• Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam (1994)
• Veterans and Agent Orange: Update 2000
• Veterans and Agent Orange: Update 2002

Veterans and Agent Orange 1994

The committee was asked to make recommendations concerning the need, if any, for additional scientific studies to resolve areas of continuing scientific uncertainty concerning the health effects of the herbicides used in Vietnam.  Based on its review of the available epidemiologic evidence and a consideration of the quality of exposure information available in existing studies, especially of Vietnam veterans, the committee concluded that a series of epidemiologic studies of veterans could yield valuable information if a new, valid exposure reconstruction model could be developed.  The committee also sees value in continuing the existing Ranch Hand study and expanding it to include Army Chemical Corps veterans.  The committee’s research recommendations emphasize studies of Vietnam veterans, rather than general toxicologic or epidemiologic studies of occupationally or environmentally exposed populations.  A substantial amount of research on the toxicology and epidemiology of herbicides and herbicide components is already under way in the United States and abroad.  Indeed, many of the studies on which the committee’s conclusions are based have been published since 1991.  Although not targeted specifically to Vietnam veterans, it is likely that this research will also contribute to the knowledge of potential health effects in this population.

The committee makes the following recommendations regarding epidemiologic studies of Vietnam veterans.

Recommendation 1.The committee endorses continued follow-up of the Air Force Ranch Hand cohort and its comparison group, and recommends that members of the Army Chemical Corps and an appropriate comparison group be followed in a similar study.  An independent, nongovernmental scientific panel should be established to review and approve a new, expanded research protocol for both study populations, and to commission and direct a common analysis of the results. 

Recommendation 2. The Department of Defense and the Department of Veterans Affairs should identify Vietnam service in the computerized index of their records. 

Recommendation 3. Biomarkers for herbicide exposure should be developed further.

Recommendation 4. A nongovernmental organization with appropriate experience in historical exposure reconstruction should be commissioned to develop and test models of herbicide exposure for use in studies of Vietnam veterans

Update: In 2003, IOM established a committee to oversee the development and evaluation of a model of wartime herbicide exposure for use in studies of Vietnam veterans, see link.

Recommendation 5. The exposure reconstruction models developed according to Recommendation 4 should be evaluated by an independent, nongovernmental scientific panel established for this purpose.

Update: The model of wartime herbicide exposure called for in Recommendation 4 was evaluated by an independent panel, as documented in report, see link.

Recommendation 6.  If the scientific panel proposed in Recommendation 5 determines that a valid exposure reconstruction model is feasible, the Department of Veterans Affairs and other government agencies should facilitate additional epidemiologic studies of veterans.

Mandated Research Efforts

For the purposes of further research on the health effects of Vietnam service, Public Law 102-4 mandates that the DVA establish four specific programs that are subject to initiation, continuance, or discontinuation, depending on the findings of this IOM report, and the committee is charged with making recommendations about these specific mandates.  The DVA has no specific plans for any of these research efforts beyond the minimal descriptions given in the law, so the committee is able to comment on them in only the broadest terms.

The committee’s recommendations speak to its legislative mandate to determine “the feasibility of conducting additional scientific research on” health hazards resulting from exposure to dioxin and herbicides used in Vietnam, the research mandate in section 8 of Public Law 102-4.  As previously stated, the committee feels that a series of epidemiologic studies of  veterans could yield valuable information if a new, valid exposure reconstruction model can be constructed. 

Section 6 of Public Law 102-4 requires the DVA to “compile and analyze, on a continuing basis, all clinical data” that (1) are obtained in connection with DVA examinations and treatment of Vietnam veterans, and (2) are likely to be scientifically useful in determining the association between disabilities experienced by these veterans and exposure to dioxin or herbicides.  Such a system, called the Agent Orange Registry (see Chapter 2), currently exists.  Section 7 of the law calls for the establishment of a system for the collection and storage of voluntarily contributed samples of blood and tissue of veterans who served in Vietnam.  Balancing the strengths and weaknesses of stored biological samples and clinical data for research purposes, the committee feels that systems of this sort have scientific value, but only to the extent that they are components of specific, well-designed studies; see, for instance, National Research Council (1991).  In the absence of a clear study design to guide such activities, and without resolution of important design, quality control, and ethical issues regarding tissue banks, the committee does not recommend the establishment at this time of the clinical data and tissue archiving systems described in sections 6 and 7 of the law

Veterans and Agent Orange: Update 2000

Although great strides have been made over the past several years in under-standing the health effects of exposure to the herbicides used in Vietnam and dioxin, and in elucidating the mechanisms underlying these effects, there are still important gaps in our knowledge. Subsequent chapters of this report contain recommendations for further work addressing some specific research needs identified in the course of this study. Additional observations on one major research effort are offered below.

The Air Force Health Study (AFHS) is an epidemiologic study whose purpose is to determine whether exposure to the herbicides used in Vietnam may be responsible for any adverse health conditions observed in a cohort of Air Force personnel responsible for conducting aerial spray missions (the Ranch Hands). A baseline morbidity study of the Ranch Hands and a matched comparison cohort was conducted in 1982, with follow-up assessments in 1985, 1987, 1992, and 1997. In accordance with the study protocol, one additional assessment is planned for 2002, after which a final report will be issued.

Because this study represents one of the few primary sources of information on the health of Vietnam veterans and is coming close to its scheduled end, the committee believes it is timely to offer some observations and recommendations about it.

The AFHS cohorts represent an unusually thoroughly studied population. Some of the data generated in the course of the study are already or soon will be available to the public. However, there are also medical records and biological specimens that are not amenable to such public disclosure. The committee believes there is scientific merit in retaining and maintaining these medical records and samples, so that—with proper respect for the privacy of the study participants—they could be available for future research. It therefore recommends that the federal government examine whether and how the various forms of data and specimens collected in the course of the Air Force Health Study could be retained and maintained, and what form of oversight should be established for their future use. The committee further recommends that consideration be given to whether it is appropriate to continue the study past its planned completion date. It notes that the AFHS cohorts are only now reaching the age where several health out-comes of interest may be expected to manifest. The committee cannot draw a conclusion on whether or not a continuation of research on the AFHS cohorts will inform specific questions regarding the health effects of exposure to the herbicides used in Vietnam. However, the committee’s judgment is that continued research on the health of the Ranch Hand and comparison veterans is likely to yield important information on the determinants of health and disease in males who served in the military during the Vietnam era and perhaps their offspring. If the records were to be retained and maintained and/or the research continued, this would have to be done with the full knowledge and consent of the AFHS population and be subject to controls that would respect the privacy of the participants.

Veterans and Agent Orange: Update 2002

Great strides have been made over the last several years in understanding the health effects of exposure to the herbicides used in Vietnam and in elucidating the mechanisms underlying the effects, but there are still important gaps in our knowledge. On the basis of its review of the epidemiologic evidence and consideration of the quality of exposure information available in existing studies, especially of Vietnam veterans, the present committee concludes that continuation of epidemiologic studies of veterans could yield valuable information, especially as the Vietnam-veteran population ages and as a new exposure-reconstruction model is developed and validated. The committee sees value in continuing the Air Force Health Study (AFHS), expanding studies of Army Chemical Corps veterans, and following the experience of Vietnam veterans as they age, with emphasis on diseases associated with aging. Continued study of other exposed cohorts (for example, the cohort studied by the National Institute for Occupational Safety and Health) could also provide information on diseases of aging.

The AFHS is an epidemiologic study whose purpose is to determine whether exposure to the herbicides used in Vietnam might be responsible for any adverse health conditions observed in a cohort of Air Force personnel responsible for conducting aerial spray missions (the Ranch Hands). Five health assessments have been conducted, and, in accordance with the study protocol, one additional assessment is under way and will be completed in April 2003. The AFHS is one of the few primary sources of information on the health of Vietnam veterans. An assessment of herbicide exposure of the AFHS participants and other Vietnam veterans is under revision, and more accurate and precise data are expected in the near future. In addition, the AFHS cohorts are now reaching the age where several health outcomes of interest may be expected to manifest, such as cancers and diseases related to aging. Therefore, the committee recommends continuing the study past its planned completion date. The committee further recommends retaining and maintaining medical records and samples on the AFHS cohort so that—with proper respect for the privacy of the study participants—they could be available for future research. It also recommends that the federal government examine whether and how the various forms of data and specimens collected in the course of the AFHS could be retained and maintained and what form of oversight should be established for their future use.

Members of the Army Chemical Corps constitute the largest cohort of Vietnam veterans exposed directly to the herbicides, and preliminary studies on this cohort have demonstrated increased 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) concentrations in Army Chemical Corps veterans who reported spraying herbicides as part of their duties. Some research on the health effects in this population has been and is being conducted. The committee recommends continued and expanded long-term study of this cohort.

Veterans have raised concerns about glioblastomas and possibly astrocytomas. The committee considers those tumors worthy of further investigation despite previous evidence of no association. They are extremely rare tumors, and investigating them in epidemiologic studies is difficult. Recording or monitoring trends in those tumors, as well as other diseases of aging, in Vietnam veterans could be useful for indicating which diseases might warrant further study.

The committee is aware that an assessment of herbicide exposure of Vietnam veterans is nearing completion. That assessment should provide more accurate and precise data on the potential exposure of individuals to herbicides sprayed in Vietnam, and the data could be used in epidemiologic studies to increase their power to detect health effects associated with exposure to the herbicides in Vietnam. In light of the anticipated availability of this database, it is even more important to continue research into the health effects of the herbicides in Vietnam veterans themselves, making use of this potentially valuable tool. The federal government should consider the its actions that might best facilitate such research and ensure the scientific validity of any such studies of Vietnam veterans.

Another population that has been understudied is the Vietnamese. Anecdotal evidence and studies published in non-English-language journals suggest an array of long-term health effects that are potentially related to the chemicals used by US troops in Vietnam. Although collaborative research by scientists in the two countries presents challenges, such research has the potential to fill a number of gaps in our understanding of the long-term health consequences of exposures to TCDD and herbicides used in Vietnam. The committee supports steps that would continue development of a collaborative programs of research. The possibility of using the newly established exposure database for assessing exposures of the Vietnamese also warrants consideration.