The pH of acid rain typically lies between 4 and 5. Damage caused by acid deposition affects lakes, rivers, forests, soils and buildings with profound impacts also observed on fish and wildlife populations. Furthermore, sulphur dioxide in the air can combine with other pollutants and water to form fine particles that can increase the risk of serious health complications for people with heart and respiratory disease. The haze that these particles form also contributes to visibility reductions, especially in parts of central and eastern Canada. In addition, sulphate particles contribute to climate change by scattering incoming sunlight and stimulating cloud formation, thus causing local and regional cooling.
Acid rain is a global problem.
It is a major concern in North America, parts of Europe, particularly Scandinavia, and it is a developing issue in China and other industrialized areas of Asia. Because the emissions that cause acid rain often cross national borders, acid rain is an important issue on the international agenda. The problem that acid rain posed to Canadian lakes and forests was identified in the 1960s, but it was not until the late 1970s that governments funded research to determine the extent of the problem in Canada. It was not until the 1980s, however, that Canadian governments began to act on the issue. Since then, much has been done to control the sources of acidifying pollution, but the problem is still far from resolved.