The share of stubble burning in Delhi’s pollution rose to 42 % on Thursday, the maximum so far this season, according to a central government air quality monitoring agency.
Experts said raging farm fires and a fall in the wind speed and temperatures pushed air quality in Delhi-NCR to the worst levels in around a year on Thursday.
The Ministry of Earth Sciences’ air quality monitor, SAFAR, said the farm fire count in Punjab, Haryana, Uttar Pradesh, Uttarakhand, and neighbouring areas increased significantly and stood at 4,135 on Wednesday, the highest this season so far.
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SAFAR said the boundary layer wind direction is northwesterly — favourable for the transport of pollutants from farm fires.
“The share of stubble burning in Delhi’s PM2.5 pollution was estimated at 42 % for Thursday,” it said.
Stubble burning accounted for five percent of Delhi’s pollution on Wednesday, 10 % on Tuesday, 16 on Monday and 40 on Sunday.
Last year, the stubble contribution to Delhi’s pollution had peaked to 44 % on November 1, according to SAFAR data.
NASA’s satellite imagery showed a large, dense cluster of fire dots covering Punjab and parts of Haryana and Uttar Pradesh.
SAFAR predicted conducive conditions for dispersion of pollutants over the next two days.
“Better dispersion condition and not so low daytime boundary layer height is predicted for the next two days which is likely to improve AQI unless more than estimated fire-related emission takes place,” it said.
PM10 levels in Delhi-NCR stood at 561 microgram per cubic meter (µg/m3) at 10 am -- the highest since November 15 last year, when it was 637 µg/m3, according to CPCB data. PM10 levels below 100 µg/m3 are considered safe in India.
PM10 is particulate matter with a diameter of 10 micrometers and is inhalable. These particles include dust, pollen and mold spores.
The levels of PM2.5 — finer particles which can even enter the bloodstream — were 347 µg/m3 at 12 noon. PM2.5 levels up to 60 µg/m3 are considered safe.
Delhi recorded an Air Quality Index (AQI) of 472 at 12 noon. It was 279 at 10 am on Wednesday.
All the 36 monitoring stations recorded the air quality in the “severe” category.
The neighbouring cities of Faridabad, Ghaziabad, Greater Noida, Gurugram and Noida also recorded “severe” levels of air pollution.
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”.