Delhi’s air quality declined to its worst level so far this season on Friday, with most measuring stations falling in the “very poor” category in the morning. At 10 am, the overall air quality index value for the city was 308, slightly better than the index value of 315 recorded at 8.30 am.

The index values rose on Friday due to a decreased wind speed, which led to the accumulation of pollutants, PTI reported. The System of Air Quality and Weather Forecasting and Research, which is run by the Ministry of Earth Sciences, said that the air quality is likely to be in the high and middle range of the “very poor” category for the next two days due to calm surface winds.

However, the situation on Diwali may not be as bad as last year as a western disturbance is likely to hit the western Himalayan region by October 28. Diwali falls on October 27 this year.

At 11 am, the worst air quality was recorded in Bawana locality – 356. Mundka had an index value of 351, followed by Anand Vihar at 333. Loni area of nearby Ghaziabad district had an AQI of 353.

Meanwhile, the Environment Pollution (Prevention and Control) Authority, which was set up by the Supreme Court to take measures to check pollution in Delhi in the early winter, banned construction activities in the national capital and nearby towns between 6 pm and 6 am from October 26 to October 30. The authority’s chairman, Bhure Lal, told the governments of Delhi, Haryana and Uttar Pradesh to shut down coal-based industries, barring power plants, in Faridabad, Gurugram, Ghaziabad, Noida, Greater Noida, Sonepat and Bahadurgarh during this period. The EPCA also banned industries that do not use piped natural gas.

On October 18, the Central Pollution Control Board had advised private and government offices in Delhi and the National Capital Region to allow employees to work from home. The board also urged people to carpool to work, and asked schools to provide transport services to students. An action plan to tackle air pollution in the National Capital Region was enforced last week as the overall air quality slipped to “very poor” levels. The plan includes a ban on diesel generator sets, and intensified vacuum and water-cleaning of roads.

The Aam Aadmi Party-led government has decided to implement the odd-even scheme from November 4 to 15, a week after Diwali. The scheme prohibits plying of vehicles based on the last digit of their registration numbers – vehicles with odd digits are not allowed on even dates and vice versa.

Air quality index

The Central Pollution Control Board measures Delhi’s air quality based on index values recorded at up to 37 stations spread across the city. Air quality is classified as “good” or “satisfactory” if the index value is 100 or below. A value of 101 to 200 falls in the “moderate” category, the “poor” category covers values between 201 and 300, and values between 301 and 400 are said to be “very poor”. Even worse air quality – 401 to 500 – is classified as “severe”.

Very poor air quality poses a risk of respiratory illness on prolonged exposure, and severe levels can affect even healthy people and can have serious impact on those with existing diseases, according to the Central Pollution Control Board.

The national capital sees a massive rise in pollution levels during this time of the year, which makes the air in the region extremely toxic. The phenomenon is blamed on the burning of crop stubble by farmers in Punjab and Haryana, as well as construction activity and Diwali festivities during a season with low wind speeds, which prevent pollutants from settling down.

Now, follow and debate the day’s most significant stories on Scroll Exchange.