Tourist trolleys offer a breath of only slightly fresher air

The tourist ''trolleys" transporting this weekend's holiday sightseers around town now run a speck cleaner because of retrofit exhaust filters recently installed to reduce diesel emissions. But there are still miles to go before we can breathe easy.

The EPA stepped in with a $64,000 grant to the city of Boston to ease the pollution from the trolleys' black clouds of exhaust.

Diesel discharges release particulates into the air that ''go into your lungs and make you sick," according to Michael Stoddard, deputy director of the New England Diesel Initiative, an outreach and advocacy campaign to clean up diesel emissions. Research by the Clean Air Task Force shows Suffolk County is the third worst county in the nation for diesel pollution.

The grant money went to Old Town Trolleys and Beantown Trolleys, which operate 35 vehicles. (The Boston Duck Tours hybrid vehicles operate with gas, except for one diesel vehicle that did not participate in the program.) Each Old Town and Beantown trolley racks up 22,000 miles a year, according to Jim Hunt, chief of Boston's Energy and Environment Department. ''During the hot touristy season, [the retrofits] will help a lot with ground-level ozone, which is problematic," he said. However, the new filters reduce noxious particulates only by 20 percent, according to the EPA. And Beantown has not installed filters that remove particulates, which, says Stoddard, present ''the most tangible health risk." Beantown installed $1,800 exhaust gas recyclatory systems to reduce nitrogen oxide emissions, according to Larry Anzuoni Jr., vice president of Brush Hill/Beantown Trolley. But the EGR system does not cleanse particulates, said Stoddard. Old Town Trolleys has switched to ultra-low sulfur diesel fuel; Beantown has not.

MONICA COLLINS