Vietnam dioxin spray estimate quadruples
Flight
records reveal full extent of Agent Orange
contamination.
17 April 2003
DECLAN BUTLER
This story is from the News section of the journal
Nature
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The health effects
of the herbicides
spread during the
war are still
unclear. |
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© alamy.com |
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A fresh study of long-forgotten flight records of US
military aircraft that sprayed Agent Orange over Vietnam
has shed unexpected light on one of the darkest episodes
of that conflict.
The study1 revises
previous estimates of the quantity of the herbicide
sprayed during the Vietnam War sharply upwards. Together
with the earlier use of other herbicides - known as
Agent Purple and Agent Pink - it finds that the total
amount of dioxin contaminant sprayed in the war was up
to four times as great as was previously estimated.
And in a report due to be released on 17 April, the
US Institute of Medicine declares that the new work
shows that it is feasible to perform large-scale
epidemiological studies of the links between the
herbicide spraying and the health of the Vietnamese
population and US veterans. The institute calls on the
US government to support such studies.
The new analysis, performed by a group led by Jeanne
Mager Stellman at Columbia University in New York,
provides the most detailed and sophisticated
computerized maps ever produced of herbicide spraying in
Vietnam. For the first time, the authors say, it is
possible to calculate an exposure index for individuals
and populations that is accurate enough for the
epidemiological research that is needed for firm links
with health data.
Stellman's team calculated the index by compiling a
computer database that overlays staggering amounts of
various data, much of it newly unearthed, onto
geographical coordinates. The data include flight-path
information, the amount and type of agents delivered
(including releases caused by leaks, crashes and dumps),
troop locations and movements, land features and soil
type, and the location of Vietnamese populations.
"I just think, 'Wow', if only this had been around
earlier," says Alistair Hay, an environmental
toxicologist at the University of Leeds, UK. "It fills
in the gaps, giving an accurate and comprehensive
picture of where spraying took place."
Like a widely cited 1974 National Academy of Sciences
study on Agent Orange, the researchers relied heavily on
HERBS, an electronic record compiled by the US military,
which includes data on flight paths, herbicide agents
and volumes used, and other information on 10,000
spraying missions. But when digging out and cleaning up
these data, the team stumbled on valuable archive data
that had been overlooked, and discovered a connection
that allowed them to extract far more information from
existing records.
A major shortcoming of earlier analyses using HERBS
was that its spraying data were treated chronologically,
leading to mission flight paths criss-crossing the
country but without showing patterns of which areas were
sprayed over time. The new study's breakthough came when
Stellman, browsing army archives, found another source
of information: the daily logs filed by pilots after
missions. "It was a sort of 'eureka moment' when I
realized that there were 'project' numbers on each of
these reports, and that those numbers vaguely resembled
a couple of columns that we have never put together
before or used," she says. "I just thought, 'Oh my God,
look at this!'."
These columns of numbers included a column called
'missionnum', which, when linked with data in the
'military region' column, matched up with project
numbers kept in the pilots' logs. The logs contained
exactly what HERBS lacked: details of the missions'
targets. The link enabled the team to draw the first
maps of spraying patterns in Vietnam that show precise
localized target zones, and how much herbicide was
sprayed on them and when.
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It fills in
the gaps,
giving an
accurate and
comprehensive
picture of
where spraying
took place
|
|
Alistair Hay
University of
Leeds
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|
It is possible to tell from the maps, for example,
whether individual soldiers or populations were likely
to be present in a particular zone on the day of
spraying and exposed directly, or whether they arrived
later and were exposed indirectly.
The findings are set to provoke a vigorous reaction
both from US veterans' groups - some of which are still
seeking compensation for exposure to Agent Orange - and
the Vietnamese government. Using census data for 20,000
Vietnam hamlets for the first time, the study shows that
at least 3,000 of them were sprayed directly, affecting
between 2 million and 4 million people. The researchers
also plan to publish maps of spraying in relation to US
troop positions.
The model used in the study is "a valid means for
assessing wartime herbicide exposure in Vietnam
veterans", says the Institute of Medicine report,
written by a committee chaired by David Hoel, an
epidemiologist at the Medical University of South
Carolina in Charleston. It commends the team for its
"dogged pursuit of historical records" and recommends
that the Department of Veterans Affairs, which funded
the study, work with other government agencies to
support new epidemiological studies of veterans' health.
Declan Butler is European Correspondent for the
journal Nature |
