Sen. Susan Collins took out her poison pen last week and used it against a real poison.

Maine’s junior senator fired off an angry letter to the Environmental Protection Agency over its new – and terrible – rules on mercury emissions.

“I am very concerned that, in developing the Clean Air Mercury Rule, the EPA failed to live up to the high standards required of an agency so vital to the well-being of our health and environment,” Collins wrote Thursday to Stephen Johnson, the agency’s acting administrator.

The EPA’s mercury rule-making has been plagued from the onset. The agency’s inspector general found that good science was replaced with political dictates. And a report last week from The Washington Post shows that evidence contrary to the desires of large power plants was purposefully omitted from the EPA’s report.

A Harvard University study, which was paid for by the EPA, co-authored by an EPA scientist and reviewed by the agency found that the costs of aggressive pollution control would be dwarfed by health benefits from stricter requirements, the Post reported. Benefits outweighed costs by 100 times.

The EPA cut the study and any information about it from its public documents.

With its new mercury rules, the EPA has failed on its mandate to protect public health from the dangers of mercury and other toxic pollutants. The political leadership of the agency was content with watered-down restrictions that put the financial interest of industry above the health and welfare of children and pregnant women.

With Collins’ letter requesting a face-to-face meeting with the new EPA administrator, we are hopeful that this short-sighted policy can be reversed. If not, a congressional investigation by the Senate’s Homeland Security and Government Affairs Committee, which Collins chairs, is necessary.

A scientist on the committee told the Sun Journal that the Environment and Public Works Committee would be the appropriate place for such an investigation. Unfortunately, that committee is headed by senators who lack Collins’ commitment to the environment and to clean air.

Collins has the authority to launch an investigation of any wrongdoing by a government agency. Disregarding its own science and procedures to reach a predetermined, politically mandated outcome should certainly qualify.

“I fail to see how the EPA can possibly maintain the appearance of propriety when a Harvard University study allegedly paid for and peer-reviewed by the EPA, and demonstrating a much higher level of health benefits than EPA’s official estimates, was apparently not even considered in the rulemaking process,” Collins wrote in the letter.

The senator’s words are strong. We hope responsive action is equally so.