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Why in news?
The deteriorating air quality and suffocating smog have led to closure of primary schools in Delhi.
What are the causes?
- Smog - Smog refers to a smoky fog (smoke+fog) and is a kind of air pollution.
- Fog is a hazy condition which is a result of suspension of water droplets close to the ground.
- Smog, on the other hand, is a mixture of pollutants in the atmosphere which consists of fine particles and ground level ozone.
- When pollution is high, nitrogen oxides and dust particles interact with sunlight to form ground-level ozone, leading to hazy smog.
- This condition is a result of a range of factors including:
- geography of the place.
- sunlight
- calmness of winds.
- post-harvest crop burning.
- firing of brick kilns.
- dust from construction sites and unpaved roads.
- vehicular pollution.
- domestic and industrial emissions.
- Wind - Smog occurs in a location that is far away from the actual source of pollution after the hazardous pollutants have drifted away in the wind.
- Delhi experiences two kinds of winds in winter which are:
- wind carrying pollutants from stubble burning in Punjab.
- wind bringing in moisture from Uttar Pradesh.
- These two winds collide in the upper atmosphere above the region.
- However, Delhi and its neighbouring areas have nearly still wind conditions near the ground, which is due to prevailing anti-cyclone conditions around the region during winter.
- The two winds, combined with the near still wind conditions, effectively trap the pollutants leading to persistent smog.
- Crop burning - The smog that envelops the region is exacerbated by the burning of biomass in nearby Punjab and Haryana.
- The post-monsoon burning of rice and wheat residue releases maximum aerosols.
- And this contributes to the volume of PM2.5 in the air.
What should be done?
- The Delhi government has taken various measures in the past including:
- the ban on Deepavali crackers.
- shift to compressed natural gas for commercial vehicles.
- restricting car use to odd and even number plates on alternate days.
- However, air quality index has touched extremely hazardous levels in some parts of Delhi, turning into a public health emergency.
- The burden of such chronic problems has outweighed the benefits conferred by the above measures.
- Therefore, besides these minor corrections, the Centre and States must urgently address farm residue burning in north India.
- A workable solution demands a coordinated effort from the governments of Delhi, Punjab, Haryana and Uttar Pradesh, assisted by the Centre.
- Delhi’s unique weather conditions require a comprehensive, well informed solution to the pollution crisis.
Quick Fact
Particulate matter (PM)
- PM or particle pollution is a mixture of small particles including black carbon, mineral dust, sulphate, nitrates, ammonia, sodium chloride, and liquid droplets in the air.
- WHO classifies particulate matter into two broad types - PM10 and PM2.5, indicating the diameter of the particles in microns.
- Chronic exposure to both PM10 and PM2.5 can lead to cardiovascular and respiratory diseases, as well as lung cancer.
- PM2.5 can cause skin diseases and reduction in life expectancy. It can cross into the blood, causing damage in many organ systems, .
- In Delhi, the ground-level ozone and PM 2.5 play a significant role in formation of smog.
Source: The Hindu, Indian Express
