Updated 4:39 p.m.
The U.S. Environmental Protection Agency has announced the first-ever national standards for air pollution from power plants.
The rule will require Ameren and other electricity companies to reduce emissions of toxic pollutants like mercury and arsenic, which can cause developmental effects, cancer, asthma, and other serious health problems.
EPA Regional Administrator Karl Brooks in Kansas City says the health savings will far outweigh the cost of compliance.
"If you take a look at just our part of the country here in the Midwest, expectations are that somewhere between $3 billion to $7 billion in health benefits will be enjoyed by people in terms of doctor's visits they don't need, hospital admissions they don't have to have, days of work and school they don't have to miss," Brooks said. "So that's real dollars and cents."
Ameren's Vice President of Environmental Services, Mike Menne, says all of Ameren's Missouri power plants will need new pollution controls.
Menne says bringing those plants into compliance will cost hundreds of millions of dollars - a cost that will eventually drive up rates to consumers.
"It's really difficult to say what the impact might be on rates, because we're talking three to five years down the road when these costs will actually be incurred," Menne said. "But it obviously is going to force some upward pressure in our electric rates."
Power plants have until 2016 to get into compliance.