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) |