Michigan and eight other states sued the Bush administration Tuesday, saying the White House failed to adequately regulate emissions of mercury and other pollutants at cement plants.
The states contend a rule issued by the Environmental Protection Agency in December does not comply with the federal Clean Air Act.
Mercury comes from raw materials used to make cement — such as limestone, clay, sand and iron ore — and from fuels such as coal, which fires the kilns where the ingredients are baked at high temperatures.
In December, the EPA announced new limits on mercury and hydrocarbon emissions from cement kilns built after Dec. 2, 2005.
But for kilns built earlier, the agency imposes lesser requirements such as operating kilns properly to ensure complete combustion and removing kiln dust when it can no longer be recycled.
Critics say the Clean Air Act requires the EPA to limit mercury from all kilns, not just new ones.
"I think they should have explored some of the options a bit more in detail than they did," said Vince Hellwig, air quality chief with the Michigan Department of Environmental Quality.
The lawsuit was filed in the U.S. Court of Appeals in the District of Columbia, where several environmental groups filed a separate action last week. The other eight states are Connecticut, Delaware, Illinois, Maryland, Massachusetts, New York, New Jersey and Pennsylvania.
EPA spokesman John Millett said the matter was under review and declined to comment further.
The agency says it has reduced mercury air emissions by 45 percent since 1990. It estimates the nation's 118 cement plants give off a combined 12,000 pounds of mercury a year, although some state regulators say the actual amount is higher.