Issues and Uncertainties in Estimating the Health Benefits of Air Pollution Control

The estimation of health benefits from reductions in ambient air pollution requires information both about the relationship between concentrations and health effects and about the ultimate value of health outcomes. In this commentary, I discuss significant issues and uncertainties that must be addressed for both elements. Critical issues for concentration-response estimation include the shape of the concentration-response curve at current and projected ambient levels, the relevant exposure period, the existence of high-risk subpopulations, and the ability to generalize across study settings. Health outcomes can be valued using either health-based measures like quality-adjusted life years or economic measures like value of statistical life; the choice of measure has a significant effect on the magnitude and distribution of health benefits. Analysts estimating health benefits for ultimate benefit-cost applications should provide results using multiple valuation frameworks and multiple assumptions about health evidence to facilitate interpretation and to determine whether policy decisions depend on these assumptions.