The air quality in the National Capital Region continued to be bad on Tuesday as people complained of smog and haze in several places. The overall air quality index in Delhi as of 4 pm was 392, or in the “very poor” category, according to the Centre-run System of Air Quality and Weather Forecasting and Research, or SAFAR. The index measures air quality in real time.

However, according to the National Air Quality Index, given by the Central Pollution Control Board, the overall air quality level in Delhi was 395 at 3 pm. The CPCB data is a 24-hour average, and it was only marginally better than Monday’s high of 397 at 8 pm.

According to the CPCB data, Anand Vihar in Delhi had the worst pollution, with an air quality index of 446, followed by Nehru Nagar, where it hit the 436-mark. Air quality index in neighbouring cities of Ghaziabad and Noida according to the CPCB were 449 and 438, respectively.

An air quality index reading between 301 and 400 is said to be “very poor”, while even worse air quality – 401 and beyond – is classified as “severe”. While SAFAR measures Delhi’s air quality based on index values recorded at up to nine stations spread across the city and one each in Noida and Gurugram, CPCB’s reading is based on up to 37 measuring stations in Delhi.

The air quality in Delhi on Monday morning after Diwali celebrations touched the 463 mark, which falls in the “severe” category. Delhi Chief Minister Arvind Kejriwal claimed that the post-Diwali pollution level in the national Capital was the lowest in five years.

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.

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