Home Cities Toxic heavy metals, high salinity found in groundwater, says report

Toxic heavy metals, high salinity found in groundwater, says report

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The rampant use of borewells — often illegal ones — in the Capital may have unforeseen health impacts, as a study has found the presence of heavy metals, such as manganese, iron and even uranium, beyond permissible limits in groundwater tested in some areas of Delhi.

While experts say using this water occasionally for bathing is largely harmless, drinking it can lead to chronic toxicity and impact organs, such as the kidneys or intestines, in the long-run. There are over 8,000 unsealed borewells remaining in the Capital, with officials saying the process to seal them will take over a year.

The latest annual report of the Central Groundwater Board (CGWB) for 2020-21, released in August 2021 after collecting data in May 2020, has found the presence of uranium beyond the permissible limit of 30 parts per billion (ppb) in five locations in the city, including Janakpuri, Harewali, Jharoda Kalan, Nizamuddin Bridge, and Kanjhawala. The uranium concentration was found to be as high as 128.9 ppb in Jharoda Kalan.

Similarly, it found manganese levels to be over four times the permissible limit in parts of Delhi, peaking at 1.39 parts per million (ppm) at Ujwa in sout-west Delhi, in comparison to a permissible limit of 0.3ppm, while iron was found to be over the permissible limit of 1mg/litre at four locations in Delhi – Najafgarh, Nangli Rajpura, Ujwa and Bhalswa.

Delhi gets about 945MGD of piped water against a demand of 1,150MGD, according to the Delhi Jal Board. To be sure, the study only mentions groundwater extracted directly, ostensibly by residents to make up for the 200MGD shortfall.

While heavy metals in small quantities are tolerable for the human body, its consumption and accumulation over the years can lead to organs developing problems, said experts.

According to the report, seen by HT, the groundwater at Khera Kalan in north Delhi, Rohini’s sector 28, Majara Dabas in northwest Delhi, Sanjay Van, Vikaspuri in west Delhi and Jhuljhuli in southwest Delhi has high fluoride levels above 1.5mg/litre that is likely to cause erosion of tooth enamel and stiffness in the bones. While a range from 0.8 to 1.2mg/litre helps protect teeth, levels of over 1.5 mg/l are enough to cause the enamel to start staining and over 5mg/litre can cause bone stiffness over time, the report said.

Nitrate compounds, largely from leaching of chemical fertilisers, were found to be beyond the Bureau of Indian Standard (BIS) limit of 45mg/litre in large parts of northwest, central and south Delhi districts, and high electrical conductivity (EC) – a sign of salinity – was found in parts of Tagore Garden, Nizampur, Jharoda Kalan, Hiran Kudna and some pockets of Shahdara, where the EC values were high even at shallow depths.

Suresh Rohilla, programme lead at the International Water Association (IWA), said due to the significant gap in the demand and supply, many parts of Delhi depend on groundwater, the extraction of which not only leads to a decline in the water table but also causes health impacts when consumed.

“Around 95% of the groundwater being extracted is for non-potable purposes, where the presence of heavy metals and other elements is not much of a problem, but in cases where…it is being consumed, then these heavy metals can certainly impact the individual. In such cases, a water purifier is also not used generally, so it is unclear what is being consumed and in what quantities,” said Rohilla, stating there was a need to educate people on groundwater extraction, particularly to ensure that the water table did not fall any lower.

Professor Shashank Shekhar, from the department of Geology at Delhi University (DU), who carried out a study to asses heavy metals in groundwater in 2017, found high iron concentration along the Yamuna floodplains, which he believes is partially due to human sources.

“Extensive agriculture and urbanisation has led to release of various contaminants into the river as well as groundwater system. While iron concentration could already be high, human sources include leachate and sewage, alongside industrial effluents,” he said.

This in turn can return to humans through multiple sources, including vegetables grown along the plains. In 2019, a study by National Environmental Engineering Research Institute (NEERI), following a National Green Tribunal (NGT) order, found the presence of heavy metals in vegetables grown along the Yamuna floodplains in Mayur Vihar, Usmanpur and Geeta Colony. The vegetables, mainly cabbage, cauliflower, radish, brinjal and fenugreek, contained metals such as lead, nickel, cadmium and mercury in high concentration.

Manoj Mishra, environmentalist and convener of the Yamuna Jiye Abhiyaan, said groundwater extraction remains a problem across the city, with the Yamuna equally contaminated in most locations due to human interventions. “While these elements and heavy metals may be found naturally underground, human sources such as leachate or effluents entering the groundwater could also be factors,” he said, adding that high chromium and arsenic concentration was found in the groundwater in areas where fly ash is being dumped in Delhi.

Dr (Col) Vijay Dutta, Internal Medicine & Respiratory Medicine at the Indian Spinal Injuries Centre (ISIC), said consuming contaminated water can lead to transmission of diseases such as cholera, diarrhoea, dysentery, hepatitis A, typhoid and polio, with heavy metals acting posing the greatest risk. “While some of these heavy metals are even essential for the growth, development and health, they are required in small quantities only. Meanwhile, there are other heavy metals, like uranium, which are non-essential as they are indestructible and toxic for our body. Long-term exposure to such heavy metals can lead to severe health issues such as cancer and organ damage,” he said.

According to an assessment carried out by the Delhi Jal Board (DJB) in 2019, following another NGT order, it was discovered that there are 19,661 illegal borewells in Delhi. While a Delhi Pollution Control Committee (DPCC) report on October 25, 2021, said that 11,634 borewells have been sealed by the revenue department so far, the process to seal the remaining 8,000 may take close to a year.

“An environmental compensation of 70.6 crore has been imposed by us on these illegal borewells. So far, an amount of 54 lakh has been recovered, and the process to seal more such units and to recover the remaining amount is still underway,” a senior DPCC official said.

A DJB official said several projects had been planned to bridge the gap between the demand and supply of water, including plants for using unutilised Yamuna water share from Himachal Pradesh; waste water exchange with UP in which Delhi will provide treated waste water for irrigation in exchange of 140MGD raw water; and the Palla project, based on Singapore NeWater model in which highly treated water from a coronation plant will be lifted and put back in river in Palla. “While borewells are being sealed, we also plans to develop a large number of water extraction points in areas with very high groundwater levels to augment supply,” said the official.

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