Describe air pollution. How can it be controlled?

(N/A) Air is essential for the respiration of all living organisms. Air pollution is the presence of harmful substances in the atmosphere that cause damage to the environment and human health.
Pollutants reduce the growth and production of crops and can lead to the premature death of plants.
The harmful effect of pollution on all living organisms depends upon: $(a)$ Concentration of pollutants,$(b)$ Duration of exposure,and $(c)$ The specific organisms involved.
Thermal power plants,smelters,and other industries release particulate and gaseous air pollutants along with harmless gases such as nitrogen and oxygen.
These pollutants must be filtered out before releasing the gases into the atmosphere.
There are many methods for removing particulate matter; the most widely used is the electrostatic precipitator and the scrubber.
$1$. Electrostatic Precipitator: It can remove over $99 \%$ of particulate matter present in the exhaust from a thermal power plant. It has electrode wires that are maintained at several thousand volts to produce a corona that releases electrons. These electrons attach to dust particles,giving them a net negative charge. The collecting plates are grounded and attract the charged dust particles,allowing clean air to pass through.
$2$. Scrubber: $A$ scrubber can remove gases like sulfur dioxide $(SO_2)$. In a scrubber,the exhaust is passed through a spray of water or lime. The lime reacts with sulfur dioxide to form a precipitate,which is then removed.