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UNITED STATES RESEARCH: IMPLICATIONS FOR AIR POLLUTION POLICY
Emissions Trading
Research Team: Denise Mauzerall, Babar Sultan (undergrad), Namsoug Kim (programmer), David F. Bradford (late professor of economics)
Within the United States, we examined environmental implications of the increasingly widely used “cap-and-trade” system to control nitrogen oxide (NOx) emissions from large stationary sources. The concept of “cap-and-trade” was initially introduced over 30 years ago. It showed that, in theory, an emissions-trading system in which rights to emit pollution are available in a limited aggregate quantity and are freely tradable would induce rational firms to reduce pollution at the least possible cost and would encourage technological innovation. Recognizing these advantages, “cap-and-trade” programs have been implemented nationally to control sulfur dioxide emissions under Title IV of the 1990 Clean Air Act Amendments and to control regional nitrogen oxide (NOx) emissions under the Ozone Transport Commission in 1999, the NOx Budget Program in 2004 and the Clean Air Inter-state Rule in 2005 in order to reduce surface ozone concentrations during the summer ozone season (May-September).
Reducing total NOx emissions usually results in reductions in ozone concentrations. However, our research findings contradict implicit policy assumptions that controlling total emissions of NOx, while permitting free trading among emitters, reduces environmental damage in proportion to the total NOx reduced. Using a regional atmospheric chemistry transport model we show that a shift of a unit of NOx emissions from one place or time to another across the eastern United States can result in large changes in resulting premature mortalities and morbidity due to ozone formation and exposure [Mauzerall, et al., 2005]. We demonstrated that within a short period in July 1995, depending on temperature, local biogenic hydrocarbon emissions, and the size of the downwind population, a difference of a factor of six in mortalities can result from an identical change in the quantity of NOx emitted. We suggest that rather than controlling total emissions, the emphasis be shifted to controlling total damages. The type of modeling used in our analysis might be used to attach externality-correcting prices to emissions. Charging emitters fees that are commensurate with the damage caused by their NOx emissions would create an incentive for emitters to reduce emissions at times and in locations where they cause the largest damage.
Total Effect of US Air Pollution on Premature Mortalities and
State Level Source-Receptor Relationships
Research Team: Denise Mauzerall and Daniel Tong (post doc)
The total number of premature mortalities occurring in the United States due to air pollution exposure is not well known. Using a sophisticated regional atmospheric chemistry transport model (Models3-CMAQ/MM5/SMOKE) coupled with recent epidemiological concentration-response relationships, we found that premature mortalities resulting from exposure to ozone and particulate matter in 1996 were approximately 20,000 and 70,000, respectively [Mauzerall and Tong, in preparation]. This represents about 4% of annual U.S. mortalities and is four times larger than the 23,000 premature mortalities predicted to be averted in 2010 from implementation of the 1990 Clean Air Act Amendments. Our analysis indicates that tens of thousands of lives could be saved each year in the United States by substantial further reductions in the emission of air pollutants.
Our next objective is to quantify source-receptor relationships between states in order to determine where pollution in a specific state comes from and where it goes. As a first step in this analysis we evaluated the ability of the continental-scale version of the CMAQ model to simulate surface ozone concentrations across the US [Tong and Mauzerall, in press]. Inter-state source-receptor relationships have policy importance as states are responsible for meeting National Ambient Air Quality Standards (NAAQS) and have been expected to do so by controlling their own emissions. In some cases, we show that a large fraction of a state’s pollution comes from upwind states making regional controls on emissions necessary in order to meet the NAAQS [Tong and Mauzerall, in preparation]. An understanding of source-receptor relationships is valuable for designing regional air pollution control strategies.
NRC / NAS Committee
A multi-disciplinary National Research Council / National Academy of Science committee, of which I was a member, was directed by Congress to evaluate the effectiveness of the Clean Air Act's major air quality provisions and to develop scientific and technical recommendations for strengthening the nation’s air quality management system. Our committee’s key recommendations for improving the air quality management system in the United States were to strive to 1) identify and assess more clearly the most significant exposures, risks and uncertainties; 2) take an integrated multi-pollutant approach to controlling emissions of pollutants; 3) take an airshed-based approach by assessing and controlling emissions of important pollutants arising from local, multi-state, national and international sources; and 4) emphasize results over process. Our committee report, entitled Air Quality Management in the United States [2004] (422pp), is presently assisting the Environmental Protection Agency improve our national air quality management system. Our on-going research on state-level source-receptor relationships (described above) and inter-continental transport of air pollutants (described below) are critical for determining appropriate airsheds for air pollution control (recommendation 3).
PUBLICATIONS:
Mauzerall, D. L., Sultan, B., Kim, J, Bradford, D., “NOx Emissions: Variability in Ozone Production, Resulting Health Damages and Economic Costs,” Atmospheric Environment, 39, pp. 2851-2866, 2005. [full text (pdf)]
Committee on Air Quality Management in the United States, National Research Council/National Academies of Science, “Air Quality Management in the United States,” 426 pages, 2004. [full text (http://www.nap.edu/catalog/10728.html)]
Tong, D. Q., Mauzerall, D. L., “Spatial variability of summertime tropospheric ozone over the continental United States: Implications of an evaluation of the CMAQ model,” Atmospheric Environment, in press 2005. [full text (pdf)]