WASHINGTON -- Four leading medical, health care and public health groups will continue their legal challenge of three clean air mercury rules from the U.S. Environmental Protection Agency (EPA) by filing a brief in a lawsuit now assigned to the D.C. Circuit Court.

The groups will ask the court to overturn the weak EPA rules, which they claim threaten public health. The organizations, representing more than 300,000 health professionals, are the American Academy of Pediatrics (AAP), American Nurses Association (ANA), American Public Health Association (APHA) and Physicians for Social Responsibility (PSR).

The groups say many Americans are exposed to unsafe levels of methyl mercury from environmental sources, including power plant emissions. Methyl mercury emissions from coal-fired power plants make up more than 40 percent of all such emissions into the U.S. environment, making power plants the single largest source of uncontrolled mercury pollution in the United States.

The Clean Air Act requires the EPA to make public health its first and only priority, and the law mandates that these plants reduce their mercury pollution by up to 90 percent of current emission levels by 2008.

However, the EPA's final mercury rule delays significant mercury reductions for 10 to 15 years longer than the federal Clean Air Act requires.

This is the latest legal action in a series of challenges by the organizations to ensure clean air for all Americans, including children. John Suttles of the Southern Environmental Law Center is representing the groups. One lawsuit covers three EPA rules, and oral arguments in the case are expected sometime next summer or fall.