(i) On 3rd Decembers, 1984 at Bhopal city in India, by the early morning, an explosion at Union carbide pesticide plant released a cloud of toxic gas (Methyl isocyanate) CH₃NCO into the air.
(ii) Since the gas is twice as heavy as air, it did not drift away but formed a blanket over the surrounding area.
(iii) It attacked people's lungs and affect their breathing staying there or in the nearby areas. Thousands of people died and lives of many were ruined. The lungs, brain, eyes, muscles as well as the gastrointestinal, neurological and immune system of those people who survived were severely affected.

(i) Thus Greenhouse effect may be defined as the heating up of the earth surface due to trapping of infrared radiations reflected by earth's surface by CO₂ layer in the atmosphere.
(ii) The heating up of earth through the greenhouse effect is called global warming.
(iii) Without the heating caused by the greenhouse effect, Earth's average surface temperature would be only about -18 ^oC (0 ^oF). Although the greenhouse effect is a naturally occurring phenomenon, it is intensified by the continuous ernission of greenhouse gases into the atmosphere.
(iv) During the past 100 years, the amount of carbon dioxide in the atmosphere increased by roughly 30 percent and the amount of methane more than doubled. If these trends continue, the average global temperature will increase which can lead to melting of polar ice caps and flooding of low lying areas. This will increase incidence of infectious diseases like dengue, malaria, etc.

a) The growth of algae in extreme abundance covers the water surface and reduces the oxygen concentration in water. Thus, bloom-infested water inhibits the growth of other living organisms in the water body. This process in which the nutrient rich water bodies support a dense plant population, kills animal life by depriving it of orygen and results in loss of biodiversity is known as eutrophication.
b) Chemicals from industries
c) Toxic pesticides
d) Detergents and oil floats
e) Acids from mine drianage and salts from various sources.

Particulate pollutants are small solid particles and liquid droplets suspended in air. Many of particulate pollutants are hazardous.
Examples : dust, pollen, smoke, soot and liquid droplets (aerosols) etc,.

Thus Greenhouse effect may be denned as the heating up of the earth surface due to trapping of infrared radiations reflected by earth's surface by CO₂ layer in the atmosphere.

Particulate pollutants are small solid particles and liquid droplets suspended in air. Many of particulate pollutants are hazardous.
Examples : dust, pollen, smoke, soot and liquid droplets (aerosols) etc,.
They are blown into the atmosphere by volcanic eruption, blowing of dust, incomplete combustion of fossil fuels induces soot. Combustion of high ash fossil fuels creates fly ash and finishing of metals throws metallic particles into the atmosphere.
The non- viable particulates are small solid particles and liquid droplets suspended in air. They help in the transportation of viable particles. There are four types of non-viable particulates in the atmosphere. They are classified according to their nature and size as follows.
(i) Smoke : Smoke particulate consists of solid particles (or) mixture of solid and liquid particles formed by combustion of organic matter. 
For example, cigarette smoke, oil smoke, smokes from burning of fossil fuel, garbage and dry leaves.
(ii) Dust: Dust composed of fine solid particles produced during crushing and grinding of solid materials.
For example, sand from sand blasting, saw dust from wood works, cement dust from cement factories and fly ash from power generating units.
(iii) Mists : They are formed by particles of spray liquids and condensation of vapours in air.
For example, sulphuric acid mist, herbicides and insecticides sprays can form mists.
(iv) Fumes : Fumes are obtained by condensation of vapours released during sublimation, distillation, boiling and calcination and by several other chemical reactions.
For example : organic solvents, metals and metallic oxides form fume particles.

(i) Green chemistry is a chemical philosophy encouraging the design of products and Processes that reduce or eliminate the use and generation of hazardous substances.
(ii) For this, scientist are trying to develop methods to produce eco-friendly compounds. This can be best understood by considering the following example in which styrene is produced both by traditional and greener routes. To avoid carcinogenic benzene, greener route is to start with cheaper and environmentally safer xylenes.
(iii) Green chemistry means science of environmentally favourable chemical synthesis.

Ozone is formed by a series of reactions that occur from the sun shines

i. Bio-degradable pollutants :
The pollutants which can be easily decomposed by the natural biological processes are called bio-degradable pollutants.
Examples: plant wastes, animal wastes, etc.
ii. Non bio-degradable pollutants :
The pollutants which cannot be decomposed by the natural biological processes are called Non bio-degradable pollutants.
Examples : metal wastes (mainly Hg and Pb), D.D.T, plastics, nuclear wastes, etc., These pollutants are harmful to living organisms even in low concentration. As they are not degraded naturally,it is difficult to eliminate them from our environment.

1. Waste management : Environmental pollution can be controlled by proper disposal of wastes. 
2. Recycling : a large amount of disposed waste material can be reused by recycling the waste, thus it reduces the land fill and converts waste into useful forms.
3. Substitution of less toxic solvents for highly toxic ones used in certain industrial processes. 
4. Use of fuels with lower sulphur content (e.g., washed coal)
5. Growing more trees
6. Control measures in vehicle emissions are adequate.
7. Green chemistry philosophy can be followed.
8. Eco-friendly compounds should be developed.
g. Greener routes should be followed in our day to day life.
10. For dry cleaning liquified CO₂ or H₂O₂ may be used.
11. Paper may be bleached by H₂O₂.
12. Methanol maybe used instead of petrol.
13. Neem based pesticides may be used.
14. Awareness among students and public may be created by using slogans like "Save water; Water will save You".

It binds with haemoglobin and form carboxy haemoglobin which impairs normal oxygen transport by blood and hence the oxygen carrying capacity of blood is reduced. This oxygen deficiency results in headache, dizziness, tension, Loss of consciousness, blurring of eye sight and cardiac arrest.

(i) BOD and COD

(ii) Viable and non-viable particulate pollutants