Grap 4 back in Delhi; schools set to go ‘hybrid’

Delhi’s air quality index (AQI) tipped into the “severe” zone on Monday evening for the first time in 23 days, snapping a period of relatively reprieve for the city and prompting central panel to reimpose a host of curbs on construction and vehicles in NCR as part of stages 3 and 4 of the Graded Response Action Plan (Grap).

The Capital recorded a 24-hour average AQI of 379 at 4pm on Monday, with the number rising to 401 at 10pm, as pollution levels spiked dramatically in two days. Delhi clocked an AQI of 294 (poor) at 4pm on Sunday and 193 (moderate) at the same time on Saturday.

This deterioration was largely due to a significant drop in wind speeds that allowed local pollutants to concentrate, said weather experts.

While initially, Stage 3 was announced during the day, a steady increase in AQI prompted CAQM to hold an emergency meeting late in the evening, and invoking Stage 4 with immediate effect across NCR.

Grap Stage 3 brings with it a ban on BS-3 petrol and BS-4 diesel four-wheelers in Delhi, Gurugram, Faridabad, Ghaziabad, and Gautam Budh Nagar, blanket curbs on private construction and demolitions, along with restrictions on the use of stone crushers, mining and associated activities. It also restricts Delhi-registered Diesel operated medium goods vehicles (MGVs) to BS-4 standards or below, in Delhi, along with BS-4 and lower diesel operated light commercial vehicles registered outside Delhi from plying in Delhi. The only exception being vehicles carrying essential commodities or providing essential services.

Further, as part of stages 3 and 4 of GRAP, all construction in NCR — both private and public projects are now halted.

Other vehicular restrictions under Stage 4 include stopping entry of trucks into Delhi (except CNG, LNG, electric, BS-4 diesel or those involved in essential or emergency services) and a ban plying of BS-4 and lower heavy vehicles, unless they are involved in essential or emergency services.

Further all classes in schools barring classes 10 and 12 in Delhi and its neighbouring districts will also have to shift to “hybrid” lessons, said the Commission for Air Quality Management (CAQM) in a notification issued on Monday.

As part of Stage-3, an order was issued by the Delhi’s Directorate of Education (DoE) on Monday which moved primary classes to hybrid, however, an order for senior classes was yet to be shared till the time of filing this copy.

Monday’s 4pm reading was Delhi’s highest AQI since 412 (“severe”) on November 23. Before Monday, Delhi recorded only one “very poor” air day this month – on December 8, when the AQI was 302.

The Central Pollution Control Board (CPCB) classifies an AQI between 0-50 as “good”, between 51 and 100 as “satisfactory”, between 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor”, and over 400 as “severe”.

“Strong surface northwesterly winds prevailed in Delhi-NCR till December 15. However, wind speeds dropped in the last 24 hours due to an approaching western disturbance. Winds, which were between 10-15 km/hr till Sunday, are now averaging less than 5km/hr. They are also becoming calm at night-time, further trapping local pollutants,” said Mahesh Palawat, vice-president at Skymet.

Palawat said the winds may remain slow on Tuesday, before gathering speed from Wednesday.

“We may see an improvement in AQI from Wednesday,” he said.

Potent surface winds this year gave the Capital its cleanest first half of December ever since the AQI was launched in 2015. The average AQI from December 1 to 15 this year was 238, considerably better than the previous low of 301 in 2022.

Delhi’s AQI typically nosedives in the second half of December when conditions once again become adverse, due to dipping temperatures and the return of dense fog.

Data from last December showed the average AQI was 348, with three “severe” air days recorded — all in the second half of the month. The lowest AQI recorded last year’s December was 286, while the highest was 450 which came on December 23.

Stage 3 and 4 measures under Grap have been implemented in Delhi after 11days.

Stage 3 came into force on November 15, followed by Stage 4 measures on November 18. These were lifted on December 5, after a go-ahead from the Supreme Court. However, the apex court at the time said that Stage 3 should be imposed when the AQI crosses 350, instead of the original threshold of 400. It similarly asked for Stage 4 to be imposed at 400, instead of 450.

“IMD and the Indian Institute of Tropical Meteorology (IITM) noted that the average AQI of Delhi has crossed the 350 mark and is showing an increasing trend owing to extremely calm wind conditions and buildup of an inversion layer also adversely affecting the vertical mixing height. Forecasts also indicate a likelihood of the average AQI of Delhi to fluctuate between the higher end of ‘Very Poor’ to ‘Severe’ category in the coming days owing to continued adverse meteorological conditions,” said CAQM in a statement, asking the NCR state pollution control boards to strictly implement stage-3 measures, in addition to the existing stage-1 and stage-2 measures in the region.

Anumita Roychowdhury, executive director, research and advocacy, Centre for Science and Environment (CSE), said the respite was primarily down to improved meteorological conditions such as strong winds and better ventilation. “The cold is once again returning, along with moisture, which is again trapping pollutants locally,” she said.