Mumbai’s PM2.5 levels twice the safe limit

Concentration of PM2.5 — breathable particulate matter which is 2.5 microns in size or smaller — in the city’s air on Wednesday was the highest this season and twice

Concentration of PM2.5 — breathable particulate matter which is 2.5 microns in size or smaller — in the city’s air on Wednesday was the highest this season and twice the safe limit.

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PM, a mix of organic and chemical particles suspended in air, enters the respiratory system and can cause health ailments. The concentration was 123 micrograms per cubic metre (µg/m3), against the daily safe limit of 60µg/m3, according to the System of Air Quality Weather Forecasting and Research (SAFAR). PM2.5 levels are expected to be 121µg/m3 on Thursday and a sharp rise of 128µg/m3 is expected on Friday. PM10 (larger particles) concentration was 213µg/m3, more than twice the safe limit of 100µg/m3. Researchers said high levels of PM2.5 were rare during February.

“This is the first time we are witnessing such high levels during this time of the year,” said Gufran Beig, project director, SAFAR. “It is a unique situation wherein pollution levels continued to be high for the third consecutive day due to high temperatures and low winds. There is a surge in local sources of air pollution, which is the main cause. The wind speed has been very low for the past two days, and current levels are expected to continue for at least two more days.”

“People sensitive to air pollution should avoid outdoor activities completely. Asthmatics need to keep relief medicine handy,” read the health advisory issued by SAFAR.

Estimation of PM2.5 concentration is different from the air quality index (AQI) which is determined by pollutants. The AQI for PM2.5 on Wednesday was 266 (poor). It was 263 on Tuesday and 281 on Monday, all under the ‘poor’ 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.

On Wednesday, all 10 areas where SAFAR monitors air quality recorded either ‘very poor’ or ‘poor’ AQI. Navi Mumbai had hazardous pollution levels at 388, followed by BKC at 317, Worli 312, Mazgaon 304, Malad 302. All remaining areas recorded ‘poor’ air quality.

Meanwhile, the city and suburbs both witnessed a 2-degree drop in day temperatures from Tuesday to Wednesday. The suburbs recorded 34.8 degrees Celsius, 3.9 degrees above normal, while south Mumbai recorded 33.4 degrees Celsius, 3.6 degrees above normal. Humidity levels were marginally higher than previous days. “The setting in sea breeze was delayed, but still earlier than what was witnessed on Monday and Tuesday that allowed temperatures to touch 38 degrees Celsius due to hot southeasterly winds,” said an official from the India Meteorological Department.