What does pollution actually mean ? Pollution is the addtion of a substance that alters our environment and harmfully affects the living organisms. The substance which does so is called pollutant.

Nature Of Pollutants:

Bio-degradable : These are organic substances which are decomposed by the action of micro organisms.The pollution is thus negligible.These cause pollution when they occur in large quantities such that the microorganisms are unable to decompose them.

Non Bio-degradable:- Substances like iron,lead,aluminium,plastic etc. do not decompose or even if they do they do so at a very slow rate.These keep accumulating and thus causing pollution.These enter our bosy through food etc.

Water Pollution :

The living organisms require water .Humans need water for various purposes such as irrigation,domestic,industrial etc. But unmanaged use of water resources has lead to its pollution causing various diseases like cholera,typhoid,jaundice,diarrhoea etc. Water pollution has been caused due to some of the below factors:

2. Effect of pesticieds and agricultral runoff:-
Pesticides from agricultural run off , metals and processed chemicals from industries etc. enter the food chain of the aquatic animals leading to disastrous consequences.The toxic substances accumulate in the body of fishes which are eaten by man and other animals.These chemicals thus reach the human body which cause various diseases and sometimes even death.

3.Effect of Oil Spills :-
These are perhaps the most dangerous water pollutants of the ocean. By accident or purposely millions of tonnes of oil is deposited in the ocean every year which causes extreme harm to aquatic life.

Air Pollution : In cities and industrialised zones the effect of air pollution is becoming more and more widespread.This is caused due to increased amounts of gases like Sulphur dioxide , carbon monoxide , oxides of nitrogen etc . These are a health hazard. The chief causes are automobiles , industries, volcanic wastes , thermonuclear explosions , burning of wastes etc.

1. Effect of Industrial and domestic wastes : -
Industrial fumes carry both solid as well as gaseous pollutants. The solid components include soot , fine metabolic particles and varying amounts of hydrocarbons. Soot forms the nuclei on which the water vapour condenses to form smoke haze and fog. Smog is a thick persistent fog that is formed when polluted air cannot rise due to air layers of different temperatures that hang over a city.

Sulphur dioxide is the most harmful gaseous pollutant.
It readily dissolves in water to form acids that kill plants and damage buildings(acid rain). The acidity of the soil is increased ,leading to loss of nutrient ions.

Hydrogen Sulphide
It is formed during the putrifaction of animal and vegetable substances containing sulphur. It is also created in petroleum refineries and volcanoes. It has the smell of rotten eggs. It takes up the oxygen from the blood to form iron sulphide. Thus it reduces the oxygen content in the blood.

2. Automobiles : They also release soot .Variety of other gases such as sulphur dioxide,nitrogen dioxide,carbon monoxide and hydrocarbons. Carbon monoxide formed due to incomplete combustion of hydrocarbons is a very poisnous gas.It combines with haemoglobin to form carbamino-haemoglobin.It is a permanent componud and thus it robs the blood of haemoglobin. Death is by asphyxiation.

3.Soil Pollution :
Nitrogen is an essential constituent of all living cells. Nitorgenous compounds are taken up by the plants as they cannot take in atmospheric nitrogen directly.

Nitrogen cycle helps to maintain soil fertility.Soil bacteria play an important role in this cycle.However excessive use of fertilizers and pesticides reduce the ability of bacteria to decay wastes and produce nutrients naturally.Acid rain increases the acidity of the soil.

Fertilizers are chemical substances that are added to the soil to increase its fertility and thereby increase the crop production.Those of natural origin are called natural fertilizers and those which are artificially made are called chemical fertilizers.

Bio- Fertilizers are preferred to Chemical Fertilizers :-
1. Chemical fertilizers are expensive.
2.Their production releases pollution.
3.Their production depends on exhausting sources of energy such as petroleum , coal etc.
4.They are lost as surface run off and pollute soil and water resources.

The Greenhouse Effect The burning of coals and oils release carbon dioxide into the air which is used by plants for photosynthesis. Indiscriminate deforestation upsets this balance.Normally the heat received by the Sun is radiated . But excessive carbon dioxide traps the heat just like in a green house in which the heat can enter but cannot leave.

It leads to rising of global temperatures and can also lead to melting of ice at the poles which will lead to rise in levels of water in all the water bodies .This can flood small islands and cause danger to their existence.

Ozone Layer Depletion : - About 15 to 50 km above the earth is the ozone layer which protects us from the harmful UV rays of the Sun.Scientists had discovered a hole in it in the 1980's above Antarctica as big as the United States. There are other smaller joles as weel. A record size hole was found this October.These holes are caused due to certain chemicals called CFC's or Chloro Fluoro Carbons.These are contained in aerosol cans ,deodorants,Rerigerators. etc.

The Future Of The Earth Lies In your Hands.