Point: clarifying policy evidence with potential-outcomes thinking--beyond exposure-response estimation in air pollution epidemiology

Abstract

The regulatory environment surrounding policies to control air pollution warrants a new type of epidemiologic evidence. Whereas air pollution epidemiology has typically informed policies with estimates of exposure-response relationships between pollution and health outcomes, these estimates alone cannot support current debates surrounding the actual health effects of air quality regulations. We argue that directly evaluating specific control strategies is distinct from estimating exposure-response relationships and that increased emphasis on estimating effects of well-defined regulatory interventions would enhance the evidence that supports policy decisions. Appealing to similar calls for accountability assessment of whether regulatory actions impact health outcomes, we aim to sharpen the analytic distinctions between studies that directly evaluate policies and those that estimate exposure-response relationships, with particular focus on perspectives for causal inference. Our goal is not to review specific methodologies or studies, nor is it to extoll the advantages of "causal" versus "associational" evidence. Rather, we argue that potential-outcomes perspectives can elevate current policy debates with more direct evidence of the extent to which complex regulatory interventions affect health. Augmenting the existing body of exposure-response estimates with rigorous evidence of the causal effects of well-defined actions will ensure that the highest-level epidemiologic evidence continues to support regulatory policies.

Keywords: accountability; air pollution; clean air act; health outcomes; particulate matter.

Figure 1.

Locations of 407 coal-burning power plants participating in the Acid Rain Program in the United States, 1995–1997. The size of plotting symbol is proportional to the average number of tons of sulfur dioxide emitted at each location during 1995–1997.

Figure 2.

Monthly sulfur dioxide emissions from 1995 to 2012 among coal-burning power plants participating in the Acid Rain Program during 1995–1997. Thick, bold lines correspond to facilities that had 1995–1997 sulfur dioxide emissions at each decile for the respective scrubber category.