The air quality in the national capital improved in February and March with not a single high-pollution day being recorded over the period.
A study conducted by the System of Air Quality and Weather Forecasting and Research (SAFAR), had found Delhi to be among the most polluted cities in the world. Over past two weeks Delhi had seen cleaner air than Mumbai.
On Monday, SAFAR data revealed that the air quality index (AQI) of Mumbai was 312, while Delhi recorded an overall AQI of 105, which meant Mumbai's air was almost three times worse than Delhi's.
Between 27 February and 13 March, 2017, 20 per cent of the days in Mumbai had seen 'very poor' air quality, while Delhi and Pune did not have 'very poor' days.
Further Delhi had 40 per cent 'satisfactory' air quality days, Pune had 47 per cent while Mumbai had only 13 per cent.
The improvement in Delhi's air pollution level comes as welcome news for the residents who had suffered exposure to high levels of pollutants, causing serious health risks.
The development comes after Delhi recorded the worst spell of smog in 17 years with the air pollution spiking far beyond acceptable levels in November 2016. Levels of PM2.5 and PM 10 particulate matter had been recorded at 999 micrograms per cubic metre, while the safe limits for those pollutants are 60 and 100 respectively.
''Between February and March, Mumbai had more 'poor' and 'very poor' days and less 'satisfactory' air days. Delhi and Pune did not have any 'very poor' days with cleaner air than Mumbai,'' read the conclusion of the study.
''A city like Delhi is landlocked and is more prone to pollutants getting trapped closer to the surface because weather conditions are not favourable, but high speed winds and intermittent rain helped clean the city's air, Hindustan Times reported.
However, Mumbai has the advantage of sea breeze, but that did not play a crucial role in dispersing pollutants as wind speed was lower during most days between February and March,'' said Gufran Beig, director, SAFAR.
''Factors such as rise in vehicles and increasing construction work are further adding to Mumbai's pollution woes.''