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Two or more metals have been detected in water samples from 22 Indian rivers and tributaries at 37 monitoring stations, according to a new report. The heavy metals detected beyond safe limits included arsenic, cadmium, chromium, copper, iron, lead, mercury and nickel, according to the report published in August 2024.
As many as 81 rivers and tributaries of the country have extremely high concentration of one or more trace and toxic heavy metals, the study by the Central Water Commission (CWC) indicated.
The report based on monitoring of samples from 10 river basins of India for the nine toxic heavy metals showed the presence of arsenic, mercury and chromium in 30, 18 and 16 stations across 14, 11 and 16 rivers, respectively.
Number of stations, rivers & tributaries with unacceptable levels of toxic heavy metals
As many as 141 (43 per cent) of the 328 river monitoring stations observed during January-December 2022 in India had alarming levels of one or more toxic heavy metals, according to the CWC report.
These stations placed in 13 states and 99 districts on 81 rivers and tributaries revealed the presence of extremely high concentrations of one or more toxic heavy metals, including arsenic, cadmium, copper, iron, lead, lead, mercury and nickel.
Mercury levels in samples collected at Palla U / S Delhi WQMS for River Yamuna were nine times higher than the Bureau of Indian Standards (BIS) permitted limits of 1 µg / L.
“The findings highlight the widespread presence of metal exceedance, with increased levels of arsenic, cadmium, chromium, copper, iron, lead, mercury and nickel detected at many stations,” according to the report titled Status of trace and toxic metals in Rivers of India.
At 74 per cent of the 141 stations or 104 stations, one toxic heavy metal was found to be beyond the acceptable limits prescribed by BIS. As many as 49 of these stations had only iron exceeding the limit.
In 17 stations located on nine rivers and tributaries, only arsenic was found to exceed the limit. Of these, 13 stations or around 76 per cent were in Uttar Pradesh located on rivers Ganga and Gomti.
As many as 13 water quality monitoring stations in six states, Andhra Pradesh, Karnataka, Kerala, Madhya Pradesh, Uttar Pradesh and Uttarakhand, across 17 rivers and tributaries have only lead exceeding the limit. These included Chambal and Tons, the tributaries of Yamuna.
“River water is currently being reported as contaminated with trace and toxic metals, both due to human activity and natural resources. Their presence above the established limits in water can pose significant threats to flora and fauna due to their non-biodegradable nature,” stated Kushvinder Vohra, chairman, CWC, Union Ministry of Jal Shakti (water resources) in the report.
Haripur, Honnali, Kallooppara, Karnaprayag Confluence D / S, Kirtinagar U / S, Malakkara, Singasadanapalli and Uttarkashi are the eight water quality monitoring stations in seven districts of four states — Uttarakhand, Kerala, Tamil Nadu and Karnataka — where three heavy toxic metals were found to breach the safe limits prescribed by the BIS.
Arsenic, lead and iron were found beyond the safe limits at Uttarkashi station in Uttarakhand, which is located on the Bhagirathi river, a tributary of the Ganga. In Honnali station, Karnataka located on Tungabhadra, the three metals identified exceeding the safe limits are — chromium, mercury and lead.
Madamon station in Pathanamthitta district, Kerala is found to be the most-affected station, where four metals: iron, mercury, lead and nickel are found to exceed their acceptable limits. “The metals above limit may be contributed from deposition of domestic and industrial sewage, agricultural runoff during the monsoon period and waste from quarries in the upstream of site,” stated the CWC in the report.
The report revealed the poor state of Ganga basin, which has the most WQ stations monitored. Around 47 per cent or 75 of the 161 water quality sites monitored in Ganga basin have been reported to exceed metal limits.
Ganga, the national river, was found to be polluted with four heavy metals — arsenic, lead, iron and copper. The west-flowing rivers south of Tapi basin ranked second, with 64 per cent or 23 of 36 stations indicating metal exceedance.
Rivers are contaminated with trace and hazardous metals from both anthropogenic and natural sources. The spread of heavy metal is mostly due to human activities such as metal mining, smelting, foundries and other metal-based industries.
Additionally, heavy metals are introduced into the environment through agricultural practices, including leaching from sources like landfills, waste dumps, livestock and chicken manure, runoff from automobiles and roadwork.
Their presence above the limit in water will cause serious threats to flora and fauna because of their non-biodegradability. These have hazardous effects on crops, including grains and vegetables, cultivated in soil and water contaminated with these heavy metals.
Metals such as copper detected in the rivers are essential trace elements necessary to maintain human metabolism. However, when present in higher concentrations, it can exhibit toxic effects. On the other hand, certain metals like mercury, cadmium and lead have direct harmful impacts on human health.
Heavy metals’ inherent toxicity, non-biodegradability and propensity for bioaccumulation make them a severe hazard to both human health and the environment.
For example, consuming arsenic-contaminated water causes arsenical skin lesions, which are a late indication of arsenic toxicity. Arsenicosis is a chronic sickness caused by drinking water with high arsenic levels for an extended period of time.
Recent research reveals that relatively little cadmium exposure might cause skeletal damage, including low bone mineral density (osteoporosis) and fractures. High levels of mercury can have negative consequences such as nerve, brain and kidney damage, lung discomfort, eye irritation, skin rashes, vomiting and diarrhoea.
The World Health Organization has classified these metals as being of significant public health concern.
The report emphasised the critical need for proactive actions to address metal contamination, water quality issues and implement efficient remediation methods.
According to the CWC, prioritising water resource protection is vital for sustaining ecosystem health and protecting public health from the hazardous effects of heavy metal poisoning.
Exploring new metal technologies for water treatment and incorporating innovative approaches to enhance the efficiency and effectiveness of water treatment processes is necessary, suggested the report.