The capital has frequently made it to the list of world cities with the worst air quality
Dhaka has been on a shutdown since March 26 with hundreds of vehicle off the road, however, the air pollution in the city, a common problem for years, have not developed much.
When it comes to Bangladesh standard, the quality improved significantly in Dhaka but is still behind in the world standard as the pollution of the city continues to remain worst in the world ranking table.
However, a 24-hours average, including day and night, air quality is failing to maintain Bangladesh standard too.
Particulate meter (PM) 2.5 is the most harmful element in the air which can enter into human lungs bypassing nose hair when people breath and it can cause lung cancer.
According to IQAir, which monitors air quality globally, Dhaka's air the concentration of PM2.5 was 58.4 microgram and Air Quality Index (AQI) score was 152 at 11pm on Tuesday.
PM2.5 was 51.6 microgram and AQI score was 140 at 12pm, PM2.5 was 45 microgram while AQI score was 124 at 1pm, and PM2.5 was 38.9 microgram, which is very close to US standard, while AQI score was 109, very close to achieve internationally moderate standard at 2pm on Tuesday.
According to the data, air quality in Dhaka starts worsening from evening and spikes up at night, and getting worse on early morning before sunrise, but it gradually improves an hour after another during the day time.
Daily average of concentration of PM2.5 from April 1 to April 6 stood between 70-110 which is much higher than Bangladesh standard, according to Center for Atmospheric Pollution Studies (CAPS) of Stamford University Bangladesh. Though in day time PM2.5 remains within the Bangladesh standard.
Stakeholders and officials from the Department of Environment (DoE) said air quality improved in Dhaka significantly during shutdown but still now it is lacking behind in the world standard.
Dhaka remains worst in the world ranking table because of its soil pattern, operation of brick kiln, trans-boundary pollution, local sources and vehicle running in the early morning.
An improvement in air quality has also been observed in other cities due to the worldwide shutdown.
In Dhaka, public vehicle movement came down to zero in day time while many constructions has also stopped, for which the roadside dust has gone down.
When asked on reasons behind current air pollution and what is the pattern of pollution, professor Dr Ahmad Kamruzzaman Majumder, chairman of the Department of Environmental Science at Stamford University Bangladesh told to Dhaka Tribune the air pollution in the last two weeks has dropped by almost 50% compared to that of the same period in last year.
“But it is only for daytime. Surprisingly at night, pollution increases to almost double of the day time,” he said.
The expert pointed out that some vehicles are still moving in roads during night to carry goods, and there might be some residual effects of the previously created dust, which have settled in roads and other surface.
"Brick kiln are also open around Dhaka which is a major reason of increasing average pollution in the city. Thus the average concentration of PM2.5 still remains high," he added.
Local and international standards
Bangladesh Environment Conservation Rule 1997 sets 65 microgram for PM2.5 as standard. If taken into account as per Bangladesh standard, the air is clean.
However, the city have failed to achieve international standard as World Health Organization (WHO) has set the standard of PM2.5 as 25 microgram while 35 microgram set by the United States of America.
The neighboring country India has set 60 microgram for PM2.5 limit.
A numerical value of AQI between 0 and 50 indicates good air, between 51-100 indicates moderate, between 101 and 105 indicates unhealthy for sensitive group, in between 151 and 200 indicates unhealthy, between 201 to 300 is classified as "very unhealthy." If the score is between 301 and 500, then it is classified as "hazardous."
Brick kilns are still in operation
In an attempt to reduce air pollution, the government during a drive between December 1 and January 30 closed down 428 illegal brick kilns out of a total of 2,087 in operation around Dhaka. The drive continued till March.
Statistics shows 58% of the particulate pollutants come from brick kilns around and inside Dhaka, 18% from road dust and soil dust, 10% from vehicles, 8% from the burning of biomass and 6% from other sources.
Even so, the capital has frequently made it to the list of world cities with the worst air quality.
Sources said the brick kilns were shut down by DoE, but that were reopened within 15 days of shutting down. All the brick kiln are still running, though the production of brick has reduced a little bit.
Asadur Rahman Khan, former vice president of the Bangladesh Brick Field Owners Association said: "Rain has been reported in some areas while some workers went home due to fear of coronavirus which reduced the production.”
The Bangladesh government, as part of phasing out the use of bricks, has decided to use concrete blocks in 10% of its construction projects, starting this fiscal, to reduce air pollution.
As per the plan, concrete blocks will be used in 20% of the government’s construction projects from 2020-2021, 30% from 2021-2022, 60% from 2022-2023, 80% from 2023-2024, and 100% by 2025.
"If government follow its principle to use concrete block instead of brick, then the number of brick kilns may come down. Otherwise brick is a most required construction material throughout the year" he added.
He said the country will face a serious crisis of brick for development work if the government takes hard stance on brick field without producing blocks.
Abdul Mutalib, a deputy director (Air quality) of the DoE said he does not expect Dhaka will ever have totally green air, but the air quality now is within local standard.
"Our soil pattern is different. It is powder type and there is dust on the soil surface. This pattern is enough to fail to achieve the world standard," he added.
He said the enforcement and monitoring by DoE is now closed because of closure of all government offices.
Air pollution severely affects health and is a rising cause of death.
At least 123,000 people died in Bangladesh in 2017 due to indoor and outdoor air pollution, according to a global study titled "State of Global Air 2019," released on April 3 last year by two US-based institutes—the Health Effects Institute (HEI) and the Institute for Health Metrics and Evaluation (IHME).