THE STATUS OF THE NATIONAL ACADEMY OF SCIENCES RESEARCH EFFORTS REGARDING THE HEALTH EFFECTS OF EXPOSURE TO AGENT ORANGE AND OTHER HERBICIDES USED DURING THE VIETNAM WAR
David A. Butler, Ph.D.
Senior Program Officer
Institute of Medicine
National Academy of Sciences
Subcommittee on National Security, Veterans Affairs and International Affairs
Committee on Government Reform
U.S. House of Representatives
March 15, 2000
Good morning, Mr. Chairman and members of the Committee. My name is David Butler. I am Senior Program Officer in the Division of Health Promotion and Disease Prevention of the Institute of Medicine (IOM). The Institute of Medicine is a private, non-profit organization that provides health policy advice under a congressional charter granted to the National Academy of Sciences. I am happy to be here to discuss the status of IOM's Agent Orange investigations, what has been learned to date and what the future study plans are. The IOM has three ongoing studies related to the evaluation of the health impacts of herbicide and dioxin exposure on Vietnam veterans. I serve as the study director for all three studies, which include:
* the third biennial update of the Review of the Health Effects in Vietnam Veterans of Exposure to Herbicides;
* the Review of Evidence Regarding Link Between Exposure to Agent Orange and Diabetes; and
* Phase III of the Historic Exposure Reconstruction Model for Herbicides in Vietnam.
In response to the request of the committee, I will review the status of these studies, what has been learned to date, and future study plans.
For Vietnam veterans and their families, the issue of Agent Orange exposure has been a source of great anguish. To address these concerns, Congress passed the Agent Orange Act of 1991, which directed the Secretary of Veterans Affairs to request the National Academy of Sciences to do an independent, comprehensive review and critical evaluation of the scientific studies and medical evidence concerning the health effects of herbicide exposure.
This Act prompted the first of three research efforts I will review. The goal of this effort was to establish an agreed-upon base of information from which to proceed to answer specific questions about the health impacts of exposure to herbicides and dioxin. For each disease examined, the committee was asked to determine, to the extent that available data permitted meaningful determinations: 1) whether a statistical association with herbicide exposure exists, taking into account the strength of the scientific evidence and the appropriateness of the statistical and epidemiological methods used to detect the association; 2) the increased risk of the disease among those exposed to herbicides during Vietnam service; and 3) whether there is a plausible biological mechanism or other evidence of a causal relationship between herbicide exposure and the disease.
A committee convened by the Institute of Medicine conducted this review and in 1994 published a comprehensive report entitled Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam. The Agent Orange Act also called for subsequent reviews every two years for a period of ten years from the date of the first report. These reviews were to be comprehensive evaluations of the evidence that had become available since the previous report and reassessments of the committees' determinations. On completion of the 1994 report, successor committees were formed that produced Veterans and Agent Orange: Update 1996 and ...1998.
The third biennial update, which is presently underway, will result in the publication of Veterans and Agent Orange: Update 2000. That report is scheduled to be completed by the end of this year. The future plans for this research effort are to complete the mandate specified in the Act. The committees responsible for these studies evaluate epidemiologic and toxicologic data on exposures to the types of herbicides used in Vietnam, and the contaminant dioxin. The epidemiologic studies comprise three primary categories:
* occupational studies - research on individuals who were exposed as a result of their jobs in for example the chemical industry or agriculture;
* environmental studies - research on individuals who were exposed as a result of some contact in the environment - for example, because of a nearby industrial accident; and
* veterans' studies - research on the health on Vietnam veterans themselves.
Information from all of these sources is considered in drawing conclusions.
In conducting their work, the committees operate independently of the Department of Veterans Affairs and other government agencies. They were not asked to and did not make judgments regarding specific cases in which individual Vietnam veterans have claimed injury from herbicide exposure. The committee was charged with reviewing the scientific evidence rather than making recommendations regarding policy, and their findings are not intended to imply or suggest any policy decisions. Instead, these studies provide scientific information for the Secretary of Veterans Affairs and others to consider as they exercise their responsibilities to Vietnam veterans.
The committees have followed a common approach established by the first committee to summarize their evaluations of the evidence. They have classified diseases into four categories: the first category is "sufficient evidence" of a statistical association between the disease and exposure to herbicides or dioxin; the second, "limited or suggestive evidence"; the third, "inadequate or insufficient" evidence to determine whether an association exists; and the fourth category, "limited, suggestive evidence of no association." Consistent with the mandate of the Agent Orange Act, the distinctions between categories are based on statistical association, not on causality. As a result, the committees have not applied the standard criteria epidemiologists use when judging whether a causal relationship exists between an exposure and a health outcome.
The most recent set of conclusions developed by these committee are contained in the 1998 update of the report series. I am submitting a copy of the Executive Summary of the report as a supplement to the testimony and ask to be included in the record .
Based on their evaluation of the scientific literature, the committee found sufficient evidence of a statistical association between exposure to herbicides or dioxin and three types of cancer: soft tissue sarcoma, non-Hodgkin's lymphoma, and Hodgkin's disease. The committee also found sufficient evidence of an association with chloracne, a skin condition.The committee found limited or suggestive evidence of an association between exposure to herbicides or dioxin and three other types of cancer: respiratory cancers, prostate cancer, and multiple myeloma. They also found limited or suggestive evidence that herbicide or dioxin exposure may be associated with three other conditions: porphyria cutanea tarda, which manifests as a skin disorder; the acute, transient form of peripheral neuropathy, a nerve disorder that can lead to pain, numbness, and weakness in the limbs; and the congenital birth defect called spina bifida, in the children of fathers who were exposed to herbicides. For most of the other
cancers, diseases, and conditions reviewed by the committee, the scientific data were not sufficient to determine whether an association exists.
A second Agent Orange research effort being conducted by the National Academies was prompted by a 1999 request from the Department of Veterans Affairs to call together a committee to conduct an interim review of the scientific evidence regarding one of the conditions addressed in the Veterans and Agent Orange series of reports: Type II diabetes. This disease is also referred to as non-insulin dependent diabetes mellitus and as adult-onset diabetes. The committee convened for this review conducted a workshop and meeting to hear current researchers in the field present information on their ongoing investigations and to review material published since the deliberations of the Update 1998 committee. Although limited to one health outcome, this committee adhered to the format of the update series described above. Their draft report is presently under review. It is expected to be released in May, 2000.
The third research effort underway regarding herbicide exposure in Vietnam was prompted by an observation in the original Veterans and Agent Orange report. The committee responsible for that report observed that one of the greatest problems it encountered in its work was a severe lack of information about the exposure of individual Vietnam veterans to herbicides. Except for particular groups, such as those involved in Operation Ranch Hand and other groups directly involved in spraying operations, information on the extent of herbicide exposure among veterans is practically non-existent. This lack of data is one reason why the National Academies' committees were compelled to focus largely on epidemiologic studies of groups other than Vietnam veterans. They concluded that not enough was known about the exposures of individual veterans to determine to what degree they were or are at risk. Although most veterans probably experienced lower levels of exposure than those who worked with herbicides over long periods in occupational or agricultural settings, it is difficult to determine precisely which veterans may have encountered higher levels.
In 1996, in response to the original committee's observation, the Department of Veterans Affairs (DVA) requested that the National Academies help facilitate the development and evaluation of models of herbicide exposure for use in studies of Vietnam veterans. Specifically, this effort was to: 1) develop a Request for Proposals (RFP) for herbicide exposure research and subject it to external peer review; 2) disseminate the RFP, evaluate the proposals received in response to it, and select one or more academic or other non-governmental groups to develop a model or models; 3) provide scientific oversight of the work of the subcontractor; and 4) evaluate the model(s) developed.
Phase I of the project-development of the Request for Proposals-was completed in 1997. It was comprised of a statement of work, selection criteria, and background information for potential respondents. For Phase II, the National Academies circulated the RFP and invited interested individuals and organizations to submit responses. Committee members thoroughly evaluated the technical and scientific merit of these responses, based on the criteria set forth in the RFP. In March of 1998, they unanimously concluded that a proposal submitted by Professor Jeanne Stellman of the Columbia University School of Public Health and colleagues merited funding. The National Academies and Columbia University subsequently entered into a contract to conduct the work.
The present phase of the project-III- is underway. The research proposed by the Columbia University group is being conducted with the continuing oversight of the committee. Approximately every six months, public meeting are held where reports of research progress are presented. Most recently, in December 1999, the researchers made their eighteen-month progress report. Among their accomplishments, they have assembled a database that is the first easily accessible and cross-referenced comprehensive list of all Army units that were stationed in Vietnam, and the numbers of troops actually assigned to them in Vietnam. The researchers have also created a military unit database that contains the locations of tens of thousands of military units during the war, and have begun to develop and test algorithms and programs for describing and analyzing the movement of mobile battalions and their elements. They are continuing the work of compiling data on airborne and ground spraying of herbicides, and of developing models for estimating exposure to herbicides. Present plans call for the research to be completed by the end of 2001.
These three research efforts comprise the work on Agent Orange issues presently being supported at the National Academies.
As was said in the first report on veterans and Agent Orange, the committee's responsible for these research efforts know their reports will not end the controversy over the health effects. But we hope these additional findings will lead to better understanding of the questions that remain, and the steps we must take to answer them.
Thank you for your attention. I would be happy to answer your questions.
The Executive Summary is available on the web at: http://books.nap.edu/html/update98/
The entire Update 1998 report may be accessed at: http://www.nap.edu/books/0309063264/html/