The “absolute share” of farm fires’ contribution to PM 2.5 levels in Delhi has been less than around 150 micrograms per cubic metre air (µg/m3) since nearly a month, even on 'severely' polluted days, an assessment by SAFAR, the Centre's air quality monitoring agency, claims.
As per the analysis, on November 3, when PM 2.5 in the air had reached a record high of around 600 µg/m3 — double the emergency threshold (300) — the share of farm fires in it was nearly 150 µg/m3. The acceptable 24-hour standard for PM 2.5 is 60 µg/m3. The assessment is done based on 24-hour average levels of the pollutant.
On November 12, when the pollutant rose to nearly 400 µg/m3, stubble burning contributed around 100 to it, after which its share fell. It was around 50 µg/m3 on November 15, when PM 2.5 again touched 400 µg/m3.
A combination of factors, including unfavourable meteorological conditions, local emissions and stubble burning, has pushed Delhi’s air quality to dangerous levels several times this month.
The Delhi government has blamed crop residue burning while experts have pointed out that Delhi’s high basal pollution level is also part of the problem.
On Sunday, as the city’s air quality improved, Chief Minister Arvind Kejriwal retweeted photographs of the clear blue sky above Delhi, and air quality index recorded in different parts of it, and said, “Stubble burning has stopped. And with it Delhi's air has become clean too...”
In a statement later in the day, he said, “Some people were saying that only 5% of Delhi's air pollution is due to crop (residue) burning. If this were true, how did the air quality index reduce from 500 to less than 200 today?”
Kejriwal claimed images from US space agency NASA showed that with an increase in crop residue burning instances in the first week of October, North India's air quality deteriorated.
Blaming its recent pollution crisis entirely on crop stubble burning, Kejriwal said Delhi had taken steps to reduce local emissions. “But the current crisis of air pollution in Delhi was due to stubble (burning) in nearby states,” he added.