Bangladesh's capital Dhaka has ranked ninth worst on the world Air Quality Index (AQI) as its extreme air pollution makes it one of the most polluted cities in the world.
On the real-time rankings, Dhaka showed an average AQI score of 156 at 9 am on Thursday, according to AirVisual, which monitors global air quality.
Dhaka's air quality was classified as "unhealthy for sensitive groups."
Residential areas including Baridhara and Bashundhara showed AQI scores of 168 and 189, respectively.
Chiang Mai of Thailand and Pakistan's Lahore and Delhi, India occupied the first, second, and third spots in the list of cities with the worst air quality with AQI scores of 305, 229, and 224, respectively.
A numerical value between 101 and 150 indicates that sensitive groups may begin to experience health effects.
A value between 151 and 200 indicates that everyone may begin to experience health effects. Members of sensitive groups may experience more serious health effects.
Air quality between 201 and 300 is classified as "very unhealthy." If the score is between 301 and 500, then it is classified as "hazardous."
The AQI, an index for reporting daily air quality, informs people how clean or polluted the air of a certain city is, and what associated health effects might be a concern for them.
In Bangladesh, the AQI is based on five criteria pollutants -- Particulate Matter (PM10 and PM2.5), NO2, CO, SO2, and Ozone (O3).
The Department of Environment has also set national ambient air quality standards for these pollutants. These standards aim to protect against adverse human health impacts.
As one of the most densely populated countries in the world, Bangladesh has been struggling with air pollution for a long time. Dhaka continuously ranks among the world's most polluted cities.
Brick kilns, vehicles run on fuel containing higher levels of sulphur, as well as construction work, have all been identified as major sources of air pollution.
Air quality further declines during the dry months -- from October to April -- but improves during the monsoon.
Air pollution likely to cut coronavirus survival
Air pollution from petrol and diesel vehicles is likely to increase mortality from the novel coronavirus in cities, public health experts told AFP.
The European Public Health Alliance (EPHA) warned that dirty air in urban areas that causes hypertension, diabetes and other respiratory illness could lead to a higher overall death toll from the virus currently sweeping the world.
Emissions from petrol and diesel engines were still at "dangerous" levels that could imperil the most vulnerable during this and future pandemics, said the European Respiratory Society (EPS), which is a member of the EPHA.
"Patients with chronic lung and heart conditions caused or worsened by long-term exposure to air pollution are less able to fight off lung infections and more likely to die," EPS member Sara De Matteis said.
Several European nations have implemented unprecedented measures to prevent the spread of the disease and allow health systems to treat patients.
While there is currently no proven link between Covid-19 mortality and air pollution, one peer-reviewed study into the 2003 SARS outbreak showed that patients in regions with moderate air pollution levels were 84% more likely to die than those in regions with low air pollution.
Covid-19 is similar to SARS and can cause respiratory failure in severe cases.
Mortality data for Covid-19 is incomplete, but preliminary numbers show the majority of patients who die are elderly or have pre-existing chronic conditions such as heart or lung disease.
According to the European Environment Agency, air pollution leads to around 400,000 early deaths across the continent annually, despite European Union air quality directives.
One Covid-19 hotspot, northern Italy, has particularly high levels of PM10 - microscopic particles of pollution due largely to road traffic.
The number of fatalities in Italy shot up by 368 to 1,809 on Sunday - more than half of all the cases recorded outside China.
'Clean up the streets'
A study published last week in the journal Cardiovascular Research said that air pollution shortens lives worldwide by nearly three years on average, and leads to 8.8 million premature deaths annually.
The shutdown in northern Italy has in fact led to a significant reduction in nitrous oxide and small particulate matter in the air, according to satellite data.
EPHA Acting Secretary General Sascha Marschang said that governments must prioritize a reduction in polluting vehicles to avoid unnecessary deaths during future outbreaks.
"Governments should have tackled chronic air pollution long ago, but have prioritized the economy over health by going soft on the auto industry," he said.
"Science tells us that epidemics like Covid-19 will occur with increasing frequency," added.
"So cleaning up the streets is a basic investment for a healthier future."
