Heavy and incessant rainfall may have disrupted life in Mumbai, but it has also led to a huge drop in pollution, with the Air Quality Index (AQI), the pollutant-measuring indicator, recording the lowest levels ever in Mumbai on Monday.

The AQI, which measures PM2.5 pollutant - small-sized pollutants that can enter the lungs easily and cause health hazards - stood at 13, which is the lowest AQI recorded since the monitoring and forecasting of air quality began in Mumbai in June 2015.

An AQI level between 0-50 is good, 51-100 is satisfactory, 101-200 is moderate, 201-300 is poor, 301-400 is very poor, while 401 and above is severe.

Researchers from the System of Air Quality Weather Forecasting and Research (SAFAR), which monitors pollution levels in the city, said pollution was at an all-time low. “Continuous rain with high wind speed has not allowed emissions to accumulate. Even if the rain stops for a day, AQI will rise only as much as 50,” said Gufran Beig, project director, SAFAR. “This is the lowest pollution level on record for the city so far.”

The concentration of PM2.5 pollutant on Monday was 8 microgrammes per cubic metre (µg/m3), against a 24-hour safe limit of 60µg/m3. The level of PM10 pollutant — coarse particles sized 10 microns — was 12µg/m3 as against safe limit of 100µg/m3.

SAFAR has forecast an AQI of 28 (good) for Tuesday.

Last Monday, Mumbai had recorded an AQI of 18 (good). Prior to that, the city’s cleanest air day recorded was on October 12, 2017, when AQI levels fell to 32 (good). Earlier this month, on June 4, Mumbai had recorded an AQI of 34 (good). Last year, on December 6, AQI levels had plunged to 43 (good) as a result of Cyclone Ockhi.