The ruling is a setback for environmentalists who have been pushing the city to reduce its dependence on the Wheelabrator incinerator, and to cut ties with it when its contract to supply waste to the facility expires at the end of 2021. The 35-year-old incinerator is the largest single source of air pollution in the city, and critics say its emissions contribute to high rates of asthma and other respiratory diseases in low-income neighborhoods that surround the facility.