Contamination of air by the addition of harmful substances is called pollution.
There are 3 type of pollution are as follows:
1. air pollution
2. water pollution
3. sound pollution
when we are using the refrigerator, air conditioner ,it cause air pollution.
when we are polluting the rivers by adding the waste from our homes ,it cause air pollution.
when the ultrasound is passing through the mind ,it cause sound pollution.
hope it helps you