What Is Acid Fog?

Acid fog refers to fog that becomes highly acidic when acidic substances such as sulfuric acid and nitric acid dissolve into the moisture in the air.

In general, fog droplets are much smaller than raindrops. Because of this, pollutants can become more concentrated in fog droplets than in raindrops. This can be compared to dropping the same amount of ink into a large water droplet and a small water droplet: the smaller droplet will appear darker because the ink is more concentrated.

In some cases, the concentration of pollutants in fog droplets can be much higher than in rainwater, sometimes up to about 100 times higher. Like acid rain, acid fog can contribute to the acidification of soil and bodies of water, lowering the pH of rivers and lakes.

Acid fog can also harm plants. Because fog droplets can remain around plant leaves for a relatively long time, they may directly affect leaf surfaces and weaken plant growth.

Acid fog can also be harmful to humans. The acidic substances and air pollutants in acid fog can irritate the eyes and respiratory system, and may worsen symptoms such as breathing difficulties in people with asthma or other respiratory diseases.