The air quality of Delhi was recorded in the poor category on Thursday morning and it is likely to deteriorate further due to stubble burning and unfavourable meteorological conditions, PTI reported.

The Capital’s air quality index or AQI was 201 at 9 am. An index reading between 0 and 50 puts the air quality in “good” category. A reading between 51 and 100 puts it in the “satisfactory” category, between 101 and 200 in the “moderate” category, and between 201 and 300 in the “poor category”. The air quality is said to be “very poor” when the index value falls between 300 and 400. An index value between 400 and 500 puts the quality in the “severe” category.

Delhi air quality had entered the poor category on Wednesday, the first time in since June 29. The 24-hour average AQI was 215, according to the Central Pollution Control Board. It was 178 on Tuesday.

The pollution control board data showed that PM10 (particulate matter with a diameter of less than 10 microns) in the Delhi and National Capital Region was at 234 microgram per cubic metre on Wednesday evening. PM10 levels below 100 microgram per cubic metre are considered safe in India.

Similarly, PM2.5 levels stood at 93 microgram per cubic metre on Wednesday morning. These particles, with a diameter of 2.5 micrometers, can even enter the bloodstream.

The Ministry of Earth Sciences’ SAFAR, or System of Air Quality and Weather Forecasting And Research, said that PM2.5 was becoming the lead pollutant instead of PM10. This typically happens in winter when Delhi’s air quality starts to deteriorate.

“Surface winds are calm at night,” SAFAR said. “Similar conditions are likely for another two days. The AQI is expected to deteriorate further till October 10.” It added that the boundary layer wind speed and direction were conducive for the slow transportation of pollutants from external sources and the local conditions were favourable for the accumulation of pollutants in Delhi.

Moreover, Punjab reported 169 incidents of stubble burning in the state on Wednesday, according to the government data. In Haryana, 526 farm fire incidents were recorded. Overall, 1,692 stubble burning incidents have taken place this season so far. Stubble burning is one of the major causes of the deterioration of Delhi’s air quality during winters.

Delhi’s minimum temperature settled at 19.1 degrees Celsius on Thursday morning. The wind speed was 12 kilometers per hour in the northwesterly direction. Low temperatures and stagnant winds help in accumulation of pollutants near the ground, affecting air quality.

An analysis by the Council on Energy, Environment and Water, a Delhi-based think tank, said that transportation contributes 18% to 39% to the Capital’s air pollution, the highest among any other factors. This is followed by road dust which contributes 18% to 38%, industries contribution was 2% to 29%, thermal power plants was 3% to 11% and construction adds 8%.

To tackle the problem, the Delhi government has launched an anti-air pollution campaign. Chief Minister Arvind Kejriwal said he will review the situation daily. Environment Minister Gopal Rai
will set up a war room at the Delhi Secretariat to monitor the steps taken to tackle the pollution problem.

From October 15, the Delhi government will enforce stricter measures to control air pollution as part of its Graded Response Action Plan, first started in 2017. The measures include increasing the number of buses and metros, stopping use of diesel generators and hiking parking fees.

The Graded Response Action Plan also recommends sprinkling water on roads, frequent cleaning of roads, maximising the use of natural gas for power generation and shutting down stone crushers, brick kilns and hot mix plants when the air quality enters the extreme category.

On Tuesday, the Supreme Court had said it will look into suggestions of withholding a portion of Minimum Support Price from farmers till it is confirmed that they are not indulging in stubble burning. The court was hearing a public interest litigation on air pollution in Delhi-NCR. The court also issued notices to the Ministry of Environment and Forests as well as the governments of Punjab, Haryana and Delhi in regard to the matter.