Depletion of ozone layer creates some sort of holes in the blanket of ozone which surrounds us in the atmosphere and this is known as ozone hole
(i) With the depletion of the ozone layer, UV radiations filters into the troposphere which leads to ageing of skin, cataract, sunburn, skin cancer etc.
(ii) By killing many of the phytoplanktons, it can damage the fish productivity.
(iii) Evaporation rate increases through the surface and stomata ofleaves which can decrease the moisture content of the soil.

Acetaldehyde is commercially prepared by one step oxidation of ethene in the presence of ionic catalyst in aqueous medium with 90% yield.

(i) Smog is primarily responsible for acid rain.
(ii) Smog results in poor visibility and it affects air and road transport.
(iii) It also causes bronchial irritation.

(i) The great smog of London (1952) was an instance of severe air pollution that affected the London from 5th December-9th of December, 1952 and then dispersed quickly when the whether changed.
(ii) It causes major disruption by reducing the visibility and even penetrating indoor areas.
(iii) Government medical reports estimated that 4000 people had died as a direct result of smog and 100,000 were made will by the smog effect on their respiratory tract.

The chloro fluoro derivatives of methane and ethane are referred by trade name Freons. These Chloro Fluoro Carbon compounds are stable, non-toxic, noncorrosive and noninflammable, easily liquefiable and are used in refrigerators, air- conditioners and ln the production of plastic foams. CFC's are the exhaust of supersonic air craft's and jumbo jets in the upper atmosphere. They slowly pass from troposphere to stratosphere. ,They stay for very longer period of 50 - 100 years. In the presence of uv radiation, CFC's break up into chlorine free radical
CF₂Cl₂ \(\xrightarrow{hv}\) CF₂ CI +Cl.
CFCl₃ \(\xrightarrow{hv}\)CFCI₂+ Cl
Cl^o+O₃ ⟶ C10+O₂
Clo^o+O ⟶ CI+O₂
Chlorine radical is regenerated in the. course of reaction. Due to this continuous attack of Cl⁰ thinning of ozone layer takes place which leads to formation of ozone hole. It is estimated that for every reactive chlorine atom generated in the stratosphere 1,00,000 molecules of ozone are depleted.

Pesticides are the chemicals that are used to kill or stop the growth of unwanted organisms. But these pesticides can affect the health of human beings. These are further classified as
a. Insecticides:
Insecticides like DDT ,BHC ,aldrin etc. can stay in soil for long period of time and are absorbed by soil . Th.y contaminate root crops like carrot, raddish, etc.
b. Fungicide :
Organo mercury compeunds are used as most common fungicide. They dissociate in soil to produce mercury which is highly toxic.
c. Herbicides :
Herbicides are the chemical compounds used to control unwanted plants. They are otherwise known as weed killers. Example sodium chlorate (NaClO₃) and sodium arsenite (Na₃ As O₃). Most of the herbicides are toxic to mammals.

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.

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

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.