The Environmental Protection Agency is charged with proposing by the end of the year mercury emission levels for coal-fired power plants using a standard called maximum achievable control technology, under the Clean Air Act. But because the White House wants to emphasize its weaker Clear Skies plan, according to an administration official, it has directed the EPA not to model this tougher standard, preventing the agency from determining what the new mercury emission level should be.

Maine’s congressional delegation, acutely aware of the air-pollution problems caused to the Northeast by these power plants, should urge the president to reverse his position on this and let his agency meet the regulatory deadline with accurate and complete data.

Mercury is one of a range of smokestack toxins the EPA is directed to regulate under the Clean Air Act.

The agency also examines hydrogen chloride, lead, cadmium, dioxin and others, but mercury is a major concern because of the amount emitted, currently around 48 tons annually, and its health effects, which can include damage to the central nervous system and presents serious health risks to pregnant women and children.

Mercury pollution is a worldwide problem. In the United States, according to the National Wildlife Federation, it has contaminated 10.2 million acres of lakes, estuaries and wetlands and 415,000 miles of streams, rivers and coasts. The Clear Skies plan, as it does with other air pollutants, sets a lower threshold for mercury than the act demands.

Maximum achievable control technology (MACT) is a measurement of the average performance of the top 12 percent of an industry and could drop the amount of mercury emissions to as low as 5 tons annually, a 90 percent reduction, according to one scenario considered by the EPA. The agency’s modeling would refine earlier estimates and propose a goal to be met by the end of 2007. The Bush administration wants to delay any reductions until 2010 and allow at least 15 tons through at least 2018. Worse, through a program that would allow plants below the allowable pollution levels to sell pollution credits to those above the level, local mercury deposition could be more intense in some areas, and the bankable nature of the credits means that actual reductions could be put off even beyond the dates in the Clear Skies plan.

Last August 44 senators, including Sen. Susan Collins, as the lead Republican, and Sen. Olympia Snowe, noted in a letter to EPA Administrator Christine Whitman that the administration’s New Source Review – rules governing modifications and expansions of power plants – were going forward without adequate analysis. The letter asked that, “EPA conduct a rigorous analysis of the air pollution and public health impacts of the proposed rule changes…” The senators are still waiting. They should not be so patient this time.

The EPA cannot propose a reasonable standard for mercury emissions this year unless it does the modeling needed to complete its work. Congress should not tolerate obstruction from the White House in this pursuit. Sens. Snowe and Collins both have pushed legislation to clean up these plants, which foul the air in the downwind states of the Northeast, so their voices are especially important on this issue. They should help the EPA do its job more effectively now by ensuring the agency is directed to develop scientifically sound and complete data on this hazardous air pollutant.