Delhi was the second most polluted city in the country in January after Ghaziabad, as it recorded a monthly average PM2.5 concentration of 169 micrograms per cubic metre, which is nearly 3 times higher than India's National Ambient Air Quality Standards limit of 60 micrograms per cubic metre.
Ghaziabad was the most polluted city, recording a monthly average PM2.5 concentration of 184 micrograms per cubic metre and breaching the daily national standard on all days of the month.
According to a monthly analysis by the Centre for Research on Energy and Clean Air (CREA), Delhi recorded 24 Very Poor days, 3 Severe days, 2 Poor days and 2 Moderate days in January.
According to the CPCB, an AQI between zero and 50 is considered 'good', 51 to 100 'satisfactory', 101 to 200 'moderate', 201 to 300 'poor', 301 to 400 'very poor', and 401 to 500 'severe'.
When contacted, there was no immediate response from the Delhi Environment Minister.
Across India, 123 out of 248 cities recorded monthly average PM2.5 concentrations above the national standard, the analysis said.
None of the cities met the World Health Organization daily safe guideline of 15 micrograms per cubic metre, it said.
"Among cities covered under the National Clean Air Programme (NCAP), air quality remained largely non-compliant. Of the 97 programme cities with sufficient data, 46 exceeded India's daily PM2.5 standard, while all 97 breached the World Health Organization guideline," it added.
Noida, Gurugram, Greater Noida, Dharuhera, Gangtok, Singrauli, Bhiwadi and Narnaul were also among the ten most polluted cities. Uttar Pradesh and Haryana had 3 cities each in the top ten.
CREA India analyst Manoj Kumar said the revision of the NCAP should focus on PM2.5 and its precursor gases, sulphur dioxide and nitrogen dioxide, along with stricter emission standards for industries and power plants, revising the list of non attainment cities and adopting an airshed-based approach.
PM2.5 are fine particles with a diameter of 2.5 micrometres or less, about the width of a human hair. These are so small that they can penetrate deep into the lungs and even enter the bloodstream, posing significant health risks.
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