Delhi’s average air quality index (AQI) worsened further into deep red on Saturday, reaching 450 at 4pm, before it began improving, with officials saying some respite may be around the corner.
Authorities reviewed the situation and decided to hold back on lifting curbs on the use of old cars and private construction work, but acknowledged pollution levels were expected to improve beginning Sunday.
“The sub-committee, while comprehensively reviewing the air quality scenario and relevant aspects, noted that GRAP stage-III has just been invoked in the evening of December 22 and it’s only reasonable to await the impact of the intensified preventive/restrictive actions, on the average AQI. Further, the forecasts also indicate a gradual improvement in Delhi’s average AQI by late evening hours onwards,” said a statement from Commission for Air Quality Monitoring (CAQM).
By 10PM, the AQI had improved to 430, though still well in the severe category.
READ | Delhi air quality ‘severe’ with AQI 400, GRAP III reimplemented: Gopal Rai
Saturday began with dense fog in some areas, with visibility dropping to as low as 200 metres near Safdarjung. The India Meteorological Department predicted morning foggy spells to continue for the next two days.
“The air quality is likely to remain in Severe category on December 24 and may improve and reach ‘very poor’ category on December 25 and remain in Very Poor category on December 26. The air quality is likely to deteriorate again from December 27 as meteorological conditions are extremely unfavourable,” the AQI forecast cited by CAQMstated.
According to officials, the fog led to 16 flights, 11 international and five domestic, to be delayed on Saturday morning, though no plane had to be diverted.
This is the second spell of toxic air for the Capital and its adjoining areas. The city’s winters are now marked by multiple episodes of hazardous air quality, beginning as early as the end of October when smoke from farm fires is the biggest trigger.
READ | Delhi-NCR residents take note: These vehicles are banned due to high AQI
A second window typically falls in the second half of December, when temperatures drop further, creating a cocktail of meteorological and human factors that make the air worse: winds are often calm and trap pollutants closer to lower altitudes, traffic stays heavy due to festivities and weddings, and people light bonfires to keep warm.
Delhi’s environment minister Gopal Rai also on Saturday held a briefing and detailed activities that will remain restricted under the Grap stage III curbs.
“Activities that will be banned include boring, drilling and digging work, loading and unloading of construction material, transporting any fly ash material manually or through conveyor belt, plying of vehicles on unpaved roads, open trench work for laying sewer or water lines, tiling, waterproofing, varnishing, polishing and stone crushing,” said Rai.
He added that only projects of national importance can continue as well as interior work like plumbing and electrical work.
This has been a particularly unhealthy winter for Delhi, with November being one of the most polluted months in recent years. The average AQI for the month was at 373, the third worst ever. But discounting some outlier days when rain helped bring pollution levels down, the average AQI in November comes close to 390, making it the most polluted ever.
In December, the month began on a cleaner note but the situation began to change from the 12th.
On Friday, after staying in the ‘poor’ and ‘very poor’ categories for almost a month, the pollution levels suddenly worsened, triggering the stage-III curbs. These include a ban on private construction as well as well as a ban on driving Bharat Stage (BS)-III emission standard petrol and BS-IV emission standard diesel cars in Delhi and the neighbouring Gurugram, Faridabad, Ghaziabad and Gautam Buddha Nagar.
There is little evidence, however, that these measures can stem or alleviate the worsening of air quality once pollution levels have already spiked. The ban on BS-III and BS-IV petrol and diesel vehicles covers around 387,000 vehicles registered in Delhi, a fraction of the 7 million registered in total.
Officials said fog is likely to persist for the next few days. “Wind speed was around 6kmph at Palam on Saturday, and it is likely to reduce further over the next two days. The western disturbance has moved forward as a result of which moderate to dense fog will be seen in the next two days over Delhi NCR and visibility is likely to be around 200 metres in many areas,” said Kuldeep Srivastava, scientist at IMD.
The western disturbance — the climatic term for the incursion of moisture-heavy winds originating from the Mediterranean Sea — is what led to the calm meteorological conditions that brought about Friday’s plunge in air quality.
The minimum temperature, meanwhile, rose to 9.6°C due to the western disturbance and was two degrees above normal. Officials said that though there was mild rain predicted for Friday night, no rain was recorded in Delhi NCR.
The maximum temperature on Saturday was 24.4 degrees, four degree above normal for this time. According to IMD forecast, maximum and minimum temperatures are expected to be around 25 and seven degrees.
Across NCR, the AQI in all neighbouring towns was recorded in the ‘very poor’ category on Saturday, CPCB data showed. Greater Noida had an AQI of 385, Noida had 390, Ghaziabad was 388, Gurugram 350 and Faridabad 367.