CPR Perspective: Emissions Trading: 'Market-based' Regulatory Tools by Rena Steinzor:. CPR's Perspectives Series is a set of monographs by CPR Member Scholars on timely and important health, safety, and environmental topics. Each Perspective provides a thumbnail sketch of the competing arguments concerning a substantive or procedural principle for developing appropriate health, safety and environmental policies, and closes with the Member Scholar-author's proposed approach to the issue.