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EVALUATING THE EFFECTS OF TITLE IV OF THE 1990 CLEAN AIR ACT AMENDMENTS ON AIR QUALITY
Impact/Purpose:
Title IV of the Clean Air Act of 1990, entitled “Acid Deposition Control,” called for a permanent 10-million-ton reduction in sulfur dioxide (SO2) emissions from 1980 levels and required installation of continuous monitoring equipment for SO2 emissions to ensure compliance and track improvements. Beginning with the 1997 National Ambient Air Quality Standards for PM, the U.S. Environmental Protection Agency (EPA) set standards for PM2.5 concentrations, and $128 million was appropriated for a nationwide array of PM2.5 monitoring stations known as the Air Quality System monitoring network.
When evaluating a regulatory action intended to improve air quality, either prospectively or retrospectively, EPA scientists frequently employ a chemical transport model, such as the Community Multiscale Air Quality (CMAQ) modeling system. One key limitation to the use of such models is that they are based on modeling estimations and not monitoring data. For the current study, Morgenstern and his team proposed a novel model that was data-driven, in that it depended on measured values of emissions and pollutant concentrations and was inherently observational. The statistical models that the investigators propose to develope would link changes in emissions of SO2 and nitrogen oxides (NOx) to changes in ambient PM2.5 concentrations that are broadly based on source–receptor models, widely used for source apportionment. More specifically, the investigators will base their work on a “spatial econometric” approach, incorporating a statistical accounting of emissions in the manner of economic analysis, adapted for the current purposes of associating emissions and air pollution levels.
Description:
The investigators’ work will contribute to the discussion of what portions of PM reductions can be attributed to an emissions reduction program, with an approach that might be a useful alternative to atmospheric models in some applications. A model that estimates ambient air quality changes secondary to emissions changes might also be applied to estimating changes in criteria pollutants secondary to regulations aimed at reducing industrial emissions or even greenhouse gas emissions. This research and these models might also be able to provide useful information to organizations that want a quick estimate of how much specific emitting facilities affect specific pollutant monitors or even communities, although atmospheric pollution dispersion models might be more readily applied.