SPRINGFIELD - Illinois power companies could be on the hook for hundreds of millions of dollars in new equipment in the coming years in an attempt by Gov. Rod Blagojevich to reduce harmful mercury emissions.

In an announcement scheduled for today, Blagojevich is expected to call for companies to reduce the toxic emissions by 90 percent by 2012, which would be more aggressive than federal standards.

"This is a major victory for public health in Illinois," said Rebecca Standfield of the Illinois Public Interest Research Group, which is backing the governor's proposal.

A spokesman for Midwest Generation, which operates six coal-fired plants in Illinois, had not seen the plan but said the company is willing to work with the state to devise rules for implementing the program.

Spokesman Doug McFarlan said the cost of adding new equipment could be "potentially hundreds of millions of dollars"

Officials at Ameren Corp., which has subsidiaries operating six coal-fired plants in Illinois as well as part ownership in another, said the company is waiting to see details of the governor's plan before commenting.

The proposal, which faces a two-step approval process that will take an estimated nine months to complete, comes as Illinois and more than a dozen other states have balked at federal rules that would regulate mercury emissions from power plants. The states have argued that the federal rules are not tough enough.

If approved, Illinois would join three other states that already have put their power plants on track to capture 90 percent of the mercury emitted from smokestacks.

Coal-fired power plants are a leading source of manmade mercury in the environment. The toxin can cause learning disabilities in children and neurological problems in adults.

The federal plan would require a 70 percent reduction by 2018.

Kurt Erickson can be reached at kurt.Erickson@;lee.net or 782-1249.