Ganga water in Varanasi contaminated with heavy metals, says study

Varanasi (UP), Dec 31: A team of Banaras Hindu University, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Lucknow and the Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, in a joint research, has found the presence of heavy metals in Ganga, putting human health and life in the city to risk.

The risk to health is from metals contaminating water and aquatic life.

The study, titled ‘Ecological and Health Risk Assessment of Heavy Metals Bioaccumulation in Ganga fish near Varanasi’, was published online in the Springer Nature on December 26.

Fish from Ganga is consumed in a huge quantity in the Varanasi region, said Prof Vijay Nath Mishra of the Department of Neurology, Institute of Medical Sciences, BHU.

“We designed our study to achieve a holistic approach by not only estimating the concentration of heavy metals (lead, manganese, chromium, and cadmium) in the river water at different sites based on human anthropogenic activities but also in aquatic life at the same sites, particularly fish netted for human consumption on daily basis,” said Mishra.

“We found that mean concentration in Ganga water was 1.29 mg/L for Pb, 1.325 mg/L for Mn, 0.169 mg/L for Cr, and 0.161 mg/L for Cd, which were above safe limit defined by the Environment Protection Agency (EPA) in drinking water,” he said, adding that fish, including exotic and invasive species, were collected from the wild and were examined for presence of metals in their tissues.

The highest accumulation of Pb was observed in liver of Carpio (Cyprinus carpio) (8.86 µg/g) and lowest in muscles of Baikari (Clupisoma garua) (0.07 µg/g). Maximum HI value was recorded in Carpio, which is the most consumed fish in the region, hence, may put human lives and health to risk.

Fisheries department assistant director, Deepanshu Singh, said, “We will look into the matter and will find out sources from which heavy metals flow into the river in order to take preventive measures.”

According to Mishra, presence of heavy metals was observed in the river water, sediment, and edible fishes of the Ganga in Varanasi district. Concentration of studied heavy metals, including Pb, Mn, Cr, and Cd, were found to exceed permissible limits set by international standards (BIS and WHO) for drinking water. The BIS permissible limit for Pb is 0.01 mg/L, Mn: 0.1 mg/L, Cr: O.05 mg/L and Cd: 0.01 mg/L.

According to the study, sediment was particularly polluted with cadmium, posing a potential threat to species dwelling at the bottom of the river.

Although the levels of heavy metals in the fish muscles were below the hazard quotient, it is evident that prolonged consumption of such contaminated fish could lead to bioaccumulation in the food chain.

This, in turn, may result in accumulation of heavy metals in human organs, surpassing the hazard index and causing various health risks to the local population. This study is of great importance because regular assessments aid identifying early signs of contamination, implementing necessary measures and raising awareness about dangers posed by toxic substances in water sources.