Diesel-powered school buses are spewing toxic exhaust linked to lung cancer, asthma attacks, and other respiratory illnesses that threaten the health of children, according to a study released Nov. 19.

“Our children are riding buses that are so old and out of date and known to be highly polluting, but there is no action from the legislature,” said Todd Campbell, spokesman for Coalition for Clean Air, the Los Angeles-based environmental group that released the report.

The group is calling for the state to use a projected $2.6 billion budget surplus to buy new cleaner-burning natural gas buses and pump up rules for school bus emissions, Campbell said.

About 69 percent of California’s 24,372 buses use diesel fuel. Some models are more than 20 years old and are among the highest-polluting in the nation, the study says.

The group said California has nearly 1,000 buses that predate 1977. Those buses emit four times more particle soot and three times more smog-forming fumes than new natural gas buses, Campbell said.

The California Air Resources Board acknowledges the danger but has not yet formed a strategy to replace the aging fleets.

Though school bus emissions are a relatively small threat to the overall population, Air Resources Board Chairman Alan Lloyd said they pose a serious danger for the tens of thousands of children who come in close contact with the exhaust each day. Medical experts also said that children are more vulnerable to the pollutant because of their low body weight and still-developing immune-systems.

Campbell said the proposal to use the budget surplus to buy cleaner-burning buses, which could carry a price tag of more than $1 billion, has the support of two people in the state Assembly: Speaker Antonio Villaraigosa, D-Los Angeles, and Assemblyman Martin Gallegos, D-Baldwin Park.

“I think the idea is an excellent idea,” Gallegos said. “Given the governor’s statement that he wants to put education as a priority for the surplus, I can’t think of a better way to improve students’ performance and ability to learn than to provide them a healthy environment.”