CHICAGO (CBS) — Mayor Rahm Emanuel has some sharp words for the operator of two coal-burning power plants in the area.

As WBBM Newsradio 780 Political Editor Craig Dellimore reports, the plants are the targets of a proposed ordinance.

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The ordinance, backed by aldermen Joe Moore (49th) and Danny Solis (25th) would force the two coal-fired power plants operated by Midwest Generation in the Pilsen and Little Village neighborhoods to convert to natural gas, restrict their operations, or shut down within four years.

LISTEN: Newsradio 780 Political Editor Craig Dellimore reports

Mayor Emanuel isn’t necessarily endorsing those outcomes, but he does say the plant owners need to come to the table.

“One of the No. 1 reasons kids go to the emergency room in the city of Chicago is asthma-related,” Emanuel said. “But in and around – I think it’s a mile, maybe a little more – but in and around that plant, within a mile, it’s much higher than anywhere else in the city. We are paying a health care cost in the city because of that plant.”

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The mayor says there will be hearings.

The two power plants — the Crawford Station at 3501 S. Pulaski Rd., and the Fisk Generating Station at 1111 W. Cermak Rd. — have been the subject of controversy and protests for years.

Twice in the past year, protesters have been arrested for trespassing at the one of the plants. In March, six protesters were arrested for climbing a 25-foot coal pile at the Crawford plant, in a demonstration coinciding with the one-year anniversary of the BP Gulf Oil Spill.

In May, eight Greenpeace activists were arrested for climbing a smokestack at the Fisk plant. They had planned to rappel down the smokestack and paint “quit coal” on it in bright yellow paint.

In both cases, the protesters called for the closure of the power plants.

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A third power plant, the State Line Power Station just over the boundary with Chicago in Hammond, Ind., announced in May that it would close no later than June 2014.