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Heavy metals contaminating Indian rivers

Date: 12 December 2019 Tags: Geography & Environment

Issue

Samples taken from two-thirds of the water quality stations across India’s major rivers showed contamination by one or more heavy metalsexceeding safe limits set by the Bureau of Indian Standards.

 

Background

The findings are part of a report, which is the third edition of an exercise conducted by the Central Water Commission (CWC) from May 2014 to April 2018.

 

Details

  • Samples from only one-third of water quality stations were safe. The rest, of the 442 samples, were polluted by heavy metals.

  • Iron emerged as the most common contaminant with 156 of the sampled sites registering levels of the metal above safe limits. None of the sites registered arsenic levels above the safe limit.

  • The presence of metals in drinking water is to some extent unavoidable and certain metals, in trace amounts, is required for good health. However when present above safe limits, they are associated with a range of disorders.

  • Long-term exposure to heavy metals may result in slowly progressing physical, muscular, and neurological degenerative processes that mimic Alzheimer’s disease, Parkinson’s disease, muscular dystrophy and multiple sclerosis.

  • The other major contaminants found in the samples were lead, nickel, chromium, cadmium and copper.

  • Lead, cadmium, nickel, chromium and copper contamination were more common in non-monsoon periods while iron, lead, chromium and copper exceeded tolerance limits in monsoon periods most of the time.

  • Arsenic and zinc are the two toxic metals whose concentration was always obtained within the limits throughout the study period.

  • Several rivers have only been sampled at a single site whereas others such as the Ganga, the Yamuna and the Godavari are sampled at multiple sites. Marked variation was found in contamination levels depending on the season.

Sources and causes of metal pollution

  • The main sources of heavy metal pollution are mining, milling, plating and surface finishing industries that discharge a variety of toxic metals into the environment.

  • The reasons for contamination were population growth and rise in agricultural and industrial activities.

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