EPA’s Efforts to Reduce NOx

The U.S. Environmental Protection Agency (EPA), states, and local governments work as partners to reduce emissions of NOx. Reducing emissions of NOx is a crucial component of EPA's strategy for cleaner air.

Emissions standards for motor vehicles

• Since the 1970's, EPA has required motor vehicle manufacturers to reduce NOx emissions from cars and trucks. Reductions achieved through auto emissions control are significant. In the last ten years, NOx emissions from highway vehicles decreased by more than 5 percent, while vehicle miles traveled increased significantly. In a related effort, the use of reformulated gasoline has resulted in cleaner-burning engines. EPA and states continue to examine vehicle emissions-testing programs to ensure that readings accurately reflect emissions levels.

Emission standards for electric utilities

• To help reduce acid rain, EPA devised a two-phased strategy to cut NOx emissions from coal-fired power plants. The first phase, finalized in a rulemaking in 1995, aimed to reduce NOx emissions by over 400,000 tons per year between 1996 and 1999. The goal of the second phase is to reduce emissions by over 2 million tons per year beginning in the year 2000.

NOx Transport rule for 22 States

• The Clean Air Act requires states to reduce ground-level ozone. Since NOx and ozone can be transported long distances, the Act also requires “upwind” states to implement programs that will help “downwind” states meet the ozone standards. EPA issued a rule in 1998 that requires 22 states and the District of Columbia to revise their Implementation Plans to further reduce NOx emissions by taking advantage of newer, cleaner control strategies.

The rule does not mandate how the reductions are to be achieved, but gives each affected state a NOx emission target. States have flexibility in determining how to reduce emissions. The goal of this rule is to reduce total emissions of NOx by 1.2 million tons in the affected states by 2007.