NEW DELHI: Though September 2024 had relatively cleaner air in the country, with only four cities breaching National Ambient Air Quality Standards (NAAQS). However, the number of cities exceeding daily World Health Organisation(WHO) standards rose to 220 in September, up from 177 in August, coinciding with the end of the monsoon season.Overall, September experienced a shift from the Good to the Satisfactory category compared to August, largely due to changes observed in the states of Haryana, Uttar Pradesh, and Rajasthan within the Indo-Gangetic Plain (IGP).According to the analysis by Centre for Research on Energy and Clean Air (CREA) in September 2024, a total of 201 Indian cities were categorised as ‘Good (0-30 μg/m3)’ on the PM2.5 AQI scale, while 59 cities were ‘Satisfactory (31-60μg/m3)’ and 4 cities were ‘Moderate (61-90 μg/m3)’. India’s NAAQS set the annual average limits for PM2.5 at 40 µg/m³ and for PM10 at 60 µg/m³ whereas WHO guidelines, which recommend annual average limits of 5 µg/m³ for PM2.5 and 15 µg/m³ for PM10.Further, Delhi recorded an average PM2.5 concentration of 43 μg/m3 in September, with 9 days categorized as “Good,” 16 as Satisfactory, 4 as Moderate, and 1 day in the Very Poor category (121-250 μg/m3). This represents a deterioration from August’s average of 27 μg/m3, which saw 24 days in the “Good” category.Byrnihat in Assam/Meghalaya ranked as the most polluted city in India, with a monthly average PM2.5 concentration of 73 μg/m3. Byrnihat has consistently been among the top 10 most polluted cities throughout the year.
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