New York, Jun 8 (IANS): Researchers have found widespread uranium contamination in groundwater from aquifers in 16 Indian states.

The findings suggested that the main source of the uranium contamination is natural, but human factors such as groundwater-table decline, over-exploitation of groundwater for agricultural irrigation and nitrate pollution may be aggravating the problem.

According to the researchers, several studies have linked exposure of uranium in drinking water may lead to chronic kidney disease.

"Nearly a third of all water wells we tested in one state, Rajasthan, contained uranium levels that exceed the World Health Organization (WHO) and US Environmental Protection Agency's safe drinking water standards," said co-author Avner Vengosh from the Duke University in US.

"By analyzing previous water quality studies, we also identified aquifers contaminated with similarly high levels of uranium in 26 other districts in northwestern India and nine districts in southern or southeastern India," Vengosh added.

For the study, published in the journal Environmental Science and Technology Letters, the researchers sampled water from 324 wells in the states of Rajasthan and Gujarat to analyze the water chemistry.

In a subset of samples, they measured the uranium isotope ratios. They also analyzed similar data from 68 previous studies of groundwater geochemistry in Rajasthan, Gujarat and 14 other Indian states.

"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.

"Developing effective remediation technologies and preventive management practices should also be a priority," Vengosh noted.