What is the connection between the Cross-State Air Pollution Rule and the Acid Rain Program?

The Cross-State Air Pollution Rule (CSAPR) requires certain states in the eastern half of the U.S. to improve air quality by reducing power plant emissions that cross state lines and contribute to smog and soot pollution in downwind states. EPA sets a pollution limit for each of the states covered by CSAPR. Authorizations to emit pollution, known as allowances, are allocated to affected sources based on these state emissions budgets. CSAPR and the Acid Rain Program affect power plants, and both have allowances with trading programs.