Acid rain and snow occurs when atmospheric oxides of sulfur and nitrogen react with other atmospheric gases and water vapor to form nitric acid and sulfuric acid. Acidic precipitation causes ecological damage by increasing the acidity of water and soil, and can damage buildings as well. In 1990, Congress established the Acid Rain Program under the Clean Air Act. The principal goal of the program is to achieve reductions of 10 million tons of sulfur dioxide (SO2) and 2 million tons of nitrogen oxides (NOx), the primary components of acid rain.

The EPA Acid Rain Program home page provides basic information on acid rain and on federal regulations relating to acid precipitation and emissions monitoring. A calendar of training sessions related to acid rain is also provided, as well as numerous downloadable documents and reports on various aspects of acid rain. The site also provides a list of federal laws and regulations relating to acid rain. 

The National Acid Precipitation Assessment Program (NAPAP) is an interagency scientific research, monitoring and assessment program on the effects of sulfur and nitrogen oxides on the environment and human health. Participants include NOAA, EPA, DOE, DOI, USDA, and NASA.

STAPPA and ALAPCO are the two national associations of state and local air pollution control agencies in the United States. Their Clean Air World website includes information on many topics, including a section on Acid Deposition.

The USGS is the lead federal agency for the monitoring of wet atmospheric deposition of chemical constituents. Data from the National Atmospheric Deposition Program, National Trends Network can be accessed through the USGS website, as well as presentations and reports on acid rain and deposition monitoring.

The Acid Rain Retirement Fund is a nonprofit organization that purchases sulfur dioxide pollution allowances and retires them.

On-line Articles and Publications 

Acid Rain Revisited: Advances in Scientific Understanding Since the Passage of the 1970 and 1990 Clean Air Act Amendments (PDF)
A 2001 report from the Hubbard Brook Research Foundation Science Links™ program on the continuing serious effects of acid rain in the Northeast.

Electricity Generation and Environmental Externalities  
The Energy Information Administration offers an executive summary and report (pdf) on regulatory approaches and externality policies.

Acid Rain
EPA provides a basic introduction to the issue of acid rain.

Acid Rain and Our Nation's Capital
USGS General Interest online publication with many images of acid rain effects.

Uphill Battle: 30 Years of Progress on Acid Deposition
A chronology appearing in Sightline magazine in 2001.

Wisconsin's Sensitivity to Acid Rain: The Role of Geologic Materials and Soils (PDF)
A 6-page publication from the University of Wisconsin-Extension.

Last updated: October 7, 2003

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