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Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
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1

Introduction

In 1991, Congress passed Public Law 102-4, the Agent Orange Act of 1991, which directed the Secretary of Veterans Affairs to contract with the National Academy of Sciences (NAS) to conduct an independent review of scientific information regarding the association, if any, between health outcomes and exposure to dioxin or other chemical compounds in the herbicides that were sprayed in Vietnam. According to that legislation, any “veteran who, during active military, naval, or air service, served in the Republic of Vietnam during the Vietnam era [January 9, 1962–May 7, 1975, for compensation purposes] . . . shall be presumed to have been exposed during such service to an herbicide agent” and “whenever the Secretary [of Veterans Affairs] determines . . . that a positive association exists between the exposure of humans to an herbicide agent and the occurrence of disease in humans, the Secretary shall prescribe regulations providing that a presumption of service connection is warranted.” With the passage of time, the straightforward interpretation of this legislation—that a “Vietnam veteran” who contracts a disease that has been determined to be associated with herbicide exposure would be eligible for compensation benefits—has been subjected to a number of challenges. The presumption of exposure to herbicides has been extended to veterans who served in the Korean demilitarized zone any time between April 1, 1968, and August 1, 1971. Another dispute has surrounded the eligibility of naval veterans from the Vietnam era; resolution of this issue by the US Department of Veterans Affairs (VA) has been that individuals who served on ships when they operated on Vietnam’s inland waterways (the Brown Water Navy) are considered eligible, whereas other era veterans (the Blue Water Navy) are eligible only if they can establish that they had “boots on the ground” in Vietnam. The current claims of the US Air Force (AF) Reservists who served in

Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
×

the United States in 1972–1982 on Fairchild UC-123 Provider aircraft that earlier had sprayed herbicides in Vietnam constitute yet another challenge concerning eligibility under the Agent Orange Act of 1991.

From 1972 to 1982, approximately 1,500–2,100 AF Reserve personnel trained and worked on UC-123 aircraft, of which about 30 formerly had been used to spray herbicides in Vietnam as part of Operation Ranch Hand (ORH) (USAF, 2009a,b; Young and Young, 2013a). ORH missions sprayed the herbicides picloram and cacodylic acid, and chemical formulations that contained the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T); 2,4,5-T contained 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin), an unintended contaminant that was later determined to be a human carcinogen. Results of air and wipe samples taken between 1979 and 2009 by the AF (or its contractors) from the aircraft formerly used in ORH (ORH C-123s) indicate that residual chemicals from the Agent Orange (AO) and other herbicides that were sprayed in Vietnam remained on the interior of some of the aircraft. In 2012, the USAF School of Aerospace Medicine conducted an exposure assessment to quantify the potential exposure to AO by the AF Reserve personnel or passengers who flew on the C-123 aircraft in the United States, and determined that AO exposures “were unlikely to have exceeded acceptable regulatory standards or to have predisposed persons . . . to experience future adverse outcomes” (USAF, 2012a).

The VA Office of Public Health interpreted these findings to mean that “the existing scientific studies and reports support a low probability that TCDD was biologically available in these aircraft. Therefore, the potential for exposure to TCDD from flying or working in contaminated C-123 aircraft years after the Vietnam War is unlikely to have occurred at levels that could affect health” (VA, 2014). Because of lingering concerns among AF Reserve personnel about the potential for adverse health outcomes as a result of their service aboard C-123 aircraft that were formerly used in Vietnam to spray defoliants, the VA requested that the Institute of Medicine (IOM) conduct a review of the available C-123 sampling data, compare the data to existing exposure safety guidelines, and make a determination about the potential for exposure to the residual chemicals by C-123 personnel and associated concerns regarding possible adverse health consequences.

CHARGE TO THE COMMITTEE

In early 2014, the VA contracted with the IOM to conduct a study to determine whether or not crew members who flew C-123 aircraft that had previously been used to spray herbicides in Vietnam, had exposures that could have been detrimental to their health. In response, the IOM assembled an expert committee (see Appendix C for the committee member biographies) to determine whether there had been exposures that could lead to excess risk of adverse health out-

Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
×

comes among AF Reserve personnel who flew in and/or maintained C-123 aircraft (outside of Vietnam) that had previously been used to spray AO in Vietnam. The committee was asked to

  • evaluate the reliability (including representativeness, consistency, methods used) of the available information for establishing exposure; and
  • address and place in context (qualitatively by comparison to established exposure guidelines) whether any documented residues represent potentially harmful exposure by characterizing the amounts available and the degree to which absorption might be expected.

The possible health effects were to be those characterized in prior IOM Veterans and Agent Orange (VAO) reports, and they were not to be reassessed for this report. VAO committees to date have found the information concerning the exposure of Vietnam veterans inadequate to establish dose–response relationships for individual health outcomes or to quantify the risk of a particular veteran experiencing any adverse effects from such exposures. In any event, the possibility of an increase in the risk of any adverse health condition is the outcome to be assessed in this report.

THE COMMITTEE’S APPROACH TO ITS CHARGE

One of the fundamental differences between this report and prior IOM reports that have focused on other veteran cohorts—Vietnam veterans, Blue Water Navy veterans, and so on—is in the existence of exposure data that are relevant to the population of interest. The primary focus of this committee’s deliberations is on the results of air and wipe sampling data, collected between 1979 and 2009, from ORH C-123 aircraft that were used by the AF Reserve personnel between 1972 and 1982. These samples were analyzed for the phenoxy herbicides and the TCDD-contaminant of 2,4,5-T. Sampling data from 1979, 1994, 1996, and 2009—in the form of laboratory reports, internal USAF reports and memorandums, or data reports—were provided to the committee by the VA at the beginning of this effort. Additional sampling results from 1996 were transmitted from the VA to the committee after the IOM staff inquired about the existence of additional samples that were referred to in an article critique (Nieman, 2014) but not received by the committee. In reviewing all the available sampling data, the committee evaluated the sampling methods, laboratory procedures and protocols, and assumptions, to the extent that information in the documents permitted such assessment.

From among the materials provided by the VA, the committee reviewed independent interpretations of the USAF C-123 sampling data authored by entities associated with the military, representatives of the Agency for Toxic Substances and Disease Registry (ATSDR) and the National Institute of Environmental

Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
×

Health Sciences (NIEHS), and several independent researchers. The committee also spent considerable time in evaluating a recently published paper by Lurker et al. (2014) that used the available C-123 sampling data to derive quantitative estimates of the exposure of the AF Reservists.

The committee held a public workshop to gather additional information and to hear from veterans and veterans service organizations, representatives of the VA, researchers, and other interested parties (see Appendix A for all open session agendas). This open session gave members of the committee an opportunity to learn more about the use of C-123s both in Vietnam and afterward by the AF Reserve personnel and related issues. Before the workshop, the committee distributed a list of questions to workshop participants that focused on issues pertaining to post-Vietnam handling and use of the C-123s by the AF Reserve personnel, collection and analysis of air and wipe samples from ORH C-123s, modeling efforts that used the existing sampling data, and interpretations of resulting exposure estimates. Participants were asked to address these questions in writing and during their presentations to the committee, and their submissions and later discussions formed the basis of in-depth panel discussions and question and answer sessions during the public workshop.

In fulfilling its charge, the committee evaluated numerous documents submitted by the VA, the C-123 Veterans Association, individual veterans, and other interested parties; and it collected relevant data from published journal articles and technical guidelines derived by authoritative international bodies, such as the World Health Organization and the US Environmental Protection Agency. In addition to information pertaining to the sampling data, the VA gave the committee an extensive collection of possibly pertinent documents, including published papers, technical exposure guidelines, internal AF memos and reports, National Institute for Occupational Safety and Health (NIOSH) reports, early exposure reports from the NAS, and photographs. The C-123 Veterans Association and other interested parties provided historical records and personal accounts of their service aboard C-123s during their AF Reserve careers, C-123 procedure manuals, examples of aircraft logs, and flight information from air squadrons and the AF Reserve bases. The committee has cited these materials extensively in its report and has provided copies of the referenced materials to the Public Access Records Office of the National Academies. They can be accessed by emailing PARO@nas.edu or calling 202-334-3543.

The committee faced several challenges during the course of its deliberations. Much of the information that the committee reviewed was anecdotal in nature and so was difficult to verify with historical documentation. A great deal of the historical information provided to the committee was in the form of memorandums and other personal correspondence, so it was difficult or impossible to acquire more specific information, especially that related to details of the AF sampling efforts, such as sampling strategies, collection procedures, and laboratory testing or analysis or to work profiles for the AF Reservists. The committee

Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
×

evaluated all of the available documentation with some skepticism, inasmuch as the likelihood of bias could not be completely ruled out.

ORGANIZATION OF THE REPORT

The remainder of this report is organized into four more chapters and three appendixes. Chapter 2 contains basic background information on the chemical properties of TCDD and a compilation of health guidelines for this compound and consideration of their applicability to the experience of the AF Reservists for use in putting the available sampling data in context. Information about the use of C-123 aircraft in Vietnam and their later use by AF Reserve personnel in the United States and the collection of air and wipe samples from some of these aircraft between 1979 and 2009, are discussed in Chapter 3. Chapter 4 reviews interpretations of those sampling results by the AF and individuals in the dioxin research community. It also evaluates exposure models applied to the C-123 sampling data in Lurker et al. (2014), addresses the plausibility that residues measured on internal surfaces could have been absorbed into the bodies of the AF Reservists, and discusses the committee’s thoughts about how the available information relates to international exposure guidelines. A compilation of the committee’s findings is presented in Chapter 5.

Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
×
Page 11
Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
×
Page 12
Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
×
Page 13
Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
×
Page 14
Suggested Citation:"1 Introduction." Institute of Medicine. 2015. Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft. Washington, DC: The National Academies Press. doi: 10.17226/18848.
×
Page 15
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From 1972 to 1982, approximately 1,500-2,100 US Air Force Reserve personnel trained and worked on C-123 aircraft that had formerly been used to spray herbicides in Vietnam as part of Operation Ranch Hand. After becoming aware that some of the aircraft on which they had worked had previously served this purpose, some of these AF Reservists applied to the US Department of Veterans Affairs (VA) for compensatory coverage under the Agent Orange Act of 1991. The Act provides health care and disability coverage for health conditions that have been deemed presumptively service-related for herbicide exposure during the Vietnam War. The VA denied the applications on the basis that these veterans were ineligible because as non-Vietnam-era veterans or as Vietnam-era veterans without "boots on the ground" service in Vietnam, they were not covered. However, with the knowledge that some air and wipe samples taken between 1979 and 2009 from some of the C-123s used in Operation Ranch Hand showed the presence of agent orange residues, representatives of the C-123 Veterans Association began a concerted effort to reverse VA's position and obtain coverage.

At the request of the VA, Post-Vietnam Dioxin Exposure in Agent Orange-Contaminated C-123 Aircraft evaluates whether or not service in these C-123s could have plausibly resulted in exposures detrimental to the health of these Air Force Reservists. The Institute of Medicine assembled an expert committee to address this question qualitatively, but in a scientific and evidence-based fashion. This report evaluates the reliability of the available information for establishing exposure and addresses and places in context whether any documented residues represent potentially harmful exposure by characterizing the amounts available and the degree to which absorption might be expected. Post-Vietnam Dioxin Exposure rejects the idea that the dioxin residues detected on interior surfaces of the C-123s were immobile and effectively inaccessible to the Reservists as a source of exposure. Accordingly, this report states with confidence that the Air Force Reservists were exposed when working in the Operation Ranch Hand C-123s and so experienced some increase in their risk of a variety of adverse responses.

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