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6. Suspended particulate matter
The finely divided solid or liquid particles suspended in air are called suspended
particulate matter. For example, dust, smoke and fly ash. They remain suspended in
the air for a long time.
a. Dust consists of tiny particles of earth. It produces allergic reactions in the human
body and aggravates diseases like bronchitis. Dust covers the leaves of plants
and trees and prevents photosynthesis.
b. Smoke is tiny particles of carbon in the air. When inhaled causes respiratory
diseases.
c. The minute ash particles formed by the burning of coal and carried into the air by
the gases produced during burning is called fly ash. These particles can cause
irritations to the eyes, skin, nose, throat and respiratory tract.

Acid Rain
It is the precipitation of acid in the form of rain. When atmospheric pollutants like oxides of
nitrogen and sulphur react with rainwater and come down with the rain, then this results in
Acid Rain.
Causes of Acid Rain
The main causes of acid rain are sulphur and nitrogen particles which get mixed with the
wet components of rain. These particles when mixed with water in clouds results in the
formation of sulphuric acid and nitric acid and comes down as rain. The major sources of
these gases are emissions from vehicles and factories.
Effects of Acid Rain
1. Acid rain is very harmful to agriculture, plants, and animals. It washes away all the
nutrients which are required for the growth and survival of plants. Acid rain affects
agriculture, as it alters the composition of the soil. It can make the soil acidic.
2. Acid rain affects the water bodies and eventually affects the aquatic ecosystem.
3. Acid rain also causes the corrosion of water pipes. Which further results in leaching of
heavy metals such as iron, lead or chemicals into drinking water.
4. It damages the buildings and monuments made up of stones and metals.
For example, the Taj Mahal, which is made up of white marble has now turned to
yellowish due to corrosion due to acid rain. This phenomenon is also known as marble
cancer.
The statue of liberty which is made of copper has also been damaged by the corrosion
of acid rain.

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