UPSC Express

The North Indian Haze

• The thick haze that has enveloped Delhi and surrounding areas is smog.
• Smog occurs in a location that is far away from the actual source of pollution.
• It is a result of various factors:

1. Geography of the place
2. Sunlight
3. Calmness of winds
4. Post-harvest crop burning
5. Firing of brick kilns
6. Pollution emitted by vehicles
7. Industrial activity

• The processes that lead to smog usually take place after the hazardous pollutants have drifted away in the wind.
• In Delhi, there are two winds:

1. One carrying pollutants from stubble burning in Punjab
2. Other bringing in moisture from Uttar Pradesh

• The two winds are colliding above the national capital and this combined with the near-still wind conditions near the ground level, have effectively trapped the pollutants, leading to the smog.
• In Delhi, the ground-level ozone and PM 2.5 play the most significant role in formation of smog.

How is smog different from fog?

Fog

• Fog is just the condensed water vapour that lies close to the ground.
• When water vapour saturates the air, the vapour starts to condense back into a liquid, as water droplets.
• These droplets, suspended in the air, appear as the thick haze that is known as fog.

Smog

• When the pollution is high, nitrogen oxides and dust particles interact with sunlight to form ground-level ozone, leading to the building up of haze.
• This haze is smog- a result of a photochemical reaction of sunlight with pollutants that have been released into the atmosphere.

What are these pollutants?

• WHO classifies particulate matter into two broad types:

1. PM10
2. PM2.5

• The numbers indicate the diameter of the particles in microns.
• The major components of these particulate matters are- sulphate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water.

How harmful is it?

• The Indian Medical Association has termed this smog has “medical emergency” and it says that this air can be equated to smoking 50 cigarettes a day.
• The most common symptoms of smog impact are: breathlessness, watering of the eyes and nose, burning sensation in the eyes, coughing, dizziness, headache and lethargy.
• The most vulnerable groups include newborns, children, pregnant woman and those with pre-existing health conditions such as asthma, chronic bronchitis, diabetes and cardiac diseases.
• There is evidence that high pollution can lead to premature birth, make pregnant women prone to miscarriage and cause foetal growth problems and lethargy.
• Chronic exposure to both PM10 and PM2.5 can lead to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer.
• Both of these matters can penetrate and lodge deep inside the lungs and PM2.5 can cross into the blood, causing damage in many organ systems.
• Higher levels of nitrogen dioxide precipitate asthma; higher levels of sulphur dioxide precipitate chronic bronchitis.
• There has been evidence that PM2.5 can also enter the bloodstream, and prolonged exposure can cause cause inflammation of heart arteries
•  It can lead to thrombosis- when clotting inside a blood vessel obstructs the flow of blood and can atherosclerosis (A condition in which the diameter of blood vessels is reduced) and can result in hypertension.