When in India, you might want to be careful where you drink water — a new study found widespread uranium contamination in aquifer-drawn groundwater in 16 Indian states. The researchers point to over-drainage of these water-bearing bodies as a probable cause.

Modhere Sacred Well, Shenzhen, China.
Image credits Bernard Spragg / Flickr.

A new study led by researchers from Duke University reports that aquifer groundwater in India shows high levels of uranium contamination. The main source, they believe, is the chemical make-up of the rock layers which hold the water. Human activity such as pollution and over-drainage may be exacerbating the problem, however.

Dangerously uranic

“Nearly a third of all water wells we tested in one state, Rajasthan, contained uranium levels that exceed the World Health Organization and U.S. Environmental Protection Agency’s safe drinking water standards,” said Avner Vengosh, a professor of geochemistry and water quality at Duke’s Nicholas School of the Environment and paper co-author.

Data recorded during previous water quality studies revealed aquifers with similarly-high levels of uranium in 26 districts in northwestern India and in 9 districts in southern and southwestern India, the paper adds. The study is the first to highlight a widespread presence of uranium in India’s groundwater. Uranium exposure has previously been linked to health complications such as kidney disease.

Based on the findings, the team believes there is a “need to revise current water-quality monitoring programs in India” and to face the potential public health risks in areas with high levels of uranium contamination.

“Developing effective remediation technologies and preventive management practices should also be a priority,” Vengosh adds.

According to provisional safety standards set by the World Health Organization (WHO), which are consistent with standards set by the U.S. Environmental Protection Agency (EPA), around 30 micrograms of uranium per liter of water should cause no adverse effects for humans. However, uranium isn’t currently on India’s water quality watchlist, the Bureau of Indian Standards’ Drinking Water Specifications.

For the study, the team sampled and analyzed the chemistry of 324 wells in the states of Rajasthan and Gujarat. In one subset of samples, they measured the ratios of uranium isotopes. The dataset was fleshed-out with measurements from 68 previous groundwater chemistry studies performed in Rajasthan, Gujarat and 14 other Indian states.

The results suggest that there are several factors contributing to this contamination. The source is natural, the team writes — uranium contained in the aquifer’s rocks leaching out into the water. The quantity of uranium contained in the rocks of each is the first factor. The others include water-rock interactions, oxidation conditions that enhance uranium’s solubility in water, as well as the presence of chemicals in the groundwater that can interact with this extracted uranium (such as bicarbonate) which further enhances the metal’s solubility. These last three factors are specific to each water-bearing body — but, in many areas of India, they compound and lead to high concentrations of uranium in the water.

Human activity also plays a central part, the team notes. The most important culprit is over-exploitation of aquifer water for crop irrigation.

Most Indian aquifers are composed of clay, silt, and gravel resulted from the weathering of rocks in the Himalayas, or from uranium-rich granites eroded by streams. If these aquifers get drained faster than they can replenish (so water levels decline), it creates an environment ripe for oxidation — in turn, this makes what groundwater is still in the aquifer leach uranium much faster.

“One of the takeaways of this study is that human activities can make a bad situation worse, but we could also make it better,” Vengosh said.

“Including a uranium standard in the Bureau of Indian Standards’ Drinking Water Specification based on uranium’s kidney-harming effects, establishing monitoring systems to identify at-risk areas, and exploring new ways to prevent or treat uranium contamination will help ensure access to safe drinking water for tens of millions in India.”

This contamination is just the latest in a long string of problems India is having with its groundwater supply lately. Over-consumption is quickly drying its aquifers, threatening to leave its population wanting for water. But these findings show that the country’s immense drain on underground water resources is already starting to have adverse effects.

Furthermore, India’s groundwater “also suffers from multiple water quality issues such as arsenic and fluoride contamination that pose human health risks,” according to the paper.

The paper “Large-Scale Uranium Contamination of Groundwater Resources in India” has been published in the journal Environmental Science & Technology.