What to Know About Acid Rain Health Effects

Medically Reviewed by Dany Paul Baby, MD on November 11, 2022
5 min read

Acid rain is a topic that pops up in the media every so often, but many of us don't know much about it. Acid rain happens when certain chemical compounds enter the atmosphere. It can cause damage to the environment, man-made structures, and human health.

Acid rain is a broad term for any precipitation that contains acidic ingredients. Precipitation includes rain but also fog, hail, sleet, and snow.

To measure how acidic something is, we use the pH scale, which ranges from 0 to 14. Seven, in the middle, is neutral. A pH under 7 indicates that something is acidic, while a pH above 7 indicates that something is alkaline. The closer to 0, the more basic something is, and the closer to 14, the more alkaline it is. The further away you get from neutral, the more corrosive the substance can be. 

Examples of products with different pH levels include:

  • 0 (Very acidic): Battery acid
  • 1: Stomach acid
  • 2: Lemon juice
  • 3: Orange juice
  • 4: Tomato juice
  • 5: Black coffee
  • 6: Urine
  • 7 (Neutral): Pure water
  • 8: Sea water
  • 9: Baking soda
  • 10: The Great Salt Lake
  • 11: Ammonia
  • 12: Soapy water
  • 13: Bleach
  • 14 (Very alkaline): Liquid drain cleaner

As you can see, pure water is neutral at 7. Normally, rain is somewhat acidic, with a pH of about 5.6. Acid rain usually falls between 4.2 and 4.4, about the same as tomato juice.

Acid rain formation begins when sulfur dioxide (SO₂) and nitrogen oxides (NOₓ) are released into the atmosphere. While some natural sources can release sulfur dioxide and nitrogen oxides, most of then are emitted by the burning of fossil fuels. Primary causes of sulfur dioxide and nitrogen oxides in the atmosphere are:

  • Power plants — two-thirds of sulfur dioxide and a quarter of nitrogen oxides in the atmosphere are produced by electric power generators
  • Vehicles and heavy equipment
  • Industries like manufacturing and oil refineries

Once these particles are released into the air, they're swept up by wind and air currents. These particles then mix with water, oxygen, and other chemicals to create sulfuric acid and nitric acids. 

These acids usually mix with water and fall to the ground as precipitation. Sometimes, when there isn’t enough moisture, the particles fall to the ground and land on surfaces like bodies of water, buildings, trees, and plants. When precipitation eventually comes, it can wash the particles into the soil and bodies of water.

Acid rain can have huge impacts on the environment. It can kill wildlife, erode surfaces, and reduce visibility.

Wildlife. Animals that live in aquatic environments, like lakes, rivers, and streams, are most affected by acid rain. While not all animals are sensitive to acidity, creatures like clams and snails need a pH of at least 6 to survive. The young of many species often don’t handle acidity as well as the adults. While a perch may be able to handle water with a pH as low as 4.5, their eggs may not hatch.

The inability of the young to survive isn’t the only threat to species. Acid rain can also disrupt the food chain. For example, while frogs can survive in water with a pH as low as 4, the mayflies they eat may not survive below a pH of 5.5. This can have a cascading effect where, even if a species can survive the acidity, they may starve. This includes not just aquatic animals but also animals like bears and wolves.

Acid rain can increase the dangers of lakes, rivers, and streams more than you might expect. When acid rain falls to the ground and flows into the soil, it absorbs aluminum from the surrounding soil. This then flows into the lakes, rivers, and streams and can make the water toxic to the creatures that live there.

Plants and trees. Acid rain can destroy the soil that plants and trees need to survive. It does this by dissolving necessary nutrients like calcium and magnesium. Acid rain also releases aluminum into the soil, which can be dangerous for plants, as it makes it difficult for them to absorb water. 

Trees at higher elevations are at an even higher risk for acid rain damage. These trees are exposed to acid clouds and acid fog. This strips nutrients from the tree leaves and needles. Without these nutrients, it’s easier for bugs, infections, and weather to damage trees.

Surface erosion. Acid is corrosive, meaning it slowly degrades materials. When acid rain lands on buildings, bridges, statues, and other structures, they start to break down. This means that they will need to be replaced or repaired, leading to increased maintenance costs. It also means that things like statues and tombstones can lose their intricate details.

Visibility. Particles in the air, like other forms of pollution, can cause smog and haze. This not only disrupts your view of scenery but can be dangerous to travel in.

If acid rain comes into contact with your skin, you won’t feel any effects. Walking in acid rain or even swimming in a lake that’s had acid rain isn’t any more harmful than regular water.

The main health effects of acid rain come from inhaling it. Inhaling acid rain can lead to respiratory illnesses like asthma or chronic bronchitis, or make these conditions worse for people who already have them. These particles can also reduce heart function, leading to heart attacks and even death.

Because acid rain is caused by burning fossil fuels, the best way to prevent acid rain is to find alternative ways to generate power. 

The Environmental Protection Agency has already started on this. The Acid Rain Program sets a cap on the amount of emissions that power plants can release into the air. It also provides incentives for reducing these emissions. 

Power plants can reduce emissions by using coal that has less sulfur or using equipment that removes sulfur dioxide from the smokestacks. Using alternative sources of energy like solar and wind is also an excellent way to prevent pollution like acid rain.