"The study, which was initiated after some residents of Sonbhadra approached the CSE in May last year, reflects signs of mercury poisoning among the people," Director General Sunita Narain told reporters while releasing the study here.
She said people from the district had approached the CSE to study pollution and health problems in their locality.
Deputy Director General Chandra Bhushan said samples of water, soil, cereals, fish as well as blood, nails and hair of people living in the district were collected for the survey at CSE's pollution monitoring laboratory.
"The area selected for the study was Dhudi sub-division, which has the largest concentration of thermal power plants, coal mines and other polluting agencies," he said.
The samples were tested for presence of mercury and other heavy metals like arsenic, while fish were tested for methyl mercury, the most poisonous form of mercury, he said.
"During the study, mercury was found in 84 per cent of the blood samples at a very high level -- an average level of 34.3 parts per billion. Though India does not have a standard, the safe limit as per the US Environment Protection Agency is 5.8 ppb," he said.
Bhushan said mercury was found in 58 per cent samples of human hair, with the average level at 7.39 parts per million.
"According to Health Canada, 6 ppm is considered safe.
The highest amount of mercury found in the study was 31.3 ppm - five times the safe limit," he said.
He said mercury has contaminated groundwater in Sonbhadra.
"The highest concentration of mercury was found in the hand pump water sample of Dibulganj (0.026 ppm) which is 26 times the standard of .001 ppm set by the Bureau of Indian Standards," he said.
Gobind Ballabh Pant Sagar Reservoir was also contaminated with mercury, he said.
"The fish in the area were found to be contaminated with mercury. Fish near Dongiyanallah had 0.447 ppm of methyl mercury, which is almost twice the standard set by Food Safety and Standards Authority of India," he said. (MORE)