CNN Central News & Networks / ITDC India ePress / ITDC News /Agencies/ Delhi: Rain brings Delhi temporary air relief, pollution returns within five days
New Delhi. People in Delhi often hope that an improvement in air quality after rain will bring long-lasting relief from pollution, but a new study has questioned this assumption. A 22-year study has found that, in many cases, pollution particles present in the atmosphere return to pre-rain levels within five days. This makes it clear that the capital’s air cannot be kept clean by relying on rain alone.
Researchers studied 612 rainfall events in Delhi between 2003 and 2024. In 310 of these cases, or more than half of the events, pollution particles returned to pre-rain levels within five days. In about 45 percent of the events, the particle levels had still not returned to their earlier condition even after 30 days.
According to the study, rain provides temporary relief by bringing pollution particles in the atmosphere down, but vehicles, industries, construction activities and other sources continue to emit pollutants. Chemical processes in the atmosphere also create new pollution particles. This is why pollution starts rising again after the rain stops.
The research also found that heavier rainfall does not mean cleaner air for a longer period. No significant link was found between the amount of rainfall and the speed at which pollution particles returned. The period varied according to the season. During the monsoon, pollution particles took an average of six days to return to earlier levels, five days in summer and winter, and three days in the post-monsoon season.
The study was conducted by researchers Gayatri Balachandran and Dr. Sumit Satindran S of Kerala-based Amrita Vishwa Vidyapeetham. The research was published in September 2026 in the Journal of Atmospheric and Solar-Terrestrial Physics.
The study used satellite data for Aerosol Optical Depth (AOD). This measure indicates the extent to which particles present in the atmosphere block or scatter light. However, it is not a direct measure of the Air Quality Index (AQI) recorded at ground level.
The study concludes that rain can certainly provide relief from pollution for some time, but sustained control over emissions from vehicles, industries and construction activities is necessary for lasting improvement.
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