Mumbai records cleanest air day for first time this year

Researchers said that the changing weather factors were responsible for the improvement in air quality.

The air quality index (AQI) was ‘good’ for the first time this year in Mumbai on Wednesday, which also happened to be the 50th anniversary of Earth Day.

The air quality index (AQI) was ‘good’ for the first time this year in Mumbai on Wednesday, which also happened to be the 50th anniversary of Earth Day. (Pramod Thakur/HT Photo)

According to the System of Air Quality Weather Forecasting and Research (SAFAR), the pollutant-measuring indicator AQI for PM 2.5 was 46, making it the cleanest air day so far this year and lowest pollution levels during lockdown.

Prior to this, Mumbai had recorded its lowest air pollution levels with an AQI of 61 on Monday, 63 on Tuesday, and 65 on March 22 (Janta Curfew day), all falling under the ‘satisfactory’ category.

SAFAR categorises AQI for pollutants in the 0-50 range as good; 51-100 as satisfactory; 101-200 as moderate; 201-300 as poor; 301-400 as very poor and above 400 as severe.

Eight of 10 locations in Mumbai, where SAFAR monitors air quality, recorded ‘good’ AQI levels. While Mazgaon had the cleanest air in the city with an AQI of 18 followed by Colaba 32, Navi Mumbai had comparatively worse air quality at 75 followed by Malad 58, both ‘satisfactory’ levels.

Researchers said that the changing weather factors were responsible for the improvement in air quality.

“Wednesday’s AQI is the optimal air quality Mumbai should be recording during lockdown when external emissions are minimal. However, over the past three weeks, we observed that owing to rising temperatures or late setting in of sea breeze, the wind pattern allowed dust and other pollutant particles to settle close to the surface,” said Gufran Beig, director, SAFAR under the Indian Institute of Tropical Meteorology (IITM), Pune.

The day temperature over Mumbai witnessed a sharp drop from Monday’s high of 37.8 degrees Celsius to 34.3 degrees Celsius on Tuesday, and even the minimum temperature on Wednesday was close to the normal mark.

Humidity levels were high with 92% in south Mumbai and 74% in the suburbs. “The drop in temperature, high moisture content and early setting in of sea breeze allowed pollutant concentration to reduce significantly on Wednesday,” said Beig. “The drop in pollution however maybe temporary due to fluctuating weather and rising temperatures.”