New York City\'s cleanest air in 50 years is preventing nearly 800 deaths and 2,000 emergency room visits annually, the mayor says. Mayor Michael Bloomberg said New York City\'s air quality is the best its been in more than five decades, with dramatic reductions in airborne pollutants. Since 2008, the level of sulfur dioxide in the air dropped 69 percent and since 2007 the level of soot pollution dropped 23 percent. Since the beginning of the administration\'s comprehensive, long-term sustainability blueprint -- PlaNYC -- the city\'s most heavily polluting heating oils were phased out. \"As Mayor Bloomberg often says, \'you can\'t manage what you can\'t measure\' and that\'s why five years ago we set up a ground-level monitoring system that found heavy heating oil was one of the most serious sources of local air pollution,\" Deputy Mayor Cas Holloway said. \"This enabled us to craft regulations to phase out heavy oil with broad stakeholder support and to develop a data-driven, innovative program to assist building owners in converting to cleaner fuels, leading to the dramatic improvement in air quality that we see today.\" The cleaner air is preventing hundreds of deaths, and thousands of hospital emergency room visits and hospitalizations, from lung and cardiovascular diseases annually, compared with 2008, the city health department said. \"Air pollution poses a major threat to the health of all New Yorkers, but especially young children, seniors, and those with chronic heart and lung disease,\" said Dr. Thomas Farley, the city\'s health commissioner. \"Switching to cleaner heating fuels is contributing to dramatic improvements in the air quality of New York City and will help all of us stay healthier.