The U.S. District Court of Appeals for the District of Columbia has upheld a determination made by EPA in 2006 that current air emission controls on synthetic organic chemical manufacturing plants are adequate to protect the public with an ample margin of safety. In a decision on June 6, the court dismissed a claim by environmental groups that the agency's interpretation of the residual risk and technology review provisions of the 1990 Clean Air Act Amendments is too lenient and exposes the public to cancer-causing air pollution. The 1990 law required EPA to determine whether any risk remained after the chemical industry installed controls to limit emissions of hazardous air pollutants and whether additional controls were needed. After conducting a review largely based on emissions data supplied by chemical manufacturers, EPA concluded that the application of maximum achievable control technology since 1994 has resulted in a substantial reduction of hazardous air pollution from the nation's chemical plants. In 2006, EPA issued a final rule that left the 1994 standard in place, saying no further tightening was necessary because emissions of hazardous air pollutants have been reduced to levels that present "an acceptable level of risk" to people who live near chemical facilities.