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The mixture of chemical emissions and water droplets in the air that fall as rain.  It causes habitats to become too acidic and can destroy living organisms.

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The mixture of chemical emissions and water droplets in the air that fall as rain.  It causes habitats to become too acidic and can destroy living organisms.

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Acid rain is rain that is unusually acidic. The acids are made when certain gases are carried high into the sky and react with the water in the atmosphere.

Acid rains can be harmful to plants, animals, and humans.

Robert Angus Smith is credited with the term "acid rain." In 1852, he showed the relationship between acid rain and atmospheric pollution in Manchester.

Although some natural gases, such as carbon dioxide, and gases from volcanoes can cause acid rain, it is now believed that mankind causes most acid rain. When people began building and using factories and power stations, they burned coal or oil. These compounds have sulfur in them that releases into the air, mixes with other elements, and produces acid rain.

Since the 1970s, governments have tried to clean smoke from factories and power stations to keep too much sulfur from rising into the atmosphere. This has had good results, but it is expensive.

In 2001, Great Britain still produced about five million tonnes (metric tons) of these gases every year, while China produced 18 million tonnes. The United States produced more than 20 million tonnes, but in 2010 that number fell to 8.1 million.

Adverse effects

Effects on lake ecology

The pH level in lakes needs to be correct for fish to be able to survive, and acid rain can affect a lake's pH level. If there is too much acid in the water several things can happen:

The enzymes that help fish larvae to hatch will not be produced.

Aluminum travels more easily through water, causing fish to make more mucus around their gills. This makes it harder for fish to breathe.

Phytoplankton will not grow well and the animals that feed on it would suffer.

Effects on soil biology

Acid rain can damage soil by killing microbes that are needed in the soil. The hydrogen ions of acid rain also allow toxins to move in the soil and take away nutrients that the soil needs. Forests usually are the home to fungi, but acid rain changes the soil, making it more filled with bacteria. Many trees in the forest depend on the fungi for water and minerals, while the fungi take carbohydrates from the trees. This symbiotic relationship, called mycorriza, can be destroyed by acids.

Other adverse effects

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Acid rain affects both living and non-living things. The leaves and roots of trees are damaged, making them less able to make food ( photosynthesis) and absorb nutrients. Toxic ions released due to acid rain are dangerous to humans. It is believed that copper (mobilized by acids) has caused outbreaks of diarrhea in young children. Statues and other ancient structures have also been harmed by acid rain.

Prevention methods

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In the U.S., the method for keeping sulfur from escaping into the air from the smokestacks of factories is called Flue Gas Desulfurization (FGD). One popular example is a wet scrubber, which pulls the gases from the stack into a tower and cleans them using lime or limestone. This changes the form of the chemical into a calcium sulfate that can be taken out of the scrubber. Sometimes the sulfates are sold to chemical companies. Other times, they are put in a landfill.

Some people do not want power generation to be controlled because they feel that pollution is a natural consequence of factories and power stations. They believe that if the pollution is not handled properly, it could be dangerous. Others install pollution controls for the benefits that they will receive from them.

Interesting facts about acid rain

Acid rain is a result of gases mixing with water high in the atmosphere.

Sulfur dioxide is released into the air by machines, houses, and vehicles and is the main chemical that creates acid rain.

Acid rain makes it more difficult for aquatic animals to survive.

Acid rain can damage the soil and the plants that live in it.

There are ways to prevent so much sulfur dioxide from escaping into the air. Many companies install pollution-controlling machinery in their factories.

Images for kids

Since 1998, Harvard University wraps some of the bronze and marble statues on its campus, such as this " Chinese stele", with waterproof covers every winter, in order to protect them from corrosion caused by acid rain and acid snow

In Spanish: Lluvia ácida para niños

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emissions include dust and soot particles, carbon dioxide and sulfur dioxide gases.  They cause irritation and coughing, can damage lungs, and cause serious diseases such as lung cancer.

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emissions include dust and soot particles, carbon dioxide and sulfur dioxide gases.  They cause irritation and coughing, can damage lungs, and cause serious diseases such as lung cancer.

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Ozone is a chemical with the symbol O3. This means one molecule of ozone is made of 3 oxygen atoms.  In our upper atmosphere it protects our Earth from harmful rays from the sun.  In the lower atmosphere it reacts with other molecules and forms harmful substances

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Ozone is a chemical with the symbol O3. This means one molecule of ozone is made of 3 oxygen atoms.  In our upper atmosphere it protects our Earth from harmful rays from the sun.  In the lower atmosphere it reacts with other molecules and forms harmful substances

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Smog is a mixture of smoke and fog and harmful for humans to breathe

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Smog is a mixture of smoke and fog and harmful for humans to breathe

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Click to watch a video and practice what you know

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Click to watch a video and practice what you know

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BrainPOP - Animated Educational Site for Kids - Science, Social Studies, English, Math, Arts & Music, Health, and Technology

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Click to learn more and practice what you know

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Click to learn more and practice what you know

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Click to read:  What might be hurting our Earth?

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Click to read:  What might be hurting our Earth?

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Chlorofluorocarbons (CFC) are gases used for various purposes including solvents, refrigerants and aerosol sprays. They are organic chemicals and contain carbon, (sometimes hydrogen,) chlorine, and fluorine. They were much used in the middle 20th century, replacing chemicals that were toxic or flammable or had other problems. In 1978, Sweden became the first country that banned CFC products. Later, the US and Canada did the same. Now, CFC products are not allowed in most countries, because they cause ozone depletion. CFCs also are greenhouse gases. An alternative is hydrofluorocarbons (HFCs). These do not destroy the ozone layer or increase global warming.

Related pages

Images for kids

Ozone-depleting gas trends

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Chlorofluorocarbons (CFC) are gases used for various purposes including solvents, refrigerants and aerosol sprays. They are organic chemicals and contain carbon, (sometimes hydrogen,) chlorine, and fluorine. They were much used in the middle 20th century, replacing chemicals that were toxic or flammable or had other problems. In 1978, Sweden became the first country that banned CFC products.

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Far above Earth's surface, the ozone layer helps to protect life from harmful ultraviolet radiation. Learn what CFCs are, how they have contributed to the ozone hole, and how the 1989 Montreal Protocol sought to put an end to ozone depletion.

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Is smog an issue in the city where you live? What exactly is it like to live in an area prone to long time periods where citizens are exposed to smog? Read this article: Here are some of the world's worst cities for air quality. To find out the cities with the most air pollution issues, click here and here. This American Chemical Society article: In the Fog about Smog: Solving the Smog Puzzle on Earth and from Space describes how smog is being studied from space and discusses the formation of smog and what comprises it! Finally, China's toxic smog from BBC News shows actual footage and descriptions from people living in smog ridden areas. This multimedia presentation also provides interviews and first person account of how it is to live in a polluted city on a daily basis: Beijing's smog: A tale of two cities.

There are methods being designed that may help cities fighting smog to decrease the impact of this nuisance on its citizens. Visit this link to see a new air mask design from Swedish entrepreneurs. Decreasing worldwide dependence on coal can also help stop smog formation. Here is a recent article on that topic. How difficult will it be to cut coal out of the energy equation? What measures has China taken to decrease smog? This article: China Bans Cars As Air Pollution Hits Red-Alert Status may provide some ideas. National Geographic also has this recent article: China's Surprising Solutions to Clear Killer Air.

What exactly is a temperature inversion and how does it form? The science behind temperature inversions is a great resource describing how smog and other types of air pollution can become trapped due to lack of vertical mixing of atmospheric layers. Where do these inversions commonly form?

Health problems associated with smog can be both acute and chronic. This article describes issues that arise when exposed to smog on a frequent basis. Tehran smog blamed for hundreds of deaths is another article that discusses the hazards of smog exposure. With Every Breath : Health Effects Of Smog addresses California's SMOG problems and the health effects on people living in the area. Does exposure to smog affect the nervous system? Read: Smog in our brains and find out more. Visit the Center for Disease Control for more information about particulates, air pollution and exposure to high tropospheric ozone levels.

Studying historic smog events could give us great insight into how to prevent future ones. Learn more about the Smog Almost Killed New York City, Here's How! Here is a photo-essay of SMOG through the years in Los Angeles. London, England also has had some serious and deadly bouts with SMOG. One was the Great Smog of 1952. Read more about it here: Scientists finally know what caused a mysterious fog to kill 12,000 people in London in 1952.

People all over the world are looking for ways to reduce smog. This TED Talk discusses one idea.

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On July 26, 1943, Los Angeles was blanketed by a thick gas that stung people's eyes and blocked out the Sun. Panicked residents believed their city had been attacked using chemical warfare. But the cloud wasn't an act of war. It was smog. So what is this thick gray haze actually made of?