Mumbai breathes worst air since FebruaryUpdated: Dec 26, 2019 00:10 IST
The city recorded its worst air quality this season on Wednesday, with the pollutant-measuring indicator — air quality index (AQI) for particulate matter (PM) 2.5 — shooting up to 240, to fall under the ‘poor’ category, on Christmas day.
The last time Mumbai had recorded such high pollution levels this year was on February 10, when the AQI was 264 (poor).
By the evening, it had further increased to 257. PM is a mix of chemicals, dust, pollen and other substances that can enter the respiratory system and cause or aggravate chest ailments.
Researchers from the System of Air Quality Weather Forecasting and Research (SAFAR) said air quality had worsened significantly owing to high humidity. According to the India Meteorological Department, the suburbs and south Mumbai both recorded 84% humidity. Cloudy conditions were witnessed on throughout Wednesday and light drizzles were recorded in some suburbs during the afternoon.
“High moisture availability owing to a weather system in the Arabian Sea led to cloud cover while southeasterly winds have been bringing dust and moisture over the city,” said Gufran Beig, project director, SAFAR.
Along with this, the wind speed is low, which is allowing the pollutant boundary layer to suspend close to the surface leading to foggy conditions,” he added.
“Current conditions will last for the next two to three days.” SAFAR has predicted an AQI of 242 (poor) for Thursday.
On Wednesday, Bandra Kurla Complex, Andheri and Malad were the three most polluted locations in the city with AQI at 314, 302, and 305 (very poor), respectively. Bhandup had the cleanest air in the city at 77 (satisfactory).
AQI levels for PM2.5 pollutant between 0-50 is good; 51-100 is satisfactory; 101-200 is moderate; 201-300 is poor; 301-400 is very poor; and 400 above is severe.
In March, the readings had been poor on three days (246 on March 26; 243 on March 25; 254 on March 24). Even during Diwali this year, the AQI hadn’t fallen below the ‘moderate’ category.
“A number of cyclones in the Arabian Sea and the extended impact of the southwest monsoon helped control air pollution over Mumbai throughout most of the year.
However, the last week of 2019 may witness a further rise in air pollution,” said Beig.
PM2.5 is the smaller variety of particulate matter with a diameter of not more than 2.5 micrometers.
These can stay in the air for days or weeks and are small enough to invade even the narrowest of airways leading into the body. PM2.5 or lesser are the most toxic pollutant particles and can cause serious health ailments.
As against the safe limit of 60 microgrammes per cubic metre (µg/m3), Mumbai recorded 114µg/m3. For PM10 (slightly larger, coarser particles), Mumbai recorded 228 µg/m3 as against 100 µg/m3, which is the safe limit.
Independent meteorologist Akshay Deoras, who is a PhD researcher at the University of Reading, said, “Moisture incursion from the Arabian Sea was at its peak.”
This has clearly worsened the air quality compared to the previous days since high moisture content helps in trapping air pollutants, said Deoras.
He further said that low wind speed and high relative humidity were likely to contribute in deteriorating the air quality for the remainder of this week.
This year, the AQI during Christmas day was worse than the readings of 2018, when the AQI had dropped to 13, owing to Cyclone Ockhi.
Last year’s AQI on Christmas day was one of the lowest since air monitoring began in 2015. However, in 2017, the AQI was 258 (poor) on the Christmas day and in 2016, it had shot up to 311 (very poor), making it the most polluted Christmas day of the past five years. The AQI on December 25, 2015 was 304 (very poor).