Forests are generally considered a source of clean air. However, a recent study has found a different picture in the Sundarbans, the world’s largest mangrove forest. The study detected harmful fine particulate matter, or PM2.5, and coarse particulate matter, or PM10, in several locations across the forest.
The findings emerged from a study conducted in the Khulna, Satkhira, Sharankhola and Chandpai ranges of the Sundarbans during January and February in both 2024 and 2025.
Experts say salinity is present not only in the water of the Sundarbans but also in its air. When pollutants such as PM2.5 are added to the mix, they can harm trees, bees, birds and other wildlife.
The study was conducted by the Center for Environmental and Geographic Information Services (CEGIS), an organisation affiliated with the Ministry of Water Resources, and the Arannayk Foundation. It was the first baseline study under a project titled “Ecological Monitoring of Sundarbans”, examining the forest’s wildlife, air, soil, water, trees and overall ecosystem. Air quality was also assessed as part of the study.
The findings were released at a workshop at the Forest Department headquarters in Agargaon, Dhaka, on 14 September.
According to the study, PM2.5 concentrations in the air of the Sharankhola range reached 102 micrograms per cubic metre, while PM10 levels stood at 114 micrograms per cubic metre. The Chandpai range recorded the second-highest levels of air pollution, with PM2.5 at 89.3 micrograms per cubic metre and PM10 at 98.1 micrograms per cubic metre.
Under the Air Pollution Control Rules 2022, PM2.5 concentrations exceeding 35 micrograms per cubic metre are considered unhealthy. For PM10, the threshold is 45 micrograms per cubic metre.
The World Health Organization’s (WHO) 2021 air quality guidelines set a much lower threshold for PM2.5, with concentrations above five micrograms per cubic metre considered unhealthy. The WHO’s guideline for PM10 is the same as the threshold specified in Bangladesh’s air pollution control rules.
Apart from PM2.5 and PM10, the concentrations of sulphur dioxide, nitrogen oxides, ozone and carbon monoxide were found to be within acceptable limits.
Sources of pollution
Mutasim Billah, an environmental expert at CEGIS, was involved in the study. He told Prothom Alo that the highest concentrations of PM2.5 were found in the Sharankhola and Chandpai ranges. Clinker, a raw material used in cement production, and coal imported for the Rampal power plant are unloaded from ships in the Pashur Channel in Chandpai.
The dust generated during unloading could be responsible for the presence of fine particulate matter, he said.
Cement factories unload clinker at their own jetties along the banks of the Pashur River. Coal imported for the Rampal coal-fired power plant, meanwhile, is unloaded in the Pashur Channel.
Billah said dust levels in the Sundarbans often rise during the dry season when strong winds blow. Transboundary air pollution also reaches the forest during this period, contributing to the problem.
According to Bangladesh’s National Air Quality Management Plan, transboundary pollution accounts for 21 per cent of the country’s air pollution.
Ahmed Kamruzzaman Majumder, dean of the Faculty of Science at Stamford University Bangladesh and founding chairman of the Centre for Atmospheric Pollution Studies, told Prothom Alo that forest fires and fly ash released during the unloading of clinker and coal from ships were two sources of air pollution in the Sundarbans during the dry season.
He suggested that the Bangladesh Navy and the Forest Department could take action to address air pollution caused by the transportation and unloading of clinker and coal.
The problem could worsen
The first study of air quality in the Sundarbans has raised concerns that pollution could further threaten the ecologically important mangrove ecosystem, which is already experiencing salinity and other environmental changes.
Although the level of air pollution was described as moderate, the study warned that it could intensify existing pressures on vegetation. It could also alter the way nutrients enter and are supplied to the soil and tidal waters.
Researcher Mutasim Billah said the study had provided an initial picture of air pollution in different parts of the Sundarbans. However, it had not established how pollution levels change over time. Continuous monitoring using a consistent methodology is therefore essential, he said.
The study recommended long-term monitoring, with priority given to PM2.5 and sulphur dioxide. It also stressed the need to regularly monitor weather conditions, including temperature, humidity, wind speed and direction, and rainfall, to better understand how these pollutants spread.
MA Aziz, a professor in the Department of Zoology at Jahangirnagar University, told Prothom Alo that the Sundarbans was home to far more than tigers and deer, including many smaller creatures such as bees and butterflies. These animals would be among the first to suffer from air pollution, he said.
Air pollution causes fine particles to accumulate on the leaves and flowers of trees in the Sundarbans. This can interfere with bees and other insects that collect nectar from flowers. The process of pollination can also be disrupted.
“The pollution in Chandpai and Sharankhola is caused by industries centred around Mongla. We have long warned that cement factories and emissions from burning coal at the Rampal power plant would affect the Sundarbans. This study has confirmed those concerns,” he said.