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Pollution in Delhi spikes to ‘severe’ again, may improve today

On Thursday, the average AQI in Delhi hit 469, more than a 100 points higher than the 359 on Wednesday. An AQI value above 400 on a scale of 500 is considered “severe”.

delhi Updated: Dec 22, 2017 07:25 IST
HT Correspondent
HT Correspondent
Hindustan Times, New Delhi
Delhi,air quality,Delhi air quality
Residents walk amid heavy smog at India Gate in New Delhi on December 20, 2017.(AFP Photo)

Delhi’s air quality plunged to ‘severe’ levels on Thursday after a gap of more than a month as dangerous pollutants spiked sharply in the national capital but officials said the situation was likely to ease within a day.

The last time Delhi breathed such foul air was on November 13 when the Air Quality Index (AQI) – which measures harmful pollutants in the air – had gone above 400.

On Thursday, the average AQI hit 469, more than a 100 points higher than the 359 on Wednesday. An AQI value above 400 on a scale of 500 is considered “severe”.

“The wind has already started to pick up speed from Thursday evening and will gather more strength over the next two days...We are expecting a clear sky by Saturday,” said Kuldeep Srivastava, a senior scientist with the Regional Weather Forecasting Centre.

He also predicted fog on Friday morning but said the sky will clear as the day progresses.

During winters, Delhi has been battling severe air pollution, attributed mainly to vehicular emissions and crop residue burning in neighbouring states. The notoriously foul air, which has put Delhi among the top polluted cities across the globe, had prompted drastic measures including shutting down coal-fired industries and a road-rationing scheme called odd-even.

On Thursday, the air quality in some places such as Anand Vihar, ITO, Siri Fort and Punjabi Bagh were close to the ‘emergency’ levels with AQI values spiking more than 490 during the day.

The levels of PM10 and PM2.5 – fine particulate matter which can penetrate deep into the lungs and cause severe ailments -- were at least eight times above the healthy limits in some areas.

“It was mainly because of the low wind speed over the past few days that the pollutants had started accumulating...The moisture level was also high. While the moisture trapped the pollutants, the calm winds failed to flush them out,” said D Saha, head of the air quality laboratory at Central Pollution Control Board.

Both the local meteorological department and SAFAR – India’s official pollution forecasting system – said air quality could improve from Friday.

As the wind velocity increased marginally on Thursday evening, the level of PM10 and PM2.5 also dropped.

As the air quality deteriorated throughout Thursday, a CPCB-led task force recommended the closure of all coal-based industries operating in Delhi-NCR for a fortnight from January 15 to contain air pollution during the upcoming ASEAN summit, scheduled between January 19 and 30.

The Supreme Court-mandated panel, the Environment Pollution-Prevention and Control Authority (EPCA), also directed the states in the region to gear up for another round of action under the ‘emergency’ category.

Under the Centre-notified Graded Response Action Plan (GRAP), pollution is considered severe plus or emergency when

readings of PM2.5 or PM10 are above 300 and 500 ug/m3 respectively. Measures listed under the emergency category are rolled out when these conditions prevail for 48 hours at a stretch.

First Published: Dec 22, 2017 07:25 IST