There is rapidly growing interest in the use of market-based (MB) instruments in environmental policy. The papers in this session discuss three relatively new areas for such policies: groundwater contamination, nonpoint source surface-water pollution and carbon sequestration. The papers point out the potential for MB policies in these areas, but significant challenges remain. This comment highlights challenges related to five issues: monitoring and enforcement, trading ratios, baselines, transaction costs, and risk and uncertainty. All these issues must be addressed before MB policies can take the full step from economic theory to regulatory reality.
