The Cross-State Air Pollution Rule (CSAPR) is a rule by the United States Environmental Protection Agency (EPA) that requires member states of the United States to reduce power plant emissions that contribute to ozone and/or fine particle pollution in other states.
[1][2] The EPA describes this rule as one that "protects the health of millions of Americans by helping states reduce air pollution and attain clean air standards.
"[1] The CSAPR requires 23 United States states to reduce their annual emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) to help downwind states attain the 24-hour National Ambient Air Quality Standards, and 25 states to reduce ozone season nitrogen oxide emissions to help downwind states attain the 8-hour NAAQS.
Group 1 is required to make additional emissions reductions by 2014.
[2] The CSAPR has been defended by environmental groups such as the Environmental Defense Fund,[11] progressive think tanks such as ThinkProgress,[12] and publications such as the Huffington Post.