cause chronic health problems later in life. The amount of diesel being emitted by buses is substantially greater than what government regulations allow -- sometimes as much as ten times greater. Diesel exhaust emitted from idling school buses may also be accumulated inside the bus.
Idling
Idling contributes to the pollution generated by buses and wastes fuel. For each hour a typical school bus idles, it burns a half-gallon of fuel. Idling reduction helps improve air quality and saves money. A number of states have obtained agreements between state environmental agencies and school transportation associations to reduce idling.
Particulates and Diesel
Diesel exhaust is recognized by the Environmental Protection Agency (EPA) as one of the largest sources of particulate matter and among the greatest public health risks. It also contains more than 40 individual toxic air contaminants, including smog forming pollutants, and contributes to acid rain, haze, global warming, and ozone.
Many school buses were built before 1991, when standards were set, and do not meet pollution control standards. These older buses can generate as much as six times more toxic soot and three times the amount of smog forming nitrous oxides than newer models.
Alternatives
A cleaner, quieter and less expensive alternative to diesel is compressed natural gas (CNG). Natural gas vapors are not toxic when inhaled. Major metropolitan cities using cleaner bus alternatives include Los Angeles, Chicago, Philadelphia, Tulsa, and New York. Two of the three U.S. full size bus manufacturers offer CNG buses.
Another way to reduce pollution from school buses is to retrofit them with catalytic converters that clean their exhausts. Retrofit efforts by the EPA uses diesel oxidation catalysts that break down exhaust stream pollutants into less harmful substances through chemical processes. The installation of these devices can reduce particulate matter up to 20 percent, hydrocarbons by 50 percent, and carbon monoxide by 40 percent. The EPA is also using diesel particulate matter filters that collect particulate matter in the exhaust stream by using very high temperatures to break down particulate matter.
Health
Children are at a greater risk than the general population because they breathe 50 percent more air per pound of body weight than adults. Children may breathe in diesel exhaust when waiting to board the bus at a bus stop and when boarding idling buses during school dismissal. In fact, the particles in diesel exhaust are so fine that they can easily pass though the nose and throat, become lodged in the lungs and may cause lung damage and premature death. Studies have linked soot emitted by diesel engines to missed school days, asthma hospitalizations and heart disease. According to the EPA, fine particulate matter is responsible for 15 thousand premature deaths each year nationwide. The EPA has also determined that diesel exhaust is a likely human carcinogen. In addition, more than one national association of regulators has claimed that diesel exhaust is the main culprit responsible for 125,000 cancers nationwide. NRDC’s study, “No Breathing in the Isles,” estimated that for every one million children riding the school bus, 23-46 may develop cancer from excess diesel exhaust inhalation. This translates into a cancer risk 46 times greater than what EPA considers to be significant.
Success
To combat the problems associated with diesel school buses, the EPA has developed the Clean Bus Program to reduce both pollution and child exposure through anti-idling strategies, engine retrofit and cleaner fuels, and bus replacement.
The EPA also has implemented new standards requiring that buses built after 2007 emit 90 percent less soot and 95 percent less smog causing emissions than buses built today. Unfortunately, these regulations do not encourage cleaner fuel substitutes.
One hundred thirty school districts in 17 states currently operate natural gas school bus fleets. Tulsa Independent School District, Oklahoma’s largest public school district, converted 179 of its bus fleet to natural gas. A fuel technician for the district claims that converting to natural gas saved the school district approximately 1.6 million dollars. Savings were still being accomplished even after the increase in the price of natural gas.
Houston had its Texas Adopt-A-School Bus Program debut this spring. So far it has received $300,000 in grant money that will be used to retrofit school buses with particulate matter traps in HISD and other local school districts. According to the Education Foundation of Harris County, the replacement of 500 of Houston/Galveston’s oldest and dirtiest buses would reduce concentrations of nitrogen oxide and particulate matter as much as one ton per day. The EPA states that approximately 200 tons/year of emissions reductions could be achieved if Houston were to replace 500 buses in three fiscal years.
Reducing diesel emissions by utilizing cleaner fuel alternatives, retrofitting, and anti-idling strategies may help achieve cleaner air and improve children’s health. To protect your children against dirty diesel exhaust: contact your senator and ask them to support a federal clean bus school program to get older, more polluting buses off the road; and/or write a letter to the editor of your local paper.
