New Modeling Shows Additional Benefits - Country-wide and in Texas - from Clear Skies Act

For more information, contact Lou Corio at 410.312.7912.

This past July, EPA released revised modeling results showing that the Clear Skies Act of 2003 (Clear Skies) would result in greater benefits to human health than previously estimated. The revised analysis also shows that Clear Skies would help the country come close to full attainment of the National Ambient Air Quality Standard (NAAQS) for fine particulate matter (PM) (i.e., PM with a diameter of less than or equal to 2.5 µm - PM2.5).

The updated (2003) analysis considers the combined effect of Clear Skies, EPAs proposed nonroad diesel engines rule, and other existing federal and state emission restrictions, such as pollution controls for cars, trucks, and industry and utility boilers. Emission reductions associated with these programs would start before 2010 and would increase dramatically between 2010 and 2020.

Using the most recent air quality (ambient) monitoring data, census information, and computer modeling methods, EPA projects that Clear Skies health benefits estimated in the 2003 analysis are greater than estimated in the 2002 analysis. For example, the 2003 analysis shows, by 2020, an increase in premature deaths avoided and new chronic bronchitis cases avoided of nearly 20%, and an increase in total hospitalizations and emergency room visits (for cardiovascular and respiratory cases) avoided of about 150%, annually.

Clear Skies is projected to significantly reduce fine PM levels in the air, resulting in more areas in attainment of the new fine PM NAAQS and improved visibility. Compared to existing emission reduction programs, Clear Skies is projected to bring 35 additional counties into attainment with the fine PM NAAQS by 2020. The remaining 8 nonattainment counties (in the Eastern U.S.) are expected to move closer to attainment. Projected reductions in fine PM levels also would improve visual range in parks and wildernesses areas (e.g., Great Smoky Mountains, Yellowstone, and Big Bend National Parks) by approximately two to seven miles.

Clear Skies also is projected to help ozone nonattainment areas reach attainment status. Compared to existing emission reduction programs, Clear Skies is projected to bring 3 additional counties into attainment with the new 8-hr ozone standard by 2020. The remaining nonattainment counties are expected to move closer to attainment with the help of Clear Skies.

At full implementation, Clear Skies (with other existing programs) would reduce SO2, NOx, and mercury emissions from fossil fuel-fired combustion units by more than two-thirds over levels in 2000. The reduction in SO2 emissions would result in reductions in sulfur deposition by 30-60% over much of the Eastern U.S. These reductions are projected to eliminate chronic acidity in the Adirondack (NY) region lakes by year 2020 and slow further deterioration of acidic Southeastern U.S. streams. The reduction in NOx emissions would reduce nitrogen loading over much of the Eastern U.S. by up to 35%, with larger reductions in many areas. For instance, most of the Chesapeake Bay watershed would see reductions in nitrogen deposition of 35-50%. Many areas of the country would see decreases in mercury deposition of 15-60%.

EPA used State-of-the-Art computer models to predict the changes in concentration and deposition resulting from Clear Skies. The REgional Modeling System for Aerosols and Deposition (REMSAD) is used to estimate fine PM concentration, sulfur deposition, nitrogen deposition, mercury deposition, and visibility impacts. The Comprehensive Air Quality Model with Extensions (CAMx) is used to estimate ozone concentrations for the ozone attainment analysis. The Environmental Benefits and Mapping System (BenMAP) is used to quantify the human health and visibility benefits using the results from the REMSAD and CAMx models.

In addition to analyzing the benefits of Clear Skies to human health and the environment on a national scale, the EPA also analyzed the benefits on a state-by-state basis. For example, Clear Skies would help areas of Texas achieve compliance with the ozone NAAQS. CAMx modeling results project that 10 of the 12 counties that currently exceed the 8-hr NAAQS for ozone would be brought into attainment by 2020 with the help of Clear Skies (and existing programs). The two remaining counties - Galveston and Harris - would be brought closer to attainment. Also, fine PM concentrations would decrease by up to 10% in most of the State, although such a decrease in the Houston area may not be realized.

Under Clear Skies, Texas would achieve reductions in emissions of 40% for SO2, 22% for NOx, and 45% for mercury by year 2020, above-and-beyond reductions to be gained through current state initiatives. These emission reductions are due mainly to emission controls that would be installed on Texas power plants under Clear Skies. By 2020, under Clear Skies, 27% of coal-fired capacity would install SCR technology; 24% would install scrubbers, and 3% would install mercury controls. As a result, sulfur deposition would decrease by up to 30%, nitrogen deposition would decrease by up to 20%, and mercury deposition would decrease by up to 15% in parts of the State, above-and-beyond the reductions realized by existing programs.