After 12 years and four lawsuits, the Environmental Protection Agency on Monday for the first time set rules governing how much mercury and other pollutants existing cement plants can release.

The agency says the rules will cut mercury emissions by these plants by 92%, particulate matter by 92% and sulfur dioxide by 78%, saving $7 to $19 in public health benefits for every dollar in costs.

Cement plants are the United States' third-largest airborne source of mercury, after coal-fired power plants and industrial and commercial boilers, the EPA says.

Cement is made by heating limestone and clay, then grinding it to a fine powder. Mixed with water, it forms a slurry which can bind sand and gravel to make concrete, says Donald Janssen, a professor of construction engineering at the University of Washington in Seattle.

It is sometimes called portland cement because the resulting material resembles a kind of building stone quarried on the Isle of Portland in England.

In terms of the health impacts of mercury, the largest concern is that once mercury in air pollution falls to the ground and enters the water system, it is consumed by organisms which turn it into methylmercury, a highly neurotoxic substance that can damage the developing brains of children, says Gina Solomon of the Natural Resources Defense Council.

These are "really, really good standards," says Jim Pew, a lawyer with Earthjustice, an environmental legal non-profit. He filed all four of the suits for a coalition of environmental and public health groups. The new rules reduce the amount of mercury that cement plants can release to 55 pounds per million tons of cement produced, he says.

"What it really took was a new EPA administration and a White House that wanted to do the right thing," Pew says. "It's a whole lot better than 'Emit as much as you like,' which is what we had before."

The rules, although less stringent than those originally proposed, will cost the industry "several billion dollars, and require investments in pollution control equipment at a time when available capital is considerably constrained due to the state of the economy," says Brian McCarthy, CEO and president of the Portland Cement Association in Skokie, Ill.

There are approximately 100 cement plants in the nation, an estimated 10 of which, mostly older plants, might need to close because it would be too expensive to bring them into compliance with the new rules, Pew says.

McCarthy fears limits on the U.S. cement supply "could constrain the U.S. government's efforts to stimulate the economy, create jobs and rehabilitate the nation's infrastructure.

"Additionally," he says, "imports of cement, most likely from developing nations, will cause global increases of greenhouse gas, mercury and other pollutant emissions."

Elizabeth Weise