More generally called acid precipitation or acid deposition, acid rain is the deposit of wet or dry acidic materials from the atmosphere to the earth's surface. Sulfuric and nitric acids are the main causes of acid rain. Smokestacks produce sulfur dioxide emissions and exhaust from vehicles produce nitrogen oxides. These pollutants are picked up by the wind and can move hundreds to thousands of miles away from their original source. The acidity of the rain is measure by its Ph level, the lower the Ph level the more toxic it can become. The average range of normal rain has a Ph of about 5 to 6.5.
Down to a Ph of 1 the toxicity is equivalent to raining battery acid. From around 3 to 4 Ph, fish actually die from the rain. The northwest seems to have the most toxic rainfall. Canadians have complained that there significant acid rainfall from upwind pollutants coming from older power plants in Tennessee and Ohio. In 1991, United States and Canada signed the Air Quality Agreement for transboundary air pollution. In 1990, the United States signed the Clean Air Act Amendments which allowed the EPA to monitor the acid rain levels.
When a lake is poisoned by the toxins in rain, plants and fish that live in a balance under the water die off, leaving little chance of reproduction and no food for birds who live off the fish. Toxic levels in the rain not only affect human health such as difficulty breathing and but the cycle of life is also affected. When the rains come in contact with plants and animals and humans ingest these toxic foods. Long term results such as Alzheimer's, kidney problems and brain damage occur. Plants and trees also lose the protection they need from leaves turning brown and falling off and bark becomes infected from the toxic water. The soil around these plants and trees actually poisons the roots and stunts the normal growth of the plant.
The amount of acidic rain can be reduced by the amount of sulfurs oxide and nitrogen oxides, mainly from reducing the amount of coal burnt. Less smokestacks, less acid rain. More carpooling, taking the bus and walking will also decrease acid rain. If the coal was cleaned before it was burnt, the coal would give off less sulfur into the air. Unfortunately, it costs too much for electricity companies to invest in this method.