Bangladesh is a riverine country where rivers and waterways have long supported industries, trade, livelihoods and daily life. River fish are popular among people in both urban and rural areas because of their distinctive taste and flavour. However, plastic pollution is also increasing alongside population growth. Non-biodegradable plastic waste accumulates on riverbeds, posing a serious threat to the environment and aquatic life. As a result, microplastic pollution is becoming an increasing concern.

Recent studies conducted by researchers at Bangladesh Agricultural University (BAU) have detected microplastics in river and waterbody sediments, as well as in the intestines, gills and muscles of fish collected from different parts of the country. Researchers warn that the presence of these tiny plastic particles in fish may pose potential risks to human health in the long term.

Microplastics detected in fish from Arial Beel

A study by Professor Dr Md Shahjahan of BAU’s Department of Fisheries Management found significant levels of microplastics in five fish species among 150 specimens collected from Arial Beel. The species were climbing perch (koi), bata, menni (Nandina), gulsha tengra and punti.

The research paper was published in the international journal Journal of Hazardous Materials Advances. Microplastic particles were detected not only in the fish intestines and gills but also in their edible muscle tissues. Among the species studied, climbing perch contained the highest concentration of microplastics, which researchers attributed to its omnivorous feeding habits.

The study also detected between 11 and nearly 32 microplastic particles per litre of water in Arial Beel, while sediment samples contained between 12 and more than 127 particles per kilogram.

Microplastic pollution in commercial fish farms in Trishal

Another study by Professor Dr Md Badiuzzaman Khan of BAU’s Institute of Environmental Science and Disaster Management found microplastics in bottom sediments and fish from commercially operated ponds in Trishal upazila.

The study examined bottom sediments and fish samples from 25 commercial fish ponds. Rui and pangas showed comparatively higher rates of microplastic contamination. However, the average number of particles in the digestive tract was highest in sarpunti.

Researchers examined the digestive tracts of 150 fish belonging to six species rui, katla, pangas, mrigal, common carp and sarpunti and detected microplastic particles in 90 of them. The study also found an average of 11 microplastic particles per kilogram of pond-bottom sediment.

The research, titled “Microplastic in Freshwater Aquaculture: Evidence of Sediment-Fish Transfer and Associated Ecological Risks in Bangladesh”, was published in the international scientific journal Environmental Pollution.

Professor Dr Badiuzzaman Khan said one of the major sources of microplastics entering fish bodies was discarded plastic bags and packaging materials that were not recycled. Other sources included nylon and polyester fishing nets, abandoned plastic bottles and the deterioration of plastic pipes.

He said tiny plastic particles released from these materials enter water and eventually find their way into fish bodies.

Dried fish contain far more microplastics than fresh fish

A separate study by Professor Dr Md Shahjahan of BAU’s Faculty of Fisheries found that dried fish contained significantly higher concentrations of microplastics than fresh fish.

The research examined fresh and dried loittya, churi and faissya fish collected from Fishery Ghat in Chattogram and the Mohipur Fish Landing Centre in Kuakata.

Researchers investigated the presence of microplastics in the gills, digestive tracts and muscle tissues of the fish. The findings showed that microplastic concentrations were higher in the gills and digestive tracts than in the muscle tissues.

According to the study, fresh loittya contained an average of 0.21 microplastic particles per gram, while dried loittya contained 41 particles per gram. Similarly, fresh churi contained an average of 0.2 particles per gram, compared with 46 particles per gram in dried churi. Dried faissya contained an average of two microplastic particles per gram.

Researchers believe the higher concentration of microplastics in dried fish may be linked to plastic pollution in river water and the loss of water from fish during the drying process which increases the concentration of particles relative to the fish’s weight.

However, they said there is still no conclusive research evidence on the specific health risks microplastics may pose to the human body.

Potential long-term risks to human health

Speaking about the potential health risks of microplastics, Professor Dr Md Shahjahan of BAU’s Department of Fisheries Management said environmental pollution had led to the presence of microplastics in various environmental components and aquatic organisms, including river fish.

He said although no major immediate harm from these particles was visibly apparent, their effects could emerge over the long term, particularly after 25 to 30 years or in future generations.

He further said nanoplastics were an even greater concern than microplastics. These extremely small particles can enter and be absorbed by the human body, potentially creating various health risks. He added that they may also have possible links to serious diseases, including cancer.