Delhi impatiently hoped for favourable meteorological conditions to blow away the pungent haze lingering over the city for three days, as health experts on Thursday said the hazardous air pollution has become a serious health concern for about 2 crore residents.
"Intake of every 22 micrograms per cubic metre of polluted air is equivalent to smoking a cigarette. So whether the PM2.5 level is 700 or 300 units, the impact is still as bad. People need to take precautions, especially those suffering from asthma, bronchitis or other respiratory illness," said Dr Arvind Kumar, lung surgeon at Sir Ganga Ram Hospital here.
Despite a little improvement in the air quality towards Thursday evening (AQI 410), the crowd at India Gate in central Delhi had already thinned out. And even most of those visiting the popular place had their safety masks on, according to a traffic police personnel on duty there.
People say they prefer to stay indoors.
"My daughter is seven years old. She cannot be allowed outdoors in these conditions. Even I feel trouble breathing outside. I want the government to shut schools," said a journalist.
The air quality in Delhi took a hit after Diwali night due to a combination of firecracker emissions, stubble burning and unfavourable meteorological conditions. Since then, pollution levels have been oscillating between the lower end and the higher end of the very poor category.
The air quality oscillated between satisfactory and moderate categories till October 15.
Central Pollution Control Board Member-Secretary Prashant Gargava told PTI that preemptive measures and meteorological conditions provided a cushion and that's why Delhi's air quality did not slip into the "emergency" category, like previous years.
"But action on the part of implementing agencies has not been satisfactory," he rued.
A report from Delhi-based think tank Centre for Science and Environment said favourable weather conditions contributed to the comparatively lower pollution levels in Delhi and NCR towns since September 15. It said emergency interventions have also been important.
Kuldeep Srivastava, a senior scientist at India Meteorological Department, said favourable weather played an important role in keeping pollution levels in check during the initial days.
"As a result of an elongated monsoon, easterly winds continued to blow in the region till October 11. It protected Delhi from the early effect of stubble burning.
"Later, increased wind speed under the influence of a western disturbance helped the city a great deal. A squall, with winds gusting up to 80 kilometers per hour, had hit the national capital on October 18," he said.
Favourable meteorological conditions played an important role in keeping the pollution in check and experts hope they again help improve the conditions and blow away the toxic haze.
The air quality started deteriorating when the wind direction changed to westerly and northwesterly around October 20-22, data showed. Westerly and northwesterly winds bring smoke from stubble burning in Haryana and Punjab to Delhi.
"We have been pinning hopes on a fresh western disturbance which will increase the wind speed November 2 onwards. Winds gusting up to 25 kilometers per hour are very likely from November 3 to 5 and will help disperse the pollutants," Srivastava said.
Mahesh Palwat of Skymet Weather, a private forecaster, said the winds were strong (15-20 kmph) and favourable until Diwali but became calm and very light on October 28, trapping pollutants from firecracker emissions and stubble burning.
"Besides all other sources of pollution, unfavourable weather has been the main reason behind the deterioration of air quality. Until there is relief in terms of weather, a similar situation is likely to prevail," he said.
The Ministry of Earth Sciences' air quality monitor, SAFAR, on Thursday said the transport-level wind direction is likely to remain northwesterly, which is favourable for plume transport, for the next three days.
"An increase in surface wind speed is expected on Thursday. AQI is likely to improve slightly on Friday," it predicted.
A fresh western disturbance as a trough runs roughly along the Afghanistan-Pakistan border as of Thursday. It will approach northwest India by November 2.
"It is likely to influence Delhi's air quality positively. An improvement to the lower end of the very poor category is expected by November 2," it said.
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