US school buses could pose unacceptable cancer risks

A new report has found evidence that diesel school buses expose passengers with exhaust levels up to 46 times higher than those considered a significant cancer risk by the EPA.

Currently more than 23 million US children ride a diesel school bus, the most commonly used kind, to school, but a report released on 13 February by the NGOs Natural Resources Defense Council (NRDC) and Coalition for Clean Air has cast shocking aspersions on the traditional ride. It says that 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 Environmental Protection Agency (EPA) and federal guidelines. No Breathing in the Aisles: Diesel Exhaust Inside School Buses also shows that children who ride a diesel school bus may be exposed to up to four times more toxic diesel exhaust than someone travelling in a car directly in front of it.

“Children are especially sensitive to environmental hazards, yet they’re the ones getting dosed with diesel riding to school,” said Gina Solomon, a senior scientist with NRDC, a national NGO dedicated to protecting public health and the environment.. “The levels we measured on some of these buses both surprised and worried us. Worse still, we have reason to believe that these high levels are fairly typical.”

Researchers from NRDC, the UC Berkeley School of Public Health and the California-based NGO, Coalition for Clean Air, rode rented school buses along actual elementary school bus routes in the Los Angeles area. Using sophisticated equipment to continuously sample the air inside the buses for diesel exhaust, they compared air quality inside the front and back of the bus and with the windows open and closed. They also tested air quality outside the bus and in a passenger car travelling ahead of it. Buses were tested while idling, climbing or descending hills, and travelling slowly with frequent stops.

The nearly 20 hours of sampling results on four school buses produced dramatic results, they said. Assuming bus rides totalling 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 NGOs said. This level of cancer risk is 23 to 46 times the level considered to pose a significant cancer risk by the EPA under the federal Clean Air Act and the Food Quality Protection Act.

Under California’s Safe Drinking Water and Toxic Enforcement Act, it also could trigger an obligation to provide warnings to children that they are being exposed to a cancer-causing chemical. “Parents have a right to expect their kids will have a healthy and safe ride to school every day, but our monitoring results tell a different story,” said Gail Ruderman Feuer, NRDC senior attorney. “We were troubled to learn that kids are getting more toxic diesel exhaust inside the school bus than outside, even if it’s not a ‘smoking’ diesel bus. These monitoring results teach schools a tough lesson – they need to clean-up their bus fleets in order to protect the health of their kids.”

Increasing numbers of health authorities, including EPA and the state of California, have recognised the cancer-causing effects of diesel exhaust as well as it being a major source of asthma-producing fine particles. In addition, NOx also emitted from diesel engines in large quantities, have recently been linked to decreased lung function growth in children, it says.

The vast majority of the nation’s school bus fleets still run on diesel fuel with many including large numbers of buses that are over 10 years old, which are much more polluting than the diesel buses manufactured today. Some fleets, including those in California, Washington and Texas, even include buses manufactured prior to 1977, before federal highway safety standards were adopted, the groups say.

Cleaner alternatives to diesel buses, such as those that run on natural gas and propane, are however, starting to used nationwide. NRDC says that there are currently 2,600 such buses in school use and federal, state and local governments have begun to set aside funds earmarked exclusively to help public and private school fleet operators cover the incremental costs of purchasing such vehicles.

“School districts can reduce a child’s exposure to smog-forming chemicals by as much as 43% and toxic particles by another 78% just by making a switch to alternative fuel school buses,” said Todd Campbell, policy director for the Coalition for Clean Air. “Diesel school buses remain the dirtiest option available on the market today.”

Interim solutions exist in the form of particulate traps and low-sulphur diesel fuel, NRDC says, adding that the latter is only currently available in California, New York City and Houston, Texas, and it will not be required nationally until 2006. Last year the EPA proposed a 97% reduction in the sulphur content of diesel fuel (see related story). The NGOs recommend that bus operators improve air quality by keeping the windows open on the bus where possible and seating children closer to the front of the bus before seating children in the rear.

The South Coast Air Quality Management District, meanwhile, will soon decide whether to force Southern Californian local school districts to only purchase alternative fuel school buses.

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