Grey Christmas in Mumbai as air quality plunges to ‘poor’ category
Mumbai recorded its worst air quality this season so far on Christmas Day, after the pollutant-measuring indicator - air quality index (AQI) for PM2.5 - shot up to 240, falling under the ‘poor’ category. This was the worst AQI for Mumbai in more than nine months.
Cloudy conditions were witnessed on Wednesday as researchers from the System of Air Quality Weather Forecasting and Research (SAFAR) said AQI had increased significantly owing to high humidity in the city. According to the India Meteorological Department, the suburbs and south Mumbai both recorded 84 per cent humidity on Wednesday.
PM2.5 is the smaller kind of particulate matter with diametre not more than 2.5 micrometers. These are “fine particles” that 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 are the most toxic pollutant particles that are carried to lower airways of the lungs and deposited in alveolar wall causing serious health ailments.
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.
SAFAR and independent meteorologists had predicted that air quality was likely to deteriorate on Wednesday. SAFAR has predicted an AQI of 242 (poor) for Thursday. “High moisture availability owing to a weather system in the Arabian Sea led to cloud cover while southeasterly winds have been brining dust and moisture over the city. All these factors are further getting enhanced with cold conditions prevailing over north India. Along with this the wind speed is low, which is allowing the pollutant boundary layer to suspend close to the surface,” said Gufran Beig, project director, SAFAR.
The concentration of PM2.5 and PM10 was almost twice the safe limit. As against 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 the safe limit of 100 µg/m3.
Bandra-Kurla Complex, Andheri and Malad were three most polluted locations in the city with AQI at 314, 302, and 305, all under the ‘very poor’ category. Bhandup had the cleanest air in the city at 77 (satisfactory).
The last time the city recorded such high pollution levels this year was in March when the AQI was 246 (March 26), 243 (March 25), and 254 (March 24). Even during Diwali, the air quality did not exceed the ‘moderate’ category this year. “A number of cyclones in the Arabian Sea and 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,” added Beig.
AQI during Christmas Day this year was much worse than 2018 when the AQI had dropped to 13, one of the lowest pollution levels since air monitoring began in 2015 owing to Cyclone Ockhi that brushed past the Mumbai coast then. However, it was much worse in 2017 when the AQI had shot up to 258 (poor). On December 25, 2016, Mumbai recorded an AQI of 311 (very poor), which was the most polluted Christmas Day in the past five years.