Residents of Dhaka have been experiencing a much poorer quality of air in the capital since the onset of winter after a favourable autumn.
The drastic drop in air quality is evident in the latest data published by the Air Quality Index, or AQI, on Sunday. Dhaka once again topped the list of cities with the worst air quality, surpassing China’s Shenyang and Chengdu, Vietnam’s Hanoi and India’s Kolkata.
The air pollution score was 271, which is described as 'very unhealthy'.
HOW AIR QUALITY IS MEASURED
The air quality depends on the particulate matter or PM10 and extra fine particulate matter or PM2.5 measured on a scale of parts per million.
Besides PM2.5 and PM10, sulphur dioxide, carbon monoxide, nitrogen dioxide, and air pollution in the ground-level ozone are considered while determining the air quality index. The higher the AQI score, the more hazardous the air becomes.
The air quality in an area is considered 'good' when the AQI ranges from 0 to 50. When the AQI remains in the range of 51-100, the air quality is considered 'moderate'.
With an AQI of 101-150, the air becomes unhealthy for vulnerable groups, including children, elderly people and asthma patients. The air becomes unhealthy for everyone when AQI hovers from 151-200. An AQI in the 201-300 range is considered 'very unhealthy' and the air becomes hazardous when the index rating crosses 301.
Shenyang and Chengdu ranked second and third in the index with scores of 245 and 227, respectively. Meanwhile, Hanoi and Kolkata took the fourth and fifth positions, scoring 224 and 222.
Earlier in October, people in Dhaka could breathe a little easier as the Eid holidays and rainfall in the second week of the month contributed to an improvement in the air quality.
The phenomenon was rather unique because more dust particles are found in the air in October.
However, experts raised alarm at the time, cautioning everyone that the quality of air may worsen in the winter due to the ongoing construction projects across the city.
Prof Ahmad Kamruzzaman Majumder, chairman of Stamford University’s environmental science department, said the smoke bellowing from dumpster fires on the city’s outskirts -- especially in Matuail and Aminbazar -- is making an already bad situation worse.
“January is the continuation of the poor air quality season that kicked off in October. The situation turns worse if there’s no rain. The air quality is already in bad shape in Dhaka, and setting fire to the garbage dumped in Matuail and Aminbazar, and the subsequent heavy smoke from it is making things worse,” he said.
A World Bank study estimated that 78,145 to 88,229 deaths in Bangladesh were caused by air pollution in 2019. It was the second strongest risk factor, causing most deaths and disabilities in the country between 2009 and 2019.
The average exposure to PM2.5 in locations with major constructions is 150 percent above the World Health Organization’s air quality guideline limit, which is equivalent to smoking 1.7 cigarettes per day. This is irrespective of whether the individual is a small child or a non-smoking adult, the inhalation of these pollutants is universal.