What Causes Acid Rain? What Are the Dangers?

La Niña, Rain, Queensland, Storm, Flood
© iStock.com/Daria Nipot

Written by Marisa Wilson

Updated: November 1, 2022

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In the 19th century, Robert Angus Smith wrote about the connection between pollution and acid rain. He also came up with the term “acid rain.” When was acid rain a problem, and what happened to it? If you lived in the 80s, you probably remember it being talked about everywhere, or you may be curious about it; whatever the reason, you’ll find helpful information here. Keep scrolling to learn about the causes and effects of acid rain.

What Is Acid Rain, and What Creates It?

Lightning striking the Sonoran Desert

Acid rain results from these acids dissolving into water droplets in the clouds; they can also appear as snow or fog.

©Mike Hardiman/Shutterstock.com

Acid rain is caused more by human activities than natural ones. There are several causes of acid rain, but all the causes are classified as a form of pollution. Extensive animal farming also causes ammonia to be produced through the breakdown of organic materials, but in a smaller amount. When these pollutants interact with oxygen in the air, they produce sulphuric acid and nitric acid, which may be detected thousands of miles away.

Acid rain results from these acids dissolving into water droplets in the clouds; they can also appear as snow or fog. Acid rain isn’t only rain like the name suggests. All precipitation falls from the sky as an acidic mixture, including sulfuric and nitric acids. The pH of acid rain ranges from 4.2 to 4.4, while that of ordinary rain is 5.6.

The acidification of the Earth’s surface and oceans has devastating effects on ecosystems and threatens all forms of life on the planet. Microbiological processes, earthquakes, natural fires, lightning, and volcanic eruptions all contribute to releasing sulfur dioxide and nitrogen oxides into the atmosphere. However, burning fuel in industry and power plants is the primary source of sulfur dioxide emissions. Half of all nitrogen oxide emissions come from vehicles. It is evident that humans have caused quite a few environmental issues.

When Was Acid Rain Discovered?

Even though acid rain was first discovered in the 19th century, it was in the 1980s that the phenomenon gained widespread attention. By this time, most people were aware of the connection between the rise in industrial emissions and the prevalence of acid rain. Midwest coal plant pollution caused acid rain to begin in the United States in the 1950s.

What Area Was Most Affected by Acid Rain?

Effects of acid rain in Germany

In certain areas of the Black Triangle, whole forests were dead or deteriorating, and the acidic precipitation was corroding railroad tracks.

©iStock.com/Achim Schneider / reisezielinfo.de

The Black Triangle, which includes parts of the Czech Republic, Germany, and Poland, was a region that experienced severe acid rain through the 70s and 80s. In certain areas of the Black Triangle, whole forests were dead or deteriorating, and the acidic precipitation was corroding railroad tracks. To stop additional acid rain pollution, the Geneva Convention of 1979 placed strict regulations on the emissions of coal-burning plants in Eastern Europe. As a result, acid deposition in the region has been dramatically reduced.

What Are the Effects of Acid Rain?

When rain is mixed with sulphuric acid and nitric acid, its pH changes, compromising the ecosystems’ delicate equilibrium when it falls on the land or in bodies of water. This condition, known as environmental acidification, has negative consequences.

Ocean productivity and biodiversity can decline. This lowers the pH of marine waters and damages phytoplankton. This is an issue because it serves as a food supply for various creatures. It can change the food chain and cause the extinction of several marine species.

While only 1% of the world’s water is fresh, 40% of fish reside there. Therefore, the rising acidification of inland waters is very concerning. This acidification raises the levels of metal ions, especially aluminum ions, which may cause many fish, amphibians, and aquatic plants to perish in acidified lakes. Additionally, heavy metals are dispersed into underground waters, rendering them unfit for human consumption.

Vegetation cannot absorb the water and nutrients it requires in forests because of the low pH level of the soil and the high concentration of metals, such as aluminum. This weakens plants and increases their susceptibility to disease and pests. It also damages roots and hinders growth.

Cultural, historical, and artistic legacies are also impacted by acid rain. In addition to eroding the metallic components of structures and infrastructure, it damages the monuments’ outward look. Constructions made of calcareous materials, like marble, sustain the most damage since they gradually dissolve under the influence of acids and water.

Acid Rain and the Health Risks It Poses to Humans

In the air, sulfur dioxide or nitrogen oxides can create respiratory disorders or worsen existing conditions. Breathing becomes difficult for individuals who have respiratory conditions such as chronic bronchitis or asthma. Even smaller particles can be produced by the same pollutants that cause acid rain. These particles can also cause health issues or exacerbate ones that already exist when they enter a person’s lungs. 

Nitrogen oxides also contribute to ground-level ozone. This ground-level ozone can permanently damage the lungs and cause respiratory issues like pneumonia and bronchitis. People’s health impacts, which are a concern, are not brought on by acid rain but rather by breathing in these particles or ozone. However, people can swim or walk in acidic lakes without experiencing greater health risks than in clear water.

Is Acid Rain Still an Issue?

The United States Congress aimed at limiting acid pollution with the 1970 Clean Air Act. In 1990, they strengthened the law even more. The regulation appeared to have an impact because, by the turn of the millennium, the acidity of rainfall had decreased by 40%. Even though acid rain is still a problem in 2022, it isn’t as severe. 

Why isn’t it a big issue? The BBC reports that Gene Likens made the initial discovery after taking a rain sample in the White Mountains of New Hampshire. Additional research was undertaken, and it was continually explored. Researchers watched and changed the pH levels of lakes, particularly those in North America, and eventually discovered that some bacteria were naturally reducing the acidity. 

Even though some people continued to deny that acid rain existed, scientists persisted in their investigation. After the Clean Air Act was finally passed in 1990, because it was primarily the result of excessive levels of air pollution, the problem was substantially under control. In addition to Canada, the United States launched the Acid Rain Program. Even though physical recovery took longer, acid rain isn’t as big a problem anymore. Other things, like renewable energy, are more critical.


Acid rain is primarily caused by two pollutants produced when soft coal is burned in factories and power plants: nitrogen oxide and sulfur dioxide. Precipitation, such as rain, snow, and fog, is produced when these chemicals react with water and airborne particles to form acid rain, known as nitric and sulfuric acid precipitation. Acid rain does not endanger people; therefore, coming into contact with tainted snow or water has no adverse health effects. 

However, the gases (nitrogen oxides, sulfur dioxide, and trioxide) responsible for this rain are dangerous. These gases, which are carried by the wind and breathed in by individuals, contain sulfate and nitrate particles. This can lead to respiratory conditions. It has been reduced and is a wonderful example of how humans have fixed the damage they have created. The action plan in the 1900s worked, and there was a significant improvement from the damages. We can only hope that global warming will have a success story such as this one.

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About the Author

Creepy-crawly creatures enthrall Marisa. Aside from raising caterpillars, she has a collection of spiders as pets. The brown recluse is her favorite spider of all time. They're just misunderstood. You don't have to worry about squishing the creatures as her catching, and relocating abilities can safely move stray centipedes or snakes to a new location that's not your living room.

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