Evidence of widespread arsenic contamination of groundwater has been found in parts of Vietnam that had been assessed by the British Geological Survey.
News of the discovery follows the launch of a lawsuit against the BGS concerning its role in testing arsenic-contaminated groundwater in Bangladesh.
But the Swiss scientist whose team identified a similar problem in Vietnam criticised the litigation. The suit has the potential to deter future research, according to Michael Berg, leader of the contaminant hydrology research group at the Swiss Federal Institute for Environmental Science and Technology.
London-based solicitors are pursuing a test case on behalf of Bangladeshi victims of arsenic poisoning that could cost the Natural Environment Research Council, the parent body of the BGS, millions of pounds.
They claim that the BGS was negligent for not testing for arsenic in groundwater during survey work it conducted in Bangladesh in 1992. It subsequently emerged that about 35 million people in the region had been drinking contaminated water from wells bored in recent years, which had led to large-scale chronic arsenic poisoning.
Between June 1994 and March 1995, the BGS also assessed groundwater in the Vietnamese capital Hanoi in the Red River Delta to look at the effect of urbanisation on water quality. Again, the BGS did not test for arsenic.
A spokeswoman for Nerc, which is handling legal matters for the BGS, said the chemical was not considered a threat to the water supply at the time.
The possibility of contamination in Bangladesh was raised in February 1995 at an international conference on arsenic in groundwater, which was attended by a BGS scientist.
Vietnam was not singled out, but a two-year survey by Dr Berg has identified contaminated groundwater in and around Hanoi. In some areas, levels were 300 times higher than the World Health Organisation's recommended safety limits.
The Red River and Bengal deltas share a common geology in which deep-bored wells can become contaminated. Although no cases of arsenic poisoning have been reported among the Hanoi region's 11 million inhabitants, Dr Berg believed this might be because they had not been drinking groundwater long enough for signs of chronic poisoning to show.
Dr Berg said that mitigation, not litigation, would help victims of the tragedy.
He felt that the BGS's survey work had been valuable in helping scientists get to grips with the problem, and he warned that legal action could stymie similar studies.
"A lawsuit against the BGS, and possibly other organisations, will probably not really encourage others to conduct such important research," he warned.