Delhi air back in ‘severe’ zone, 1st time since November

NEW DELHI: Air quality in the capital dipped on Thursday into the “severe” zone — levels last seen in November when Delhiites choked on a killer smog for a week — as the city was wrapped in an early morning fog and later a grey haze that cleared only by late afternoon.

The overall air quality index, which stood at 359 (very poor) on Wednesday, jumped to 469 on Thursday, which is well into the severe category of Central Pollution Control Board’s index. Air quality had dipped to severe levels on Wednesday evening itself, and this reflected in Thursday’s 24-hour AQI reading.

The sudden spike in pollution levels was attributed to a drop in wind speed, coupled with an increase in relative humidity – thus trapping pollutants and not allowing them to disperse. Met officials, however, forecast air quality to start improving from Friday onwards with wind speeds expected to increase once again.

Wind getting faster, haze may go today
Delhi last saw “severe” air quality on November 13, the last day of the smog episode which saw AQI levels remain above 400 for seven straight days between November 7 and 13. According to the CPCB, “severe” air quality levels can “affect healthy people and seriously impacts those with existing diseases”. Officials from the Regional Weather Forecasting Centre (RWFC) said wind speeds had dropped below 5 km/hour on Wednesday night. However, winds have started picking up again and Friday is likely to see the haze starting to clear out, officials said.

“The sudden spike has been attributed to a rise in relative humidity and wind speeds dropping to a minimum. The trend, however, is changing and Friday will again see winds speeds between 10-15 km/hour in the afternoon and evening which will clear out pollutants. We are also seeing westerly winds blowing currently and the westerly component will be dominant over the next few days as well,” said Kuldeep Shrivastav, scientist at RWFC, adding that wind speeds and temperatures are once again expected to drop from Sunday onwards.

Delhi’s average PM 2.5 and PM 10 levels hit their peak at 2pm on Thursday, according to CPCB’s central control room with PM 2.5 levels also crossing the “emergency” mark under the Graded Response Action Plan (GRAP). The average PM 10 levels at 2pm were recorded at 497 micrograms per cubic metre, while average PM 2.5 levels at that time were recorded at 320 micrograms per cubic metre – five times the safe standard. If both these pollutants remain above 500 and 300 micrograms respectively for a period of 48 hours, “emergency” measures under GRAP kick in, which include banning entry of trucks into Delhi, stopping construction activities and implementing the odd-even scheme.

Both the minimum and maximum temperatures were above normal on Thursday. The maximum was recorded at 25 degrees Celsius while the minimum was at 12 degrees – both four notches above normal.

In NCR, Ghaziabad and Noida were the most polluted locations, touching an AQI of 500 which is the maximum limit on the index. Gurgaon and Faridabad meanwhile were in the “very poor” category with AQIs at 346 and 358, respectively.