Over the past several years, members of Congress have proposed "multi-pollutant" power plant bills that would mandate reductions in air emissions from the Nation's fleet of fossil-fired power plants.

Some of these proposals include all of the major pollutants and greenhouse gases generated from fossil fuel combustion: nitrogen oxides (NOx), sulfur dioxide (SO₂), mercury, and carbon dioxide (CO₂), so-called "4-P" bills.  Others are limited to just NOx, SO₂, and mercury, so-called "3-P" bills.

This page answers common questions about these multi-pollutant legislative initiatives and provides some background on the Clean Energy Group's Clean Air Policy Initiative.  More detailed information about the multi-p bills is available from our Resources page.