CHATTANOOGA (WRCB/AP) - A study issued by an environmental advocacy group ranks the four states in the Chattanooga area among the dirtiest in the nation as measured by emissions from coal-fired power plants.

Tennessee is on the list at 15th of the so-called "Toxic Twenty" according to the report which was released by the Natural Resources Defense Council and Physicians for Social Responsibility.

Alabama holds the 12th spot on the list. North Carolina ranks tenth and Georgia ranks ninth-dirtiest in the report.

Ohio, Pennsylvania, Florida, Kentucky and Maryland hold the dubious top five positions as having the dirtiest air in the nation.

The study, "Toxic Power: How Power Plants Contaminate Our Air and States," used data from the 2009 Environmental Protection Agency's Toxics Release Inventory.

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The Birmingham News reports that the study was released as the U.S. Environmental Protection Agency solicits comments on changes to toughen standards on power plant emissions.

Georgia Power officials told The Atlanta Journal-Constitution the company plans to close or convert some of its coal units and has added equipment to others to cut toxic emissions.