is capable of removing all impurities from the groundwater," Director Nuclear Research Centre at Indian Agricultural Research Institute, Dr PS Datta told PTI.
"Some of the water purifiers available in the market treat bacteria but let fluoride and nitrate pass while the others filter heavy metals but are ineffective for killing bacteria in groundwater," he said.
People who cannot afford expensive water purifiers generally assess the quality of groundwater on parameters such as clarity, odour and taste, Datta said adding "these methods do not guarantee the quality of water."
"Impurities such as fluoride and nitrate are more difficult to deal with as health problems due to their intake surface after 10-15 years, he said adding there is no known geological source which cause fluoride and nitrate levels to rise in groundwater.
Excessive use of pesticides and mining activities to a great extent are responsible for the increased level of fluoride in groundwater while human excreta causes increased nitrate levels, Datta said.
Fluoride poses a problem in about 17 states of the country with Rajasthan being worst hit. All the districts in the state are effected by fluoride contamination in groundwater, he said.
Fluoride levels of over 4 gram per litre (gpl) of water might result in death and amount over 1.5 milligram per litre could cause skeletol fluorosis leading to crippling, he said.
Speaking on nitrate contamination he added, "Though nitrate level below 10 milligram per litre of water is not harmful but at some places in Najafgarh region it was recorded 150 mg per litre," he said.
Everybody in that region is at risk because of high level of nitrate in groundwater but children below nine months are at higher risk as their immunity level is not so strong. 'Blue baby syndrome' is very common in places where the level of nitrate exceeds the permissible limit, Datta said.
High levels of nitrate in water affect lymph nodes in adults and also cause cardiovascular diseases and stomach cancer, he said.
He said most of the industries dump their waste without treating it which slowly percolates into groundwater. "Since there is no division of groundwater, the contaminated water flows towards the capital due to low pressure created by excessive pumping of groundwater," he said.
Datta called for an integrated approach which ropes in various government agencies and non-government organisations for providing potable water to the people.
"Most of the work done by various agencies is relevant. By integrating efforts of all the agencies more value can be added to it," he said.