They said the household filtration process costs less than Tk 240 for a family of about four people a year.

The speakers pointed out that in practice community-based arsenic removal plants like harvesting of rainwater and pond-sand filters are not popular because of technical reasons.

On the other hand, the low cost filters have already proved acceptable and popular during the field-testing, they added.

The speakers said removal of arsenic from three different types of water by oxidation and co-precipitation methods has proved very effective.

After filtration, contamination level almost comes down to zero, said the experts studying the filters at field level.

"We want to find a meaningful, practical and cost-effective solution to the arsenic problem," said Nasrin R Karim, director general of an NGO Earth Identity Project that organised the roundtable titled 'Dhaka Water': Policy, Strategy, and Dialogue.

During the briefing session, Unicef officials informed that out of 464 upazilas, 265 have been identified as 'hot spots' where more than 60 percent tubewell water is contaminated.

"Epidemiology of the arsenic is still uncertain. In same family one member is seen to have serious effect from drinking contaminated water while others drinking from the same source have no effect at all," they added.

"It is not understood yet but we have a big challenge ahead," said Naseem-ur-Rahman, chief of information and advocacy section of Unicef.

Paul Edwards, head of water and sanitation of Unicef, Dr Han Heijnen, head of environment department of WHO, Enayetullah Khan, editor of the New Age, Khoda Bux, director of Bangladesh Arsenic Mitigation Water Supply Project and Unicef officials from West Bengal spoke at the roundtable supported by Embassy of Finland, Unicef and DFID.

The roundtable was a follow up of the roundtable titled 'Arsenic Crisis Today-Strategy for Tomorrow' held in July, 2001.