New Delhi: The air quality in New Delhi on Saturday (December 13) evening worsened drastically, prompting authorities to issue orders at 6.30 pm to immediately implement GRAP-IV and prevent the air quality from worsening further.

With the city’s Air Quality Index (AQI) rising to 401 on the morning of December 13, authorities had just implemented GRAP-III in the morning of the same day. By 6 pm, the AQI had steadily climbed to 441, and then to 448 by 7 pm, according to the Union environment ministry. Following an urgent meeting, authorities invoked GRAP-IV in the national capital at 6.30 pm.

The GRAP is an emergency response mechanism for Delhi-NCR, based on average AQI levels and forecasts for meteorological weather conditions in the area. GRAP-IV is the highest level of this plan and is implemented when air quality levels breach an AQI of more than 450 in the national capital. Under GRAP-IV there are numerous restrictions on activities that contribute to air pollution.

Monitoring stations record high values

The Union government’s AQI is a measure of at least three prominent air pollutants, fine particulate matter (PM2.5, particles below 2.5 microns in diameter, which are emitted by activities including fossil fuel use and construction) being one of them.

An AQI of 0-50 is considered ideal or good, between 50-100 is considered satisfactory, between 100-200 is moderate, 200-300 is poor, 300-400 is very poor and an AQI of 400-500 is listed in the ‘Severe’ category. In the final stage, air pollution can cause respiratory impact even on healthy people, and serious health impacts on people with lung or heart disease. The health impacts may be experienced even during light physical activity, as per the Union government.

At 10 pm on December 13, Jahangirpuri and Bawana recorded an AQI of 496 on the SAMEER mobile application (which provides data from stations run by the Central Pollution Control Board), just four points short of the limit at which AQI is capped in India. This means that even if the AQI ranges higher than this, this will not be recorded in the monitoring stations. Only four of the 38 active air monitoring stations recorded AQI below 400 on the SAMEER app at this time on December 13.

Meanwhile, IQAIR, a Swiss air technology company which uses both government and other data sources (including satellite imagery) of air quality showed the AQI in Greater Noida at 827 at around the same time. However, the CPCB and IQAIR calculate Air Quality Indices differently and therefore the numbers may not be directly comparable. The IQAIR site listed the main pollutant in Greater Noida as being PM10, at 898 micrograms per cubic meter (the CPCB’s air quality monitoring station in the area was also listed as a contributor to the data point).

However, the CPCB’s Sector 1 Noida-based Uttar Pradesh Pollution Control Board (UPPCB) air monitoring station recorded a PM10 concentration of only 646 ug/m3 as per its reading (from 16:45 to 17:00 on December 13). At 10 pm on December 13, the same monitoring station recorded a ‘Severe’ AQI of 489, with PM2.5 being the prominent pollutant. While the average concentration of PM2.5 was at 489 ug/m3 as per this government portal, the minimum value was at 410 and the maximum hit 500 for most hours of the day.

As per the Indian Institute of Tropical Meteorology’s Air Quality Early Warning System for Delhi, the AQI of the city was at 455 at 10 pm on December 13.

‘Calm winds’

“The AQI of Delhi which was recorded at 401 at 10 am (‘Severe’ Category), further exhibited a continuous increasing trend owing to very low speed wind, stable atmosphere, unfavourable weather parameters and meteorological conditions for dispersal of pollutants, resulting into trapping of the pollutants in the region,” read the order issued by the Commission for Air Quality Management (CAQM) in the National Capital Region and Adjoining Areas.

The order, issued on the night of December 13 stated that Delhi’s AQI was recorded at 431 (‘Severe’ Category) at 4 pm, 436 at 5 pm, 441 at 6 pm and 448 at 7 pm. It also forecasts that this “situation of calm winds, stable atmosphere and unfavourable meteorological conditions with partly cloudy sky/ mist / haze during night” was likely to prevail further.

While meteorological factors do play a role in the levels of air pollution that Delhi witnesses, emissions from vehicles, dust from construction and emissions from coal-fired power plants are also contributors to the city’s poor quality. However, government press releases usually blame the poor air quality on weather conditions.

A press release by the Union environment ministry on the night of December, mentioned:

“The significant reason for this spike is not contributed by the emissions but the feeble Western Disturbance approaching north-west India. This prevailing meteorological condition has marked reduction in wind speed, at times becoming calm, a shift in wind direction from westerly to easterly, and an increase in moisture content in the lower atmosphere. Such conditions during the winter season are conducive to the formation of smog and fog, resulting in poor dispersion and trapping of pollutants near the surface. Owing to these adverse meteorological conditions, a sudden deterioration in air quality has been observed.”

GRAP-IV in effect

As of the night of December 13, the GRAP-IV is under effect in the Delhi-NCR. Under this stage, all BS-IV trucks are now banned from entering Delhi (except for trucks carrying essential commodities or providing essential services). However, all LNG/CNG/Electric/ BS-VI Diesel trucks are permitted to enter the city.

Other actions being implemented by authorities include banning all schools to mandatorily conduct classes (including higher grades i.e. from class VI to IX and XI) in a “Hybrid” mode i.e., both in physical and online mode (wherever online mode is feasible) in the territorial jurisdiction of the NCT of Delhi and in the districts of Gurugram, Faridabad, Ghaziabad and Gautam Buddha Nagar.

State governments may also consider additional emergency measures like closure of colleges/ educational institutions and closure of non-emergency commercial activities and permitting running of vehicles on odd-even basis of registration numbers, the press release noted.

The release also advises children, the elderly and people with respiratory, cardiovascular, cerebrovascular or other chronic diseases to avoid outdoor activities and stay indoors “as much as possible”, and to wear masks if required to move outdoors.

GRAP Stages I, II and III are also currently in force – they came into effect on October 14, October 19 and December 13, respectively.

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