New Delhi, Nov 17: A study by the government’s air quality research body SAFAR found that dust travelling thousands of kilometre from a severe storm in the Gulf was largely responsible for smog that choked Delhi and National Capital Region (NCR) for a week starting from November 7. The analysis also revealed that stubble-burning in Punjab and Haryana contributed around 25 per cent. The remaining 35 per cent was pollution produced locally in Delhi-NCR.

Dust coming in from the Gulf constituted nearly 40 per cent of pollutants in the smog that choked Delhi-NCR, concluded the study by SAFAR. According to SAFAR chief Gufran Beig, favourable upper winds carried the dust from the Gulf and smoke from crop burning into Delhi-NCR were trapped towards the surface because of an anti-cyclonic wind circulation over the region and calm surface conditions. The incursion of these pollutants began on the night of November 6 and continued till November 10.

Delhi Smog: Officials Surrender, Say 'Only God Can Save us' as Pollution Level Scales 12 Times Above Recommended Limit

Delhi Smog: Officials Surrender, Say 'Only God Can Save us' as Pollution Level Scales 12 Times Above Recommended Limit

“By 5 pm on November 7, the air quality had dropped to severe levels,” Gufran Beig was quoted as saying by Times of India. Delhi-NCR recorded PM 2.5 concentration at 537 micrograms (g)/m3 on November 7, nine times the 24-hour average standard. It rose to a peak of 640 g/m3 the next day. If external sources of pollution had not played a role, Delhi’s air quality on November 8 would have been closer to 200 g/m3, said the SAFAR analysis.

On October 29, a storm had hit Saudi Arabia, Iraq and neighbouring countries, which created a massive cloud of sand and dust into the air that was visible in NASA satellite images. “This dust rose 1.5 to 3km into the atmosphere where winds became very strong (15-20kmph) and direction became towards India (westerly, north-westerly) and dust affected larger region of Delhi,” the SAFAR analysis concluded.

The incursion had ceased by November 10, SAFAR said. “There was no pumping and influence of stubble burning and Gulf storm dust after November 10 night, owing to slowing down of upper air winds and change in wind direction,” the analysis stated. The study also said the pollution level in Delhi can be reduced by as much as 15 per cent with the help of the measures initiated by the environment pollution control authority (EPCA) under the graded response action plan (GRAP).