Tinsley's report said EPA staff discussed various scenarios to justify the "predetermined target."
"They didn't want to outperform their Clear Skies legislation," said John Walke, clean-air director for the Natural Resources Defense Council, an environmental advocacy group. He argued that the flat reduction approach was deliberately designed to look worse than the cap-and-trade solution. If the flat reduction seemed "better than Clear Skies, the public would see it was being shortchanged by a decade."
In a back-and-forth rebuttal at the end of the report, the EPA's assistant administrator for air and radiation, Jeffrey R. Holmstead, disagreed sharply with Tinsley's conclusions, and described her report as inaccurate and flawed.
"The report characterizes the process as incomplete before it is even finished," said Bergman, the spokeswoman.
Bergman did not dispute that administrators settled early on the 34-ton mercury limit, but she said the target had been chosen after considerable work had been expended by the agency in developing the Clear Skies initiative.
"It's not biased," Bergman said. "It factors in the status of mercury control technologies, what works for specific coal types, and we don't want to trigger massive fuel switching. The Clean Air Act allows us to consider those things."
Scott H. Segal, a spokesman at the Electric Reliability Coordinating Council, said that more ambitious targets would have prompted power plants to switch from coal to natural gas, "which is pretty hard on the elderly and those living on fixed incomes."
"This report from the IG is another in a long line of reports that office has done that go well beyond the expertise of the office in either legal or policymaking areas," he said.
Environmentalists, EPA officials and industry scientists agreed that in the short run, the best way for Americans to protect their health is to follow safety guidelines issued last year that call for reduced consumption of fish known to have high mercury levels. Women of childbearing age in particular should avoid shark, swordfish, king mackerel and tilefish, as well as larger tuna species such as albacore, health authorities said.