Over the week, concentration of pollutants has been higher during the day than night, said researchers from the System of Air Quality Weather Forecasting and Research (SAFAR) which measures air quality in the city.
Air pollution levels continued to rise for the fifth day in a row as the pollutant measuring indicator – air quality index (AQI) - rose from 243 to 267 by the evening, falling under the ‘poor’ category. An AQI between 200 and 300 is considered poor and people with heart or lung diseases, older adults and children should reduce prolonged or heavy exertion.
An AQI of 265 (poor) was predicted in the city for Saturday and researchers said ‘poor’ pollution levels are likely to continue for another week.
SAFAR officials said that a high pollution level during the night due to a drop in temperatures was affecting the overall 24-hour air quality average for Mumbai. “The trend is generally observed during December and January in Mumbai, but this year it has begun from November itself,” said Neha S Parkhi, senior programme officer, SAFAR. “With combined weather factors such as low temperatures currently over the city and calm winds, the buildup during the night time has increased. However, solar radiation during the day and a marginal increase in wind speed allows the pollution boundary layer to be away from the surface.”
For the second day in a row, the minimum temperature recorded at 5.30am at the Santacruz weather station, representative of Mumbai, was 16.4 degrees Celsius, 5.5 degree Celsius below normal, which was the lowest November night temperature since 2012. “With cold winds from northern parts of the country and an upper-air circulation over north-western India, cold wave conditions have prevailed over the northern parts of the state with below-normal temperatures both at the suburbs and south Mumbai,” said KS Hosalikar, deputy director general, western region, India Meteorological Department (IMD). “We expect temperatures to continue at this level for the next three days.”
Parkhi added that citizens should avoid heavy exertion from the evening onwards. “The boundary pollution layer is closer to the earth’s surface and can cause issues for people with already existing lung ailments,” said Parkhi.
From Monday onwards, the city saw a gradual rise in AQI levels at 216 (poor) to 267 (poor) till Friday with locations such as Malad, Andheri, BandraKurla Complex and Navi Mumbai, being the most polluted across Mumbai.
On Friday, four out of 10 locations in Mumbai where SAFAR forecasts and monitors air quality recorded ‘very poor’ AQI levels, and the remaining six locations fell under the ‘poor’ category.
Meanwhile, day temperatures both at the suburbs and south Mumbai were more than a degree Celsius above normal and the night temperature at Colaba was 21.8 degrees Celsius, 1.8 degree Celsius below normal. Locations such as Nasik, Pune and Badlapur recorded the lowest night temperatures in the state at 8.8 degrees Celsius, 9.4 degrees Celsius and 13.5 degrees Celsius in the last 24 hours.
