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Letter in Response to Fraas & Lutter Article: “Uncertain Benefits Estimates for Reductions in Fine Particle Concentrations”

In their article, Fraas and Lutter argue that the U.S. EPA can, and should, do more to characterize uncertainty in its benefits estimates—and to that end, they pilot an array of quantitative uncertainty analyses.(1) We agree that additional probabilistic uncertainty analysis is desirable and commend the authors for their creativity in identifying new approaches. However, we find that the article does not: (1) accurately depict EPA’s current methods for uncertainty analysis; (2) rely on data, but instead makes specious assumptions; and (3) document clearly their analytical approach. Taken together, these limitations undermine the utility of their preferred approach to characterizing uncertainty. We argue that the central premise of the article—that the Agency has done too little to respond to the 2002 National Research Council (NRC) report—is not supported by the historical record.(2) In the decade since the report was first issued, the Agency has made significant improvements to how it estimates and characterizes both the human health benefits of air quality improvements and the attendant uncertainties in those estimates. In addition to the ground-breaking expert elicitation of PM mortality noted in the article, the Agency also performed a preliminary influence analysis.(3,4) This assessment, which the Agency undertook in direct response to the NRC report, was a first step toward identifying the analytical inputs that posed the strongest impact on the overall size of the benefits estimates.