Philadelphia-based PennEnvironment released the report titled "America’s Dirtiest Power Plants", with analysis based on federal data from 2011, the most recent available.

According to the report, combined power plant carbon-dioxide emissions from Pennsylvania made it the third-highest emitting state, behind Texas and Ohio.

The report said that seven of Pennsylvania’s coal-fired power plants ranked in the nation’s top 100 carbon-dioxide emitters.

The report said the seven plants were the Bruce Mansfield, Keystone, Conemaugh, Hatfield's Ferry and Homer City plants in southwestern Pennsylvania, and the Brunner Island and the PPL Montour plants in central Pennsylvania.

The group is calling on state senators Bob Casey and Pat Toomey to advocate for state-level strategies to enforce limits on carbon-dioxide emissions from coal-fired power plants.

US President Barack Obama wants his Environmental Protection Agency to draft regulations for existing power plants by next June, and new power plants by the end of the month.

“Pennsylvania is the third-biggest emitter of carbon pollution from the biggest sources. We can’t afford to wait to act on climate, so it’s critical that Senator Casey and Toomey step up and support action now,” PennEnvironment Research & Policy Center spokeswoman Elowyn Corby said.

“America's dirtiest power plants are the elephant in the room when it comes to global warming.”

However, since 2011 when the federal data was collected, Pennsylvania power plant owners have announced plans to close or convert at least eight of the state's approximately 36 coal-fired power plants, including Hatfield’s Ferry.