Uranium in groundwater in Karnataka villages: Study

Chemical analysis of groundwater in 73 villages of Karnataka has found high and unsafe levels of uranium concentration in 78% of these locations, said a new study.

The World Health Organisation’s (WHO) recommended upper safety limit is 30 micrograms per litre (μg/l), while India’s Atomic Energy Regulatory Board has set a higher safety limit of 60 micrograms per litre.

The study conducted by the Divecha Centre for Climate Change, Indian Institute of Science (IISc), and the Centre for Advanced Research in Environmental Radioactivity, Mangalore University, attributed the contamination to natural causes and not due to anthropogenic activity.

For the study, researchers surveyed 73 villages in the eastern part of the state. They found that 57 villages had a uranium concentration of more than 30 micrograms per litre while 48 of them had concentration of more than 60 micrograms per litre.

In the latter category are two villages in Bengaluru Urban (Gollahalli and Gottigere) and two in Bengaluru Rural (Avathi and Kodagurki).

Scientists found that uranium concentration exceeded 1,000 micrograms per litre in one village each in Tumakuru and Chitradurga districts, five in Kolar and seven in Chikkaballapur district. The findings were detailed in a paper in Current Science.

Uranium exposure can lead to health problems. Speaking as an independent expert, Dr Subrata Das, an internal medicine specialist and diabetologist at Sakra World Hospital, said that adverse effects are determined by the concentration of uranium a person ingests.

“Immediate effects are haziness of the mind, headaches, low grade fever, vomiting. However, long-term exposure, over a period of months to years, leads to cancer of the liver, the bones and lungs,” he said.

Researchers wrote that none of the borewells from which the water had been sampled were anywhere near the “vicinity of nuclear facilities or urban waste disposal channels”.

The reason

The researchers stressed that the high uranium concentration is a result of decline in the groundwater table plus the geological makeup of Karnataka.

Gamma-ray spectrometric surveys have shown that there is a higher abundance of potassium, uranium and thorium in the eastern part of Karnataka compared to the western part, which the geologists refer to as the Eastern and Western Dharwar craton
respectively.

“Karnataka being dominantly made up of ancient granites, gneisses and schistose rocks is called hard rock terrain,” explained Dr R Srinivasan, lead author of the study and a Visiting Professor at the Divecha Centre.

“In hard rocks, water occurs in fractures at depth and the top of the saturated zone which is usually at the base of the weathered zone (soil layer) and constitutes the water table. The thicker the weathered zone, greater is the thickness of the oxidised layer. This promotes oxidation of uranium in the minerals.”

Bengaluru levels

A high radon content from localities in Bengaluru Urban and rural belt resulted in high levels of uranium being detected at three villages sampled in Bengaluru Rural district.

Samples from Avathi village showed high uranium varying from 174 to 942 micrograms per litre, while samples from Kodagurki village had 356 μg/l uranium, which, researchers said, tallies with observations made by the Central Ground Water Board.

A sample from Gudla Muddenahalli in the district also had more uranium than the WHO’s prescribed limit (56).

In Bengaluru Urban, repeat sampling at Gollahalli village found that the uranium concentration varied from 9 to 310 micrograms per litre throughout the year.

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