WASHINGTON--The U.S. Environmental Protection Agency will early next week, possibly as soon as Monday, officially declare carbon dioxide a public danger, a trigger that could mean regulation for emitters across the economy, according to several people close to the matter.

Such an "endangerment" decision is necessary for the EPA to move ahead early next year with new emission standards for cars. EPA Administrator Lisa Jackson has said it could also mean large emitters such as power stations, cement kilns,...