Groundwater in 16 States found to be contaminated by uranium

Aquifers in as many as 16 States in the country are contaminated by uranium, whose presence in drinking water has been linked to chronic kidney disease by several studies, a recent study has shown. More importantly, uranium doesn’t figure on the list of contaminants monitored under the Bureau of Indian Standards’ drinking water specifications.

The main source of this contamination is natural, but groundwater depletion by extensive withdrawal of water for irrigation and nitrite pollution due to the excessive use of nitrogenous fertilisers may be exacerbating the problem, said the study.

The study was carried out by a team of researchers led by Avner Vengosh, professor of geochemistry and water quality at the Nicholas School of the Environment at Duke University in the US.

The team, which also included experts from the Central Ground Water Board, the Rajasthan government’s Ground Water Department and Gujarat Water Resources Development Corporation, analysed groundwater samples from 226 locations in Rajasthan and 98 in Gujarat.

“Nearly a third of all water wells we tested in Rajasthan contained uranium levels that exceed the World Health Organization’s safe drinking water standards,” said Vengosh, in a statement.

The WHO has set 30 parts per billion as the provisional safe drinking water standard for uranium. The study appeared in a recent issue of the journal Environmental Science and Technology Letters.

The scientists, who analysed data from 68 previous studies of groundwater geochemistry in Rajasthan, Gujarat and 14 other states, also found the problem is widespread in many aquifers in 26 districts in northern States such as Punjab and Haryana as well as some districts in southern and eastern States.

“One of the takeaways of this study is that human activities can make a bad situation worse,” Vengosh said.

“The results of this study strongly suggest there is a need to revise current water-quality monitoring programmes in India and re-evaluate human health risks in areas of high uranium prevalence,” Vengosh said.

According to Rachel Coyte, a PhD student in Vengosh’s lab, over-exploitation of groundwater for irrigation may contribute to the problem. Many aquifers are composed of clay, silt and gravel carried down from Himalayan weathering by streams or uranium-rich granitic rocks. “When over-pumping of these aquifers’ groundwater occurs and the water levels decline, it induces oxidation conditions that, in turn, enhance uranium enrichment in the shallow groundwater that remains,” Coyte said.