WASHINGTONA new evaluation of existing scientific
studies has found "limited or suggestive" evidence to link servicemen’s
wartime exposures to herbicides in Vietnam with the development of acute
myelogenous leukemia (AML) in their children. However, the Institute of
Medicine (IOM) committee that reported the finding emphasized that the evidence
for the association is not conclusive.
"No firm evidence links exposure to the herbicides with
most childhood cancers, but new research does suggest that some kind of
connection exists between AML in children and their fathers’ military service
in Vietnam or Cambodia," said committee chair Irva Hertz-Picciotto, PhD,
professor of epidemiology, University of North Carolina, Chapel Hill.
"Additional studies are needed," she said.
The new report is one of a continuing series of evaluations of
the effect of herbicides on human health. Many of the herbicides used in
Vietnam, particularly the defoliant known as Agent Orange, contained dioxins.
AML accounts for 8% of all childhood cancers. Previous IOM
reports cited "inadequate or insufficient" evidence to show an
association between a father’s exposure and AML or other cancers in the
children of Vietnam veterans.
According to the IOM, labeling the link "limited or
suggestive" means the association is not conclusive enough to preclude
that the finding was the result of chance or other factors, or that the studies
reviewed failed to isolate all the variables that could have affected the
outcome. "Inadequate or insufficient" means the available studies
lacked scientific rigor, consistency, or statistical power to reach even
Some of the studies reviewed by the committee involved US Air
Force and Army personnel who worked with the herbicides. Most of the studies,
however, report the effects of herbicides on civilians who were exposed to the
chemicals on their jobs or in industrial accidents.
Two major studies published in 2000 support the new AML
finding. The two studies lack direct exposure measurements, but they provide
persuasive evidence for several reasons, the IOM committee said.
Researchers conducting both studies used Vietnam veterans and
specifically examined the risk of AMLnot all childhood cancersin their
offspring. Moreover, in both studies, the strongest link was found in children
diagnosed at the youngest ages, "a pattern that suggests that the cause of
a disease stems from a parent," the IOM said.
A third study reviewed by the committee found that AML was more
likely to develop in the children of men who were exposed to pesticides or
herbicides in their work.
The report also reaffirmed earlier IOM findings. It found, for
example, sufficient evidence to link herbicide exposure in Vietnam to the
development in veterans of soft tissue sarcoma, non-Hodgkin’s lymphoma,
Hodgkin’s disease, and chloracne.
Moreover, the committee said, studies continue to provide
"limited and suggestive" evidence of a tie between herbicide exposure
and several other diseases in veterans. These diseases include type 2 diabetes,
respiratory cancers, prostate cancer, and multiple myeloma, as well as spina
bifida in veterans’ children.