The Environmental Defense Fund, a national environmental group, recently issued its own report saying that just 1 percent of all buildings in the city  about 9,000 large commercial, residential and institutional structures  create 87 percent of the soot pollution arising from heating oil. (The group has posted a list at www.edf.org/dirtybuildings so New Yorkers can see which kind of oil their buildings burn.)

If those buildings were to burn cleaner oil, the fund’s report said, the amount of airborne pollutants they release would decline by as much as 65 percent to 95 percent.

The numbers by which heating oil is classified are based on boiling temperature, composition and other factors. No. 2 heating oil, which is cleaner but more expensive than No. 6 or No. 4, accounts for an estimated 73 percent of the heating oil burned in the city, the environmental group found.

Evan Thies, a spokesman for the group, said users of the most polluting fuels tended to be larger buildings that could accommodate huge boilers that generate the heat necessary to burn heavy oil.

The dirtiest oils can cost about 60 cents less a gallon, which has been another disincentive for buildings to upgrade their boilers. But in its report, the Environmental Defense Fund said that cleaner fuels improve the efficiency of burners and reduce operating costs, compensating for the up-front costs and the higher price of No. 2 oil.

The group, using records from the city’s Department of Environmental Protection, which approves boiler permits, points out in its report that heavy oil heats buildings in some of the wealthiest ZIP codes in the city, most of them in Manhattan.

The pollution is aggravated by diesel fuel emissions from heavy car and truck traffic in some areas. But Stuart M. Saft, chairman of the Council of New York Cooperatives and Condominiums, says the assumption that only the rich live in the buildings at issue ignores the reality that even at wealthy addresses, “there are people living on fixed incomes or on Social Security who bought their apartments 40 years ago.”