The city’s air quality on Monday slipped from the ‘good’ to ‘satisfactory’ category for the first time in three months since the onset of the monsoon in June. The Air Quality Index (AQI) recorded on Monday for PM10 was 55 and PM 2.5 was 31, while just 12 days earlier, on August 16, the AQI of PM 2.5 in Mumbai was 10 (lowest ever recorded for the second time). PM (particulate matter) is a microgram per meter, which is used to measure the size of the pollutants, the smaller the PM, the higher the toxicity levels of the pollutant.
As per the System of Air Quality and Weather Forecasting And Research (SAFAR), Mumbai was experiencing some of the most clean-air days owing to the monsoonal conditions. Speaking about the size of the pollutants and the increase in the pollution levels of the city, SAFAR project director Gufran Beig, said, “If Mumbai experiences good quality air, it’s because of the rains which wash away the pollutants, and strong winds which move them far from the city. However, due to the current lack of both high-speed winds and rainfall, the city is slowly moving towards higher air pollution levels again. This will gradually get severe as monsoon retrieves.”
PM includes microscopic matter suspended in air or water. PM10 includes particles less than 10 µm in diameter while PM2. 5 are those less than 2.5 µm. The categories of the AQI levels like good, satisfactory, poor, severe, etc, are different for different pollutants with varying sizes. For example, the pollutants of PM 2.5 will be more harmful compared to PM 10, because the smaller the pollutant particle size, the more harmful it will be, he added.
Moreover, as the rainfall has been less across the country, cities like Delhi, Pune and Ahmedabad have also been experiencing moderate to satisfactory quality air. According to SAFAR, Delhi, Pune, and Ahmedabad on Monday recorded an AQI of 135, 64, and 55, respectively.
In the month of July, the AQI mostly remained below 20, while August had been experiencing even better air days with the AQI mostly remaining below 15. This month also witnessed an AQI of 11 on August 6.
Mumbai recorded the year's worst AQI of 309 on May 20, which was worse than that of Delhi’s AQI, due to the repeated dust storms from northwest.
