Friday, 22 December 2017

Class 7/8/9/10 - Science - Clean Air: From Donora to Delhi - Can we breathe safely? (#eduvictors)(#cbse-notes)

Clean Air: From Donora to Delhi -
Can we breathe safely?

Class 7/8/9/10 - Science - Clean Air: From Donora to Delhi - Can we breathe safely? (#eduvictors)(#cbse-notes)

With the industrial revolution, the human mankind experienced the air pollution for the first time and realized it as a potential threat to human life. The black smoke of locomotives, factories from the industrial towns of England blackened its cities.

In 1950s, the smoke of industrialized Pennsylvania valley in USA made the air murkier. In the small town of Donora, population 14,000, residents suffered eye, nose, and throat irritation and breathing difficulties resulting in 20 deaths.

In 2008, on the 60th anniversary of the event, the town opened the Donora Smog Museum with the
slogan "Clean Air Starts Here".

Watch TV Byte of Poison Fog (1948) 

In 1952, a similar event of poison smog occurred in London (popularly called as Great Smog of London 1952)

Now, Delhi has become one of the most polluted city in the world.

Although many countries have passed law on environment and pollution control but in totality, it appears to be a loosing battle.


Various agencies worldwide have identified six major air pollutants which are harmful and require regular monitoring. These are:
Particulate Matter
Sulphur dioxide
Carbon monoxide
Nitrogen oxides

Particulate Matter
Smoke, soot, and ash contribute to particulate matter. Due to burning of coal, smoke from automobiles these smaller particles (size in micrometers) of organic and inorganic element enter in our air. The environment agencies revised the standard in 2012 and proposed PM 2.5 to be the measure of Air Quality Index.

PM2.5, particles in this category are so small that they can only be detected with an electron microscope. Since they are so small and light, fine particles tend to stay longer in the air than heavier particles. They enter into our lungs and circulatory system and cause chronic diseases like asthma, heart attack, bronchitis and other respiratory problems.

Health organizations has showed concerns that PM pollution has almost doubled the risk of death due to respiratory and cardiac failures.

Sulphur dioxide
The major source of SO₂ is coal burning. SO₂ reacts with water and becomes acidic and leads to acid rain. Sulphur dioxide irritates the respiratory tract and damages it. Industrial towns usually have high concentration of SO₂ levels in air.

Carbon monoxide
Carbon monoxide (CO) is highly toxic and is the one of major automobile emission. Blood has more affinity towards CO than oxygen. Its high concentration in human body damages brain and heart attacks.

Note: Carbon dioxide is not strictly an air pollutant, but its increasing proportion in the air attributes to global warming.

Nitrogen oxides
Coal burning is source of another major pollutant i.e. oxides of Nitrogen. The yellowish-brown gas emitting from the chimneys of power plants mixes with mositure and causes acid rain. It also affects our cardio-vascular systems.

Low priced availability of Diesel as automobile fuel is also responsible for SO₂, NO₂ and CO based pollution.

Lead has an adverse effect on our kidneys, nervous system and immune system. Exposure to Lead(Pb) leads to cancer, low IQ, neurological disorders in infants. Earlier petrol was the major source of Lead based pollution because petrol companies used to add lead to avoid knocking in engines. After the government's initiative to ban leaded petrol, decreased its pollution level. Lead-acid based car batteries and waste incinerators are the other major sources of Lead pollution.

Ozone is highly posionous and reactive variant of oxygen. It is a double edge sword. At high altitudes its presence acts as filter of UV radiation. Depletion of ozone layer due to air pollution is another major concern. Detection of chlorofluorocarbons (CFCs) in ozone hole led to decline its production and use in refrigerants and jet propellants. UV radiation increases the risk of skin cancer and is a a major threat to life on the planet.

On the other hand, high concentration of ozone at lower altitudes is harmful to respiratory system.


For last two decades indoor air quality has become more significant. Air trapped inside our homes and buildings have have high concentration of carbon oxides, radon gas and biologial pollutants like mold, bacteria, dust mites etc.

Smoking is one of the major player in indoor air pollution. Carbon oxides emission due to tobacco smoking is carcinogenic and hazardous to our health. Wood burning, coal burning angithis (stoves) are major contributor of CO, CO₂ SO₂ and NO₂ gases and particulate matter. Radon, a radioactive nobel gas, is responsible for lung cancer. (See Time Of India Post)

Other chemicals that pollute indoor air are pesticides, dry-cleaning solvents, paints, hair sprays, air fresheners and mosquito repellants.

Air pollution does not respect political boundaries, it is very important to have collaborative effort by all the nations of the world to check air quality.


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