Frequently Asked Questions

Q. If petroleum diesel is so harmful, what types of alternative fuels are available instead?

A. Liquefied and compressed natural gas (LNG & CNG), liquefied petroleum gas (LPG or propane), battery-electric, synthetic diesel derived from natural gas (Fischer-Tropsch diesel), and biodiesel made from plant oils, animal fat, and used grease. Other alternative fuels such as hydrogen and fuel cells are still under development and are expected to be available within the next ten to twenty years.

Natural gas is currently the best, most-developed alternative to petroleum. It is available in combination with diesel and, better yet, in combination with battery electric power. There is a stable and plentiful supply of natural gas, most of which comes from North America. However, natural gas, just like petroleum and coal, is a non-renewable fossil fuel, so it also contributes to global warming and will some day be used up unless we use multiple alternative fuel sources.(1)

Q. Aren’t new diesel buses as clean as natural gas?

A. New emissions control devices for diesel engines can reduce pollutant emissions significantly. One diesel school bus manufacturer has installed pollution control equipment that “traps” toxic soot, cutting emissions by over 85 percent in certification tests. Particulate traps and other diesel pollution controls will only function if the engines are run on low-sulfur fuel, which will not be nationally accessible until required by federal law in 2006. Plus, these new pollution control technologies have not yet proven effective over the range of real-world operating conditions. If they fail, degrade, or are disengaged, diesel buses will continue to pollute the air with black toxic soot and smog-forming emissions. While diesel cleanup technologies show promise, natural gas engines remain the cleanest alternative available today across the country. And, natural gas engines are already becoming even cleaner by adopting additional pollution controls.(2)(3)

The following 2 questions are taken from the Union of Concerned Scientists online article, “Clearing the Air On Alternative-Fuel School Buses.”

Q. Aren’t natural gas buses too expensive to be practical?

A. A natural gas school bus initially costs $30,000 - $40,000 more than a diesel bus. This initial investment is often recouped by school districts, which benefit from lower maintenance and operational costs. There are also federal funds and funding in some states and local districts to offset the cost of investing in cleaner technologies. More important, investing in cleaner vehicles pays off in reduced asthma rates, fewer hospital visits, lower cancer rates, less absenteeism, and healthier children.

Q. Isn’t the natural gas bus a new, unproven technology?

A. Natural gas buses have been on the road for over a decade and have a long track record of success. Approximately one in seven transit buses currently on order in the United States is powered by natural gas and half of California’s new buses use natural gas. Natural gas transit buses are being used in cities throughout the country, including Los Angeles, California; NewYork, New York; Tacoma, Washington; Phoenix, Arizona; State College, Pennsylvania; Cleveland, Ohio; Dallas, Texas; and, Atlanta, Georgia. School districts are learning from these transit districts and joining the clean air bandwagon on alternative fuel school buses. One hundred thirty school districts in 17 states transport children to and from school in buses powered by alternative fuels.

Q. What is a hazardous air pollutant?

A. According to Section 112(b)(1) of the Clean Air Act, U.S. Environmental Protection Agency (EPA) must compile a list of hazardous air pollutants (HAPs). These are pollutants that cause or may cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental and ecological effects.

Q. What is particulate matter (PM) and how is it harmful to our health?

A. Suspended particulate matter (PM) is an air pollutant derived from the combustion of fossil fuels in the form of dust, soot, or smoke.

Diesel engines account for about one quarter of the particulate air pollution from all on-road sources. More than 98 percent of the particles emitted from diesel engines are fine particles, less than 1 micron in diameter, which can bypass respiratory defense mechanisms and penetrate deep into the lungs. Numerous studies have found that fine particles impair lung function, aggravate respiratory illnesses such as bronchitis and emphysema, and are associated with premature deaths. Also, dozens of studies link airborne fine-particle concentrations to increased hospital admissions for respiratory diseases, chronic obstructive lung disease, pneumonia, and heart disease, including an increased risk of acute myocardial infarction (heart attack).(4)

Q. What are nitrogen oxides (NOx) and how are they harmful to our health?

A. Nitrogen oxides (NOx) are a family of reactive gaseous compounds that contribute to air pollution. NOx emissions are produced during the combustion of fuels at high temperatures.

Nitrogen oxides can irritate the lungs, cause bronchitis and pneumonia, and lower resistance to respiratory infections. They are an important precursor to both ozone and acid rain, and may affect both terrestrial and aquatic ecosystems.(5)

Q. What are volatile organic compounds (VOCs)?

A. VOCs include gasoline, industrial chemicals such as benzene, solvents such as toluene and xylene, tetrachloroethylene, and perchloroethylene (the principal dry cleaning solvent). Many volatile organic compounds are hazardous air pollutants, and are known, or suspected, carcinogens. Benzene, for example, causes cancer.

Organic chemicals include the basic chemicals found in living things and in products derived from living things, such as coal, petroleum, and refined petroleum products, primarily carbon. Many of the organic chemicals we use do not occur in nature, but were synthesized in laboratories. Volatile chemicals produce vapors readily; at room temperature and normal atmospheric pressure, vapors escape easily from volatile liquid chemicals.(6)

The following 2 questions are taken from the U.S. Environmental Protection Agency’s Voluntary Retrofit Program Glossary.

Q. What is a particulate trap or filter?

A. A particulate trap or filter is an after-treatment device that filters or traps diesel particulate matter from engine exhaust until the trap becomes loaded to the point that a regeneration cycle is implemented to burn off the trapped particulate matter.

Q. What does it mean to retrofit an engine?

A. An engine retrofit includes, but is not limited to, any of these activities:

• Addition of new or better pollution control after-treatment equipment to certified engines;
• Upgrading a certified engine to a cleaner certified configuration;
• Upgrading an uncertified engine to a cleaner “certified-like” configuration;
• Conversion of any engine to a cleaner fuel;
• Early replacement of older engines with newer, presumably cleaner, engines, in lieu of regular expected rebuilding; and
• Use of cleaner fuel and/or emission reducing fuel additive (without engine conversion).

Q. Why are children more susceptible to air pollution and diesel exhaust?

A. Children are more susceptible to air pollutants because their lungs are still developing and their airways are narrower than those of adults. In addition, children often play outdoors during the day and may be more exposed. Children raised in heavily polluted areas have reduced lung capacity, prematurely aged lungs, and increased risk of bronchitis and asthma compared to peers living in less urbanized areas.(7)(8) Both NOx and particulate matter have been linked to a significant decrease in lung function growth among children living in the Southern California.(9) Elevated levels of particulate pollution have also been linked with an increased incidence of respiratory complaints in children.(10) In a study comparing air pollution in six U.S. cities and the respiratory health of individuals living in those cities, the frequencies of cough, bronchitis, and lower respiratory illness in preadolescent children were significantly associated with increased levels of acidic fine particles.(11) Illness and symptom rates were twice as high in the community with the highest air pollution concentrations compared with the community with the lowest concentrations. In addition, some studies have suggested that children with preexisting respiratory conditions (e.g., wheezing, asthma) are at an even greater risk of developing symptoms from exposures to diesel-related pollutants.(12)(13)

Q. Why do cost/benefit estimates, put out by industry and by non-profit policy organizations, differ so greatly?

A. Historically, the EPA has understated the benefits and overestimated the costs of complying with most air pollution standards. For example, in 1990, the EPA estimated the costs of an allowance to emit a ton of sulfur dioxide at $400 to $800. The actual costs today are less than $100.(14)

Cost estimates produced by various industrial companies have been even more blatantly off target. On average, industry has overestimated the costs of pollution control by a factor of 14 in the last two major air quality rulemakings in California, based on actual costs of compliance.(14)

Just as costs are chronically overestimated, the economic benefits of pollution control are systematically minimized. According to the EPA, the public health benefits of their proposed particle standard are at least ten times greater than the costs – $65 billion to $140 billion per year in benefits compared to $ 6.3 billion per year in pollution control costs. Yet, even this impressive cost / benefit ratio understates the true economic value of the clean air that the standard provides. For example, EPA benefits projections exclude the economic value of reduced lung and bronchial cancer incidence from cleaner air.(14)

Q. Why are industrial polluters so reluctant to change their ways?

A. Because industry tells the public that changes are too costly. This is partially because industry tends to squander so much money in advertising and media blitzes, trying to convince the public that achieving the status quo for ambient air quality is not a worthwhile endeavor.

In fact, in 1995-1996, the combined gross annual revenues of 105 of the nation’s major particulate polluters averaged $1.2 trillion dollars. This is 200 times the cost of achieving proposed particulate standards.(14)