Reports & Studies

CARB Releases Study Comparing CNG
and Low Sulfur Fuel Buses

SACRAMENTO, Calif. -- A transit bus equipped with a particulate filter running on low sulfur diesel fuel produced lower emissions than a compressed natural gas bus, according to a study released April 18 by the California Air Resources Board.

The particulate-filtered bus released lower amounts of particulate matter (PM) and toxic organic compounds, but produced an increase in nitrogen oxide (NOx) emitted as nitrogen dioxide (NO2) compared to the CNG bus, CARB said.

However, while the study, which also examined a low sulfur fuel bus without a diesel particulate filter (DPF), said both CNG and DPF buses are "significantly superior" to conventional diesel buses, "no single technology is clearly superior to the others."

"Both technologies are proven and offer a verified benefit for reduction of total PM mass emissions," the report said.

CARB studied emissions from a CNG 40-passenger transit bus; a diesel 40-passenger transit bus running on low-sulfur ECD-1 Arco diesel fuel; and the same diesel bus retrofitted with a Johnson Matthey Continuously Regenerating Technology DPF and running on ECD-1.

The DPF bus performed better in eight of 11 emission categories tested. The CNG bus only recorded lower levels of NOx, NO2 and CO2. Furthermore, the report said the mutagenicity findings suggest that "CNG PM is not inert and may pose a toxic risk." Mutagenicity is the measure of mutations in an organism and evidence of substance's potential toxicity. The report cautioned, however, that the mutagenic numbers cannot be used directly to determine cancer risk by inhalation.

The CNG NOx emissions were approximately a third lower than the diesel vehicle emissions, but, according to the report, because of the "PM and non-methane hydrocarbon reductions achieved by DPFs, a modest increase in tailpipe-out NO2 emissions offers more benefits than disbenefits."

According to CARB, the data suggested levels of some toxic pollutants, such as benzene, in CNG exhaust "require further study and may warrant additional control."

The CNG bus, however, was not equipped with a particulate filter or other after-treatment equipment, such as an oxidation catalyst. The agency plans to conduct additional tests with the CNG bus refitted with an oxidation catalyst and a new CNG bus equipped with an installed oxidation catalyst. Results are expected in mid-2002.

Officials from the CNG and low sulfur fuel camps both reacted positively to the study, though for obvious different reasons.

"CARB's research suggests the possibility of significant adverse health impact from widespread use of natural gas vehicles," said Dr. William B. Bunn, Vice President, health, safety and productivity of International Truck and Engine Corporation, which manufacture's a low sulfur fuel-compatible bus engine. "Assertions that natural gas exhaust is not toxic are not credible. In fact, as this new study corroborates, low-emitting diesel exhaust may include fewer pollutants than natural gas exhaust."

CNG officials took a different tack, saying the research shows that yesterday's natural gas technology compares with tomorrow's diesel technology.

"This comparison might be valid if the natural gas engine producers were not already equipping engines with pollution controls, but the fact is-they are," said Michael Eaves, chairman of the California Natural Gas Vehicle Coalition. "The natural gas industry is committed to being the cleanest transportation fuel, and we are working continually to improve our engines so that all Californians can benefit."

Source: School Transportation News, May 2002.

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Study Concludes Nation's Students
Susceptible to School Bus Fumes

BERKELEY, Calif. - School buses in all 50 states release toxic air pollutants that are harmful to the health of school children, according to a study conducted by the Union of Concerned Scientists (UCS) on particulate matter, smog-forming pollutant and greenhouse gas emissions.

"In a single year, America's average school bus emits as much soot as 125 cars," said Patricia Monahan, senior analyst in the UCS Clean Vehicles Program and author of the 80-page report.

In February, UCS published "Pollution Report Card: Grading America's School Bus Fleets," the first empirical and quantitative analysis of the 454,154 school buses in the United States and the pollutants they emit. It found that not only do most states rely on diesel school buses to transport children, but there are limited or no programs in place nationwide that monitor the amount of pollution released from school bus tail pipes or that require school districts to purchase low-emission buses.

UCS collected data from individual state directors of pupil transportation pertaining to the total number of vehicles in the fleet, age distribution by model year, the number of pre-1977 buses and the existence of bus replacement policies. The organization also compiled data from R.L. Polk, a provider of advanced automotive information services and statistical reporting of DMV records, based on the age distribution of vehicles and the types of fuel used.

Assigning grades to each state, UCS concluded that 19 states are "behind the curve" with "C-" or "D+" marks. Monahan explained that the study did not hand out "F" grades, but said that because California and Washington were the only states to receive straight "Ds," they flunked outright. Twenty-three states ranked in the "middle of the road" with "B-", "C+" or "C" grade averages and six states and the District of Columbia were "ahead of the curve" with "B" grades. Delaware and Maryland joined the district as the only municipalities with strong and effective bus replacement policies. However, no state came close to receiving an "A" for superior marks.

Monahan stressed that the findings are in no way a reflection of the state directors' job performance. "This issue is a new one for a lot of states," she said. "In the report, I recognized that funding is a big issue. School districts should never have to choose between books and buses."

The Methodology

A sophisticated analysis of the data from the state directors and R.L. Polk was then calculated utilizing government methodologies. To estimate the levels of nitrogen oxide, hydrocarbons and carbon monoxide in diesel and gasoline emissions, Monahan plugged the data into the most recent version of the soon-to-be-released MOBILE6, the Environmental Protection Agency's first highway emissions factor model for school buses. Monahan found that the average diesel school bus releases 417 pounds of smog-forming pollutants and 14 pounds of soot. Those numbers drop to 322 and 5.6 respectively for the average new standard diesel and 215 and 0.5 for average natural gas buses.

The relied on in-use data from the Department of Energy's Alternative Fuels Data Center (AFCD) to calculate soot levels in diesel buses and found that grams per mile have dropped from 1.939 in pre-1988 diesel buses to 0.256 grams per mile in 1994 and newer buses. To calculate the same emissions in gasoline buses, she used California's EMFAC2000 model, which relied on emissions testing from light-duty trucks to estimate potential estimates from heavy-duty trucks. It assumed that gasoline vehicles would emit 0.054 grams per mile across the board, regardless of the vehicle's age. However, Monahan noted that while EMFAC might underestimate particulate releases because new gasoline heavy-duty trucks have improved engineering improvements, most gasoline school buses were built more than a decade ago and the data was based only upon light-duty trucks.

Monahan used the Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET) model from Argonne National Laboratories to gauge the effects of school bus emissions on global warming. It measured the level of upstream emissions of methane, nitrous oxide and carbon dioxide, as well as tailpipe releases of carbon dioxide and concluded that 10,672,975 tons of greenhouse gases are released in the United States each year, with New York leading the way with nearly 1.05 million tons. In all, the study deduced that school buses nationwide emit nearly 95,000 tons of smog-forming pollution and more than 3,000 tons of soot each year.

The study asserts that a new diesel bus emits 11 times more toxic soot and about 50 percent more smog-forming pollution than a new natural gas bus. It said that replacing a 1990 diesel bus with a new natural gas bus would reduce toxic soot by 98 percent and smog-forming pollutants by 50 percent. Replacing pre-1977 buses, which pose the greatest health risks, would result in a 99 percent reduction in toxic soot and 75 percent reduction in smog-forming matter. UCS also said that diesel exhaust also rapidly destroys the ozone and contributes to global warming, demonstrating that each gallon of diesel releases 27 pounds of carbon dioxide equivalent emissions, or greenhouse gases, through the tailpipe. Conversely, a gallon of natural gas releases 21 pounds. A 1990 diesel bus releases 16 percent more global warming pollutants while a pre-1977 diesel bus produces 25 percent more toxins than a new natural gas bus. The study was silent on the specific effects of low-sulfur or Green Diesel fuel.

The report cited numerous scholarly references as to the harmful effects of diesel.

"Diesel pollution harms everyone, but our children and their developing lungs are hurt the most," said Michelle Robinson, senior advocate for clean vehicles at UCS. "Going to school should not be hazardous to our kids' health."

The report said that cost-effective investments in new clean-up technologies could dramatically reduce pollution by allowing school districts to switch their transportation operations to buses that run on cleaner-burning fuels. The study stated that natural gas buses exhibit a proven track record of success, as this new type of fuel currently powers one in seven newly ordered municipal transit buses. In addition, Monahan said that if all states implemented school bus replacement and retirement programs, the level of pollutants would significantly decrease.

However, she added that no matter what fuel is used, school buses would continue to contribute to global warming and the greenhouse effect. All fossil fuels, including diesel, gasoline, natural gas and propane, emit pollutants that harm the earth's atmosphere.

To download the complete study, visit www.ucsusa.org/publications/PollutionRptCard.pdf.

Source: School Transportation News, April 2002.

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Industry Officials Suspicious of EHH Report

NORTH HAVEN, Conn. - School transportation officials expressed skepticism about a February report that claims diesel school bus exhaust exposes children to significant health risks.

Released by the environmental advocacy organization Environment and Human Health, Inc., the study said "children are exposed to diesel exhaust from school buses at levels far above those predicted by current government monitoring efforts."

Mike Martin, executive director of the National Association of Pupil Transportation, questioned the report and its findings, referring to an early study with similar results that has since been contradicted by a peer review and another study that came to opposite conclusions.

"I think its safe to say that from my perspective their results are viewed with suspicion, that's for sure," Martin said. "It's conceivable that they came to conclusions and then looked for the facts to prove them."

The study placed "ultra-sensitive" monitors on children and recorded air quality readings throughout the day. "For short periods, the research showed exhaust levels 5 to 10 times higher than government standards," said the study's lead author Dr. John Wargo, Yale professor of risk analysis and environmental policy.

These "short periods," however, were just 10-second intervals when students entered and exited buses.

The study monitored levels of coarse particles, which are caused by dust, and fine particles, which are produced by fossil fuel combustion. But in one chart that measured fine particle exposure of five children, the two children with the highest rates of exposure did not ride buses; they walked to school.

According to Charles Gauthier, Executive Director of the National Association of State Directors of Pupil Transportation Services, school transportation industry officials are eager to conduct a peer review of the EHH study, questioning the organization's political agenda. "Let's wait and make sure we understand everything before we make decisions that affect health of our children," Gauthier said.

The study also drew a link between childhood asthma and diesel exhaust.

"One of the things I find ironic is that during the Olympics there was a report that one in five U.S. athletes suffered from some form of asthma," Martin said. "These are world-class, Olympic-caliber athletes and one in five has asthma. I don't know how many of them rode school buses, but to hold school buses responsible for the increase in asthma is a bit of a stretch."

Released on "Good Morning America," the study was portrayed as a Yale University product, though the EHH commissioned and financed the study. The University of Connecticut's Environmental Research Institute conducted the study's air quality monitoring.

The report offered several recommendations, including retrofitting buses by 2003 with particle traps and catalytic converters to reduce emission, requiring use of ultra-low sulfur fuels and prohibiting bus idling.

Martin said the industry probably would support voluntary anti-idling restrictions, pointing to a number of states that already use such policies. But he questioned why the pupil transportation industry should be held to higher standards than other diesel-dependant industries.

Source: School Transportation News, April 2002.

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Study Finds Link Between Children's
Health and Diesel Exhaust

NORTH HAVEN, Conn. -- Diesel school bus exhaust exposes children to significant health risks, according to a report released Feb. 7 by Environment and Human Health, Inc. (EHHI), an environmental advocacy organization. The report was presented on a segment of Good Morning America.

In a press release EHHI called its study "a ground-breaking report indicating that children are exposed to diesel exhaust from school buses at levels far above those predicted by current government monitoring efforts."

The latest in a series of controversial studies examining diesel fumes and children's health, the study placed ultra-sensitive monitors on children and recorded air quality readings throughout the day.

For short periods of time, the research showed exhaust levels 5 to 10 times higher than government standards, said the study's lead author Dr. John Wargo, Yale professor of risk analysis and environmental policy.

"Levels of fine particles and black carbon were higher under certain circumstances: when buses were idling with doors or windows opened; when buses moved through intense traffic; when buses followed other diesel vehicles; and especially when buses were queued to load or unload students while idling. Particle and black carbon levels on buses powered by natural gas were not distinguishable from background levels," according to the report.

"There is no known safe level of exposure to diesel exhaust for children," said Robert LaCamera, M.D., Clinical Professor of Pediatrics at the Yale School of Medicine and a reviewer of the study.

Released on "Good Morning America," the study was portrayed as a Yale University product. However, according to an Environment and Human Health press release, EHH commissioned and financed the study. The University of Connecticut's Environmental Research Institute conducted the study's air quality monitoring.

According to Charley Gauthier, Executive Director of the National Association of State Directors of Pupil Transportation Services, school transportation industry officials are eager to conduct a peer review of the EHH study, questioning the organization's political agenda.

"Let's wait and make sure we understand everything before we make decisions that affect health of our children," Gauthier said.

Source: School Transportation News, March 2002.

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Fairfax County Study Finds No
Environmental Risks in School Buses

SPRINGFIELD, Va. - An extensive, scientific study of a representative sample of 12 school buses in the fleet of Fairfax County Public Schools (FCPS) concluded the concentration of diesel exhaust inside the buses is below the limits of detection. The study concluded, "Breathing the air on Fairfax County Public Schools buses poses no health risks to our students and staff."

FCPS operates a fleet of 1,428 school buses of various makes and models to transport, daily, approximately 105,000 students to 234 schools and education centers. Approximately half of the buses are more than ten years old, and all but seven are powered by diesel engines.

FCPS transportation officials were concerned by media reports out of Los Angeles about research findings on the possible negative health effects of diesel exhaust from older school buses.

Twelve buses, representing different makes, models, sizes, ages, and engine types were selected for evaluation. Those selected included diesel fuel general education buses and special education buses with wheelchair lifts, a bus fueled by CNG, and one dual-fuel bus. The buses were monitored without student passengers during a simulated 90-minute bus run over an exact 19.9-mile-route in normal traffic with periods of loading, unloading, and idling. The tests were conducted from mid-February through early March.

The school buses ranged in age from 17 years to brand new. They included one 1984 model, three 1987 buses, one 1988 bus, one 1989 bus, two 1991 buses, one 1993 bus, one 1994 bus, one 1995 bus, and one 2001 model bus. Makes included Ward, Wayne, Bluebird, Thomas, International, AmTran, and Ford. By contrast the Los Angeles study by the Natural Resources Defense Council tested four buses, all manufactured prior to 1988 diesel emission standards.

Air samples were collected by filtration in accordance with standardized methods prescribed by the Occupational Safety and Health Administration for respirable particulates and the National Institute of Occupational Safety and Health [NIOSH] for elemental and organic carbon particulates. Analysis of the filtrates was performed Data Chem Laboratories, Salt Lake City, Utah, using standard methods NIOSH 0600 and NIOSH 5040.

Researchers concluded that there was "no detectable elemental carbon and subsequently no evidence that the bus air is contaminated by diesel/exhaust at a concentration that would be of any concern. ... All of the twelve respirable samples were below the Occupational Safety and Health Administration occupational threshold for respirable particulates for an 8-hour Time Weight Average."

Moreover, researchers said, "The detection of exhaust odor while riding a school bus may suggest to some passengers that exhaust is significantly being contaminating the bus air. The smell of the diesel exhaust is pungent and unpleasant but the intensity of an odor should not be construed to be representative of a health threat.

A complete copy of the report, "A Representative Sample of Fairfax County Public School Buses," can be found in PDF format on the website of Fairfax County Public Schools. Access requires Acrobat Reader.

Source: School Transportation News, April 2001.

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Peer-Review Challenges NRDC
Diesel-Fuel Report as Bogus Science

NEW YORK -- Calling it unsupported "opinion" and "replete with invalid and unsupported assertions," the American Council on Science and Health (ACSH) fired broadside at the claims by the Natural Resource Defense Council (NRDC) and Coalition for Clean Air (CCA) that diesel exhaust emissions from school buses pose a cancer risk to school children. The ACSH charges are found in a published a report titled School Buses and Diesel Fuel, a peer-review analysis by ACSH, that is highly critical of the science in the NRDC/CCA report, No Breathing in the Aisles.

The NRDC/CCA report was issued earlier this year and was instrumental in the decision by the Los Angeles-based South Coast Air Quality Management District to ban the purchase of school buses powered by clean diesel technology. Public fears generated by the report even found their way into the recent election of the school board of the Los Angeles Unified School District.

ACSH is a consumer education consortium of more than 350 scientists and physicians concerned with issues related to food, nutrition, chemicals, pharmaceuticals, lifestyle, the environment and health. It publishes reports to help the public deal with health risks productively. ACSH's top priority is to help Americans distinguish between real and hypothetical health risks. It was founded in 1978 by a group of scientists who had become concerned that many important public policies related to health and the environment did not have a sound scientific basis. These scientists created the organization to add reason and balance to debates about public health issues and bring common sense views to the public.

The ACSH report is not another study of non-occupational diesel exhaust. Instead, it is a peer-review of the NRDC/CCA report that seeks to evaluate its scientific merit and the basis behind its conclusions. ACSH charges the NRDC/CCA with "failure to follow standard scientific protocols and a lack of attention to methodological details." Twelve emminent scientists participated in the peer review.

• ACSH concluded the monitoring study, which forms the basis of the report and from which the NRDC/CCA based its risk estimates for children, is not described in sufficient details, nor are enough data presented to allow for a thorough and informed critique of its validity. Thus, the conclusions regarding cancer risk to children from diesel exhaust exposure cannot be confirmed.
• ACSH concluded the estimated diesel exhaust exposures for children riding a diesel-fueled school bus have not been confirmed through other indpendent studies. It notes that quantitative human exposure data are rarely available, and therefor comparisons to the NRDC/CAA findings are not possible.
• ACSH concluded that no published studies are known that link ambient or non-occupantional exposure to diesel exhaust with increased cancer risk.
• ACSH concluded the estimated cancer risk for children calculated by the NRDC/CCA uses a unit risk factor that has not received general acceptance by the scientific community and is not currently used by the U.S. Environmental Protection Agency.
• ACSH concluded that no case reports or studies are known to link childhood exposure to diesel exhaust, either on buses or in any other exposure scenario, with an increased risk of developing cancer.

CASTO Says School Buses Should Not
Be Pawns in Environmental Battle

California school transporters have begun to fight back against charges by environmentalists that riding in a school bus increases the likelihood of developing lung cancer.

Calling the recent study by the Natural Resources Defense Council bogus, the California School Transportation officials (CASTO) have issued a statement disputing the validity of charges and the methodology of the study. CASTO says the charges are part of a campaign by environmentalists to ban diesel buses altogether in favor of school buses powered by compressed natural gas.

The statement said the environmental broadside is part of a political agenda that has nothing to do with school buses and more to do with frightening parents into losing confidence in the state's pupil transportation system.

CASTO President Larry Laxon said, "Our industry is not deaf to environmental concerns and believes we all must do our part to conserve resources and improve air quality." He said his association supports the move toward alternate fuels, and cites the fact that "since the early 1990's our industry has participated in alternative fuel demonstration programs. With $100 million funded by the California Legislature, 826 older diesel-powered buses were replaced with cleaner-buring diesel and alterantive fueled models."

Recently California Gov. Gray Davis approved a $50 million grant to purchase 375 new school buses, and retrofit 1,875 existings buses with more low-emission diesel and CNG school buses. CASTO said the environmentalits charges are a veiled attempt to order acquisiton of CNG buses with the governor's grant. CASTO noted that CNG buses are 30 percent more costly than buses powered with the new generation of clean burning diesel engines.

Laxon stressed the safety record of school bus transportation in California. He said, "Riding in a California school bus is nearly 100 times safer than riding in any other vehicle." He noted, "Over the last decade, we have averaged zero fatalities to children who ride with us."

Source: School Transportation News, March 2001.

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Yahoo! Carries School Bus Information Council's
Response to Diesel Fumes Charges

SANTA CLARA, Calif. -- Yahoo's PR Newswire carried a response by the School Bus Information Council charges that diesel fumes cause increased cancer risk to children riding diesel school buses in California.

Citing a need to put perspective on the charges, the SBIC noted that the allegations by environmentalists are based on anecdotal evidence from four buses in Los Angeles -- manufactured beffore 1988 diesel engine emission requirements were impelemted.

The school bus industry has taken the lead on diesel engine technology improvements, said the SBIC, using an an example International's development of Uultra-low sulfur Green Diesel diesel fuel with particulate emissions as low or lower than other alternative fuels, such as CNG.

In addition, the safety record of the school bus industry is unequaled in motor vehicle transportation, said the SBIC, noting some 600 children are killed annually nationwide because they opt to ride other vehicles to and from school rather than a school bus. "People who are truly concerned about student safety should work to ensure that more than 16% of the kids in California -- the lowest percentage in the nation -- ride the bus to and from school," said the SBIC.

The Council called the charges a typical, but unfair, publicity technique to frighten parents and children about school bus transportation, at a time when school buses appear to be cauught in the middle of a bigger political battle in California.

Source: School Transportation News, February 2001.

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School Bus Manufacturer
Assails Anti-Diesel Report

LOS ANGELES, Calif. --The report on diesel emissions released by the Natural Resources Defense Council is fundamentally flawed, according to the manufacture of Green Diesel TechnologyT buses, International Truck and Engine Corporation.

"We agree with NRDC that we should retire these older, more polluting buses as fast as possible--we just differ on how to go about doing it," said Trueblood, Manager of Public Affairs International for International Truck and Engine Corporation. Trueblood added, "California has the oldest school bus fleet in the nation. The best way to ensure that school kids ride on safe buses is to invest in new, clean buses - fueled by clean diesel OR natural gas."

The report leads people to believe that exhaust fumes inside old, 1980's diesel school bus pose a serious health risk to children, and that therefore school districts should abandon diesel technology altogether and purchase compressed natural gas buses.

"Green Diesel TechnologyT buses release a lower level of particular matter than natural gas buses," said Trueblood. "They offer a cost effective way for schools to meet their transportation needs while reducing air pollution."

"This study sampled only four 20-year old buses," said Trueblood. "The purported results conflict with many other studies in the field, including a recent study by the respected European research firm EcoTraffic, which found that the cancer risk from emissions from natural gas buses is 2 1/2 times greater than that from advanced clean diesel buses."

Further undermining public understanding of the issue, the Los Angeles Times and the Associated Press reported this morning that Dr. Katherine Hammond of UC Berkeley authored the study. Hammond did not author the study. Rather, natural gas advocates wrote it from the two environmental organizations.

The study -- and its interpretation by the media -- fails to recognize important recent findings by the California Air Resource Board. In December of last year, the California Air Resources Board found that buying $30 million worth of Green Diesel TechnologyT buses reduces emissions by 196 tons MORE than $30 million worth of natural gas buses. It also found that you could buy nearly 100 more Green Diesel Technology buses than natural gas for the same $30 million. That means that we could retire 100 more older, polluting buses by buying Green Diesel rather than natural gas buses.

Technical notes about the NRDC methodology:
Accurate measurement of diesel exhaust is crucial to interpretation of the NRDC report. The accepted method of analysis is the NIOSH 5040 method that identifies elemental carbon which is fairly characteristic of diesel and excludes interferences from other carbon sources such as tobacco smoke, paint and other organic compounds, pollen, limestone dust, etc. The two methods used in this NRDC study are fairly indiscriminate and are not therefore accurate measures of diesel. One method measures all particles of a certain size, no matter what source they come from.

The other method used in the NRDC study measures the darkness on a strip of paper caused by various materials, mostly carbon bearing. The fact is most carbon samples contain much greater levels of non-diesel carbon materials than they do of elemental carbon from diesel. Total carbon samples may contain less than 10% diesel related elemental carbon in known exposure scenarios. The NRDC report does not fully describe the sampling methodology. It indicates that a couple of correction factors are applied to estimate the diesel content, but the factors are inaccurate. Moreover one of the factors is applied backwards and multiplies the result when it should be divided, thereby doubling the concentration reported.

Source: School Transportation News, February 2001.

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Environmental Group Charges Diesel
Fumes Inside School Buses Endanger Children

BERKELEY, Calif. -- The National Resource Defense Council (NRDC) and Coalition for clear Air published a report, No Breathing in the Aisles: Diesel Exhaust Inside School Buses, that charges "children who ride a diesel school bus may be exposed to up to four times more toxic diesel exhaust than someone traveling in a car directly in front of it."

School bus manufacturers and industry groups lashed back, charging the study is biased, flawed, and part of an effort by environmentalists to force school districts in Southern California to purchase only alternative fueled buses, primarily compressed natural gas.

According to the NRDC report, "The excess exhaust levels on the buses were more than eight times the average levels found in the ambient air in California and 23 to 46 times higher than levels considered to be a significant cancer risk according to the U.S Environmental Protection Agency (EPA) and federal guidelines."

The NDRC report, released February 13, 2001, states that researchers from the NRDC, the U.C. Berkeley School of Public Health and the Coalition for Clean Air, a Santa Monica-based environmental organization, rode rented school buses along actual elementary school bus routes in the Los Angeles area. The report states that researchers conducted "nearly 20 hours of sampling results on four school buses produced dramatic results."

According to the report, "Assuming bus rides totaling one or two hours per day, 180 days per year for 10 years, the groups estimated the diesel exhaust exposures are likely to result in an additional 23 to 46 cancer cases per million children exposed."

The findings of the report were not corroborated. A standard methodology when researches seek to establish verifiable scientific evidence is for other researchers to independently verify the results. To date, no other research group has verified the NRDC findings.

International Corp., a manufacturer of school buses, assailed the study as flawed and biased. "The study -- and its interpretation by the media -- fails to recognize important recent findings by the California Air Resource Board," said Tom Trueblood, manager of Public Affairs International for the company. International manufactures a school bus that operates on low sulphur diesel known as "green diesel." The fuel formulation has been accepted by the California Air Resources Board as an alternative fuel.

"In December of last year, the California Air Resources Board found that buying $30 million worth of Green Diesel TechnologyT buses reduces emissions by 196 tons MORE than $30 million worth of natural gas buses," he said. "It also found that you could buy nearly 100 more Green Diesel Technology buses than natural gas for the same $30 million. That means that we could retire 100 more older, polluting buses by buying Green Diesel rather than natural gas buses."

The School Bus Information Council, an industry group, weighed in on the issue. "Unfortunately, school buses appear to be caught in the middle of a bigger political battle in California. As the Times also pointed out, '...environmental groups have mounted a major campaign to reduce the use of diesel engines in California.' Sadly, it is a typical publicity technique to heighten public concern for your agenda by sensationalizing the alleged adverse affects on children. Frightening parents and children about the safety of school bus transportation is an unfair way for the environmental advocates to promote their agenda and stoke the fires of debate about air quality in California."

The Council said a far more immediate danger to school children is the high number of fatalities that occur to children riding to and from school in vehicles other than the school bus. "Some 600 children are killed every year because they opt not to ride a school bus and use some other form of transportation. In fact, it is far more dangerous, going to and from school, for a student to drive or ride with a parent or friend than it is to ride a school bus. People who are truly concerned about student safety should work to ensure that more than 16 percent of the children in California - the lowest percentage in the nation - ride the bus to school and from school."

The South Coast Air Quality Management District is scheduled to vote later this month on whether to ban the purchase of diesel powered school buses in the five-county air management district. The District's Feb. 21 vote on Rule 1195 is intended to expedite implementation of Gov. Gray Davis' "Lower Emisnewsion School Bus Program." a proposal to spend up to $50-million for the purchase of new school buses and retrofits of existing school buses to reduce particulate matter emissions. School bus proponents say that release of the report just weeks before the vote is a public relations gimick on the part of environmentalists.

Source: School Transportation News, February 2001.

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WASHINGTON, D.C. -- Improving air quality in urban areas, the US General Accounting Office notes, has been a long-standing national objective but achieving it comes at a steep cost to transporters. The GAO published its "Mass Transit Use of Alternative Fuels in Transit Buses" report, confirming what many have said for years: alternative fuels marginally improve air quality but the cost to purchase, operate and maintain those vehicles is lofty.

The report noted that less than 5 percent of the nation's estimated 50,000 transit buses operate on some form of alternate fuel and of those, approximately 75 percent of the full-sized transit buses are powered by compressed natural gas.

On a national scale, transit buses do not significantly affect air pollution levels since they represent only about 0.02 percent of the estimated 208 million automobiles in the United States, according to the Department of Transportation. Diesel fuel technology advances in recent years have also brought emissions from vehicles powered by that fuel closer to the levels of alternative fuels, according to the report. Transit operators across the country pay more to operate natural gas buses than they do for diesel buses. Eight of the 12 operators documented in the report use compressed natural gas. Those operators pay 15 percent to 25 percent more per bus than they do to purchase a diesel bus. The construction and maintenance of fueling stations often runs into seven digits in addition to higher maintenance and fuel costs when compared to diesel.

The report concludes that while stricter emission standards and public concerns over transit bus pollution encourage operators to utilize alternative fuel vehicles, the increased costs and reduced reliability of those vehicles serve to discourage that move, particularly with diesel fuel technology improvements.

Source: School Transportation News, February 2000.

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Engine Builders Scoff at Claims
that Diesel Poses Cancer Threat

Source: School Transportation News, May 1998.