The New York Independent System Operator (NYISO) has issued a briefing paper that claims power plants in the state significantly reduced emissions of three pollutants over a 10-year period. The paper asserts that sulfur dioxide emissions declined by 82 percent from 1999 to 2009, while nitrogen oxide emissions declined by 62 percent and carbon dioxide by 31 percent.  

NYISO is a not-for-profit company governed by a 10-member independent board of directors responsible for nearly 11,000 miles of higher-voltage transmission lines and more than 500 electric power operators in New York. According to the briefing paper, New York power plants nationally ranked ninth cleanest in carbon dioxide emissions, 13th cleanest in nitrogen oxide emissions and 12th cleanest in sulfur dioxide emissions. The briefing paper contains graphs showing the emission declines in New York and comparative rates in other states.