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Clear Skies

Health and Environmental Benefits

Information provided for informational purposes onlyNote: EPA no longer updates this information, but it may be useful as a reference or resource.
Unless otherwise noted, the data presented throughout this Web site reflect EPA’s 2003 modeling and analysis of the Clear Skies Act of 2003. Clear Skies legislation was intended to create a mandatory program that would dramatically reduce power plant emissions of sulfur dioxide (SO2), nitrogen oxides (NOx), and mercury by setting a national cap on each pollutant. The Clear Skies bill was proposed in response to a growing need for an emission reduction plan that will protect human health and the environment while providing regulatory certainty to the industry. The proposed legislation for air regulation never moved out of the Senate Environment and Public Works committee in 2005 and was therefore never enacted.

Clear Skies would protect public health and the environment by improving air quality, decreasing exposure to fine particles and ozone, and reducing deposition of sulfur, nitrogen, and mercury.

In 2010, early reductions in fine particle and ozone levels under Clear Skies would result in 7,800 fewer premature deaths and $55 billion in annual health and visibility benefits nationwide each year.

Under Clear Skies, each year, by 2020, Americans would experience approximately:

  • 14,100 fewer premature deaths;
    • An alternative estimate projects 8,400 fewer premature deaths.
  • 8,800 fewer cases of chronic bronchitis;
  • 30,000 fewer hospitalizations/emergency room visits for cardiovascular and respiratory symptoms; and
  • 12.5 million fewer days with respiratory illnesses and symptoms, including work loss days, restricted activity days, and school days.

The monetized benefits of Clear Skies would total approximately $113 billion annually by 2020, substantially outweighing the annual costs of $6.3 billion. This includes:

  • $110 billion dollars in health benefits;
    • An alternative estimate projects annual health benefits of $21 billion.1
  • $3 billion in benefits from improving visibility at select National Parks and Wilderness Areas.

This does not include the many additional benefits that cannot currently be quantified but are expected to be significant, including the health benefits associated with reduced exposure to mercury and ecological benefits associated with reductions in acid rain and coastal eutrophication.

Clear Skies would help states meet the National Ambient Air Quality Standards (NAAQS). By 2020, based on initial modeling, Clear Skies is expected to:

  • bring 35 additional eastern counties, home to approximately 12 million people, into attainment with the new fine particle standard (beyond what is expected from existing programs in 2020).
  • bring 3 additional counties, home to approximately 6 million people, into attainment with the new ozone standard (beyond what is expected from existing programs in 2020).2
  • The counties remaining out of attainment are expected to move closer to attainment, providing health benefits to the people who live there.
  • Under Clear Skies and existing programs, most counties would meet the fine particle and ozone standard by 2020.


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114 counties in the East (129 counties nationwide) are currently estimated to exceed the annual fine particle standard. 43 million people currently live in Eastern Counties.

Clear Skies and existing air programs (including motor vehicle rules and the NOx SIP Call) would bring most counties into attainment with the fine particle standard by 2020 (compared to current conditions).

268 counties in the East (290 counties nationwide) are currently estimated to exceed the 8-hour ozone standard. 87 million people currently live in Eastern counties.

Clear Skies and existing air programs (including motor vehicle rules and the NOx SIP Call) would bring most counties into attainment with the ozone by 2020 (compared to current conditions).

By 2020, Clear Skies, along with implementation of existing programs, would achieve many environmental improvements. Compared with existing conditions:

  • Nitrogen deposition (one component of acid deposition) would be reduced over much of the Eastern U.S., including sensitive coastal areas, by up to 35% across most of the country with larger reductions in many areas.;

Nitrogen Deposition Map showing the percent reduction in 2020 compared with deposition in 2001

  • Fine particle concentrations in large portions of the East and Midwest would be reduced by up to 25%;
  • In a large portion of the East and Midwest, visibility would be improved by 2-3 deciviews from current levels (a one deciview improvement is a perceptible change).
  • Sulfur deposition (one component of acid deposition) would be reduced over much of the Eastern U.S., including sensitive areas, by 30-60%;
  • Many areas would see large decreases in mercury deposition of 15-60%, including the mid-Atlantic, many parts of the Southeast and Northeast, and southeastern Michigan; and
  • Chronic acidity -- the most serious form of acidification -- would be eliminated in the Adirondacks and virtually eliminated in other Northeastern lakes. The long-term decline in stream condition in the Southeast would be slowed.

Bar chart projecting percentage of Adirondack Lakes that are acidic, current at 21 percent, base (2030) at 12 percent, with Clear Skies in 2030 at zero percent.

  • The figure above presents results for chronic acidity only in modeled lakes. As such, model results apply to a subset of lakes in the Adirondacks and cannot be generalized to all waters in that area.
  • These results do not include lakes that experience episodic acidification, or short periods of low Acid Neutralizing Capacity or high acidity, during storms or snowmelt.
  • A significant proportion of Adirondack lakes could still experience episodic acidification at levels potentially harmful to fish and other aquatic species.

Detailed Benefits Information

You will need Adobe Acrobat Reader, available as a free download, to view some of the files on this page. See EPA's PDF page to learn more about PDF, and for a link to the free Acrobat Reader.

Section B of the 2003 Clear Skies Technical Package (PDF, 49 pp., 4.6MB)
This document features an in-depth analysis of the expected benefits of Clear Skies. It includes maps and information on the improvements in human health and the environment that would be achieved with Clear Skies. This document also includes monetized benefits.

Technical Addendum: Methodologies for the Benefit Analysis of the Clear Skies Act of 2003 (PDF, 86 pp.,1.7MB)
This document details the methods used to analyze the benefits of the Clear Skies Act of 2003 and presents the results of the analysis. It quantifies the health and visibility improvements that would be achieved by Clear Skies and projects the monetary value of those improvements.

Overview of the Human Health and Environmental Effects of Power Generation: Focus on Sulfur Dioxide (SO2), Nitrogen Oxides (NOx) and Mercury (Hg) (PDF, 15 pp., 1.1MB)
Clear Skies is intended to reduce the health and environmental impacts of power generation. This document summarizes the effects of power generation, particularly those associated with sulfur dioxide (SO2), nitrogen oxides (NOx), and mercury. This document does not address the specific benefits of Clear Skies.

Related Environmental and Health Information


Emissions Cap-and-Trade and Hot Spots (PDF, 17pp., 17.3MB)


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1The two sets of estimates reflect alternative assumptions and analytical approaches regarding quantifying and evaluating the effects of airborne particles on public health. All estimates assume that particles are causally associated with health effects, and that all components have the same toxicity. Linear concentration-response relationships between PM and all health effects are assumed, indicating that reductions in PM have the same impact on health outcomes regardless of the absolute level of PM in a given location. The base estimate relies on estimates of the potential cumulative effect of long-term exposure to particles, while the alternative estimate presumes that PM effects are limited to those that accumulate over much shorter time periods. All such estimates are subject to a number of assumptions and uncertainties. It is of note that, based on recent preliminary findings from the Health Effects Institute, the magnitude of mortality from short-term exposure (alternative estimates) and hospital/ER admissions estimates (both estimates) may be overstated. The alternatives also use different approaches to value health effects damages. The key assumptions, uncertainties, and valuation methodologies underlying the approaches used to produce these results are detailed in Technical Addendum: Methodologies for Benefit Analysis of the Clear Skies Initiative, 2003. (PDF, 86 pp., 1.7MB)

2 This analysis shows the counties that would come into attainment due to Clear Skies alone in 2020. Additional federal and state programs are designed to bring all counties into attainment by 2017 at the latest. Clear Skies is not expected to bring additional counties into attainment for 2020 in the West. Therefore, the Western region is not presented here.


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