Chemical analysis of water samples collected as a part of ground water monitoring, carried out by the Central Ground Water Board (CGWB), has thrown up worrying results. Besides nitrate, fluoride, salinity being above normal levels, fluoride and radon gas have emerged as the new ingredients in the city’s ground water above permissible levels.

“We have found radon gas and fluoride in some areas of Bangalore. Radon contamination, which was found in Bangalore North and South taluks, and parts of Anekal taluk, will not have any health impact unless it is inhaled,” K.M. Najeeb, Regional Director of CGWB, told The Hindu, warning that there are chances of the vapours being inhaled if person is having a shower. Gas escapes into air after three days once it is exposed to the atmosphere, K.M. Najeeb, he says.

Referring to a study done by a team of officials from the Mines and Geology Department, he said fluoride content was as high as 5.54 mg/l in borewell water in parts of Bellandur. The permissible limit for human consumption is 1.5 mg/l.

Tests must

M.V. Shashirekha, former chief chemist in the Department of Mines and Geology, said contamination of groundwater in Bangalore was mainly because of pollution by overflowing sewage, effluents discharged by industries and indiscriminate dumping of garbage. “These factors have transformed the city’s groundwater from potable to a toxic cocktail of heavy metals and bacterial pollution,” she said.

Asserting that residents who use groundwater for drinking or cooking should get the water tested every year, Ms. Shashirekha said: “Various studies conducted by us have shown that 50 per cent of the city’s groundwater is not fit for consumption.”

While the groundwater in industrial areas such as Peenya, K.R. Puram and Bommanahalli has always shown alarming quantities of heavy metals, including carcinogenic chromium, those in old Bangalore areas have been found to be contaminated with sewage and chemicals such as nitrate, she said.

Referring to another study done by the Rural Development and Panchayat Raj Department, Mr. Najeeb said it had found the presence of arsenic above the maximum permissible limit of 0.05mg/l (0.01mg/l is the permissible limit) in 76 villages of the State.

“Out of 147 samples analysed for arsenic in Shorapur Taluk of Gulbarga district, arsenic was found beyond permissible limits in 25 samples,” Mr. Najeeb said, adding that rainwater harvesting is the best solution to dilute the presence of these chemicals in groundwater.

RO water filters

Ms. Shashirekha said that although reverse osmosis (RO) is the best available option for purifying borewell water with high levels of nitrate, it was better to get the water tested before opting for RO purifiers.

“If the water does not have nitrate content, a normal purifier will serve the purpose. It is not advisable to consume water that is too soft or too hard. Both can cause heart problems directly or indirectly,” she said.

Moreover, it is always better to get the water tested, even if you are boiling it before drinking because boiling doubles the nitrate in it, she added.