More than 230 experts from around the world are meeting on Sunday in the country's capital, Dhaka to suggest possible remedies.

Kazi Quamruzzaman, the conference convenor, said two thirds of water samples from 8,000 wells tested had levels of contamination above the maximum permissible limits set by the World Health Organisation.

"The Bangladesh arsenic contamination is possibly the largest mass poisoning case in the world now," a booklet published by the Dhaka Community Hospital says.

The World Bank has offered to pay more than three quarters of the $76m (£46m) cost of a government project to study the extent of the problem, support treatment and preventative measures and raise awareness of the problem.

This must be done with caution, however. Doctors fear a move away from underground water to surface sources could expose water drinkers to diarrhoea that already claims thousands of lives each year.