How is acid rain formed?

Updated June 13, 2017

The air around us contains natural gases such as carbon dioxide. When water in the air reacts with carbon dioxide, acid is produced. This safe natural process means that all rain is slightly acidic. However, when rain becomes too acidic due to the presence of gases produced through industry, it becomes extremely harmful to the environment.


When fossil fuels, like coal or oil, are burned, sulphur is produced and released into the atmosphere. This reacts with the water naturally present in the air, producing sulphur dioxide. Nitrogen, mainly produced by cars, lorries and other traffic, also causes acid rain. This gas, when it reacts with water, produces nitrogen oxides. Humans are responsible for the majority of the production of the chemicals that cause acid rain, although these chemicals are also produced in nature by phenomena such as volcanic eruptions and lightning.

Forests and vegetation

When rain becomes too acidic, it has disastrous effects on trees and vegetation. It can wash away the nutrients in the soil that trees and plants need to grow. It can also wear away leaves and bark making trees and plants more susceptible to disease and more vulnerable to insects.


Acid rain can fall directly into lakes, or it may enter through rivers that flow into them. Whole lakes can become acidic. Even low levels of acid can kill fish eggs and harm fish. Acid also causes harmful levels of aluminium to be released from the soil into the water, again harming fish and other creatures. If birds then eat the affected fish, they too become ill. Any animal that relies on fish as a source of food is in danger of starvation. Lakes can become so acidic that no life can survive in them at all. A lake that is too acidic will look very clean and clear because of the few creatures living in its waters.


Sulphur dioxide and nitrogen oxides can cause breathing problems in humans. This is a particular problem for those who already have asthma. Acid rain can get into the water supply and cause headaches and swelling in the eyes, nose and throat.


Acid rain can eat away at the surfaces of buildings, in particular those made from sandstone or limestone. It can also damage plastic and glass. Metal surfaces can also be affected; for instance, the Statue of Liberty had to undergo restoration work because of the damage done by acid rain.


Clean energy such as wind and solar energy is on the rise. Catalytic converters can help by removing most of the pollutants released by cars. Everyone can help, by cutting the amount of energy they use. Using draught excluders, having proper insulation in the home, turning down the heating and not relying on cars can save money as well as reducing acid rain. Many countries have successfully reduced their emissions – however, industrialisation in countries like China has seen further reliance on fossil fuels which could lead to an increase in sulphur emissions.

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About the Author

Based in Hampsire in the south of England, Alison Williams has been writing since 1990. Her work has appeared in local magazines such as "Hampshire Today" and "Hampshire the County Magazine." Williams is qualified in newspaper journalism and has a Bachelor of Arts in English language and literature from the Open University. She has recently published her first novel "The Black Hours" and has a master's in creative writing.