The Environmental Protection Agency recently issued 946 pages of new rules requiring that U.S. power plants sharply reduce their (already low) emissions of mercury and other air pollutants. EPA Administrator Lisa Jackson claims that while the regulations will cost electricity producers $10.9 billion annually, they will save 17,000 lives and generate up to $140 billion in health benefits.

There is no factual basis for these assertions. To build its case against mercury, the EPA systematically ignored evidence and clinical...