Emission trading and public health.

Emission trading policies are increasingly important in environmental protection, especially in controlling air pollution in the United States. Their popularity results in part from the limitations and frustrations of centralized command and control regulation. Well-designed emission trading programs can achieve the same or better environmental and health outcomes as command and control regulations but provide regulated industries with greater flexibility. This lowers costs and improves the process of negotiating environmental policy. We present key concepts and important applications of emission trading, focusing on health impacts. These programs generally are well-designed, speeding emission abatement; improving health outcomes; and reducing compliance costs. Flaws have stopped a few poorly designed emission trading programs. A key issue in evaluating emission trading is our inability to know what the environmental outcome would have been under another approach.