What Is the Cause of Acid Rain? 10 Things (2024) You Should Know

Acid rain first started affecting the world in the 1950s when coal plants in the Midwestern United States began spewing sulfur dioxide (SO2) and nitrogen oxides (NOX) into the air.

This began to turn clouds and the rain that fell from them acidic.

When acid rain falls, it impacts everything it touches.

It leaches calcium from the soil and robs plants of important nutrients.

It can also poison lakes that serve as home to wildlife, water sources for humans, and recreational outlets.

So, as this problem became worse (not better), Congress imposed acid emission regulations in 1970 through the Clean Air Act.

These regulations were strengthened in 1990.

Finally, by the 2000s, both sulfate and nitrate in precipitation decreased by around 40 percent.

However, acid rain isn’t “over.”

If you’re not already aware of what is the cause of acid rain, read on!

Here’s what you need to know about keeping the environment clean, so you can keep yourself safe. 

1. What is acid rain?

Acid rain is any type of precipitation — snow, fog, or tiny bits of dry deposition — that contains high levels of sulfuric and nitric acids.

Though normal rain is slightly acidic (pH level of 5.6), acid rain has an even more extreme pH between 4.2 and 4.4.

While acid rain can occur due to natural causes, it is primarily prompted because of human actions.

2. What is the cause of acid rain?

Acid rain is most often caused by fossil fuels.

When coal and oil are burned by power companies (or other industries), sulfur is released into the air.

Sulfur is then combined with oxygen to form sulfur dioxide.

Sulfur dioxide will dissolve — along with nitric acid that forms due to car exhaust — into water vapor in the air.

When precipitation occurs, acid rain will pour down and wreak havoc on the environment.

Most often, acid rain will originate in urban areas or near power plants.

However, acid rain can still occur in rural areas because the gases will drift hundreds of miles.

That said, there are some natural causes of acid rain, including rotting vegetation and erupting volcanoes.

These release some chemicals that can cause acid rain.

However, these natural activities often pale in comparison to the air pollutants that result from human activities, like coal-burning power plants, factories, and automobiles.

If you want to read more natural causes of acid rain, see below.

3. What are the effects of acid rain?

As noted above, the gases that cause acid rain are sulfur dioxide and nitrogen oxide.

Both of these gases cause environmental and health concerns.

They spread easily via air pollution, and they cause acid rain.

Here are the impacts that acid rain has on the environment:


Acid rain makes the water more acidic.

Everything from freshwater macroinvertebrates to plants to fish populations is damaged by the presence of acid rain.

It entirely disrupts organisms’ reproductive cycles and alters the chemistry of their bodies.

Additionally, acid rain causes more aluminum absorption in soil, which is then carried into lakes and streams.

The combination of chemicals makes the water toxic to crayfish, clams, fish, and other aquatic animals.

Although some animals can tolerate more acidic environments, any animals being affected will cause an impact on the food chain.


Acid rain lowers the biological productivity of lakes.

As a result, it impacts the food chain at all levels.


Acid rain and fog damage forests, especially when they’re at higher elevations.

This is because forests can be highly-sensitive ecosystems, and sulfur and nitrogen deposition can cause adverse effects by draining nutrients in the soil and negatively affecting tree growth.

Acid deposits can also harm tree leaves and needles.

Overall, acid rain leaves both trees and plants less healthy and more vulnerable to cold temperatures, insects, and disease.

Pollutants may also inhibit a tree’s ability to reproduce, which leaves forests significantly less viable.


Pollutants that cause acid rain can also degrade air quality.

Poor air quality often results in reduced visibility even in remote areas like mountains.


Acid rain deposition can cause damage to buildings, bridges, and cultural resources.

Sulfuric acid can have a corrosive effect on limestone and marble buildings and monuments.

bulletHuman Health

Interestingly, for humans, walking in acid rain is no more dangerous than walking in non-acid rain.

However, that doesn’t mean that there are no adverse health effects.

The pollutants that cause acid rain can be harmful to people.

Sulfur dioxide and nitrogen oxide react with water oxygen and other chemicals to form fine sulfate and nitrate particles.

If these particles enter the lungs, then they can cause lung disease, heart attacks, and difficulties for people with asthma.

Acidified water can also cause metals to be leached from the soil into water sources — streams, lakes, reservoirs, etc. — which can impact home water supplies.

All of this can result in serious illness for humans.

4. How do you prevent acid rain (as an individual)?

Acid rain both sounds and feels like a huge problem in the larger picture of our environment.

However, there are numerous ways that individuals (like you) can help prevent it.

The core way to prevent acid rain is to stop its formation.

How does it form?

With fossil fuels that we use for energy.

Here are the top ways you can directly impact the number of fossil fuels that are used.

bulletPurchase energy-saving appliances

bulletCarpool to work, school, or anywhere else you can think of

bulletUse public transportation

bulletWalk or bike whenever possible

bulletKeep your thermostat low in the winter and high in the summer

bulletInsulate your house

bulletTurn off your lights, computers, and appliances when not in use

5. How should we avoid acid rain (as a society)?

Humans are the leading cause of acid rain, and as a result, we must come together to solve the problem of the consistent acidification of the environment.

To reduce acid rain, we must decrease pollutant emissions.

Here are ways that we, as a society, can help to avoid acid rain in the future.

Many of these are too big for an individual to do by themselves.

bulletFilter and detoxify the water used by the factories before returning it to the rivers

bulletReduce the emission of pollutant gases by the industry

bulletEncourage the production and use of renewable energy rather than fossil fuels

bulletReduce the energy consumption of factories and companies

bulletPromote innovation and new technologies aimed at optimizing energy consumption and developing renewable energy

bulletPlant trees to absorb polluted air

bulletRaise awareness of the importance of reducing household energy consumption

bulletEncourage the use of electric vehicles and other non-polluting vehicles (e.g., bicycles)

6. What are the natural causes of acid rain?

Most of the problems we see with acid rain in our environment are due to the human use of fossil fuels.

However, there are quite a few natural causes of acid rain that are worth keeping in mind.

bulletVolcanic eruptions


bulletNatural fires


bulletSome microbial processes

All these release sulfur dioxide and nitrogen oxides into the atmosphere.

As discussed above, these gases are what cause acid rain.

7. What are the primary forms of acid rain?

Acid precipitation isn’t limited to one form.

You can see acid rain, snow, sleet, hail, fog (wet deposition), acid particles, aerosols, and gases.

Acid deposition occurs when sulfur dioxide and nitrogen oxides combine with moisture in the atmosphere to produce sulfuric acid and nitric acid.

Acid deposition has been particularly destructive to certain areas of the U.S. in the past.

For example, in the 1960s, scientists noticed that this was occurring in New York, particularly in the Catskill and Adirondack Mountains.

In these areas, the soils were becoming too acidic to maintain healthy forests, so trees were dying off at higher elevations.

Additionally, many lakes, mountain streams, and some rivers were unable to support healthy populations of fish.

When this occurs, natural resources can also be hit particularly hard.

8. Where has the problem of acid rain decreased?

Acid rain was a huge problem a few decades ago, but it’s not as widely talked about today.

When it comes to environmental issues in North America, it’s not at the top of the list.

Climate change has taken over as one of the top issues.

However, just because both North America and Europe have gotten their sulfur dioxide and nitrogen oxide levels under control thanks to legislation, that doesn’t mean the problem doesn’t exist elsewhere.

Countries like China and India have continued to develop and industrialize.

As a result, their emissions of sulfur dioxide and nitrogen oxide have increased.

Furthermore, parts of Latin America and Africa (particularly those that are urban) have seen more acid rain in recent years.

Acid rain has real impacts.

It’s not something that can be passed over for years.

One study showed that acid rain in China may have contributed to a deadly landslide in 2009.

China has since started implementing controls around its sulfur dioxide emissions.

They have fallen by 75 percent since 2007. However, India’s has increased by half.

So, while the United States, Canada, and other European countries are in the clear when it comes to acid rain, that’s not the case for the whole world.

9. What regulations have helped the U.S.?

 The United States used the Clean Air Act of 1970 as one of the first measures to control its emissions.

The Clean Air Act Amendment was added in 1990.

This law set limits on how much pollution was allowed in the air anywhere in the U.S..

This helped to prevent gases like sulfur dioxide from getting into the air, to begin with, so acid rain couldn’t form.

Additionally, the Canada-United States Air Quality Agreement in 1991 also added another layer of protection.

This agreement addressed transboundary air pollution.

While it initially focused on reducing levels of acid deposition in each country, the agreement was updated in 2000 to include ground-level ozone.

Finally, the EPA established the Acid Rain Program (ARP), which was established under Title IV – Acid Deposition Control.

This program requires major emission reductions of sulfur dioxide and nitrogen oxides from the power sector.

It sets a permanent cap on the total amount of sulfur dioxide that can be emitted by electric generating units in the contiguous U.S.

This program was initially phased in, and the final cap was set in 2010 at 8.95 million tons.

This cap is one-half of the emissions permitted from the power sector in 1980.

The program began in 1995 and the ARP has seen significant emissions reductions.

Overall, the ARP uses market-based incentives to reduce pollution.

It was the first national cap and trade program in the country.

10. Are sulfur dioxide and nitrogen oxide greenhouse gases?

No, sulfur dioxide and nitrogen oxide at not considered the main greenhouse gases despite being the primary cause of acid rain.

They are considered indirect greenhouse gases along with carbon monoxides and non-methane volatile organic compounds (VOCs).

An indirect greenhouse gas has an effect on atmosphere warming either through a chemical reaction or changing the Earth’s capability to balance radiative energy.

For reference, the 7 major greenhouse gases are carbon dioxide, methane, nitrous oxide, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and ozone.

Note: nitrogen oxides and nitrous oxides are two different gases despite both containing the element of nitrogen.

Final Thoughts

Acid rain may not be prominently present in public discourse like it was a few decades ago, but that doesn’t mean that the problem has gone away.

So, what is the cause of acid rain? Fossil fuels!

When we use fossil fuels, it impacts forests and aquatic ecosystems to an extreme degree.

It makes the water toxic, which thus poisons the soil and deprives it of essential nutrients.

As landowners, it’s our job to be stewards of the land.

Protecting the environment from disasters (like acid rain) is important to ensure that generations can enjoy the Earth for years to come.

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Erika Gokce Capital

Disclaimer: we are not lawyers, accountants, or financial advisors and the information in this article is for informational purposes only. This article is based on our research and experience and we do our best to keep it accurate and up-to-date, but it may contain errors. Please be sure to consult a legal or financial professional before making any investment decisions.


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