Regulators say parts of five Indiana counties with older, coal-fired power plants don't meet a new federal standard for the pollutant that causes acid rain and aggravates respiratory ailments.
The U.S. Environmental Protection Agency says parts of central Indiana's Marion and Morgan counties, southwestern Indiana's Daviess and Pike counties and western Indiana's Vigo County exceed the agency's beefed-up sulfur dioxide standard.
That colorless gas that smells of rotten eggs contributes to the formation of acid rain that damages lakes, streams and forest ecosystems and worsens people's breathing problems.
Indiana regulators have 18 months to draft a plan detailing how the areas intend to come into compliance with the standard within five years.
An environmentalist says the pollution woes are the legacy of Indiana's overwhelming reliance on coal for power.