Topeka ? The EPA’s official declaration that greenhouse gases, such as carbon dioxide, pose a public health threat and should be regulated is another reason to abandon Sunflower Electric Power Corp.’s proposal to build two 700-megawatt coal-burning electric plants in southwestern Kansas, environmentalists said Friday.

“Sunflower’s project becomes more and more risky, and all indications are new coal plants will be a substantial burden for ratepayers and will hinder our state’s ability to move forward with today’s clean-energy technologies,” said Stephanie Cole, a spokeswoman for the Kansas chapter of the Sierra Club.

Supporters of the project say that the plants will be among the most clean-burning coal-fired units in the country, and that they will stimulate the economy.

The Legislature has approved four bills that would require the state to grant permits for the project, but Gov. Kathleen Sebelius has vetoed each of them, including one last week.

Lawmakers return April 29 and are expected to try to override the latest veto.

Officials with Hays-based Sunflower had no immediate response to the EPA action. EPA Administrator Lisa Jackson said the Obama administration wants Congress to approve a “cap and trade” system to limit greenhouse gases.