Representational Image.

By Ridwan Ahmed

CHITTAGONG UNIVERSITY, March 5, 2025 (BSS) - Rising levels of toxic metals in the southeastern coastal regions of Bangladesh are posing significant risks to fisheries, marine ecosystems and public health.

A joint study conducted by Professor Dr. Mohammed Ashraful Azam Khan and Research Assistant Kazi Nusrat Jahan Ouishi of the Department of Fisheries at Chittagong University (CU) has identified the Bakkhali River and the Moheshkhali Channel as major pollution hotspots for heavy metal accumulation.

The findings were published on November 30, 2025 in the international journal Science of the Total Environment, published by Elsevier. The field research was carried out between May 2024 and April 2025.

The study, titled "Trace Element Dynamics and Ecological Risk Indices in Coastal Sediments along the Southeastern Bangladesh", examined several key coastal locations including the Matamuhuri River, Bakkhali River, Moheshkhali Channel, Naf River and Saint Martin's Island.

Using advanced ICP-MS (Inductively Coupled Plasma Mass Spectrometry) technology, the researchers measured the concentrations of cadmium, copper, chromium, nickel, lead and other heavy metals in riverine and estuarine sediments.

The results showed that the Bakkhali River and Moheshkhali Channel face the highest levels of contamination. Pollution load index (PLI) values in these areas exceeded 2, indicating significant pollution. 

Cadmium was identified as the most critical pollutant, with potential ecological risk (PER) values reaching 331.91 percent in the Bakkhali River and 295.43 percent in Moheshkhali Channel, placing both locations in the category of "very high ecological risk".

In comparison, the Naf River and Saint Martin's Island showed relatively lower levels of contamination.

Researchers attributed the increasing pollution mainly to untreated industrial waste, urban sewage discharge, ship-breaking activities, port-related maritime transport and agricultural runoff. The concentration of such activities in the Chittagong and Moheshkhali areas has intensified environmental pressure in the region.

The contamination is directly affecting fisheries, as toxic metals accumulate in sediments and gradually enter the aquatic food chain through plankton and other small organisms. These metals eventually reach fish and shrimp, causing reduced reproduction, stunted growth, weakened immune systems and declining fish populations.

Such impacts not only threaten marine biodiversity but also create serious economic challenges for fishermen while posing potential health risks for consumers of contaminated seafood.

The researchers warned that prolonged contamination could disrupt coastal ecosystems, including mangrove forests in the areas, benthic organisms and marine food chains, which may eventually lead to a collapse of fisheries if appropriate measures are not taken in time.

The study recommended declaring the Bakkhali River and Moheshkhali Channel as "priority pollution hotspots" and called for the rapid establishment of effective waste treatment facilities, regular monitoring of water and sediment quality, stricter control of ship-breaking operations and stronger community awareness initiatives.

Research Assistant Kazi Nusrat Jahan Ouishi said the highest level of heavy metal pollution was found in the Bakkhali River and Moheshkhali Channel.

"The likely sources include industrial waste, ship-breaking activities, port and maritime transport operations, urban runoff and the use of agrochemicals. In contrast, pollution levels in the Naf River and Saint Martin's Island are comparatively lower due to limited industrial and urban activities and reduced anthropogenic impact," she said.

She added that the main objective of the study was to evaluate trace metal contamination in coastal sediments, identify possible sources of pollution and assess environmental risks.

"These findings will help identify pollution hotspots and support initiatives to protect coastal ecosystems, fisheries and marine biodiversity, contributing to effective environmental management and pollution control," she added.

Lead researcher Professor Dr. Mohammed Ashraful Azam Khan said the growing presence of toxic metals in coastal regions poses a major threat to fisheries, marine biodiversity and human health in Bangladesh.

"To ensure sustainable fisheries and a healthy coastal environment, it is essential to strengthen policies, enforce strict regulatory measures and enhance science-based environmental monitoring without delay," he said.

He also noted that the research supports several United Nations Sustainable Development Goals (SDGs), particularly Clean Water and Sanitation (SDG 6), Climate Action (SDG 13), Life Below Water (SDG 14) and Life on Land (SDG 15).

Professor Mohammad Mamun Chowdhury, Chairman of the Department of Fisheries at Dhaka University, described the research as an important step toward protecting the ecological balance of Bangladesh's coastal areas.

He said pollution levels in coastal regions are increasing rapidly, leading to biodiversity loss and environmental degradation.

"Heavy metal contamination is affecting coastal vegetation, fish populations and human health, pushing the environmental balance toward a critical stage. In particular, rising levels of toxic cadmium could further intensify risks for both the environment and public health," he said.

He also noted that the use of advanced ICP-MS technology in the study is significant, as the technology is available in only a limited number of research facilities worldwide.

The Professor further added that, the research provides an important foundation for future studies aimed at identifying specific pollution sources, particularly those linked to industrial waste, ship-breaking activities, maritime transport, urban discharge and agricultural chemicals.