Delhi's air quality 'severe' for fifth day in a row, quick relief unlikely

The blanket of smog over Delhi thickened on Monday, reducing visibility in parts of the city to just 400 metres as the air quality remained "severe" for the fifth consecutive day.

Government agencies and experts said calm wind was exacerbating the effect of stubble burning and a "quick recovery" is not possible unless the number of farm fires reduces drastically.

V K Soni, the head of the India Meteorological Department's environment research centre, said a major improvement in Delhi-NCR's air quality was "highly unlikely" in the coming days.

"The air quality is likely to be recorded in the upper end of the 'very poor' category on Diwali if we discount firecrackers emissions. If people burst crackers, pollution levels can increase to 'severe plus' category (meaning emergency level)," he said.

The National Green Tribunal on Monday imposed a total ban on sale or use of all kinds of firecrackers in the National Capital Region (NCR) from November 9 midnight to November 30 midnight, saying, "Celebration by crackers is for happiness and not to celebrate deaths and diseases."

The city's air quality index (AQI) stood at 477, the highest since November 3 last year when it was 494, according to Central Pollution Control Board data. Its 24-hour average AQI was 416 on Sunday, 427 on Saturday, 406 on Friday and 450 on Thursday.

The neighbouring cities of Faridabad (456), Ghaziabad (482), Noida (477), Greater Noida (478), and Gurgaon (482) also recorded "severe" air quality.

An AQI between zero and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".

PM 10 levels in Delhi-NCR stood at 609 microgram per cubic metre (g/m3) at 4 pm, the highest since November 15 last year, when it was 637 g/m3, according to CPCB data. PM10 levels below 100 g/m3 are considered safe in India.

PM 10 levels are considered in the "severe plus" category if their concentration is more than 500 microgram per cubic metre, according to the Graded Response Action Plan for Delhi-NCR notified by the Ministry of Environment and Forests in 2017.

PM 10 is particulate matter with a diameter of 10 micrometers and is inhalable into the lungs. These particles include dust, pollen and mold spores.

The levels of PM 2.5 finer particles which can even enter the bloodstream were 386 g/m3 at 4 pm. PM 2.5 levels up to 60 g/m3 are considered safe.

The Ministry of Earth Sciences' air quality monitor, SAFAR, said, "Low dispersion condition continues in Delhi along with high fire-related intrusion. This has led to the accumulation of pollutants near the surface."

"No quick recovery is expected unless a drastic reduction in fire counts takes place," it said.

SAFAR said the farm fire count in Punjab, Haryana, Uttar Pradesh and Uttarakhand stood at 3,257 on Sunday and the share of stubble burning in Delhi's PM 2.5 pollution was 38 per cent on Monday.

"In terms of magnitude with respect to current levels of PM 2.5 in g/m3, this is one of the highest mass loadings (~ 140 g/m3) of the season," it said.

According to the India Meteorological Department (IMD), the wind speed was 3 to 4 kilometres per hour in the morning and the minimum temperature 10 degrees Celsius. Calm winds and low temperatures trap pollutants close to the ground, while favourable wind speed helps in their dispersion.

There was moderate fog in the morning which led to smog. It reduced visibility to 600 metres at the Safdarjung Observatory, Kuldeep Srivastava, the head of the IMD's regional forecasting centre, said.

He said the current situation is likely to continue till November 15 as the wind speed is not expected to pick up significantly.

"A marginal improvement is likely on Thursday and Friday due to change in the wind direction, but it will not be substantial," he said.

Mahesh Palawat, an expert at Skymet Weather, a private forecasting agency, said the visibility dropped to 400 at some places due to dense smog in the morning. The air pollution situation in Delhi-NCR is expected to be as bad as last year, he added.

The central government's Air Quality Early Warning System for Delhi also said a "significant improvement in air quality is not likely" owing to slow wind speed, particularly during night time, and contribution from farm fires.

The farm fire count over Punjab remains very high which is likely to impact the air quality of Delhi-NCR and other parts of northwest India, it said.