And incidentally, these are state programmes to which Centre extends funding. States are relatively slow on taking up quality-related interventions not merely because of cost, but treatment plants also need to be maintained constantly," the official said.

Scientists said treating water contaminated with high levels of arsenic-a chemical known to cause cancer-was complex and it would be more practical to implement methods such as rainwater harvesting to develop alternate sources of potable water.

According to C.K. Jain, a senior hydrologist at the National Institute of Hydrology, Guwahati, consumption of water with above-permissible amounts of arsenic, even if it is in minute quantities, for more than 10 years can be fatal. "Detecting the arsenic, as well as treating water using methods such as reverse osmosis and electric dialysis are extremely expensive and not permanent," said Jain.

"The best way is to collect rainwater during monsoon months, treat it, which is far cheaper, and use it during non-monsoon months," he added.

Though not as dangerous as arsenic, excess fluoride, responsible for a range of non-fatal but extremely painful conditions rainging from skeletal deformities to dental infirmities, is also a matter of concern, with more than 17 states reporting fluoride content in water above permissible limits.

"Fluoride in excess amounts is a problem, but there are well known methods (to treat such water), the most popular being the Nalgonda treatment," Gangadhar Panigrahi, dental surgeon at Sir Ganga Ram Hospital, said.

The Nalgonda treatment, popular in South India, and named after a district in Andhra Pradesh, involves filtering fluorinated water with aluminium sulphate and lime, and is one of the cheapest and most effective ways to control fluoride content in water, according to experts.
"Often it may be much cheaper to get an alternative source provided by piping (water) from a distance rather than treating for quality specifically.

And incidentally, these are state programmes to which Centre extends funding. States are relatively slow on taking up quality-related interventions not merely because of cost, but treatment plants also need to be maintained constantly," the official said.

Scientists said treating water contaminated with high levels of arsenic-a chemical known to cause cancer-was complex and it would be more practical to implement methods such as rainwater harvesting to develop alternate sources of potable water.

According to C.K. Jain, a senior hydrologist at the National Institute of Hydrology, Guwahati, consumption of water with above-permissible amounts of arsenic, even if it is in minute quantities, for more than 10 years can be fatal. "Detecting the arsenic, as well as treating water using methods such as reverse osmosis and electric dialysis are extremely expensive and not permanent," said Jain.

"The best way is to collect rainwater during monsoon months, treat it, which is far cheaper, and use it during non-monsoon months," he added.

Though not as dangerous as arsenic, excess fluoride, responsible for a range of non-fatal but extremely painful conditions rainging from skeletal deformities to dental infirmities, is also a matter of concern, with more than 17 states reporting fluoride content in water above permissible limits.

"Fluoride in excess amounts is a problem, but there are well known methods (to treat such water), the most popular being the Nalgonda treatment," Gangadhar Panigrahi, dental surgeon at Sir Ganga Ram Hospital, said.

The Nalgonda treatment, popular in South India, and named after a district in Andhra Pradesh, involves filtering fluorinated water with aluminium sulphate and lime, and is one of the cheapest and most effective ways to control fluoride content in water, according to experts.