Date: April 19, 2001 Contacts: Saira Moini, Media Relations Officer Kathi McMullin, Media Relations Assistant (202) 334-2138; e-mail <email@example.com>
FOR IMMEDIATE RELEASE
New Review Suggests Possible Association Between Agent Orange and Form of Childhood Leukemia
WASHINGTON -- New evidence supports the possibility of an association between chemicals used in herbicides during the Vietnam War and the development of a form of leukemia in veterans' children, but it stops short of establishing a direct connection, says a new report from the Institute of Medicine (IOM) of the National Academies. The report is the latest in a series examining the impact of Agent Orange on human health.
Using the most recent scientific data, the committee that wrote the report evaluated whether veterans' exposure to the chemical defoliant Agent Orange and other herbicides used in Vietnam, some of which contained dioxin, is linked with the development of several types of cancer and other health problems in veterans and their children. The evaluation revealed new "limited or suggestive" evidence of an association with acute myelogenous leukemia (AML) in veterans' children, but the finding is not conclusive. Previous IOM reports found "inadequate or insufficient" evidence to determine whether a link existed for AML or other cancers in the children of veterans.
Leukemia is the most common type of childhood cancer. Acute myelogenous leukemia is a rapidly spreading form that originates in certain bone marrow cells. The disease accounts for about 8 percent of all childhood cancers. Little is known about what causes such diseases in children, how parental chemical exposures affect their offspring, or potential environmental risk factors for kids, the report notes.
"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, professor of epidemiology, University of North Carolina, Chapel Hill. "Additional studies are needed to shed more light on the issue."
Classifying evidence as "limited or suggestive" means that while there is evidence suggestive of an association between exposure and disease, it is not conclusive enough to say definitively that chance or other factors did not influence the results of the studies that were evaluated, or that the studies have isolated all of the variables that could have affected the outcome. A classification of "inadequate or insufficient" indicates that available studies lack the scientific rigor, consistency, or statistical power necessary to draw even tentative conclusions.
The ability of researchers to pinpoint the health risks faced by veterans is hampered by inadequate information about exposure levels of troops in Vietnam. Some of the evidence reviewed by the committee came from evaluations of U.S. Air Force and Army troops who worked with herbicides. Most information, however, was from studies of civilians who were exposed to herbicides on the job or in industrial accidents. Although most veterans probably experienced lower levels of exposure than people who worked with the chemicals over long periods in occupational or agricultural settings, it is difficult to say precisely which troops may have been exposed to higher levels.
A review of current literature, which included two major studies published last year, supported the new finding about AML, the committee said. Although the two key studies lacked direct measures of exposure, the research was persuasive for several reasons. For example, both studies were conducted with Vietnam veterans, and the associations were specifically with AML -- and not other forms of childhood leukemia. In addition, the strongest link was seen in children diagnosed at the youngest ages, a pattern that suggests that the cause of a disease stems from a parent. A third study found that the development of AML was more likely in the children of men who used pesticides or herbicides in their work.
The committee's congressionally mandated report also reaffirms earlier findings. There is sufficient evidence of a link between exposure and the development of soft-tissue sarcoma, non-Hodgkin's lymphoma, Hodgkin's disease, and chloracne in veterans. Additionally, scientific studies continue to offer "limited or suggestive" evidence of an association with other diseases in veterans -- including Type 2 diabetes, respiratory cancers, prostate cancer, and multiple myeloma -- as well as the congenital birth defect spina bifida in veterans' children.
U.S. forces sprayed Agent Orange and other defoliants over parts of south Vietnam and Cambodia beginning in 1962. Most large-scale sprayings were conducted from airplanes and helicopters, but considerable quantities of herbicides were dispersed from boats and ground vehicles or by soldiers wearing back-mounted equipment. A 1969 scientific report concluded that one of the primary chemicals used in Agent Orange could cause birth defects in laboratory animals. The U.S. military therefore suspended the use of Agent Orange in 1970 and halted all herbicide spraying in Vietnam the following year.
The committee's work was sponsored by the U.S. Department of Veterans Affairs. The Institute of Medicine is a private, nonprofit institution that provides health policy advice under a congressional charter granted to the National Academy of Sciences. A committee roster follows. Read the full text of Veterans and Agent Orange: Update 2000for free on the Web, as well as more than 1,800 other publications from the National Academies. Printed copies are available for purchase from the National Academy Press Web site or by calling (202) 334-3313 or 1-800-624-6242. Reporters may obtain a pre-publication copy from the Office of News and Public Information (contacts listed above).
INSTITUTE OF MEDICINE Board on Health Promotion and Disease Prevention
Committee to Review the Health Effects in Vietnam Veterans of Exposure to Herbicides
Irva Hertz-Picciotto, Ph.D. (chair) Professor Department of Epidemiology School of Public Health, and Fellow Carolina Population Center University of North Carolina Chapel Hill
Margit L. Bleecker, M.D., Ph.D. Director Center for Occupational and Environmental Neurology The Children's Hospital Center for Reconstructive Surgery Baltimore
Thomas A. Gasiewicz, Ph.D. Deputy Director Environmental Health Sciences Center, and Professor of Environmental Medicine Department of Environmental Medicine School of Medicine University of Rochester Rochester, N.Y.
Tee L. Guidotti, M.D., M.P.H. Professor and Chair Department of Environmental and Occupational Health School of Public Health and Health Services, and Director Division of Occupational Medicine Department of Medicine School of Medicine George Washington University Washington, D.C.
Robert F. Herrick, Ph.D., C.I.H., Sc.D. Lecturer on Industrial Hygiene Department of Environmental Health Harvard School of Public Health Boston
David G. Hoel, Ph.D.* Distinguished University Professor Department of Biometry and Epidemiology, and Associate Director Hollings Oncology Center Medical University of South Carolina Charleston
Loren D. Koller, D.V.M., Ph.D.* Professor College of Veterinary Medicine Oregon State University Corvallis
Howard Ozer, M.D., Ph.D. Eason Chair; Chief of the Hematology/Oncology Section; Director of the Cancer Center; and Professor of Medicine University of Oklahoma Oklahoma City
John J. Stegeman, Ph.D. Senior Scientist and Chair Department of Biology Redfield Laboratory Woods Hole Oceanographic Institution Woods Hole, Mass.
David S. Strogatz, Ph.D., M.S.P.H. Associate Professor and Chair Department of Epidemiology School of Public Health State University of New York Albany, and Adjunct Professor Department of Epidemiology University of North Carolina Chapel Hill