Heavy metals in Varanasi Ganga pose risk to health and life: study

In a joint research project, a team from Banaras Hindu University (BHU), CSIR-Indian Institute of Toxicology Research (CSIR-IITR) Lucknow, and the Academy of Scientific and Innovative Research (AcSIR) Ghaziabad has found the presence of heavy metals in the Ganga, putting human health and life in the city of Varanasi to risk, primarily 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 Springer Nature on 26 December.

Fish from the Ganga is consumed in huge quantities 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 lead, 1.325 mg/L for manganese, 0.169 mg/L for chromium, and 0.161 mg/L for cadmium, which were above safe limit defined by the Environment Protection Agency in drinking water,” he said, adding that fish, including exotic and invasive species, were collected from the wild and examined for the presence of metals in their tissues.

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

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

According to Mishra, the presence of heavy metals was observed in the river water, sediment, and edible fish of the Ganga in Varanasi district. Concentration of studied heavy metals, including lead, manganese, chromium, and cadmium were found to exceed permissible limits set by international standards (BIS and WHO) for drinking water. The BIS permissible limit for lead is 0.01 mg/L, manganese 0.1 mg/L, chromium O.05 mg/L and cadmium 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 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 help identify early signs of contamination, implementing necessary measures and raising awareness about dangers posed by toxic substances in water sources.