Measuring the Effects of the Clean Air Act Amendments on Ambient PM₁₀ Concentrations: The Critical Importance of a Spatially Disaggregated Analysis

Maximilian Auffhammer, University of California - Berkeley
Antonio M. Bento, Cornell University
Scott E. Lowe, Boise State University

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This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at Journal of Environmental Economics & Management (doi: 10.1016/j.jeem.2008.12.004) published by Elsevier. Copyright restrictions may apply.

Abstract

We examine the effects of the 1990 Clean Air Act Amendments (CAAAs) on ambient concentrations of PM₁₀ in the United States between 1990 and 2005. We find that non-attainment designation has no effect on the 'average monitor' in non-attainment counties, after controlling for weather and socioeconomic characteristics at the county level. In sharp contrast, if we allow for heterogeneous treatment by type of monitor and county, we do find that the 1990 CAAAs produced substantial effects. Our best estimate suggests that PM₁₀ concentrations at monitors with concentrations above the national annual standard dropped by between 7µg/m³ and 9µg/m³, which is roughly equivalent to a 11-14% drop. We also show that monitors which were in violation of the daily standard experience two fewer days in violation of the daily standard the following year. Empirical results suggest that this treatment effect is independent of whether the EPA has finalized the non-attainment designation.