A federal appellate court in Washington, D.C. ruled today that the U.S. Environmental Protection Agency failed to justify its lax approach to setting emission standards for medical waste incinerators.

“Medical waste incinerators are among the most substantial emitters of mercury, dioxins, and other harmful air pollutants,” said Howard Fox of Earthjustice Legal Defense Fund, which handled the suit on behalf of the two plaintiffs, Sierra Club and Natural Resources Defense Council. “It is crucial that emissions be well-controlled, so that our already excessive exposure to these persistent toxins is not further increased.”

Dioxin is the most potent carcinogen ever evaluated by EPA. Mercury is known to damage the central nervous systems of unborn babies and children, resulting in symptoms similar to congenital cerebral palsy. Even small amounts of these pollutants can cause cancer or similarly tragic health effects. “These pollutants are so toxic that exposure is measured in billionths and trillionths of a gram,” said Fox.

Dioxin and mercury both bioaccumulate (i.e., accumulate in fatty tissue, and increase in concentration as they move up the food chain). Thus any increase in these pollutants is magnified in humans, who occupy the top of the food chain. EPA has concluded that 1% to 3% of all women of childbearing age are presently at risk of bearing children with irreparable birth defects as a result of mercury contamination in the fish they eat.

In addition to dioxin and mercury, medical waste incinerators emit several other harmful pollutants such as lead, cadmium, hydrogen chloride, and particles.

In 1990 Congress revised the Clean Air Act to require EPA to write regulations limiting medical waste incinerator emissions. Congress directed that the regulations require, at a minimum, the degree of emission control achieved by the best performing sources. Specifically, in the case of existing incinerators, standards were not to fall below “the average emissions limitation achieved by the best performing 12 percent of units,” and in the case of new units, were not to fall below “the emissions control that is achieved in practice by the best controlled similar unit.”

The emission floors underlying EPA’s standards, however, were based on the performance of the worst units, not the best. As a result, EPA’s standards would allow pollution levels that could be controlled substantially better through application of available technologies. Indeed, the rules would allow medical waste incinerators to emit sufficient dioxin to contaminate the entire U.S. population with more than sixty times the agency’s estimated reference dose for that pollutant.

The court expressed “serious doubts” about the reasonableness of EPA’s approach, and ruled that “EPA’s method looks hopelessly irrational.” The court sent the rule back to the agency for further explanation. In the meantime, the challenged rule will remain in effect, so as not to “eliminate any federal control at all” during the period of EPA’s reconsideration.

“The court’s ruling recognizes a simple point of common sense that EPA tried to deny: the worst is not the best,” said Fox. “We are hopeful that the agency will now turn seriously to the task of protecting mothers and children from toxic, persistent emissions of dioxins and mercury.”

The ruling was issued by the United States Court of Appeals for the District of Columbia Circuit in Sierra Club and Natural Resources Defense Council v. USEPA, No. 97-1686.

Earthjustice Legal Defense Fund is a non-profit, public interest, environmental law firm that employs approximately 50 attorneys in nine offices across the country. The group has headquarters in San Francisco and field offices in Juneau, Honolulu, Seattle, Denver, New Orleans, Tallahassee, Washington, D.C., and Bozeman, Montana.