New Delhi, September 30: Despite heavy monsoon rainfall, Delhi recorded only one day of ‘Good’ air quality during the 92-day monsoon season, according to a new assessment by the Centre for Science and Environment (CSE).
The study found that Delhi received 576.9 mm of rainfall during the monsoon, yet the city’s air quality remained largely in the ‘Moderate’ category. Out of 92 days, 53 days (57.6 per cent) recorded ‘Moderate’ air quality, while only one day was classified as ‘Good’. The highest single-day rainfall of 101.05 mm on August 8 also resulted in only ‘Satisfactory’ air quality.
CSE said rainfall provided only temporary relief from particulate pollution. During six isolated monsoon rainfall events analysed, the average PM2.5 level fell from 40.6 micrograms per cubic metre before rainfall to 32.7 during rainfall. However, it rose to 36.2 within 24 hours and reached 45.1 micrograms within 48 hours—37.9 per cent higher than the level recorded during rainfall.
The assessment noted that Delhi’s average PM2.5 concentration declined by 33.2 per cent from 60.2 micrograms per cubic metre in summer to 40.2 during the monsoon. However, the quick rebound after rainfall indicated that underlying emissions remained largely unchecked.
CSE also highlighted the role of gaseous pollutants, particularly ground-level ozone, nitrogen dioxide and carbon monoxide, which became more prominent as rainfall washed out particulate matter.
CSE Executive Director Anumita Roychowdhury said the findings underline the need to move beyond temporary weather-related relief and winter emergency measures. She called for sustained, year-round emission reduction measures across the entire Delhi-NCR airshed.
The CSE recommended stronger public transport and electric mobility, cleaner industrial fuels, better waste management, reduced dependence on diesel generators and coordinated year-round pollution control across NCR districts.
