President Bush’s choice to head the Environmental Protection Agency isn’t likely to face real opposition from Congress, but Steve Johnson, a longtime EPA staffer, should expect lots of questions from Maine’s senators. They should expect detailed answers.

Although it is clear the Bush administration is moving forward with rules that weaken many environmental protections, it is important that these changes get as much scrutiny as possible. Sens. Olympia Snowe and Susan Collins have long histories of providing such scrutiny and they should continue to do so.

The senators will likely ask why the administration proposed rules on mercury pollution that are not as stringent as possible, especially in light of last month’s report from EPA’s inspector general finding that the proposed mercury rules were developed by working backward from a predetermined standard favored by industry. The rule, announced Tuesday, calls for a 70 percent reduction in mercury emission by 2018. In 2001, the agency estimated that mercury emissions could be reduced by 90 percent if the best available technology were used.

Sen. Snowe joined with Sen. Patrick Leahy of Vermont in writing to the EPA last week to express their opposition to the mercury rules. “EPA’s mercury proposals fell far short of what the law requires and that the proposed approach fails to protect the health of our children and our environment,” the senators wrote.

Currently, 45 states have fish warnings for mercury, and EPA and the Food and Drug Administration warn women of childbearing age, nursing mothers and young children from eating more than six ounces a week of fish caught in local waterways. In Maine, 19 rivers and lakes have been under such advisories for a decade.

The senators should want to know how the EPA can continue to support the president’s Clear Skies package, which was held up by a committee deadlock, when the existing Clean Air Act and other proposals would result in bigger and quicker reductions in pollution. The Clean Power Act, sponsored by Sen. Collins, would set a more rigorous timetable and allow for more local control, an important issue for Maine, which has had to go to court to try to compel the EPA to enforce existing pollution regulations.

On the issue of climate change, they will wonder why the administration has been slow to fund research into its causes and consequences. The Climate Stewardship Act, sponsored by Sen. Snowe, would set up a cap-and-trade system to reduce emissions of carbon dioxide, the most prevalent greenhouse gas. It would require the head of the Environmental Protection Agency to develop rules to reduce emissions from the electricity generation, transportation, manufacturing and commercial sectors, which account for 85 percent of U.S. greenhouse gases.

Mr. Johnson is in the unenviable position of taking over an embattled agency in the midst of congressional wrangling over a cornerstone of the administration’s pollution policy. Given the importance of recent and impending regulatory decisions, senators would be remiss if they didn’t take this opportunity to express their concern and, often, displeasure with the agency’s direction.