WASHINGTON (AP) — The EPA is clamping down on pollution from power plants in 27 states that contributes to unhealthy air downwind.

EPA Administrator Lisa Jackson announced the final rule Thursday. The regulation will clean up smog, soot and acid rain in downwind states — where they add to locally produced pollution, making it impossible for those states to meet air quality standards.

The rule differs from one proposed in July. Power plants in the District of Columbia and five states — Delaware, Connecticut, Florida, Louisiana and Massachusetts — will no longer have to control for two pollutants — sulfur dioxide, responsible for acid rain, and nitrogen oxides, which contribute to smog and soot.

The regulation replaces a 2005 Bush administration proposal that was rejected by a federal court.