Speech Air Pollution: Definition, Effects and Methods for Reducing it (explained with diagram)


Pollution of air is a greater problem in urban and industrial areas than in rural areas. The common pollutants of air and their sources are mentioned in Table 16.1.

Sources of the chief pollutants of air

The products obtained on the combustion of fossil fuels are the major pollutants. Fossil fuels contain some compounds of nitrogen and some of sulphur. Therefore, on combustion, such fuels give the oxides of nitrogen and sulphur (collectively known as NOx and SOx) apart from carbon dioxide and carbon monoxide. When petroleum fuels burn and the combustion is incomplete, soot is also formed.

Effects of air pollution:

Effect on health:


Air pollution causes many health problems.

SOx and NOx:

The oxides of sulphur and nitrogen cause breathing problems and increase vulnerability to respiratory infections. They also trigger asthma attacks.


Carbon Monoxide:

Carbon monoxide (CO) is a poisonous gas. It can kill a person without warning as it is colourless and odourless. As you know, blood transports oxygen in our body. When we inhale air, the oxygen of the air combines with haemoglobin of the blood to form oxy-haemoglobin. Oxy-haemoglobin runs through blood vessels and gives up its oxygen to cells, which use it for respiration.

But CO displaces oxygen from oxyhaemoglobin to form carboxyhaemoglobin. The affinity of CO for haemoglobin is 325 times greater than that of oxygen. So the displacement takes place easily. The formation of carboxyhaemoglobin cuts off oxygen supply to cells, and adverse effects are seen.

The severity of the symptoms depends on the amount of CO in the blood. As we have just said, inhaling air with a high CO level may even be fatal. A person may die if he or she sleeps in a closed room heated by a coal fire.


Effects of CO poisoning

Carboxyhaemoglobin slowly loses CO on being exposed to an excess of oxygen, and oxyhaemoglobin is again formed. So, a person suffering from CO poisoning should be kept on oxygen till he or she recovers.

The CO level in cities can vary from 5 to 100 ppm—mainly due to motor vehicles.



CFCs convert ozone to oxygen. CFC pollution is, therefore, reducing the amount of ozone and creating a ‘hole’ in the ozone layer of the atmosphere. This layer shields us from the harmful effects of the ultraviolet (UV) rays of the sun. The depletion of ozone has led to an increase in skin cancer and eye problems.


The solid particles that pollute the air get inhaled by us. These particles irritate and damage the lungs. They cause frequent attacks of asthma and bronchitis.

Acid rain:

The oxides of sulphur and nitrogen present as pollutants in the air react with the water present in the atmosphere to form sulphuric and nitric acids. These acids come down with rain, making rainwater significantly acidic. Such rain is called acid rain.

In some industrial areas, hydrogen chloride gas is also present in the air as a pollutant. It dissolves in water to form hydrochloric acid, which comes down with the rain, making it more acidic.

Effects of acid rain:

1. The water of lakes and rivers becomes acidic and, thus, unsuitable for aquatic plants and animals.

2. The soil becomes acidic and, therefore, unsuitable for cultivation.

3. Sculptures, monuments and buildings are eroded.

The greenhouse effect:

A greenhouse is an enclosure of glass in which plants are kept to protect them from the cold air outside. The glass traps the heat of the sun, making the air inside warmer. In much the same way, the CO2 in the air traps the heat of the sun radiated back by the earth.

This makes the air warm and comfortable for living beings, and in fact makes it possible for life on earth to exist. (Otherwise, the nights would be too cold.) But an increase in the level of the CO2 in the air has meant that the atmosphere has become warmer as more heat is trapped.

This is known as the greenhouse effect, and the increase in temperature worldwide is called global warming. Environmentalists feel that global warming leads to changes in the climatic pattern worldwide, causing frequent floods and cyclones. Some also feel that it may lead to the melting of the polar ice caps, raising the sea level and submerging many coastal areas.

Products obtained upon the combustion of fossil fuels

Methods of reducing air pollution:

The following methods are commonly used to reduce air pollution:

Modifying automobile engines:

Automobile engines are so modified that complete combustion of fuel takes place. This reduces the proportion of carbon monoxide and particulate matter in air.

Using compressed natural gas (CNG):

Nowadays, CNG is preferred over petrol or diesel in trucks, buses and other vehicles. It contains methane (CH4) which, on burning, produces much less pollutants than do coal, petrol, etc.

Using unleaded petrol:

In the past, a lead compound was mixed with petrol to help automobile engines run smoothly. This produced poisonous lead compounds in the exhaust, which polluted the air. So unleaded (or lead-free) petrol is now used.

(a) Smoke from the combustion of coal and (b) exhaust fumes from vehicles pollute the air

Removing pollutants from industrial waste gases:

You may have seen waste gases coming out of the chimneys of factories. But, before being discharged, the gases must be freed from most pollutants.

Smoke from a factoty chimney is an air pollutant

Duststroms are a great source of particulate matter in air

The ozone hole as photographed from a satellite

Using cleaner sources of energy:

A major part of the electricity in our country is produced by thermal power plants. Coal is burnt in these plants to get heat. The burning of coal produces gases that pollute the air. Hence, we must utilise cleaner sources of energy. For example, we can use hydroelectricity, solar energy, wind energy and hydrogen energy (the burning of hydrogen produces water, which is not a pollutant).We should use cleaner source of energy, e,g (a) hydroelectricity, (b) solar energy, and (c) wind energy

No comments yet.

Leave a Reply