For the past few decades, the world has been grappling with severe plastic pollution. Tiny plastic particles, known as microplastics, are now being found in the human brain, blood, breast milk, arteries and veins.
Plastic particles have also been detected in the stomachs of fish from rivers and seas, raising concerns that plastic pollution is no longer confined to distant oceans or industrial zones—it is now reaching people’s dinner tables and entering the human body through food.
A recent study found that the riverbeds of the Bhairab and Rupsha rivers in southwestern Bangladesh are becoming reservoirs of microplastics and toxic heavy metals. Researchers detected microplastics along with hazardous metals such as cadmium and lead in sediment samples collected from depths of 10 to 30 centimetres.
Environmentalists warn that this poses growing risks to the coastal ecosystem, including the Sundarbans, and could have serious public health consequences.
The findings were published in January in the international journal Emerging Contaminants by researchers from the Department of Environmental Science and Technology at Jashore University of Science and Technology.
Researchers Nishat Salsabil, Md Touhiduzzaman, Tapas Kumar Chakraborty and Gopal Chandra Ghosh conducted the study using sediment samples collected from nine densely populated locations along the Bhairab and Rupsha rivers, from Jashore to Khulna.
Microplastics found deep in riverbeds
The study found up to 5,700 microplastic particles per kilogram of sediment, with an average concentration of 3,600 particles in the upper layer. The concentration declined to 2,744 in the middle layer and 1,077 in the lower layer.
Among the microplastics identified, fragments accounted for 51%, fibres 26% and films 18%. Researchers identified seven types of polymers, including polyethylene (23%), polystyrene (21%) and polypropylene (18%).
The presence of microplastics at depths of 10 to 30 centimetres indicates long-term accumulation in the riverbed.
In addition to plastic pollution, researchers detected high concentrations of toxic heavy metals including chromium, nickel, copper, lead and cadmium.
Environmental experts warn that fish and other aquatic species ingest these particles, allowing toxic substances to enter the human food chain and potentially increasing the risk of cancer and other complex diseases.
Waste flowing into rivers
According to the study, large volumes of waste from Khulna city, Jashore’s Nawapara area and surrounding regions are entering the Bhairab and Rupsha rivers.
More than 22 drains connected to canals and sewage lines under Khulna City Corporation discharge waste directly into the rivers. Industrial waste, including effluents from tanneries and factories in Nawapara, is also flowing untreated into the Bhairab River.
As a result, the riverbeds are accumulating increasing levels of toxic materials.
According to a 2021 survey conducted using the United Nations’ Waste Wise Cities Tool, Khulna generates around 732 tonnes of waste daily. Of this, the city corporation manages about 461 tonnes, while the remainder is dumped into drains, canals and rivers.
The waste includes food scraps, plastic films, paper products, hard plastics, glass, metal and textile materials. Researchers estimate that the actual daily waste generation in the city may reach between 1,000 and 1,200 metric tonnes.
Environmentalists said the pollution level in the river sediment now falls under “very high” or Class V according to the Pollution Evaluation Risk Index (PERI).
They warned that excessive concentrations of cadmium and nickel are pushing river biodiversity toward collapse.
Sundarbans under threat
Experts say plastic waste and untreated sewage are also threatening the fragile ecosystem of the Sundarbans.
Plastic packets, bottles, disposable plates and cups discarded by tourists and residents in areas surrounding the forest are being carried into the Sundarbans through rivers and canals.
Plastic waste has been observed along the banks of rivers such as the Shakbaria, Koyra and Sibsa, where tidal water washes debris deeper into the mangrove forest.
Jabed Hossain, a fisherman who has worked in the Rupsha, Atharobeki and Bhairab rivers for more than two decades, said fish populations are declining rapidly.
“The river water is no longer clean. Earlier, we could catch fish easily by casting nets, but now that is no longer possible. Plastic bottles and other waste float in the river every day,” he said.
What research says about health risks
A study cited by the Kolkata-based research magazine Shudhu Sundarban Charcha found between 450 and 1,200 microplastic particles per cubic metre in the Hooghly River.
In Bangladesh’s Pashur River, researchers recorded an average of 81,056 particles per square kilometre before the monsoon season.
Assistant Professor Sayan Bhattacharya of the Department of Ecology at Nalanda University said abandoned plastic fishing nets are a major source of microplastics in the Sundarbans.
“Microplastics have been found at multiple levels of the Sundarbans food chain. These particles hinder plant growth and germination,” he said.
He added that coastal residents who regularly consume fish from the Sundarbans face the highest risk of accumulating microplastics in their bodies.
“These tiny particles can damage the lungs and other organs,” he said.
Warning from experts
Professor Dr Md Mujibur Rahman of the Department of Environmental Science at Khulna University described the presence of lead and cadmium in river sediment as alarming.
“Industrial chemicals and urban waste are continuously flowing into rivers such as the Bhairab and Rupsha, which are directly connected to the Sundarbans. Tidal movement is carrying these pollutants deep into the mangrove ecosystem,” he said.
He warned that without modern waste management systems and pollution control measures, the region could face an environmental disaster.
Sundarbans East Division Forest Officer Md Rezaul Karim Chowdhury also stressed the need to stop the direct dumping of industrial and household waste into rivers.
“Public awareness and strict enforcement of environmental laws are essential to protect both human health and the environment,” he said.
How to reduce exposure to microplastics in fish
Experts say it is difficult to avoid microplastics completely, but exposure can be reduced through proper food preparation and safer choices.
They recommend removing the stomach and intestines of fish before cooking, as microplastics often accumulate in digestive organs.
Fish should also be washed thoroughly under running water after cleaning.
Smaller fish and deep-sea fish are considered relatively safer than fish from heavily polluted rivers and coastal waters.
Experts also advise avoiding fish skin and stomach areas where harmful particles may accumulate more frequently.
Although completely eliminating exposure may not be possible, awareness and careful food preparation can significantly reduce health risks linked to microplastics.
