The air quality reached "severe" levels in parts of Gurgaon and near-"severe" levels in Faridabad, Gautam Buddh Nagar and Ghaziabad in the National Capital Region on Friday, according to a government agency.
Concentration of major air pollutants PM 2.5 and PM 10 remained in "severe" category during the morning hours in the four immediate neighbouring districts of Delhi, according to the air quality index (AQI) maintained by the Central Pollution Control Board (CPCB).
According to the index, an AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.
In Gurgaon, an AQI of 401 was recorded at the station in Sector 151 followed by 325 at the Teri Gram, 305 at Vikas Sadan and 287 at NISE Gwal Pahari, according to the CPCB data at 7 pm.
In Faridabad, the AQI was recorded 383 at Sector 30 followed by 376 at New Industrial Town, 362 at Sector 16A and 351 at Sector 11, it showed.
In Gautam Buddh Nagar's Noida, the AQI was 383 at Sector 62 followed by 374 at Sector 1, 322 at Sector 116, while the station at Sector 125 showed “insufficient” data for the last 24 hours.
In Greater Noida, an AQI of 388 was recorded in Knowledge Park V and 337 at Knowledge Park III, according to the CPCB figures.
Adjoining district Ghaziabad's Loni had an AQI of 386 at 7 pm followed by 331 at Sanjay Nagar, 305 at Indirapuram and 277 at Vasundhara, it showed.
The concentration of PM 2.5 and PM 10 in Gurgaon, Faridabad, Gautam Buddh Nagar and Ghaziabad around 8 am on Friday was upwards of 400 in the “severe” category, according to the CPCB data.
As a possible health impact, an AQI in the "very poor" category can lead to respiratory illness on prolonged exposure, while "severe" affects healthy people and seriously impacts those with existing diseases.
The worsening of the air quality comes even as the Graded Response Action Plan (GRAP) has been implemented in the Delhi-National Capital Region (NCR) from October 15 to check air pollution, which spikes around this time of the year.