The annual concentration of major pollutant PM2.5, or particles with diameter less than 2.5 micrometres, was more in Gurugram, Kanpur, Lucknow and Faridabad, the study by the Energy Policy Institute at the University of Chicago (EPIC-India) said.
‘Delhi suffered 146 days of bad air quality, that is "very poor" PM2.5 levels on 120 days and "severe plus" on 26 days, while Gurugram was worse off with 190 days of bad air quality.’
It said Patna and Agra had annual concentration of pollutants similar to Delhi. The study analysed records from 18 monitoring stations of the Central Pollution Control Board (CPCB) from November 2016 to October 2017.
This includes the monitoring station in R.K. Puram area of south-west Delhi, which is among the most polluted areas with an average PM2.5 concentration of 256 units, compared with an average 191 units in Delhi on Tuesday.
The study found that between the said period, Delhi suffered 146 days of bad air quality -- "very poor" PM2.5 levels on 120 days and "severe plus" on 26 days. Gurugram was worse off with 190 days of bad air quality, including 133 days under "very poor" and 57 days under "severe plus" category.
Kanpur in Uttar Pradesh suffered a maximum 64 days of "severe plus" pollution, compared with any other city monitored, out of 171 days of bad air quality. Lucknow recorded 167 days of bad air quality, including 134 days under "very poor" and 33 days in the "severe plus" category.
Faridabad's figure was 147 days, including 92 in "very poor" and 57 in the "severe plus" category.
In terms of "severe plus" days, nine out of the top 10 most polluted cities were ahead of Delhi. Gaya in Bihar suffered pollution for 42 days, Muzaffarpur for 34 days, Patna for 37 days and Agra for 37 days in this category.
The study shows that the annual PM2.5 concentration in Delhi was around 130 units, Faridabad (170), Kanpur (166), Gurugram (163) and Lucknow (143). Patna (128 units) and Agra (120) were close to the Delhi figure.
The safe limits for PM2.5 is 25 microgrammes per cubic metre as per international standards and 60 units as per international standards. "Lucknow, Gurugram, Kanpur, Faridabad, Patna and Agra had annual PM 2.5 concentration three times higher than the national air quality standard," the study pointed out.
"It is a problem faced throughout the year and not just during the winter times. The days we included were from all seasons and not just winter months... It also shows that there is an immediate need for long-term and systematic policy measures at the city, regional, and national levels to improve air quality," Dr Santosh Harish, senior researcher, EPIC-India, told IANS on Tuesday.