Diesel Pollution and Our Health

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Hotline, Spring 2002

by Rachel Filippini, GASP Executive Assistant

Almost all of us have had the unfortunate occasion of sitting behind an idling bus or truck while driving. If you have, then you’ve probably noticed the noxious fumes (diesel emissions) that make it difficult to breath. While it might cause your eyes to water and a headache to form, do you know how unhealthy diesel emissions really are? Diesel exhaust is a hazardous substance that has been linked to cancer and respiratory disease, especially after repeated exposure. The cancer risk from diesel emissions is about ten times higher than the cancer risks from all other hazardous air pollutants combined (in the United States).1

Did you know that even though trucks and buses make up less than 2 percent of highway vehicles and account for less than 6 percent of the miles driven each year, they are responsible for one-quarter of the smog-causing pollution from highway vehicles, over half the soot from highway vehicles, and consume over one-tenth of America’s oil? Today’s diesel trucks emit more soot and smog-forming pollution for every unit of energy they burn than a coal-fired power plant. Even worse, according to a recent study by the Health Effects Institute, more than 98% of the particles emitted from diesel engines are fine particles, less than 1 micron in diameter.2 These are especially hazardous because they can bypass respiratory defense mechanisms and lodge deep in the lungs. Studies by Harvard University’s School of Health and the American Cancer Society have established strong links between cardiopulmonary diseases (such as heart attacks, strokes and asthma) and fine particles less than 2.5 micrometers in size (1/50 the diameter of a human hair).

Diesel exhaust not only contributes to ozone formation and the production of fine particulates, it also is a global warmer. Heavy-duty trucks alone emit almost 400 million metric tons of heat-trapping gases annually, accounting for about 6 percent of US carbon emissions.

Over 40 individual chemical compounds in diesel exhaust have separately been listed as Toxic Air Contaminants (TACs) and many of these chemicals are also identified by EPA as compounds that cause cancer. In a study of the cancer risks from diesel in the 20 largest metropolitan areas in the United States, conducted by the State and Territorial Air Pollution Program Administrators and the Association of Local Air Pollution Control Officials, in March of 2000 there were an estimated 1,210 cancers from diesel particulates in Pittsburgh.

GASP is particularly concerned about school buses (nearly 442,000 nationwide), the vast majority of which are powered by diesel fuel. Over 23 million children rely upon these school buses to carry them safely to school. Children are among the most susceptible to the health effects of diesel exhaust exposure for many reasons. One is that their developing bodies are less capable of defending themselves against pollutants, such as fine particles, which can harbor in the lungs. Children also typically have a faster metabolism and breathe at twice the rate of an adult, thereby receiving and retaining greater doses of pollution. In addition, children tend to breathe through their mouths, bypassing the natural filtration protection of the nose. A final reason is that children tend to spend more time outdoors, especially when air pollution levels are at their peak. Numerous public health studies have linked diesel soot to missed school days, asthma hospitalizations, chronic bronchitis, pneumonia, heart disease, and even premature death.

According to results of a study designed by the Natural Resources Defense Council (NRDC) and the U.C. Berkeley School of Public Health to test levels of diesel exhaust inside school buses, a child sitting in the back of a school bus with the windows closed would receive an average exposure to diesel exhaust that is up to 4 times greater than a child riding in a passenger car immediately ahead of the same bus. A child riding a diesel school bus may be exposed to 23 to 46 times the cancer risk considered “significant” by EPA and under federal environmental laws.3 Diesel exhaust is believed to exacerbate asthmatic conditions, and while children make up only 25% of the population, they account for nearly 40% of all asthma cases. Research also indicates that diesel exhaust may increase vulnerability to allergens. Minor allergic reactions, to pollen for instance, may turn into major inflammatory and allergic responses when pollen and diesel exhaust exposures occur together.

Is there any hope in sight? Yes, there are cleaner, reliable alternatives to today’s dirty diesel powered engines. Currently, cleaner alternative fuels include natural gas and propane. In the future they may include hybrid-electric, battery-electric and fuel cell-powered buses. Using a statistical model based on Mobile 5, the traditional math model used to estimate emissions, the DEP estimated the average annual emissions reductions from 95 Compressed Natural Gas (CNG) vehicles used by seven transit authorities. The DEP found that their use reduced emissions of NOx, CO and VOCs by a collective total of 165.31 tons each year. They also found that 63 dedicated CNG school buses operated by a school district in Montgomery County, Pennsylvania, show NOx, VOCs and CO reductions of 85.4 tons per school year. Could this be a reality in Allegheny County as well? One conventional diesel-run school bus emits soot equal annually to 130 cars. By changing the fuel to natural gas the soot emitted could be reduced to the equivalent of 22 cars.4 Even though the initial cost of a CNG school bus is more than a diesel school bus, many fleet managers who operate CNG fleets have reported that operational and maintenance costs tend to be lower than for a similar fleet operating on diesel. This is primarily due to CNG being a cleaner-burning fuel that requires fewer oil changes and less overall maintenance.

In 1992, the Alternative Fuel Incentive Grant (AFIG) program was established to promote the use of alternative fuels, develop a refueling infrastructure and stimulate alternative fuel vehicle research and development in PA. The AFIG program is administered by PA DEP and is available statewide. Schools, municipal and transit authorities, local governments, non-profits, private businesses and individuals are eligible to apply for grants to purchase alternative fuel vehicles, to convert gasoline and diesel vehicles to alternative fuel use, to install a refueling infrastructure, and to support research, development and demonstration of advanced alternative fuel vehicle technologies. To date, $19 million has been awarded to 260 projects in 34 counties. Another opportunity to apply for grants will come in August 2002, with an October 1st deadline.

Alternatives to the dirty diesel-powered school bus are a necessity, not a luxury or something we can put off any longer. Our children’s health is at stake and so is the environmental health of our earth. In Allegheny County, 84% of the cancer risk from air pollution is from mobile sources, which include both onroad vehicles (cars, trucks and buses) and offroad equipment (ships, airplanes, agricultural and construction equipment). These startling statistics require action. The alternatives are available, we just need to take advantage of them.

GASP, along with the Clean Air Council, will be co-sponsoring the Pittsburgh Diesel Conference on Thursday, June 6 from 9 am to 3 pm at the Pittsburgh Marriott City Center. The conference is targeted to fleet managers; however, the general public is welcome to attend. There is a $15 registration fee. For more information please contact GASP at (412) 441-6650. Next fall, GASP will present a lecture on diesel as a member of Pittsburgh Women Act at the Rachel Carson Institute at Chatham College.

1. www.scorecard.org/en-release/def/hap_diesel.html

2. No Breathing In The Aisles Report, January 2001: www.nrdc.org/air/transportation/schoolbus/sbusinx.asp

3. Ibid.

4. Rolling Smokestacks report: www.ucsusa.org/transportation