Explained: Dust storm and no winds – what’s behind the air pollution in Mumbai

On Tuesday, the AQI in Mazgaon, the most polluted area in the city, rose to 495, a reading in the ‘severe’ category. At 1.30 pm, the overall AQI was in the ‘very poor’ category, worse than Delhi, Pune, and Ahmedabad, according to the Ministry of Earth Science’s System of Air Quality and Weather Forecasting Research (SAFAR).

AQI is a mean of pollutants such as particulate matter (PM2.5 and PM10), ozone (O3), nitrogen dioxide (NO2), sulphur dioxide (SO2) and carbon monoxide (CO) emissions, derived as a single value. The higher the AQI, the greater the level of air pollution and the more serious the health concern.

What is causing the increase in pollution levels in Mumbai?

According to SAFAR, the current high pollution is due to a second dust storm in less than two weeks that has hit the city. This storm originated on February 3 over Afghanistan, Pakistan, and the border areas of Rajasthan. Last month, a storm originating in the Middle East had brought dust and haze to northwestern Maharashtra, Gujarat, and Rajasthan.

Low day temperatures, weak, low-speed winds, high relative humidity, and coldness of the air are contributing to the bad air above the city. The minimum temperature has fallen over the last 24 hours—from 19.4 degrees Celsius on Monday to 17.8 degrees on Tuesday.

In Mumbai, a windswept coastal city, the bad air is regularly cleaned out by a strong sea breeze. Low wind speeds of late have, however, meant that local pollutants hanging above the city have not been effectively dispersed.

How long will this situation persist?

SAFAR, which has 10 air quality monitoring stations across the city, has said that air quality will improve slightly to the ‘poor’ category — i.e., an AQI of 201-300 — over the next two days.

As per the 24-hour air quality forecast issued by SAFAR, the AQI in Mumbai on Wednesday (February 9) is likely to be 312 (‘very poor’). Residents of Mumbai should be able to feel the difference in the air if the wind picks up.

Meanwhile, is there anything that you should or should not be doing right now?

There is a standard health advisory for various stages of air pollution, which can be accessed on the SAFAR website among other places.

SAFAR has advised all Mumbai residents to avoid outdoor activity in the early mornings and after sunset. Sensitive or vulnerable groups should avoid all physical activity outdoors, and move them indoors where possible.

Asthmatics should keep relief medication handy. They should wear N-95 masks or P-100 respirators when stepping out.

Doors and windows should be kept shut to the extent possible. Wet mopping is preferable to vacuuming.

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