Unlike many states, California does not require bus owners to take buses off the road after a set number of years. As a result, California has some of the oldest buses in the nation.
The emissions from older school buses are harmful to both children and air quality for the broader community.
Children riding in conventional diesel school buses are exposed to more air pollution than those riding in cleaner natural gas or low emission diesel buses, according to a 2003 study conducted by the California Air Resources Board.
Buses manufactured before 1990 can pollute as much as six times more than new buses, according to the Environmental Protection Agency. There are about 3,000 buses in the state built in the 1980s and earlier, according to a California Watch analysisof data maintained by the California Highway Patrol.
Some buses have been equipped with filters that greatly reduce the harmful health effects, but buses that are more than two decades old often can't be retrofitted because the pollutants clog the filters or the engine. The CHP data doesn't indicate which buses – with a combined capacity to carry about 190,000 students each day – have been modified.
Newer buses also have additional safety features such as seat belts and additional emergency exits.
The state Department of Education referred a request for comment to the California Air Resources Board.
As part of a new state regulation that's currently being phased in, the California Air Resources Board is requiring districts to add filters that trap harmful pollutants to all buses or take them off the road by 2018.
The goal of the regulatory changes has been to protect children's health, said Lisa Jennings, an air pollution specialist at the California Air Resources Board.
While the retrofits can help reduce emissions, some critics argue that they're a costly, short-term solution. Although retrofits cost less than a new bus initially, they come with additional maintenance costs and don't remove as many emissions, said Stephen Rhodes, a legislative advocate for School Transportation Coalition.
"The reason we went to retrofits is there is not enough to funding to replace all the buses in California," Jennings said.
Funding is tight for school transportation. Earlier this year, Gov. Jerry Brown proposed cutting all state funding for school transportation, but the money was ultimately restored.
Despite the fiscal climate, some school districts have found innovative ways to get old buses off the road.
Kings Canyon Unified School District recently unveiled the first electric school bus in the country. The district is in the Central Valley, where air quality is ranked among the worst in the nation. John Clements, director of transportation, has made it his mission to upgrade his school bus fleet and said he's brought in about $10 million in grant money since 1993.
"Back in the '60s and '70s, districts had budgeted school bus replacement programs," he said. "That's not the case under our stiffer fiscal situations. It would be rare to find one."
While he's tried putting filters on his buses, he said they can make the buses less reliable. "I can't send them on field trips outside the district because I run the risk of them plugging up and the light turning on, which means the bus can actually shut down," Clements said. He prefers to replace the buses when he can.
An average filter costs about $17,900, while a new bus can cost about $150,000. Clements estimated the new electric bus costs about $230,000, although he was able to access more funding sources than he would have for a traditional bus.
Seven years ago, there were almost 6,000 school buses in use that were manufactured before 1990, said Cassandra Hockenson, a spokeswoman for the Air Resources Board. "We are making progress in updating the California school bus fleet," she said.
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Story courtesy of our media partners at California Watch (A Project of the Center for Investigative Reporting)