Veterans and Agent Orange Update 2012 (2014) / Chapter Skim
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14 Conclusions and Recommendations
14 Conclusions and Recommendations
Pages 936-947
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From page 936... ...
, which take into account exposure to all dioxin-like chemicals, or because their findings consisted of observations on the aging population of primary concern, Vietnam veterans. The committee also notes that experimental data related to biologic plausibility of health conditions statistically associated with exposure to the components of Agent Orange have gradually emerged since the beginning of this series of VAO reports.
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Spina bifida in offspring of exposed people Inadequate or Insufficient Evidence to Determine an Association The available epidemiologic studies are of insufficient quality, consistency, or statistical power to permit a conclusion regarding the presence or absence of an association. For example, studies fail to control for confounding, have inadequate exposure assessment, or fail to address latency.
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From page 938... ...
Cancers at other and unspecified sites Infertility Spontaneous abortion (other than after paternal exposure to TCDD, which appears not to be associated) 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 939... ...
current committee did not modify the criteria used by previous VAO committees to assign categories of association to particular health outcomes, but decided to refer to the object of its evaluation as "scientifically relevant association" in the title of Table 14-1 to clarify that the strength of evidence evaluated, based on the quality of the scientific studies reviewed, was a fundamental component of the committee's deliberations to address the imprecisely defined legislative target of "statistical association." On the basis of its evaluation of Vietnam veterans, occupational, and environmental studies, the committee assigned each health outcome to one of four categories of relative certainty of association with exposure to the herbicides that were used in Vietnam or to any of their components or contaminants (with no intention of specifying particular chemicals)
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The committee for Update 2010 offered a high-priority recommendation that research be undertaken to address chronic obstructive pulmonary disease (COPD) from a morbidity perspective with appropriate functional diagnosis of COPD and collection of data to permit adjustment for smoking and other relevant confounders; the current committee is pleased to note that VA has started such a study on its Army Chemical Corps (ACC)
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From page 941... ...
Linking that information with the VA electronic medical-record and associated administrative databases, such as discharge-diagnosis and pharmacy-use records, should make it possible to assemble epidemiologic information on common health conditions for evaluation of possible associations with military service in Vietnam. Particular attention should be paid to the feasibility of conducting epidemiologic studies of conditions that have been noted to be of special interest but on which the current evidence is inadequate or insufficient to determine whether there is an association with herbicide exposure, such as COPD, brain cancer, tonsil cancer, melanoma (with particular attention given to ocular types)
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From page 942... ...
Distillation of existing data could be enhanced by incorporating new results derived from assays of the biologic samples. For example, analysis of banked semen samples for epigenetic markers on sperm DNA and measurement of TCDD in seminal fluid, particularly in comparison with the subjects' serum TCDD concentrations, could provide insight into the likelihood of male Vietnam veterans' transmitting effects to their offspring, as well as supplementing general knowledge on paternal transmission.
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From page 943... ...
Previous VAO committees recommended that VA conduct additional studies of ACC veterans because the population presents a unique opportunity to examine the association between health effects of exposure to TCDD and the herbicides used in Vietnam. Recently, VA launched the Army Chemical Corps Vietnam-Era Veterans Health Study to investigate the relationship between herbicide exposure during the Vietnam War and hypertension and COPD in ACC veterans.
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The committee also notes that future analyses of health outcomes in those and other important study populations should be as specific as possible because generic findings, such as those for "all respiratory outcomes," are not useful in addressing the committee's charge to determine associations of herbicide exposures with specific health conditions. • P ossible health effects in offspring of exposed men merit further investigation.
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Finally, although the committee recognizes that there is evidence that environmental exposures can affect later generations through fetal and germ line modifications, epidemiologic investigation designed to associate toxicant exposures with health effects manifested in later generations will be even more challenging to conduct than is research on adverse effects on the first generation. Thus, the committee recommends development of epidemiologic protocols to address the logistical challenge of determining whether adverse effects are being manifested in later generations as a result of paternal exposure: consideration must be given to the minimum sample size needed to detect changes if present, the most sensitive and reliable outcome measures that should be included, and the need for animal studies to provide mechanistic insight into documented epidemiologic associations.
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From page 946... ...
Furthermore, animal models elucidating the effects of paternal exposure on the development of disease in offspring would be very informative, particularly in identifying the timing and duration of exposure that are most critical and the susceptibility of specific organ systems to disease development in offspring later in life. Animal studies of the mechanisms of inhibition of fetal growth, particularly in male offspring, after maternal exposure could help to elucidate findings seen in some epidemiologic studies that examined maternal exposure and birth weight.
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2000a. Prevalence of gynecologic cancers among female Vietnam veterans.
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