Clean Air Markets
The Acid Rain Program (ARP) and Clean Air Interstate Rule (CAIR) programs significantly reduced sulfur dioxide (SO₂), annual nitrogen oxides (NOₓ), and ozone season NOₓ emissions. These reductions occurred while electricity demand (measured as heat input) remained relatively stable, indicating that the emission reductions were not driven by decreased electric generation.
These emission reductions are a result of an overall increase in the environmental efficiency of these sources as power generators installed controls, ran their controls year-round, switched to lower emitting fuels, or otherwise reduced their SO₂ and NOₓ emissions while meeting relatively steady electricity demand. Most of the emission reductions since 2005 are from early reduction incentives and stricter emission cap levels under CAIR.