The overall AQI for Friday is likely to be 19, said System of Air Quality and Weather Forecasting and Research (SAFAR). (Representational Photo)

At 17, Mumbai recorded its best Air Quality Index (AQI) for this year on Thursday afternoon. It rose to 19 by evening. The lowest AQI for the year was recorded a day after the severe cyclonic storm Nisarga hit Maharashtra coast, bringing high-speed winds and washed away particulate matter (PM).

The concentration of PM 2.5 – tiny particulate matter less than 2.5 microns in diameter that can enter deep into the lungs and even the bloodstream – was recorded recorded at 17 on Thursday evening.

The World Health Organisation safe limit of 25 µg/m3 for 24 hours and 60 µg/m3, the national safety standard for PM 2.5. The lockdown has also had helped in keeping the city’s PM2.5 concentration below 60 µg/m3 since the last week of March.

The overall AQI for Friday is likely to be 19, said System of Air Quality and Weather Forecasting and Research (SAFAR).