Acid Rain: Here’s What You Need to Know

What is Acid Rain?

Acid rain is a term that refers to any form of precipitation, including snow, containing acidic components. Such acidic components are typically produced when anthropogenically-emitted, or human-produced, sulfur dioxide and nitrous oxides react with naturally occurring oxygen and water. The resulting rain and precipitation usually have a pH between 4.4 to 4.2 compared to water’s pH of 7, with lower values indicating more acidity. This acidity leads to many adverse effects for humans, wildlife, and even infrastructure.

While acid rain can occur naturally due to sulfur dioxide and nitrous oxides found in sources such as volcanoes, it has become far more common as a result of human activity. Sulfur dioxide and nitrous oxides emissions have increased largely due to the burning of fossil fuels, vehicle emissions, and oil refining. In this way, acid rain is often seen as a symptom of climate change because they are a byproduct of fossil fuel burning.

Is Acid Rain the Same as Acid Deposition?

Acid deposition, a term you may not have heard of, is closely related to but not quite interchangeable with acid rain. Acid deposition is a broad umbrella term which is categorized into wet deposition, or acid rain, and dry deposition, which is slightly less known. Wet deposition occurs when acidic particles combine with precipitation or fog and falls from the atmosphere, while dry deposition occurs when acidic components self-deposit from the atmosphere without any moisture. During dry deposition, smaller particles often coalesce into larger masses, making them more harmful as particles collide and combine. 

How Does Acid Rain Affect Our Health?

Acid deposition, whether wet or dry, has many consequences concerning human livelihood. One of the most significant concerns regarding acid deposition is its effects on health. Acid rain itself is harmless, but the nitrous oxide and sulfur dioxide in the atmosphere that hasn’t yet formed acid rain can react to create sulfate and nitrate particles, which are known to be detrimental to both respiratory and cardiovascular health. Many EPA-cited studies correlated sulfate and nitrate particles with increased rates of heart attacks, breathing difficulty, and wor asthma. While it is safe to go outside in acidic rain or even swim in affected bodies of water, it is important to keep in mind that harmful sulfate and nitrate particles could also be present. 

Why is Acid Rain a Threat to Infrastructure?

Another major consequence of acid deposition is metal corrosion, which refers to the process by which a metal surface oxidizes. When nitric and sulfuric acids come into contact with metal, the metal tends to corrode. This problem is costly - a United States study estimated $5 billion of damage annually - and even deadly at times, as heavily corroded metal contributes to collapses and fires in buildings, bridges, and other metal structures. This also poses a threat to facilities containing waste, particularly nuclear waste, since corrosion could expose the radioactive waste, endangering humans and wildlife in the area.

What Can You Do? 

The problem of acid rain most directly stems from pollution. Although as individuals, we cannot control emissions from large factories or corporations, one of the biggest actions we can take to minimize the risk of acid rain is reducing our emissions, whether it be through switching to renewable sources or cutting back vehicle use to limit emissions from cars. Additionally, we can raise awareness to the issue and push companies to prioritize using green energy sources to avoid some of the worst impacts of climate change. 

References

United States Environmental Protection Agency. (2019). Acid Rain Students Site: What is Being Done? Epa.gov. https://www3.epa.gov/acidrain/education/site_students/beingdone.html

Shabecoff, P. (1985, July 18). Draft Study Puts Acid Rain Damage at $5 Billion for 17 States. The New York Times. https://www.nytimes.com/1985/07/18/us/draft-study-puts-acid-rain-damage-at-5-billion-for-17-states.html

The Electrochemical Society. (2019). What is Corrosion? ECS. https://www.electrochem.org/corrosion-science

United States Environmental Protection Agency. (2025a, March 4). What is Acid Rain? US EPA; United States Environmental Protection Agency. https://www.epa.gov/acidrain/what-acid-rain

United States Environmental Protection Agency. (2025b, March 19). Effects of Acid Rain. US EPA; United States Environmental Protection Agency. https://www.epa.gov/acidrain/effects-acid-rain