The EPA today is expected today to declare carbon dioxide (CO2) a dangerous pollutant, and thus hand the agency sweeping regulatory authority under the Clean Air Act (CAA).

An endangerment finding under the CAA is the first step toward regulating CO2 and other greenhouse gases. The proposed endangerment finding will be issued under § 202 of the CAA, which pertains to mobile sources. However, similar “endangerment” language exists in other sections of the CAA, thus EPA’s expected announcement today is likely the first step towards the EPA regulating stationary sources as well.

The Wall Street Journal reports that the EPA’s decision is a source of major concern for businesses, in particular manufacturers, which argue that regulating greenhouse gases under the CAA will be extremely costly.

The Obama Administration’s endangerment finding coincides with the opening of the Climate Conference in Copenhagen, where it was once expected that world leaders would sign a successor to the Kyoto Protocol. However, it appears that there will be no major treaty, disappointing many environmentalists who see Copenhagen as the last chance to lock countries into an agreement to reduced GHGs.