Air Pollution:

Due to various reasons the poisonous gases increases in the air more than normal percentages, the air becomes polluted and the phenomenon is known as air pollution.

Causes of air pollution

• Combution of petrol and diesel by different sources such as automobiles and aeroplanes.
• Production of various types of chemicals, fertilizers and cement, etc.
• Industries and oil refineries.
• Excessive use of insecticides, pesticides, fungicides
• Use of refrigerators, deep freeze, air conditioned machines, etc.
• Use of radioactive materials.
• Poisonous gases such as carbon monoxide, NO, Sulphate, Hydrogen sulphide, oxides of carbon and nitrogen, chlorine, and chlorofluro hydrocarbon. These pollutants, nitrogen oxide and hydrocarbon, combine in the presence of sunlight to produce new and more toxic substances known as photochemical smog, peroxyacetyl nitrate (PAN) and ozone (O 3 ).
• These substances are extremely toxic to plants, blocks the photosynthetic process and kill the plants.

EPA uses six “criteria pollutants” as indicators of air quality and has established for each of them a maximum concentration above which adverse effects on human health may occur.

1. Nitrogen Dioxide: NO₂

• brownish gas irritates the respiratory system originates from combustion.

2. Ozone: ground level O₃

• primary constituent of urban smog

3. Carbon monoxide: CO

• reduces bloods ability to carry O₂

4. Lead: Pb

• cause learning disabilities in children , toxic to liver, kidney, blood forming organs.

5. Particulate Matter: PM10 (PM 2.5)

• respiratory disorders

6. Sulfur Dioxide: SO₂

• formed when fuel (coal, oil) containing S is burned and metal smelting
• precursor to acid rain along with Nox

Consequences of Air Pollution

• Increasing the amount of CO2 in the atmosphere reinforces this effect and is expected to result in a warming of the Earth’s surface thus causing GLOBAL WARMING.
• When emissions of sulfur dioxide and nitric oxide from stationary sources are form secondary pollutants such as nitrogen dioxide, nitric acid vapor, and droplets containing solutions of sulfuric acid, sulfate, and nitrate salts. These chemicals descend to the earth’s surface in wet form as rain or snow and in dry form as a gases fog, dew, or solid particles, it is known as ACID RAIN or ACID DEPOSITION.
• Sulfur dioxide, nitrogen oxides, ozone and peroxyacl nitrates (PANs), cause direct damage to leaves of crop plants and trees when they enter leaf pores (stomates).
• Chronic exposure of leaves and needles to air pollutants can also break down the waxy coating that helps prevent excessive water loss and damage from diseases, pests, drought and frost.