'Groundwater overexploitation linked to uranium radiation risk'

A new study of the presence of uranium in borewell water in Kolar and Chikkaballapur districts has found evidence linking overexploitation to higher concentration of the radioactive mineral, pointing to potential health risks.

The fresh set of data, which comes two years after researchers flagged high concentration of uranium in 14 of the 75 villages of Karnataka, prompted the study authors to call for rainwater harvesting as well as testing fruits and vegetables from the districts.

Done by researchers from the Institute of Science, Bengaluru, Mangalore University and University of Mysore, the study, in a nutshell, found this: there was a lower amount of uranium in the groundwater after recharge of groundwater post heavy rains and a sharp rise in the concentration of the mineral during the dry season.

As per the WHO, a litre of water with up to 30 micrograms (mcg) of uranium is safe for consumption. In India, the Atomic Energy Regulatory Board (AERB) has put the threshold at 60 mcg/litre. The latest study at G Madepalli in Chikkaballapur, where the concentration was 5,000 mcg/litre in 2021, showed higher contamination at 8,649 mcg/litre.

The researchers took two samples from the village: first one days after heavy rains and the second one during the dry season. The recharging of groundwater table after rain meant the concentration was lower at 1,000 mcg/litre, but the overexploitation had led to increase of the uranium content to a whopping 8,649 mcg/litre in February 2023.

Similarly, the concentration in Brahmanahalli had gone up from 772 to 3,561.3 mcg/litre. In Kolar, dry season samples from Kadirampalli showed 2,985.7 mcg/litre of uranium, up from 1,000 mcg/litre found in the sample drawn post rain. The concentration in Chikkevaripalli was higher at 5,995.2 mcg/litre, five times more than the 921 mcg/litre after the rains.

Even during the rainy season, the concentration is much higher than the limits set by both the WHO and AERB. The study estimated the possible amount of radiation (measured in sieverts) caused by the ingestion of the uranium-rich water. As per the safety limit, individuals ingest a dose of 3.2 millisieverts (WHO) and 6.3 millisieverts (AERB) of radiation in a lifetime of about 70 years.

However, a man who consumes the untreated borewell water at Kadirampalli will end up ingesting a dose of at least 105.6 millisieverts during his lifetime of 68 years, while a woman ingests at least 84.4 millisieverts in 71 years.

The higher concentration in the dry season means the dosage will go up to 315.3 millisieverts for men and 252 millisieverts for women.

In Madepalli, a male individual may ingest up to 913.3 millisieverts, a high-risk amount as per the International Commission on Radiological Protection. The scientists believe more studies need to be taken up in the 14 districts of eastern Karnataka to understand the people’s exposure to uranium.

“Though reverse osmosis (RO) plants have come up in villages to purify water, they are not currently equipped to handle such a high amount of uranium. The immediate solution is rainwater harvesting and conservation of shallow water resources like open wells and lakes,” Prof Ramaswamiah Srinivasan, co-author and visiting professor at IISc’s Divecha Centre for Climate Change, told DH.

The study also underscored the need to test the fruits and vegetables cultivated in such places.

S A Pandit, another co-author and visiting professor at Divecha Centre, said the medical research should focus on the risk faced by individuals consuming such water. “The findings of the study are important to build awareness on water conservation among the public and policy makers alike. Deterministic and stochastic studies have to be conducted in the coming days in view of public safety,” he added.