Drinking water in Bengal basin contains high amounts of toxins, says study

Groundwater as well as river water in the western Bengal basin has high concentrations of pesticides and toxic polycyclic aromatic hydrocarbons (PAH), a study authored by a group of scientists from the Indian Institute of Technology (IIT), Kharagpur has revealed.

The researchers tested hundreds of samples, both of groundwater and river water, which is used for drinking water supply from the Farraka Barrage to the Sunderbans, and found these chemicals in significantly higher amounts than permissible limits.

Significant findings

The Western Bengal basin has evidence of high concentration of arsenic in groundwater, and according to the researchers, the study assumes significance because, for the first time in the country, a whole region has recorded the presence of pesticides and PAH in its natural sources of water and surface sediments.

“The results of this study suggest the existence of wide presence of POPs (persistent organic pollution pollutants), as pesticide residues and PAHs, detected both in groundwater and river water of areas, variable by land use, which are historically known to be at risk from groundwater arsenic pollution,” reads the paper.

Drinking water in Bengal basin contains high amounts of toxins, says study

Titled ‘Wide exposure of persistent organic pollution pollutants (PoPs) in natural waters and sediments of the densely populated Western Bengal Basin, India’, the findings of the paper authored by Srimanti Duttagupta and Abhijit Mukherjee of IIT-Kharagpur among others, provides a new dimension to the deteriorating water quality of the region. The paper was published in a leading international peer reviewed environmental journal Science for Total Environment earlier this week.

‘46 times higher’

Samples from more than 230 locations for groundwater, 32 locations for river water and 20 locations for surface sediments across 350 km were recorded for three consecutive years and studied for the presence of pesticides and PAH, Professor Mukherjee said. He pointed out that in some samples, the pesticide content in drinking water was as high as 46 times of the permissible limits.

Srimanti Duttagupta, the lead author of the paper, said that groundwater and river water were tested only from locations at which water is sourced for drinking purposes.

Another important aspect of the study is that it shows spatio-temporal distribution of these chemicals detected predominantly in natural waters. The study also points out that the pesticides and PAHs detected in agricultural and rural areas are distinct from urban settings.

Urban, rural

“While concentration of pesticides is higher in rural areas, particularly in agricultural areas in districts like Murshidabad and Nadia, as we go down, high concentration of PAH is found to rise in urban and semi-urban areas, particularly in North 24 Parganas and south Nadia,” Professor Mukherjee said.

The researchers said PAHs as a group are aromatic hydrocarbons, the most common being napathlene, which are not only released by industrial discharge but also from fuel emissions.

Densely populated

The study has been carried in one of the most populated regions of South Asia, and the presence of hazardous chemicals in groundwater raises concerns over anthropogenic pollution due to local vehicle combustion, biomass burning and industrial combustion, apart from agricultural activities.

Professor Mukherjee said that while arsenic contamination is blamed for most of the deaths due to water contamination, the study provides another aspect for looking into how much pesticides and PAHs in drinking water contribute to the disease burden.

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Printable version | Apr 17, 2021 5:24:47 PM | https://www.thehindu.com/news/cities/kolkata/drinking-water-in-bengal-basin-contains-high-amounts-of-toxins-says-study/article30845490.ece

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