People living in West Bengal could be exposing themselves to potentially cancer-causing arsenic by eating locally grown rice, British researchers said on Tuesday.
However, the researchers from the University of Manchester said that modifying the way rice is cooked could be a way of reducing arsenic exposure.
They told an international meeting of environmental experts at Manchester that the presence of naturally occurring petroleum in West Bengal and Cambodia could be responsible for the release of arsenic into water used for drinking.
They presented their findings at a workshop on arsenic in groundwater in Southeast Asia at Manchester University.
"Arsenic in ground waters in Bangladesh and West Bengal constitutes a major hazard to human health. Several tens of millions of people are impacted by using these waters for drinking, cooking and irrigation," David Polya from the university said.
"An environmental health disaster is unfolding in these areas. Tens of millions of people in many districts are drinking ground water with arsenic concentrations far above acceptable levels.
"Thousands of people have already been diagnosed with poisoning symptoms, even though much of the at-risk population has not yet been assessed for arsenic-related health problems," he added.
Researchers at the university and the Swiss Federal Institute of Aquatic Science and Technology have been among the first to identify similar hazards in Cambodia and Vietnam.
Although the two-day meeting is focussed on those two countries, the discussions also have relevance to other parts of the world.
"We have the chance and the responsibility here to encourage mitigation largely before such health impacts take place," Polya added.
The meeting was told by a leading development worker that thousands of people in Cambodia will die of cancer and other arsenic related health issues if more action is not taken soon.
Mickey Sampson of Resource Development International Cambodia - a NGO that runs a range of projects - said that more than 1,500 Cambodian villages are at high risk from arsenic in ground water.
In a village called Preak Russey, 264 people are suffering from debilitating levels of arsenicosis, he said, adding that in such villages most of the tube wells have arsenic levels 200 times the World Health Organisation (WHO) guideline - ironically, many of them sunk by NGOs.
He said arsenicosis symptoms have been found in villagers who have been drinking drawn from tube wells for only three years.
Children are at a higher risk than adults, he warned.