Acid Rain

Another effect of air pollution is acid rain. The phenomenon occurs when sulphur dioxide and nitrogen oxides from the burning of fossil fuels such as, petrol, diesel, and coal combine with water vapour in the atmosphere and fall as rain, snow or fog. These gases can also be emitted from natural sources like volcanoes. Acid rain causes extensive damage to water, forest, soil resources and even human health. Many lakes and streams have been contaminated and this has led to the disappearance of some species of fish in Europe, USA and Canada as also extensive damage to forests and other forms of life.

It is said that it can corrode buildings and be hazardous to human health. Because the contaminants are carried long distances, the sources of acid rain are difficult to pinpoint and hence difficult to control. For example, the acid rain that may have damaged some forest in Canada could have originated in the industrial areas of USA. In fact, this has created disagreements between Canada and the United States and among European countries over the causes of and solutions to the problem of acid rain.

The international scope of the problem has led to the signing of international agreements on the limitation of sulphur and nitrogen oxide emissions. The Atmospheric Science Division evaluates the impact of acidifying emission control programs by analyzing the changes in acid deposition at regionally-representative monitoring sites in the Atlantic Region and determining which areas are exposed to continuing acidification because deposition levels exceed the environmental damage level.

The fight against acid rain is not over yet. Acid deposition exceeds critical loads across large portions of eastern Canada, including most of New Brunswick and Nova Scotia. As a result, acidification in these areas will continue, the biodiversity of aquatic ecosystems will remain under threat, and more damage to forest health and productivity will occur unless further deep cuts in sulphur dioxide and nitrogen oxide emissions in Canada and the United States are implemented.