Arsenica toxic element at the center of administrative wrangling over drinking water standards in this countryis under investigation in other countries as well. Arsenic levels in the drinking water near Hanoi, Vietnam, are dangerously high and pose a health threat to millions of people, according to scientists at the Swiss Federal Institute for Environmental Science and Technology and the Hanoi University of Science. Their results, the first published survey of arsenic contamination in Vietnam, appear in the July 1 issue of the journal Environmental Science and Technology.

The scientists sampled water from 68 private tubewells, wells that draw water from between 30 and 120 feet below the surface, in and around Hanoi. They also tested water from eight water treatment plants that serve the city and tap water from randomly selected households. The average arsenic levels were more than three times the nation's 50 micrograms per liter standard with peaks of up to 3,000 micrograms per liter. Nearly half of the water samples contained arsenic levels above the standard, and, in one particularly affected rural area, the average arsenic level was 430 micrograms per liter.

The wells, designed to provide safe drinking water by avoiding polluted surface waters, tapped into arsenic-contaminated underground aquifers, says Michael Berg, an environmental chemist and the lead author of the report. According to the study, researchers have not yet detected symptoms of chronic arsenic exposure in the citizens of Vietnam. But cases of chronic arsenic poisoning from contaminated drinking water are regularly observed after only five to 10 years of exposure, the researchers say, and early symptoms are difficult to diagnose. Because the first private tubewells were installed seven years ago, the scientists "urgently propose" early mitigation actions to reduce the risk.

"In rural areas, the untreated groundwater is consumed directly as drinking water," Berg says. "Hence, several million totally unaware people are at immediate risk."