Thick haze envelopes Delhi; air quality worsens day after tipping into severe zone

A thick haze continued to envelop Delhi on Friday as the air quality worsened a day after it tipped into the severe category for the first time this season and prompted mitigation measures including a ban on the use of older vehicles.

An average Air Quality Index (AQI) of 464 (severe) was recorded at 8am on Friday. Mundka and Bawana almost touched the top AQI limit at 498 and 496 at 7:05am. All stations other than Dilshad Garden (367) were in the severe category. Greater Noida recorded an AQI of 473 and Faridabad 442.

The rapid deterioration in air quality and fog plunged visibility to 600 metres at Safdarjung and 500 metres at Palam. “This is the lowest visibility for the day. No considerable change is expected later during the day either as wind speeds are unlikely to be beyond five km per hour,” said an India Metrological Department official.

The worsening pollution levels also prompted the closure of schools for students in Classes 5 and below for two days on Friday and Saturday.

The pollution levels worsened on Thursday after Delhi recorded a 24-hour average AQI of 392 just short of the severe mark at 4pm. The average AQI barrelled up to 427 just before midnight. Mundka (453) and Anand Vihar (449) topped the charts.

Greater Noida was on Thursday the worst off across the National Capital Region (NCR) with an AQI reading of 402 (severe) at 4pm. The AQIs in Gurugram and Ghaziabad were in the poor category at 297 and 286.

Delhi’s AQI was 362 (very poor) on Wednesday before calm surface-level winds exacerbated the impact of local sources of pollution. Delhi’s bad air was largely because of pollutants within the city even as farm fires in Punjab and Haryana continued to tick up and drive up PM2.5 levels.

A northwesterly current that the Capital was experiencing on Thursday brings smoke from farm fires into Delhi from Punjab and Haryana, which recorded 1,543 farm fires on Wednesday. On Tuesday, the two states recorded 1,556 farm fires. They were nearly double the 827 blazes that satellites tracked a week ago. The two states recorded 1,978 fires on November 1 last year, 2,477 in 2021, and 3,500 in 2020. Year-on-year data on stubble fires is not always comparable due to differences in cropping and harvest patterns.

PM2.5, a byproduct of combustion sources, was the prominent pollutant in Delhi’s air on Thursday. Delhi’s PM2.5 levels peaked at 242.7µg/m³ at 10pm. The PM10 peaked at 412µg/m³ also at 10pm. Both PM2.5 and PM10 were over four times India’s safe standards. India’s pollution norms are less stringent than global thresholds. Indian safe standard for PM2.5 is 60µg/m³. The World Health Organization’s (WHO) standard is a fourth of that at 15 µg/m³.

On Thursday, the Commission for Air Quality Management (CAQM) effected Stage 3 of the city’s Graded Response Action Plan (Grap) as part of enhanced anti-pollution curbs. The restrictions include a ban on private constructions and demolitions, excluding non-polluting work like plumbing, interior decoration, electrical work, and carpentry.

Grap Stage 3 is designed to kick in when the AQI is likely to touch the severe category. The authorities drew flak for reacting to the spike in pollution rather than pre-empting it.

The air quality was likely to get worse as farm fires were nowhere near their peak. The temperatures were also set to plummet further in the run-up to Diwali none days later.