Air Trends
Air Emissions Summary Through 2005
Accelerating Progress
The Clean Air Interstate Rule (CAIR) addresses power plant emissions in 29 eastern states plus the District of Columbia . When fully implemented, CAIR will reduce SO2 emissions in these states by over 70 percent and NOx emissions by over 60 percent from 2003 levels.
The Clean Air Act directs EPA to establish air quality standards to protect public health and the environment. EPA sets national air quality standards for six principal air pollutants (also called the criteria pollutants): nitrogen dioxide (NO2), ozone (O3), sulfur dioxide (SO2), particulate matter (PM), carbon monoxide (CO), and lead (Pb).
Looking at Growth and Emissions
Each year EPA looks at emissions that impact the ambient concentrations of these pollutants. These annual emissions estimates are used as one indicator of the effectiveness of our programs. The graph below shows that between 1970 and 2005, gross domestic product increased 195 percent, vehicle miles traveled increased 178 percent, energy consumption increased 48 percent, and U.S. population grew by 42 percent. During the same time period, total emissions of the six principal air pollutants dropped by 53 percent.
From 1990 to 2002, air toxics emissions declined by 42%. These reductions are the result of implementing stationary and mobile source regulations. Seventy-five percent of air toxics emitted in 2002 are included below as volatile organic compound and particulate matter emissions.
Estimating Emissions
EPA estimates nationwide emissions of ambient air pollutants and the pollutants that form them (their precursors). Four of the principal pollutants (CO, Pb, NO2 , and SO2) are emitted directly from a variety of sources. Ozone is generally not directly emitted, but is formed when oxides of nitrogen (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. PM can be directly emitted, or it can be formed when emissions of NOx, sulfur oxides (SOx), ammonia, organic compounds, and other gases react in the atmosphere. Emission estimates are based on many factors, including actual measurements, levels of industrial activity, fuel consumption, vehicle miles traveled, and other estimates of activities that cause pollution.
Emissions of air pollutants continue to play an important role in a number of air quality issues. About 141 million tons of pollution are emitted into the atmosphere each year in the United States . These emissions contribute to the formation of ozone and particles, the deposition of acids, and visibility impairment.
In recent years, EPA has acted to dramatically improve America's air quality by providing national programs that when fully implemented will achieve significant reductions in air emissions. The associated air quality benefits will lead to improved health, longevity and quality of life for all Americans.
The table below examines changes in national estimates of emissions for the major air pollutants or, where appropriate, precursor pollutants that form them. The table includes emissions data for 1970, 1975, 1980, 1985, 1990, 1995, 2000, and 2005. As indicated in the table, the 2005 emissions data are preliminary.
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National Air Pollutant Emissions
Estimates
Notes:
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To get detailed information about emissions estimates displayed
above, please visit EPA's Clearinghouse
for Inventories and Emissions Factors (CHIEF) Web site