Pollution is the containment of material particles or energy into the natural environment, causing adverse effects on the ecosystem.

Types of pollution

(1) Air Pollution: It occurs when any harmful gas, dust smoke enters the atmosphere and makes it difficult to survive living organisms like plants, animals, and human beings as well. And causes common respiratory diseases such as asthma, bronchitis.

(2)Water Pollution: It is due to the presence of foreign substances like sewage, algae, soluble salts, etc in water. It can also be due to the presence of some metals in water. Some metals like chromium and Arsenic cause diseases like cancer, cadium can cause Itai-Itai disease, and mercury causes Minamata disease.

For a healthy aquatic life, dissolved oxygen (DO) is 5-6ppm. For clean water, BOD (Biochemical Oxygen Demand) is less than 5ppm while for highly polluted water is 17ppm or more.

(3) Soil Pollution: It is an alternation in soil. It is caused by pesticides, insecticides, for example, DDT, BHC, etc, herbicides for example sodium chloride, fungicides like organomercury compounds.

Hazardous Effects of Pollution

Greenhouse Effect- It is the heating of the earth and its objects because of the trapping of Infra-Red radiations by carbon dioxide(CO2), methane, (CH4), nitric oxide (NO), ozone (O3), chlorofluorocarbons(CFCs), and water vapours.

.• Global Warming- It is a result of the increased concentration of greenhouse gases. It may result in the melting of ice caps and glaciers, spreading several infectious diseases like malaria, sleeping sickness, etc.

• Acid Rain- It has a pH of less than 5. It is due to the presence of oxides of nitrogen and sulphur in air that dissolve in rain water and forms nitric acid and sulphuric acid. It damages the buildings and other other structures made up of limestone and results in several diseases such as qskin infections. pH of normal rain water is 5.6.


There are the substances that contaminates the environment and of two types:

(1) Primary Pollutants: These persist in the environment in the form which they have produced, for example, sulphur dioxide(SO2), nitrogen dioxide (NO2), etc.

(2) Secondary Pollutants: These are the products of nitrogen of primary pollutants, for example, PAN (Perocyacylnitrates), nitrogen dioxide (NO2), etc. The order of different pollutants to cause pollution is carbon monoxide (CO, SO2 hydrocraban particulates nitrogen oxides.

Carbon monoxide (CO)- It is formed by incomplete combustion. It is colorless, odourless gas. It contains a triple bond and are fairly polar, resulting in a tendency to bind permanently to haemoglobin molecules, displacing oxygen, which has a lower binding affinity.

Particulates- These are minute solid particles and liquid droplets dispersed in the air, for example, mists, dust, smoke, fumes, etc. They result in causing many serious diseases like pneumoconiosis, due to inhalation of coal dust, silicosis due to inhalation of free silica (SiO2), black lung disease found in workers of coal mines, white lung disease found in textile workers, byssinosis due to inhalation of cotton fiber dust.

Smog- It is a consequence of particulate pollution and is of two types they are:

• Classical smog

• Photochemical smog