CBSE Class 11-science Answered

Pollution is contamination by a chemical or other agent that renders part of the environment unfit for intended or desired use. It deserves emphasis that the environment also refers to the place where you live. Natural processes have released toxic chemicals into the environment throughout the history of the earth. Currently, the pollution generated by human activities presents the most serious problem.

There are basically 3 types of Pollution. They are:

1)Air pollution

2) Water pollution

3) Land Pollution

Some of the major Causes of the Pollution Crisis are as follows:

i) Deforestation - For the establishment of factories, industries and due to urbanization in various parts of the world, trees are cut on a large scale without any adequate efforts to plant new trees. This leads to deforestation, which has caused a rise in the pollution levels and distortion of natural order.

ii) Polluted rivers - The wastewater and liquids from plants and factories are linked with nearby river water, which are polluted when they release disposal from these units. People in Developing/Undeveloped countries also pollute rivers by using the water in these rivers for washing clothes, utensils, bathing and other activities.

Oil spilled from ships pollute oceans around the world.

iii) Sound pollution - The machines used in factories make noise throughout the day, and this disturbs the peaceful atmosphere in the vicinity, as machines used without proper covering lead to sound pollution. This puts heavy mental strain on the people staying in the nearby areas. Noise is the most pervasive pollution in America.

iv) Air Pollution - Each year industrially developed countries generate billions of tons of pollutants. Many pollutants come from directly identifiable sources; sulphur dioxide, for example, comes from electric power plants burning coal or oil. Others are formed through the action of sunlight on previously emitted reactive materials (called precursors). For example, ozone, a dangerous pollutant in smog, is produced by the interaction of hydrocarbons and nitrogen oxides under the influence of sunlight. Ozone has also caused serious crop damage. The increasing number of vehicles have also lead to an increase in Air Pollution, due to the harmful gases like Carbon Monoxide emitted from these vehicles. Gases generated in the Chemical plants

v) Soil pollution - Dumping of wastes in many areas is a major cause of Soil Pollution. Also, when soil in and near production areas becomes dirty due to disposal of waste material, such land cannot be used for agricultural operations.

Pollution is also caused by iron and steel mills; zinc, lead, and copper smelters; municipal incinerators; oil refineries; cement plants; and nitric and sulphuric acid plants.

Effects Of Pollution Crisis

Of the suite of pollutants that taint urban air, fine suspended particulate matter, sulphur dioxide (SO2), and ozone pose the most widespread and acute risks; however, airborne lead pollution is a critical concern in many cities as well. Recent studies on the effects of chronic exposure to air pollution have singled out particulate matter as the pollutant most responsible for the life-shortening effect of unhealthy air, although other pollutants may also play an important role. These pollutants cause respiratory and other health disorders.

Besides increasing blood pressure and stress levels, noise pollution can also have deleterious effects on hearing. There are two categories of hearing loss resulting from noise exposure. Acoustic trauma is hearing loss resulting from a single exposure to a very loud sound such as an explosion. Noise induced hearing loss is hearing loss arising from repeated exposure to moderate noise. The latter is the more common form of hearing loss due to noise pollution.

Water pollution infects the water and renders it unfit for drinking and other purposes. It is also a major cause of most of the water-borne diseases.