Since the onset of acid precipitation beginning with the Industrial Revolution of the 19th century, many countries, especially in North America and northern Europe, accumulated annual environmental damage from its corrosive effects. However, little was done to stop acidic precipitation until the late 20th century. During the 1970s and 1980s, scientists began linking environmental damage to acid precipitation, generating massive publicity on the subject. This promoted development of environmental groups determined to reduce the scourge of acid precipitation.

What is being done in North America?

Acid precipitation is a problem that crosses international borders. Acid precipitation has caused significant environmental damage in Canada, with most of the problem originating from industry in the United States. The United States emits almost 5 times as much sulfur dioxide and 20 times as much nitrogen oxide per year than does Canada. This U.S. pollution is carried into eastern Canada by upper-level winds. Lakes, forests, buildings, and monuments have all been damaged. In the early 1980s, the problem was so severe that in eastern Canada almost 96% of the forests suffered damage. In Ontario, significant declines in growth rates of forests within the past 30 years were linked to acid precipitation from industrialization and urbanization.

The United States and Canada have worked together on this issue, and have made significant progress. In 1981, the Canadian Coalition on Acid Rain (CCAR) was formed, with branches in both the United States and Canada. Acting as a lobbyist group in the United States and as a charitable group in Canada, the CCAR actively promoted education regarding acid precipitation. The CCAR also promoted legislation both in the United States and Canada that would limit sulfur dioxide and nitrogen oxide emissions. In 1985, the Canadian Acid Rain Control Program was established, which required a 40% drop in sulfur dioxide emission levels from 1980. In 1990, the United States passed Amendments to the Clean Air Act of 1970, requiring reductions of sulfur dioxide and nitrogen oxide emissions under the Acid Rain Program.

Under the Acid Rain Program established by the U.S. Clean Air Act Amendments of 1990, total sulfur dioxide release from electrical utilities in the U.S. is set at a maximum of 8.95 million tons by the year 2010. This level is approximately one-half of 1980 industrywide emissions. Sulfur dioxide emissions control is achieved using an innovative strategy called cap and trade. Under the cap and trade approach, permission to emit sulfur dioxide is assigned to individual electrical utilities in the form of allowances. An allowance is an authorization to emit one ton of sulfur dioxide in a year. At the end of a given year, each electrical utility must hold an allowance for each ton of sulfur dioxide it emitted. Unused allowances may be carried over into future years, or sold to other companies. Companies seeking to build new power plants must purchase allowances from the existing pool. New allowances are not added, as the purpose of the program is to limit the total quantity of sulfur dioxide emitted nationwide regardless of increased demands for electrical power. The sulfur dioxide cap and trade program has met its goals since its start in 1995, and is expected to continue to be successful.

Nitrogen oxide emissions are treatly differently under the U.S. Acid Rain Program. A goal of the program is to reduce nationwide nitrogen oxide emissions by 2 million tons by 2010. To reach this goal, a maximum emission rate is established for each power plant, depending on the types of boilers installed at each plant. An overall ceiling value has not been set for nitrogen oxide emissions. Nationwide in the U.S., nitrogen oxide emissions have remained constant at about 23 million tons per year since the 1980s. Although nitrogen oxide emission rates have declined with the use of cleaner technologies, total electricity generation and vehicle use have increased.

In 1991, the United States and Canada formalized their cooperation on acid precipitation concerns by adopting the Canada-United States Air Quality Agreement. Under this agreement, Canada committed to a permanent national cap for sulfur dioxide emissions of 3.2 million tons per year by the year 2000. The United States committed to a permanent national cap for sulfur dioxide emissions of 8.95 million tons per year by 2010, the same level as mandated under the Clean Air Act Amendments of 1990. For nitrogen oxides, Canada committed to reduce stationary source (power plants and other industry) emissions by 100,000 tons by the year 2000, and the U.S. committed to reduce total nitrogen oxide emissions by 2 million tons by 2000. Both countries agreed to improve nitrogen oxide controls for motor vehicle sources. To date, all the goals of the Canada-United States Air Quality Agreement have been met.

What is being done in Europe?

In 1979, 34 countries in North America and northern Europe established the Convention on Long-Range Transboundary Air Pollution. The Convention was an agreement to adopt economically feasible solutions for limiting sulfur dioxide and nitrogen oxide emissions. Although this agreement did not have specific guidelines, it did establish global awareness of acid precipitation. In 1983, 21 European countries made a commitment to reduce sulfur dioxide emissions by 30% within 10 years. In 1988, 12 countries had already reached this goal. Also in 1988, a piece of legislation called the EC Large Combustion Plants Directive was implemented throughout Europe. This legislation required all European industry to reduce nitrogen oxide emissions by 40% by 1998 and sulfur dioxide emissions by 58% by the year 2003.

By the late 1990s, studies revealed that acid precipitation legislation had been successful in reducing sulfur dioxide emissions in western Europe. In 1996, the Norwegian Institute of Air Research revealed there was a significant decline in sulfur dioxide emissions in southern Norway. After measuring sulfur concentrations in the air, rainfall, lakes and streams, they determined that the reduction of sulfur dioxide was much as 75% from the levels in the early 1980s. Nitrogen oxide emissions were reduced by about 3% in Norway from 1986-1995, and by about 10% across Europe. However, nitrogen oxides are still a concern in the acid precipitation problem because legislation targeting industry can do little to stop the pumping of nitrogen oxides into the atmosphere from automobiles currently on the road.