What Causes Acid Rain and What Are the Effects of It?

Acid rain is actually a broad term that refers to a mixture of wet and dry deposited material from the atmosphere that contains higher than normal amounts of nitric and sulfuric acids. It can come from both natural sources such as volcanoes or decaying vegetation and from man made sources. Those man made sources are primarily emitted by sulfur dioxide(SO2) and nitrogen oxides (NOx) that results from fossil fuel combustion. About 2/3 of all fossil fuel emissions in the United States come from electric power generation that relies on burning fossil fuels like coal.

Acid rain will occur when these gases react in the atmosphere with water, oxygen, and other chemicals that form various acidic compounds. The result is a mix of mild sulfuric acid and nitric acid. When power plants and other sources release sulfur dioxide and nitrogen oxides, the wind can blow the compounds for hundreds of miles.

Acid rain can cause lakes and streams to become acidized and contribute to the damage of trees at high elevations. Those trees most often affected are red spruce trees because they are usually above 2000 feet above sea level. Acid rain can also damage building material and paints and is one of the more common causes of damage to national monuments.

Acid rain looks just like any rain and feels and tastes like it too. The harm to people is not direct and the EPA claims that walking in it or swimming in an acid lake is no more dangerous than walking or swimming in clean water. However, they claim the pollutants that cause acid rain, sulfur dioxide and nitrogen oxides, do cause damage.

These gases will interact in the atmosphere to form fine sulfate and nitrate particles and these are what cause the damage to people's lungs and hearts. The Acid Rain Program was supposed to lower the levels of bad particles in the air and is supposed to bring about health benefits estimated to be valued at about $50 billion. Those benefits are due to decreased mortality, hospital admissions, and emergency room admissions. It will be interesting to see if these numbers are attained.