The study showed that untreated industrial effluents are being pumped directly into the ground, contaminating the country's groundwater resources. Significantly, 80 per cent of the country's drinking water needs are met by groundwater.

The samples from three states -- Haryana, Gujarat and Andhra Pradesh -- were tested at the Facility for Ecological and Analytical Testing at IIT, Kanpur.

Results showed that there were traces of heavy metals like iron and zinc in all the samples and cadmium and lead in five samples. But according to the CSE, there was one common thread -- an unusually high level of mercury.

Mercury is responsible for causing the Minamata disease which leads to impairment of brain functioning, speech, sight and muscular coordination, besides neurological disorders and retardation of growth inchildren.