Anyone who rode in a school bus as a child remembers the sight, sound, and smell of the experience. From the sight of waiting buses idling as they line up in front of a school to the noise of an old engine wrenching gears and producing clouds of heavy black smoke, diesel school buses are a common part of American childhood. Unfortunately, many of the diesel school buses on the road are 10 to 20 years old and, despite their familiar appearance, emit some of the most dangerous compounds children will be exposed to during their young lives.
The dangers of older, diesel school bus emissions discovered in the last ten years, have been disturbing. School buses emit particulate matter, nitrogen oxides (NO x ), and other toxics. EPA has classified diesel exhaust as an environmental carcinogen, or cancer-causing agent. Long-term and short-term consequences of inhaling diesel fumes range from respiratory irritation and inflammation to premature death. Irritation occurs when individuals breathe in diesel particulate matter, tiny pieces of soot that stick to tissue when inhaled into the lungs. Because children take in more air per pound of body weight, they are especially susceptible to these risks.
In addition, traditional diesel exhaust is the source of much of the nation's NO x emissions. When combined with other atmospheric compounds, NO x contributes to the formation of hazardous ground-level ozone. Lastly, diesel exhaust contains a variety of known and as yet unstudied air toxics. The presence of particulate matter, NO x and air toxics in diesel exhaust contributes to the formation of pollutants that endanger public health. In short, the accumulation of diesel exhaust in the atmosphere results in more than an unsightly cloud of black smoke.
According to a 2001 study performed by the National Resource Defense Council and the U.C. Berkeley School of Public Health, children riding in old diesel school buses are exposed to up to eight and a half times the amount of diesel exhaust as adults living in the same area. Most notably, the authors of the study estimate that the cancer risk for a child who rides a typical diesel school bus from one to two hours a day, 180 days a year for 10 years is 23 to 46 times what the EPA defines as a "significant" risk of developing cancer later in life. (See www.nrdc.org/air/transportation/schoolbus/sbusinx.asp for the complete report.) Children walking close to streets where polluting buses and trucks drive are also exposed to dangerous diesel exhaust.
So how do we solve the problem of Houston 's diesel school buses? Currently, school districts in the Houston area must rely on limited federal, state, and local sources to buy new, cleaner engines and retrofit existing buses with technology that reduces NO x and particulate emissions. Recently, the EPA announced their Adopt-a-School-Bus program, which encourages local businesses to partner with districts to fund needed upgrades. Unfortunately, the program has a long way to go to raise the kind of funds that will be necessary to replace and retrofit all the old diesel buses in the area.
New EPA regulations mean that new school buses will be much cleaner than those in years past. Buses sold in 2004 will emit half the NO x emissions as those sold in 2003, and by 2010 new buses will emit 90% less pollution than those bought in 2004. While these standards are an important step, more needs to be done to clean up school bus emissions now. School districts tend to keep buses for over twenty years, so old, dirty buses stay on the road for a long time.
What can you do? Encourage your child's school district to prohibit unnecessary idling, retrofit buses with emission control devices, and purchase the cleanest buses available. By taking these steps, area school districts will improve student health and help clean up our region's air.
This article was written by Jane Barker , a Rice University senior and Mothers for Clean Air summer intern, provided by the Texas Public Interest Research Group (TexPIRG).