Updated

Nine states filed a lawsuit against the federal government Tuesday, challenging new regulations they say fail to protect children and expectant mothers from dangers posed by mercury emissions (search) from power plants.

The lawsuit, filed in federal court in Washington, D.C., said the reductions announced earlier this month by the Environmental Protection Agency, do not go far enough to satisfy Clear Air Act requirements.

The reductions aim to cut mercury emissions from coal-burning power plants by nearly half within 15 years, but opponents say the plan provides an out for the worst polluters by allowing them to trade "pollution credits" (search) with cleaner plants.

"EPA's emissions trading plan will allow some power plants to actually increase mercury emissions, creating hot spots of mercury deposition and threatening communities," said Attorney General Peter Harvey of New Jersey, lead plaintiff in the case. "It's an anti-human health position. The EPA is putting private profit ahead of public health, and it's a mistake."

EPA spokeswoman Cynthia Bergman said the government has already taken steps to control mercury emissions from other sources and that the rules represent a new set of controls on "our last significant source of mercury."

She urged pregnant women and women of child-bearing age to adhere to dietary guidelines issued by the federal government and limit their consumption of certain types of fish.

Mercury from smokestacks can wind up in waterways and ultimately be consumed by humans who eat tainted fish. The toxic metal causes nerve damage, which can be harmful to children and fetuses even at low levels of exposure.

Under the EPA's plan, the government allocates a pollution limit to each state, which then places a cap on its plants. Plants that exceed the limit can buy pollution credits from plants emitting less mercury pollution than they are allowed.

The program starts in 2010. Until then, utilities do not have to do anything specifically to control mercury.

The lawsuit challenges the deadline given to power plants for compliance, and assails the EPA for exempting power plants from having to install the strictest emissions control technology available. That technology would cut mercury pollution by 90 percent, according to the New Jersey attorney general's office.

The eight other states involved in the suit are California, Connecticut, Maine, Massachusetts, New Hampshire, New Mexico, New York and Vermont.