For the past two decades, fog/smog/haze has become part of the annual calendar for Delhi-NCR. Here is an explainer for terms defining this phenomenon that are part of common lexicon in this region:
Why does Delhi undergo an air pollution crisis every winter?
When pollutants accumulated in the air cannot rise into the atmosphere due to absence of wind and low temperature, they cause pollution. The severity of air pollution has been growing every year due to rise in vehicular/industrial pollution and stubble burning in adjoining states and a near absence of measures to curb it.
What is AQI?
Air Quality Index or AQI is measured on different criteria by different agencies in the world. In India, the Central Pollution Control Board (CPCB) has fixed the AQI based on the presence of major pollutants like PM 2.5, PM 10, Ozone, Lead, Carbon, Ammonia, Arsenic, Nickel, Benzene, Sulphur Dioxide and Nitrogen Dioxide, for which its average standards were fixed in 2009.
What is PM?
Particulate matter (PM) are a wide variety of airborne material like dust, smoke and soot that are directly emitted into the air or result from the transformation of gaseous pollutants. Particles come from natural sources – human activities such as burning fossil fuels, incinerating wastes, and smelting metals. PM is one of the six pollutants, prescribed by Environmental Protection Agency (EPA), considered harmful to public health and the environment. The other five are ozone, salfur dioxide, nitrogen dioxide, carbon monoxide and lead.
Out of the 258 places across the country for which CPCB monitors the air quality, as many as 153 centres reported PM 2.5 as major pollutant in the air, while in 104 places recorded mainly PM 10 on November 19. In some of these places both PM 2.5 and PM 10 are jointly mentioned as major pollutants.
What is PM 2.5?
PM2.5, or particulate matter 2.5, is a key indicator of air quality that refers to tiny particles in the air that are 2.5 microns or less in diameter. High concentrations of PM 2·5 (size less than 2.5 μg) often lead to respiratory diseases such as bronchitis, asthma, and inflammation of the lungs when such air inhaled. It is also a factor to cause heart attack and stroke. WHO says PM2·5 concentrations should not exceed 25 μg/m3 over a period of 24 hours. India’s 2009 standards also has put it at 60 μg/m3.
In Delhi, the US Embassy measures AQI around its own office location on basis of PM 2.5 and on November 18 it reported over 1,000 level, whereas CPCB data show daily average at 429, which is the maximum this winter season.
What is PM 10?
Particles larger than 10 μg are trapped in the nose and throat but do not reach the lungs. According to a IIT Kharagpur study, major contributor (56 per cent share among all) to PM 10 is dust on the road.
What are CAQM and GRAP?
As several measures since 2012 failed to control air pollution, for which stubble burning in neighbouring states is also partly blamed, in 2020, the Union Environment Ministry through an Ordinance had set up the Commission for Air Quality Management (CAQM) in National Capital Region and Adjoining Areas for better co-ordination, research, identification and resolution of problems surrounding the air quality index and for matters connected therewith or incidental thereto.
The Commission has devised Graded Response Action Plan (GRAP) for the NCR in 2022 under which actions/restrictions have been prescribed for each stage of the air pollution, while in 2021 the focus was mainly on stubble burning and construction activities. The four stages are categorised as -- Stage – I is ‘Poor’ (AQI 201 – 300), Stage – II is ‘Very Poor’ (AQI 301-400), Stage – III is ‘Severe’ (AQI 401-450) and Stage – IV is ‘Severe +’ (AQI >450).
What are the actions/restrictions under GRAP Stage I?
Ban on coal/firewood as fuel in Tandoors in hotels, restaurants and open eateries, minimising power supply interruptions, ban enforcement on open burnng of bio-mass and municipal solid waste, ban on firecrackers and ban on construction and demolition activities in sites of more than 500 sqr mtr are among some of the major steps prescribed.
What are the actions/restrictions under GRAP Stage II?
All actions under Stage I as well as some more like carrying out mechanical/vacuum sweeping and water sprinkling of identified roads on a daily basis, hike in parking fees to discourage private transport have been mentioned.
What are the actions/restrictions under GRAP Stage III?
All actions under Stage I and II as well as measures like differential rates to encourage off peak travel in public transport, ban on earthwork for excavation and filling including boring, drilling, piling and demolition works, restriction on laying of new sewer line, water line, drainage and electric cabling by open trench system and brick/masonry works are on the list.
Further, ban has to be imposed by respective states on plying of BS lll petrol and BS lV diesel four wheelers in Delhi, and its adjoining Gurugram, Faridabad, Ghaziabad and Gautam Budh Nagar of Haryana and Uttar Pradesh and also schools have to shift to online mode of classes for Class upto V.
What are the actions/restrictions under GRAP Stage IV?
Besides restrictions under previous three stages, additional measures like online classes (no physical presence) in schools for all except Class X and XII, advisory to government and private offices to allow 50 per cent of the staff to work from home, advisory to States for closure of colleges/ educational institutions, non-emergency commercial activities, for permitting vehicles on odd-even basis have been listed under the action plan.
Is there any preventive action by CAQM?
The earlier guidelines had said: “Based on the dynamic model and weather/ meteorological forecast by IMD/IITM on a day-to-day basis, actions under Stages II, III and IV of the GRAP shall be invoked at least three days in advance of the AQI reaching to the projected levels of that stage.” But, in September 2024, the CAQM removed the words “at least three days”. As a result, the CAQM announced on November 17 that GRAP would be invoked from November 18 only after AQI exceeded 450 at some places.