CONCORD, N.H. – Concerned about mercury levels in the water, Maine and nine other states have asked the Environmental Protection Agency to scrap a proposed rule on reducing mercury emissions from coal-fired power plants, saying it’s not strict enough.

The states want the EPA to propose a new rule, supported by public comment, “to achieve meaningful and timely reductions in mercury emissions,” attorneys general for the group said Thursday in a letter to Mike Leavitt, EPA administrator. They also want the EPA to extend its comment period beyond the deadline, currently the end of April.

The EPA, in a statement responding to the letters, reaffirmed that Leavitt considers mercury exposure a serious health issue and is determined to complete a final regulation by year’s end that will cut those emissions from power plants by 70 percent.

The statement said Leavitt has asked for additional analysis to ensure that cutting mercury emissions is done “in the most efficient and effective way possible” given the available technology.

The letter by the attorneys general noted that mercury is highly toxic and is linked to neurological and developmental problems and endocrine disruption in people, fish and wildlife.

The EPA has been exploring options for reducing the 48 annual tons of mercury emitted from 1,100 coal-burning power plants. It is proposing the idea of trading pollution rights, rather than making each plant reduce emissions to a designated level.