Veterans and Agent Orange Update 2010 (2012) / Chapter Skim
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1 Introduction
1 Introduction
Pages 14-30
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From page 14... ...
NAS also was asked to recommend, as ap propriate, additional studies to resolve continuing scientific uncertainties and to comment on particular programs mandated in the law. In addition, the legislation called for biennial reviews of newly available information for a period of 10 years; the period was extended to 2014 by the Veterans Education and Benefits Expansion Act of 2001 (PL 107-103)
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From page 15... ...
associated with parental exposure to any of the chemicals of interest; its review of the literature, including literature available since the review for Update 2000, was published as Veterans and Agent Orange: Herbicide/Dioxin Exposure and Acute Myelogenous Leukemia in the Children of Vietnam Veterans, hereafter referred to as Acute Myelogenous Leukemia (IOM, 2002)
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From page 16... ...
In accord with its charge, the committee examined a variety of indicators appropriate for the task, including factors commonly used to evaluate statistical associations, such as the adequacy of control for bias and confounding and the likelihood that an observed association could be explained by chance; and it assessed evidence concerning biologic plausibility derived from laboratory findings in cell-culture or animal models. The full array of indicators examined was used to categorize the strength of the evidence.
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From page 17... ...
Hodgkin's disease Chloracne Limited or Suggestive Evidence of Association Epidemiologic evidence suggests an association between exposure to herbicides and the outcome, but a firm conclusion is limited because chance, bias, and confounding could not be ruled out with confidence.b For example, a well-conducted study with strong findings in accord with less compelling results from studies of populations with similar exposures could constitute such evidence. There is limited or suggestive evidence of an association between exposure to the chemicals of interest and the following health outcomes: Laryngeal cancer Cancer of the lung, bronchus, or trachea Prostate cancer Multiple myeloma AL amyloidosis Early-onset transient peripheral neuropathy Porphyria cutanea tarda Parkinson's disease (category change from Update 2006)
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From page 18... ...
Cancers at other and unspecified sites Infertility Spontaneous abortion (other than for paternal exposure to TCDD, which appears not to be associated) b Neonatal or infant death and stillbirth in offspring of exposed people Low birth weight in offspring of exposed people Birth defects (other than spina bifida)
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From page 19... ...
on points that arise during deliberations but especially to hear from individual Vietnam veterans and others concerned about aspects of their health experience that may be service-related. The present committee was pleased by the response to its invitation, which had been circulated by VA, to the primary such session held in Chicago.
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From page 20... ...
. Third Meeting, Albuquerque Glioblastomas: The available evidence concerning cancers of the brain and • herbicide exposure is discussed in Chapter 7.
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From page 21... ...
The original VAO committee addressed the statutory mandate to evaluate the association between herbicide exposure and a given health effect by assigning each of the health outcomes under study to one of four categories on the basis of the epidemiologic evidence reviewed. The categories were adapted from the ones used by the International Agency for Research on Cancer in evaluating evidence of the carcinogenicity of various substances (IARC, 1977)
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From page 22... ...
Experimental data supporting biologic plausibility strengthen evidence for an association, but are not a prerequisite. The original VAO committee found sufficient evidence of an association between exposure to herbicides and three cancers -- soft-tissue sarcoma, nonHodgkin lymphoma, and Hodgkin lymphoma -- and two other health outcomes, chloracne and porphyria cutanea tarda (PCT)
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From page 23... ...
The committee for Update 2000 was reconvened to re-evaluate the previously reviewed and new literature regarding AML, and it produced Acute Myelogenous Leukemia, which reclassified AML in children from "limited or suggestive evidence of an association" to "inadequate or insufficient evidence to determine an association." After reviewing the data reviewed in previous VAO reports and recently published scientific literature, the committee responsible for Update 2006 determined
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From page 24... ...
The committee for Update 2000 had partitioned AML in the offspring of Vietnam veterans from other childhood cancers and put it into the category of suggestive evidence; but a separate review, as reported in Acute Myelogenous Leukemia, found errors in the published information and returned it to this category with other childhood cancers. In Update 2002, CLL was moved from this category to join Hodgkin and non-Hodgkin lymphomas in the category of sufficient evidence of an association.
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From page 25... ...
Determining Increased Risk in Vietnam Veterans The second part of the committee's charge is to determine, to the extent permitted by available scientific data, the increased risk of disease among people exposed to herbicides or the contaminant TCDD during service in Vietnam. Previous reports pointed out that most of the many health studies of Vietnam veterans were hampered by relatively poor measures of exposure to herbicides
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From page 26... ...
The committees that produced VAO and the updates found that the body of evidence was sufficient for reaching conclusions about statistical associations between herbicide exposures and health outcomes but that the lack of adequate data on Vietnam veterans themselves complicated consideration of the second part of the charge. The evidence of herbicide exposure among various groups studied suggests that although some had documented high exposures (such as participants in Op eration Ranch Hand and Army Chemical Corps personnel)
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From page 27... ...
In updates before Update 2008, a considerable amount of detail had been provided about individual newly published toxicology studies; the current committee concurs with the decision made by the last committee that it would be more informative for the general reader to provide integrated toxicologic profiles for the chemicals of interest by interpreting the underlying experimental findings. When there are specific toxicologic findings pertinent to a particular health outcome, they are discussed in the chapter reviewing the epidemiologic literature on that condition.
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From page 28... ...
Chapter 9 addresses neurologic disorders. Early-onset peripheral neuropathy is a condition long recognized as a response to herbicide exposure that is manifested shortly after exposure but unlikely to be a response that arises for the first time decades after exposed people leave Vietnam; the discussion of evidence on this short-term response has been taken from Chapter 9 and placed in Appendix B, with the information on chloracne and porphyria cutanea tarda, which are also short-term responses presumptively associated with herbicide exposure.
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From page 29... ...
2002. Veterans and Agent Orange: Herbicide/Dioxin Exposure and Acute Myelogenous Leu kemia in the Children of Vietnam Veterans.
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From page 30... ...
2006. Health status of Army Chemical Corps Vietnam veterans who sprayed defoliant in Vietnam.
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