The city’s ferries could be forced to switch immediately to ultra-low sulfur diesel fuel and eventually reduce their emissions to 85% below federal standards. In addition, ferries would gradually have to transition to new technology that filters harmful material from the ships’ exhaust fumes under legislation in the City Council.

“It will be a great step forward for the ferries and for reducing soot, sulfur dioxide, nitrogen oxide, and other things contributing to smog. All of these are also triggers for asthma,” the chairman of the council’s Environmental Protection Committee, James Gennaro, said yesterday.

The legislation parallels a variety of laws and policies initiated by the mayor and the council to reduce emissions in city-owned and other vehicles. In 2003, the council voted to require construction vehicles and equipment owned or operated by the city to use low-sulfur diesel fuels and pollution-filtering technology. Last week, the Taxi and Limousine Commission approved Mayor Bloomberg’s plan to replace the city’s taxi fleet with hybrid cars and raise fuel standards to 30 mpg by October 2009.

“This is kind of the natural extension of what we’ve tried to do with all the other bills,” Mr. Gennaro said. “It follows nicely on the heels of the carbon reduction bill we did two weeks ago because this is how we’re going to meet these targets,” he added, referring to legislation passed recently that calls for a 30% decrease in carbon emissions citywide by 2030.

Under the bill, two of the ferries must be fitted with the filter system by July 1, and the entire fleet must be upgraded by 2010. The Staten Island Ferry’s current fleet consists of 10 boats. The cost of the proposed changes could not immediately be determined.