Heavy metals in Cauvery fish, study warns against regular intake
Researchers from Tamil Nadu reported that heavy metals are polluting the Cauvery river and its fish. It also warned against consuming “regular” or “excessive” amounts of fish.
The study was conducted by a team at Bharathidasan University, Tiruchirappalli and published in the journal. Environmental Earth Sciences in August.
Scientists from the university examined the spatial distribution of heavy metals in sediments from 18 regions along the river and fish in 10 regions from August 2023 to February 2024, and their associated ecological risks. They focused their analysis on chromium, cadmium, copper, lead and zinc.
They found that heavy metal accumulation in fish tissues varied significantly between species, with some exceeding thresholds for non-carcinogenic (non-cancer-causing) and carcinogenic health risks (especially cadmium and lead).
Human and natural resources
Rajaram Rajendran, from the department of marine sciences at Bharathidasan University and one of the authors of the report, said his team’s study has significant ecological, environmental and public health relevance as it provides a comprehensive assessment of heavy metal pollution in the Cauvery river basin.
“It highlights the immediate impacts of urbanisation, industrial waste and agricultural runoff on sediment and freshwater fish quality,” he said.
The team also found what it described as a remarkable change in metal concentrations in various regions.
Dr. “The detection of cadmium and lead as primary contaminants of concern in some fish species at levels exceeding threshold limits underscores the potential risks to both ecosystem health and human consumers,” Rajendran said.
Scientists have used various pollution indices; each index was a number that assessed pollution levels of soils and sediments, calculated using concentrations of specific elements relative to background levels.
They included megeographygeographical accumulation index to determine heavy metal pollution in sediments; contamination factor; degree of contamination; pollution load index; and potential ecological risk.
Dr. Rajendran said:geography and potential ecological risk indices through multivariate statistical analysis, the study was able to “effectively” distinguish between heavy metals from anthropogenic or anthropogenic and natural sources.
Dr. “This approach provides valuable information on the dynamics of metal bioaccumulation and pollution pathways in a tropical river system under rapid industrial and urban development,” said Rajendran.
Researcher Nikita Gupta from Vellore Institute of Technology, along with her colleague Sathiavelu Arunachalam, assistant professor of the School of Bioscience and Technology, studied heavy metal pollution in tilapia fish in the Cauvery.
He added that the new paper highlights the presence as well as distribution of important toxic metals in many native fish species – “a critical concern given the importance of the river for drinking water, fisheries and agriculture in southern India.”
fish consumption
Findings have direct implications for public health: occasional fishconsumption may not pose an immediate threat, long-term exposure may lead to cumulative non-carcinogenic and carcinogenic risks, particularly from cadmium and lead.
Dr. Rajendran said the risk depends on both the amount consumed, frequency of intake and the age of the individual.
“Based on various risk assessment indices in this study, it is considered safe to consume fish at a serving size of 250g per serving, twice a week,” he estimated.
Earlier, Ms Gupta and Dr. Using atomic absorption spectroscopy, Arunachalam predicted the health risk posed by heavy metals in tilapia fish. In November 2024, they reported: Borders Public Health He stated that the hazard quotient of cadmium, cobalt, lead and chromium in the fish’s liver, cobalt and chromium in its gills and cobalt in the muscle “indicates a significant health risk resulting from the combined effects of these metals.”
They added that the potential health risk to humans comes mainly from exposure to cadmium and chromium.
As in the new study, the duo recommended moderate fish consumption to limit the bioaccumulation of heavy metals in the body.
“Our study is among the first to provide a comprehensive, multi-organ and multi-metal health risk assessment for tilapia consumers in the Cauvery basin, providing actionable data to consumers, regulators and health authorities,” Ms Gupta said.
The new study took these findings even further.
“We focused on a fish species that we could sample in our publication,” Ms Gupta said. “However, in this new publication, we learn that the same phenomenon of heavy metal accumulation in fish is observed in many regional fish species. This expands the argument that heavy metal pollution in the Cauvery is indeed a reality.”
“There is evidence that some metals, particularly cadmium and lead, pose carcinogenic and non-carcinogenic risks through biomagnification in the food chain,” he added. “This result is consistent with the findings of our study.”
Using US Environmental Protection Agency guidelines, Vellore Institute of Technology researchers found that the target hazard ratio for various metals in the liver, gills and sometimes even muscles exceeded 1; This is the anxiety threshold; This “points to real human health risks from regular exposure,” Ms Gupta said.
scientific basis
Dr. Rajendran said his study “reveals gaps in current environmental management”It highlights the need for continuous monitoring of sediments, water and aquatic organisms, stricter pollution control and regulatory practices, policy interventions to manage industrial emissions and unsustainable land use practices, and increased public awareness to reduce health risks.
Ms Gupta added that there is an urgent call for systematic, longitudinal monitoring of river pollution and stricter regulation of wastewater discharge into the Cauvery.
He added that the new study is particularly important as it provides a contemporary, site-specific health risk assessment and therefore provides a much-needed scientific basis for local authorities to design regulatory and public health interventions.
Industrial wastes, especially from textile and electroplating units operating near the Erode region, contribute significantly to the heavy metal pollution of the region. Other important sources include agricultural runoff and untreated urban wastewater, mostly from fertilizers and pesticides.
There is some natural contribution, albeit at lower levels, due to the presence of mineralized zones upstream of the river; They are especially important sources of iron. “But high and variable levels of cadmium, chromium and lead are highly indicative of human-caused contamination,” Ms Gupta said.
Similar reports came from other rivers in Tamil Nadu. For example, researchers from SRM Institute of Science and Technology in Kattankulathur studied heavy metal pollution in surface waters of the Noyyal river basin in western Tamil Nadu and reported that industrial activity was a major contributor to pollutants.
TV Padma is a science journalist in New Delhi.
