As they roared past one another on the Narayanganj-Munshiganj Highway, the container trucks created dust clouds all over the area.
The area, Char Syedpur of Gognogor under Narayanganj Sadar Upazila, which hosts some red category industries including the biggest cement factories of the country, lies between the rivers Shitalakshya and the Dhaleshwari.
It is difficult to estimate the density of the dust, but if you look at the entire area from the Muktarpur Bridge over Dhaleshwari, you will see a thick smog covering the entire Char Syedpur.
The teachers of the Char Syedpur Government Primary School are extremely worried about the health of their pupils because of the dust. Established in 1973, the school at present has 660 students.
"It seems like we are breathing dust all the time. Somehow, the students have adapted to the noise pollution. But they have to put a mask on their face while attending classes. Everything inside the classroom gets covered with dust. How often can we sweep?" said two teachers of the school, Dulali Akter and Sohel Rana.
The concerned teachers are an exception, because the Gognogor residents in general are mostly unaware about the impacts of the severe air pollution.
But how can they understand the impacts? The pollutants, which scientists call particulate matter or PM2.5, are extremely fine particles with a diameter of 2.5 micrometres or less. They cannot be seen with the naked eye.
A team from the Atmospheric and Environmental Chemistry Research Lab under the University of Dhaka (DU) have observed that the air of Gognogor and Simrail in Siddhirganj area of Narayanganj, have an alarming level of PM2.5.
Often, the air quality of these two places, which house around 400 industries, surpasses the pollution rate in Dhaka - one of the world's most polluted cities.
The air quality research has been done as a collaboration between the chemistry department of DU and Duke University.
To conduct the research, the team installed 39 sensors - laser-based particle instruments designed to simultaneously measure the fine particles, temperature and relative humidity - around Dhaka and Narayanganj districts.
Dhaka University's chemistry teacher Professor Abdus Salam, also the lead researcher, told TBS, "Overall, the baseline of Dhaka air pollution is the highest in the country. But we have observed that the air of Gognogor and Simrail often remain more polluted than Dhaka."
"The Gognogor air gets polluted mostly by cement factories. Whereas emissions from some re-rolling industries and lead-battery dismantling factories and busy traffic through the Dhaka-Chattogram Highway contribute to the air pollution in Simrail," Professor Salam said.
In January this year, the monthly average concentration of PM2.5 in Gogonor's air was 229.515 microgram per cubic metre (µgm-3), highest for the area so far. During the period of January to August, this air contained on average 84 µgm-3 of fine particles.
From September 2021 to August 2022, on average, the concentration of PM2.5 in Simrail's air was 72.3 microgram per cubic metre. In January, the monthly average concentration of PM2.5 was 157.3 µgm-3, according to data provided by Shahid Uz Zaman, research assistant at the lab.
Bangladesh National Ambient Air Quality Guidelines consider a concentration of 15µgm-3 of PM2.5 or less as healthy, while the World Health Organisation guideline value permits only 5 µgm-3 or less.
According to Narayanganj Statistic Office, around 30,000 people live in Gognogor while around 12,000 live in Simrail at present.
Ambient PM2.5 penetrates deep into the lungs. So, long-term exposure to these fine particles can cause COPD (Chronic Obstructive Pulmonary Disease), cardiovascular diseases, and lung cancer. Children and the elderly are especially vulnerable to the negative health impacts from air pollution.
Narayanganj Civil Surgeon Dr AFM Mushiur Rahman said that due to intensive industrialisation and overpopulation, the rate of air pollution in Narayanganj is higher than Dhaka.
He said as public hospitals in the district are not well-equipped to deal with neonatal respiratory distress and cardiovascular problems, sometimes the number of patients is higher in private clinics.
"As the district is well-connected to the capital city, patients tend to visit Dhaka-based hospitals in most of the severe cases. That is why the actual statistics of air pollution related patients in Narayanganj cannot be assessed," Mushiur Rahman said.
For the last three years, middle-aged Masum Billah has been running a pharmacy near the bank of Shitalakshya at Simrail. Along the bank, all the way from WAPDA Colony to Sarulla of Demra, more than hundred traders have set individual depots of construction materials like sand and rocks.
Masum said when they operate the crushers, air in the riverside areas instantly becomes smoggy. Besides, the trucks carrying construction materials also spread dust when they move.
"Air quality of the area is poor. The condition only improves if it is raining. Local residents, especially the senior ones, often come to me for cardiovascular drugs," Masum said.
Simrail falls under Ward number 4 of the Narayanganj City Corporation. Ward Councilor Noor Uddin Miah told TBS that Simrail is mostly an industrial area.
"The Kanchpur Bridge is never free of traffic. Emissions from the busy road contribute to air pollution," Noor said.
Neither the people's representative nor the residents of Simrail speak up against the industrial pollution. How could they? Most of the people living there are workers hailing from outside Narayanganj.
However, one teacher of the Simrail Government Primary School expressed her concerns. She preferred to be anonymous, fearing harsh consequences.
"Our school has been cornered by industrial expansion day by day. Our students are being exposed to air and noise pollution everyday," the teacher said.
Currently, 290 students study at the school which was established in 1972.
Department of Environment's Deputy Director for Narayanganj district, Muhammad Abdullah Al Mamun agreed that cement factories contribute air pollution around Gognogor.
When enquired about the lead-battery dismantling activities in Simrail, he replied, "We have no specific information about the lead kilns. The operators usually change places and set the lead kilns at remote places."
"They mould lead in the dark, when tracing the sources of emission is tough. Whenever we receive a tip-off, we conduct raids against them," he added.
The DoE officer also said the department busted several lead battery kilns last month.
"There is a Continuous Air Monitoring Station [CAMS] at the centre of Narayanganj. We observe the air quality on a regular basis," he said.
However, the AQI Index archived by the department shows that many times, the Narayanganj CAMS fails to provide data.
Md Shahidullah, the vice chairman of Bangladesh Cement Manufacturers Association, said cement manufacturers are equipping their production units with modern technologies. He added the manufacturers are using bag filters and other advanced filters.
"However, transforming a cement factory to 100% environment-friendly is too challenging," he said.
Shahidullah said when cement factories were established in Narayanganj and Munshiganj in the early 1990s, there were no residences near the factories. The residential plots developed over the years.
"Ideally, there should not be a single residence. Hence, the government should intervene in this and mark distinctive plots for industries and human habitat," he concluded.