The air quality in Delhi deteriorated to its worst level this season on Sunday as a thick haze enveloped the national capital, PTI reported. The overall air quality index was recorded at 381, according to data from the Central Pollution Control Board. This falls in the “very poor” category, and just a few notches shy of the “severe” level.

The air quality index is a scale from 0 to 500. A level up to 100 is considered “good” or “satisfactory”, an index value between 101 and 200 is “moderate”, between 201 and 300 is “poor”, 301 to 400 is categorised “very poor”, and a higher value is “severe”.

Twelve pollution monitoring stations in different parts of the city recorded severe air quality while 20 stations recorded very poor air quality, data showed. The stations recording the worst levels (AQI level above 400) included Mathura Road, Rohini, Mundka, Anand Vihar, Narela, Dwarka Sector 8, Bawana, Vivek Vihar and Sonia Vihar.

RK Puram recorded “very poor” air quality at 396, while Nehru Nagar recorded 394, Jawaharlal Nehru Stadium 381, and ITO at 372.

The PM 2.5 – the pollutants with a diameter of less than 2.5 micrometres – level was recorded at 225, the highest this season. The PM 10 – the pollutants with a diameter of less than 10 micrometres – was recorded at 418 on Sunday.

The decline in air quality has been attributed to vehicular pollution, construction dust as well as stubble burning in the neighbouring states of Haryana and Punjab, said authorities. The Centre-run System of Air Quality Forecasting and Research on Saturday issued a report indicating that stubble burning caused 32% of the pollution in Delhi.

However, Punjab on Sunday said it was not to blame for the pollution in Delhi, reported the Hindustan Times. According to data from the Punjab Remote Sensing Centre, there has been 60% decline in stubble burning cases from September 27 last year to October 22 this year.

“Punjab is not liable for pollution in Delhi. The latest data of stubble burning and the AQI has vindicated it,” said Kahan Singh Pannu, secretary, agriculture, state nodal officer of the anti-stubble burning campaign. “Stubble burning incidents in Punjab have decreased and the state’s average AQI is near 100.”

Pannu said that Delhi should find the “real cause” instead of blaming it on Punjab’s farmers.

The Central Pollution Control Board and SAFAR on Saturday issued separate advisories. A task force led by the CPCB recommended residents to avoid strenuous outdoor activities and minimise the use of private vehicles to reduce exposure to toxic air.

The task force suggested discontinuing all construction activities between November 1 and November 10, involving excavation, stone crushers, and stone crushers that generate dust pollution. It also recommended intensifying efforts of transport department to check polluting vehicles and controlling traffic congestion.

SAFAR’s public health advisory asked people with heart or lung disease, older adults and children to avoid prolonged or heavy exertion. It also asked people to go for shorter walks instead of jogs and wear masks while stepping outside.