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Note: EPA no longer updates this information, but it may be useful as a reference or resource.

Please see www.epa.gov/airtrends for the latest information on Air Quality Trends.

Emissions of the six principal air pollutants increased significantly between 1900 and 1970. This includes emissions of carbon monoxide, lead, nitrogen dioxide, volatile organic compounds, particulate matter, and sulfur dioxide. However, since passage of the 1970 Clean Air Act Amendments, emissions of all of these pollutants have declined, in some cases dramatically.

Economic growth and environmental protection can go hand-in-hand. Between 1970 and 1995, total combined emissions of the six principal pollutants decreased while gross domestic product, population, and total vehicle miles traveled all increased significantly.

In 1995, Phase I of EPA's Acid Rain Program alone reduced sulfur dioxide emissions from affected power plants by 5.6 million tons compared to 1980 levels. This was 39 percent below the level anticipated under the 1990 Amendments to the Clean Air Act.

Newly available monitoring data showed significant reductions in benzene concentrations and other toxic air pollutants from 1994 to 1995. At sites where these data were available, the median reduction for benzene was approximately 38 percent. Early analysis indicates this reduction may be a result of reduced vehicle emissions due to the use of reformulated gasoline.

Short-term trends between 1994 and 1995 showed a slight increase in monitored concentration levels of ozone. Monitored concentration levels of carbon monoxide, nitrogen dioxide, particulate matter, and sulfur dioxide continued to decrease, while lead remained unchanged. During this same 1-year period, emissions of all six principal air pollutants decreased.

Despite the improvements in air quality since 1970, nearly 80 million people lived in counties where air quality levels exceeded the national air quality standards for at least one of the six principal pollutants in 1995.

Air pollution, such as ground-level ozone, acid rain, and air toxics, also significantly affects ecosystems. For example, ground-level ozone is responsible for approximately 1 to 2 billion dollars in reduced agricultural crops each year. In addition, certain toxic pollutants (like some metals and organic chemicals) that are emitted from industrial sources can be deposited into water bodies and magnify through the food web, adversely affecting fish-eating animals and humans.

Over the past several years, the American public has become conscious of other air pollution issues such as protection of the stratospheric ozone layer and the effect of global warming on the Earth's climate. EPA continues to work with States, industry, and other partners to find cost-effective and innovative ways to solve air pollution problems.

This document is provided for historical purposes only. The most recent version can be found at AIRTrends

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