Scientists investigating the effects of Agent Orange in Vietnam have found that people living in a so-called hotspot have the highest blood levels of its poisonous chemical dioxin ever recorded in the country.

Agent Orange, which has the dioxin (TCDD - short for 2,3,7,8-tetrachlorodibenzo-p-dioxin) as one of its constituents, was last used in 1973.

But today, some residents of Binh-Hoa, near Ho Chi Minh City, have 200 times the background amount of dioxin in their bloodstreams.

Agent Orange was widely used by the US military during the Vietnam War as a defoliant so that Vietnam's dense jungle could not provide cover for Viet Cong forces.

'Startling' results

It was when US veterans started to become ill with a variety of health problems that investigations suggested that Agent Orange could be involved.

The most dangerous ingredient was the dioxin, a pollutant that stays in the environment for decades.

There are still about 12 dioxin hotspots in Vietnam, in areas where very heavy spraying took place.

Scientists from the United States have been working with the Vietnamese Red Cross in these areas, testing residents to see whether they are suffering any ill effects.

The lead scientist, Professor Arnold Schecter of the University of Texas, says they are "very startled" by the results.

Export worry

In a paper to be published in the journal Occupational and Environmental Medicine, he says that in Binh-Hoa, 95% of people sampled had elevated levels of dioxin in their bloodstream, and some had 200 times the average amount.

Dioxins, which include TCDD and other related compounds, can cause cancers and problems with reproductive development, the nervous and immune systems.

It is thought the high levels of dioxin found in Binh-Hoa residents result from the chemical leaching into watercourses where it is absorbed by fish and ducks, which form part of the Vietnamese diet.

The issue is very sensitive for Vietnam, which exports these foods all over the world.