After a spell of rain, the average air quality improved from "very poor" to "moderate" levels in Ghaziabad, Noida, Greater Noida and Faridabad, while it reached "satisfactory" category in Gurgaon, according to a 24-hour data issued by a government agency on Monday.
Gurgaon and Faridabad last had a 'moderate' air day on December 15, Noida on December 14, Greater Noida and Ghaziabad on November 27, official figures from corresponding dates showed.
Pollutants PM 2.5 and PM 10 although remained prominent in the air of the five immediate neighbours 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''.
The average 24-hour AQI at 4 pm on Monday was 168 in Ghaziabad, 134 in Greater Noida, 152 in Noida, 179 in Faridabad and 65 in Gurgaon, according to CPCB's 'Sameer' application.
On Sunday, it was 384 in Ghaziabad, 348 in Greater Noida, 364 in Noida, 358 in Faridabad and 260 in Gurgaon. On Saturday, it was 462 in Ghaziabad, 450 in Greater Noida, 448 in Noida, 415 in Faridabad and 336 in Gurgaon.
The CPCB states that an AQI in the "satisfactory" category may cause minor breathing discomfort to sensitive people, while "moderate" may lead to breathing discomfort to those with lungs, asthma and heat diseases.
The AQI for each city is based on the average value of all stations there. Ghaziabad and Gurgaon have three such stations, while Noida, Greater Noida and Faridabad have two stations each, according to the application.
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