Addressing a September 26 Climate Week NYC event, Mayor Michael Bloomberg (D) said air quality for the city has reached its best level in 50 years. He tied the improvement to a phase out of heavy polluting heating oils under the 2007 PlaNYC initiative. Since 2008, sulfur dioxide levels have fallen 69 percent, nickel levels have dropped 35 percent, and small particulate matter levels have dropped 23 percent.