Context

• The most recent report on the state of groundwater released by the Central Groundwater Board. It revealed that the twelve Indian states have uranium levels beyond permissible limits in their groundwater. Uranium concentrations in the country’s shallow groundwater range from 0-532 parts per billion (ppb), according to the document titled Groundwater yearbook 2021-2022 released in January, 2023.

What is a Safe level of uranium in groundwater?

• The safe levels for uranium in groundwater in India are 30 ppb as prescribed by the Bureau of Indian Standards (BIS) and the World Health Organization (WHO).
• The safe level of 30 µg/L is established to minimize the risk of these health effects. However, it should be noted that long-term exposure to even low levels of uranium can also cause health problems.

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Findings of the report

• No presence in Kerala: Uranium concentration is found to be within safe limits in 13 states and none of the samples collected from Kerala had its presence.
• Punjab worse affected: Punjab is the worst-affected state in terms of the percentage of wells found to have uranium concentration of more than 30 ppb, the safe level. Nearly 29 per cent, or about three in every 10 wells tested in Punjab, is contaminated with uranium. Uranium presence in Punjab’s groundwater is found to be 17.7 times more than the safe limit prescribed by WHO. The concentration of the element was also highest in the state, with 532 ppb.
• Haryana stands second: Haryana is the second state in terms of uranium prevalence in groundwater. The state also recorded the second-highest concentration of uranium in the country, with 518 ppb or 17.3 times the WHO-prescribed safe limit.
• Uttar Pradesh third largest in terms of uranium concentration: The state was the third-highest in terms of uranium concentration, with 532 ppb or 7.9 times more than the safe limit. For example, 9.2 per cent of the samples from Uttar Pradesh had a high concentration of uranium.
• Localised pockets of other states: Uranium concentration was found to be higher than the threshold level in localised pockets of seven other states Madhya Pradesh, Tamil Nadu, Chhattisgarh, Gujarat, Odisha, Telangana and Bihar.

Uranium: A toxic element

• Uranium is a nephrotoxic element, which means people dependent on groundwater containing the element are at a higher risk of impaired renal function and kidney disease.
• Exposure to uranium may also lead to other adverse health impacts, including bone toxicity and problems such as neurological effects, reproductive and developmental effects, and immune system effects.
• Ingestion of large amounts of uranium can lead to immediate health effects such as nausea, vomiting, and diarrhoea. Inhalation of uranium dust or fumes can cause lung irritation and damage, including lung cancer.

Causes of contamination

• Geogenic plus anthropogenic: Geogenic processes are responsible for uranium contamination, but the overexploitation of groundwater can also be a reason for it.
• High concentration largely due to natural uranium content: High levels of uranium are largely due to natural uranium content in aquifer rocks, oxidation state and groundwater chemistry, noted researchers from Duke University.
• High bicarbonate levels: Extreme bicarbonate levels were also found at the sites with high uranium levels. Bicarbonates help to bring the uranium out of the source rocks and is a reason for the high occurrence of the element, said Rachel Coyte, the lead author of the study.
• Human-made causes too be behind this: Groundwater-table decline, nitrate pollution and over-exploitation of groundwater from irrigation further exacerbate uranium mobilisation, said the study.
• Overexploitation of groundwater: Overexploitation of groundwater resources is likely to be one of the reasons for uranium and other geogenic contaminants, including arsenic and fluoride, according to the BARC study published in 2021.

Reverse osmosis could be a probable solution

• Reverse osmosis (RO) is a way to purify water.
• It uses a special membrane to filter out impurities, such as minerals and other dissolved contaminants, including toxic elements such as uranium.
• The water is forced through the membrane by applying pressure, leaving behind the impurities and creating clean, purified water on the other side.
• The impurities are removed by the membrane and the clean water is collected.

Did you know?

• BARC has conducted studies on the removal of uranium from drinking water using a hybrid membrane technique.
• Field studies are also being carried out in a few districts of Punjab based on RO technique at a village level to provide potable water, stated the BARC researchers.

Conclusion

• Uranium contamination has been attributed to geogenic processes coupled with the overexploitation of groundwater in the country. This assessment of uranium contamination in groundwater across India highlights the need for an urgent response. Reverse osmosis (RO) is one of the latest membrane-based technologies used in water purification systems to remove uranium could be a solution.

Mains question

Q. Almost half of India’s states have uranium levels in their groundwater above permissible limits. Highlight the causes and effects of uranium contamination in groundwater.

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