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:
- Geography of the place
- Calmness of winds
- Post-harvest crop burning
- Firing of brick kilns
- Pollution emitted by vehicles
- 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:
- One carrying pollutants from stubble burning in Punjab
- 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 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.
- 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:
- 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.
Section : Environment & Ecology