Bangladesh has been named the world's most polluted country for PM2.5 exposure while Dhaka has emerged as the second most polluted city in the 2019 World Air Quality Report.
Although Bangladesh has seen a small progress compared to the 2018 rankings, its air is still unhealthy.
Despite various government policies to address the issue, Dhaka's air quality has fallen from where it was two years ago.
The United Nations says PM2.5 density should not top 25 microgrammes per cubic metre of air in any given 24-hour period.
Being among the world's megacities of 10 million people or more, the annual average PM2.5 concentration in Dhaka's air in 2019 was 83.3 microgrammes per cubic metre.
Referring to the situation in Dhaka, Kinkar Ghosh, epidemiologist at Dhaka Shishu Hospital, said air pollution has short- and long-term impacts on the public health.
"Inhaling particles that are in the air leads to breathing problems, dust allergy and skin problem called dermatitis," he told The Business Standard.
Pakistan, India among 10 most polluted nations
Pakistan, India and Nepal are among the 10 most polluted countries on the index, with Pakistan ranked second and India fifth.
Delhi is ahead of Dhaka and tops the list of the most polluted cities, with Kabul and Kathmandu also among the top 10.
The report focuses on PM2.5 concentrations as this is the pollutant widely regarded as the most harmful to human health.
Data aggregated from a range of ground-based PM2.5 monitoring stations have been used to prepare the report published on Tuesday by IQAir. The report is based on data from nearly 5,000 cities worldwide.
Headquartered in Switzerland, IQAir collaborates with leading organisations and partners who work for making the world a better place to breathe.
South Asia's air most polluted
The report said regionally, South Asia, Southeast Asia, and Western Asia carry the highest burden of PM2.5 pollution overall.
Of the world's top 30 most polluted cities in 2019, 21 are in India, 27 in South Asia, and all the top 30 cities are within greater Asia.
While South Asia has the world's dirtiest air, 35 percent of global air pollution-related deaths occur in East Asia.
China – where the most pollution-related deaths occur – is home to 47 of the world's 100 most polluted cities.
Climate change has begun to amplify the health risk of PM2.5 pollution, especially through more intense forest fires and sandstorms made worse by spreading desertification, the report said.
Air pollution far deadlier than coronavirus
"Air pollution is the world's leading environmental health threat," said IQAir Chief Executive Officer Frank Hammes.
"While the new coronavirus is dominating international headlines, a silent killer is contributing to nearly seven million more deaths a year: air pollution," he added.
Air pollution continues to pose one of the biggest threats to human health, with nearly 90 percent of the global population breathing air that exceeds World Health Organisation exposure targets, the report said.
Scandinavia has cleanest air
Europe has some of the world's cleanest air, with Scandinavian skies among the world's healthiest.
But the continent is still struggling to control emissions from sources such as livestock, vehicles, industry, and commercial buildings, said the report.
More than a third of European cities are failing to meet the World Health Organisation's air quality guidelines, with the poorer eastern and southern parts of the continent suffering from the worst quality air.
What the government is doing for a change
Ziaul Haque, director of air quality management at the Department of Environment, said the authorities had formed guidelines in compliance with the High Court directives, designating roles to different agencies like city corporations, Rajdhani Unnayan Kartripakkha and Bangladesh Road Transport Authority to address the sources of air pollution.
"We have shut down 500 brick kilns around Dhaka and are asking Bangladesh Road Transport Authority to scrap unfit vehicles," he said.
Pollution by the construction sites and industries and vehicular emission have to be stopped, said Ziaul.
He said a coordinated effort is required to achieve these objectives and that is challenging.
Moreover, a new law, Clean Air Act 2010, is in the process of enactment. When it will be enforced, the act will remove legal obstacles to punishing the contributors to air pollution.
"The air in the capital will feel better than what it is now the next year," Ziaul added.