Are Tradable Permits for Mercury Worthwhile?

The success of the tradable permit system in controlling SO2 emissions has led to consideration of a similar system for mercury emissions. However, it is unlikely that such a system for mercury will generate similar success due to the probable lower variance of marginal control costs for mercury and a greater probability of local hot spots. It may be more pragmatic to implement a system of nontradable permits in which compliance may be achieved as power plants desire.