Retrofitting to trap particulates, burn cleaner fuel means less noxious exhaust.

One ride to school, hold the exhaust.

School bus emissions have gotten cleaner, through a recently completed retrofit of some Bainbridge Island School District vehicles using cleaner-burning fuel.

“You don’t see the black stuff (in the exhaust),” Bainbridge school bus driver Bill “Mr. Bill” Ehrhardt said. “Just mostly transparent, and it doesn’t smell as bad. It’s like walking behind a regular car – smells better than unleaded gas.”

Thanks to the state’s Clean School Bus Program, 10 Bainbridge Island School District buses and 12 Bremerton School District buses have been retrofitted to emit fewer fine particles in their exhaust, emissions that studies show contribute to asthma attacks and other health issues in children.

The fleet also started running on an ultra-low-sulfur diesel fuel last September, ahead of the EPA requirement to use such fuel by 2006.

Although ultra-low-sulfur diesel costs 10 cents more per gallon than regular diesel, the school district opted to adopt the fuel early.

“We have a community that cares about the environment, and supports us caring for the environment when given the opportunity to choose to do so,” said Camilla Dombkowski, transportation manager for the district.

Fine particle emissions from retrofitted buses will drop as much as 50 percent, while the cleaner fuel reduces carbon monoxide by 40 percent and hydrocarbons by 50 percent.

The opening of a facility in Tacoma brought down the price of the ultra-low-sulfur fuel, and the Clean Bus Program allowed the Bainbridge district to retrofit its 10 oldest and most heavily polluting buses.

The relatively cheaper diesel oxidation catalyst retrofit targets older buses. Newer buses will receive the more expensive diesel particulate filter which can capture 90-95 percent of harmful fine particles.

Eleven Bainbridge buses will be fitted with the diesel particulate filter next school year under the program.

A federal Environmental Protection Agency mandate will require the manufacture of low-polluting buses by 2007, but since school districts such as Bainbridge keep buses for 20-25 years, retrofits will provide a cleaner ride now, rather than years down the road.

For district-operated mini-buses not covered by the Clean Bus Program, Dombkowski says the district is looking at less expensive particulate filters. They normally run $7,500 each.

Diesel exhaust is a serious health matter. A 2002 report by the non-profit outfit Environment and Human Health, commissioned by Connecticut public schools, found that of the 500 million pounds of particles released by motor vehicles each year, about 60 percent is emitted by diesel engines.

Such emissions also have a higher concentration of very fine particles, which penetrate most deeply into the lungs of children, who have small airways.

The study estimated that children in school buses are exposed to particulate concentrations sometimes 5-15 times higher than normal background levels.

The Puget Sound Air Toxics Evaluation, released by the Puget Sound Clean Air Agency in 2003, found that up to 70 percent of cancer risk from air toxics in Puget Sound come from diesel exhaust.

On Bainbridge Island, 1,900 children ride buses each school day; the 31 buses covered 307,000 miles in 2001. Ehrhardt says that although the cleaner fuel is expensive, he’s happy the school district made the switch.

“I think it’s a good thing for all and the environment,” he said.