Millions more at risk of arsenic poisoning than previously thought

The number of people at risk of arsenic poisoning from drinking water from sunken wells may be considerably higher than previously thought, a new report from the University of Calcutta has said.

The first cases of arsenic poisoning in the Indian subcontinent were reported in India in 1983, and it has been known for several years that half the population of Bangladesh and many residents of West Bengal state were at risk (BMJ 2000;320:822). Now the danger is thought to extend beyond these areas.

“Almost 330 million people may be at risk in India and Bangladesh compared to 150 million as believed earlier,” says Dipankar Chakraborti of the School of Environmental Sciences, Jadavpur University, Calcutta.

Researchers from several Calcutta based institutions investigated water in the village of Semria Ojha Patti, in Bhojpur district, Bihar state—where tube wells were dug 20 years ago—and seemingly opened a Pandora's box. They found its water similar to that in the highly contaminated wells of Bangladesh and West Bengal.

An analysis of the arsenic content of 206 tube wells (95% of the total wells) showed that some 60% of villagers were drinking unsafe water in which the arsenic levels were five times the safety limit recommended by the World Health Organization. One in five wells exceeded the limit by 30 times. Thirteen per cent of adults and 6% of children who were examined had skin lesions typical of arsenic poisoning.

Neuropathy typical of arsenic poisoning was found in 63% of men with skin lesions, something observed earlier only in severe cases.

“Our preliminary observations … indicate a particularly severe exposure,” say the researchers, in their report published online in Environmental Health Perspectives (http://ehpnet1.niehs.nih.gov/docs/2003/5966/abstract.html).

The new findings have raised the question of whether the upper and middle plains of the Ganges plains are also affected. This would have serious implications as these are the most thickly populated areas of India comprising the states of Uttar Pradesh and Bihar. Arsenic contamination has also been reported from Chandigarh in northern India and the lower plains area of Nepal.

The geological similarities of the middle and upper Ganges plains support a test of the hypothesis that the risk of arsenic contamination may involve the entire Ganges plain, say the researchers. But they caution that as not all water sources in Bengal or Bangladesh are contaminated, the entire Ganges plain may not be uniformly affected “despite our expectation that groundwater will be arsenic contaminated over a wide region.”

“We feel our present research may be showing only the tip of the iceberg,” says Dr Chakraborti. Virtually every new survey finds new affected villages. “In 1988 we found just three affected villages. Further investigations revealed that by 2003, the number had risen to 4000 villages in India and Bangladesh,” he said.

The first cases of arsenic poisoning were reported in 1983, but now it is thought likely that more than six million people in West Bengal (in the lower Ganges) and 35 million in Bangladesh are drinking water contaminated with arsenic.

Dr Chakraborti blames international aid agencies as well as both the central Indian government and the West Bengal government for gross neglect of the worsening situation and inaction. From the 1970s onwards, Unicef paid for the sinking of millions of tube wells in the subcontinent, in an attempt to provide clean water, as protection against waterborne diseases. The organisation did not realise that the water might be contaminated by arsenic.