Fertilisers used in Bangladesh may have put millions of lives at risk, according to a new study by scientists in India.

The danger comes from the poison arsenic, which is polluting supplies of drinking water.

Two government departments in Bangladesh and four international organisations are facing legal proceedings for allegedly failing to protect the population.

Much of Bangladesh's drinking water comes from wells sunk by agencies working for the United Nations.

Poison may come from fertilizers

But a Bangladeshi MP, Rabeya Bhuyian, has accused The World Bank, the United Nations Children's Fund, the World Health Organisation and the United Nations Development Programme of failing to protect the water supply.

Some well water contains so much arsenic that an adult drinking four litres a day could start to show signs of poisoning.

Arsenic can damage most of the body's major organs and the immune system. It is also known to cause cancer.

Experts estimate that half the people in Bangladesh - that is up to 75 million individuals - are slowly being poisoned.

West Bengal faces similar problems. Arsenic occurs naturally in the ground, but it has been unclear how it gets into water supplies.

Writing in the journal Nature, researchers from the Geological Survey of India suggest that the increasing use of phosphate fertilisers might play a part.

They believe that when phosphate and arsenic compete with one another in the ground, arsenic is displaced out of the soil and can leach into water supplies.

Phosphates also encourage the growth of bacteria, which helps to release arsenic.