Estimation of exposure to Agent Orange and other defoliants among American troops in Vietnam: a methodological approach

The long-term association between exposure to wartime bombing earlier in life and post-traumatic stress later in life among today's older Vietnamese population

This analysis examines the relationship between exposure to American wartime bombardments earlier in life and later-life PTSD among current surviving Vietnamese aged 59+. It also assesses whether the relationship varies by military status during the war - formal military, informal military, or civilian - and whether associations are explained by exposure to violence and malevolent conditions. Data link survey responses from the 2018 Vietnam Health and Aging Study to provincial-wide level bombing intensity using U.S. Department of Defense records from the Theater History of Operations Vietnam database. PTSD measured using nine items from the PTSD Checklist. Analyses employ multivariate logistic quantile regression. Findings examined for a sample of 2290 Vietnamese survivors and a subsample of 736 Vietnamese that moved at least once during wartime. Results show a robust and significant positive association between province-wide bombing intensity and later-life PTSD scores. Interaction effects indicate civilians have overall lower levels of PTSD than those that were in the formal or informal military, but the association between bombing and PTSD is stronger among civilians. Much of the association is a function of exposure to violence and less is a function of exposure to malevolent conditions. Findings confirm earlier studies that have shown severe deleterious impacts of war trauma, and arial bombardments particularly, on long-term psychological health, while extending extant literature to civilian populations living in Vietnam during intense aerial bombing episodes.

Impact of Military Service in Vietnam on Coping and Health Behaviors of Aging Veterans During the COVID-19 Pandemic

Many Vietnam War veterans who experienced military trauma still exhibit PTSD symptomatology. Little is known about how new stressful situations, like the COVID-19 pandemic, affect previously traumatized people or whether they will react differently to them. We explore whether military combat experiences in Vietnam affect veterans' perceived abilities to cope with COVID-19 and whether current PTSD symptoms and later-adulthood reengagement with trauma memories are related to coping. We examine the extent that current PTSD symptoms and trauma reengagement relate to preventive practices. Participants were part of a randomly sampled cohort of American Legionnaires who responded to two previous surveys (1984, 1998), were born 1945-1953 and deployed to Vietnam 1963-1973, thus representing an aging veteran population. A survey supplement assessed coping with the pandemic and adherence to public health guidelines. The response rate was 74% (N = 507); 422 (61.6%) completed the COVID-19 supplement. Military experiences were found to affect coping with 41.4% reporting they affected ability to cope with COVID-19. Medium- and high-combat veterans were more likely to report that military experience affected coping than low-combat (OR 2.4, 95% CI 1.51–3.96; 2.6, 95% CI 1.41–4.61, respectively). Those with high PTSD scores had 7.7-fold (95% CI 4.3–13.17) increased likelihood of reporting that their coping was affected, compared to low-PTSD scorers. Few adopted social distancing (4%), staying at home (17%), or ceasing usual activities (32%); high-combat veterans were least likely to stay home. Veterans who practiced handwashing, sanitizer use, mask-wearing, and surface disinfection had significantly higher PTSD scores than those who did not. Veterans with higher scores on the LOSS-SF scale associated more reengagement with trauma memories and were more likely to engage in personal preventive strategies. Analysis of open-ended responses supported these findings. We conclude that fifty years after returning from Vietnam, PTSD scores were high for high-combat veterans, suggestive of PTSD diagnosis. Military experiences affected coping with COVID both positively and negatively, and may have helped instill useful personal health behaviors. Veterans, especially those with PTSD symptomatology, may have special needs during stressful times, like the COVID-19 pandemic, affecting compliance with recommended practices, as well as their overall health and well-being.

Exposure opportunity models for Agent Orange, dioxin, and other military herbicides used in Vietnam, 1961-1971

Nearly 19.5 million gallons of herbicides were sprayed on the Republic of Vietnam between 1961 and 1971 for military purposes. Amounts of spray and patterns of applications are available in an electronic file called HERBS that contains records of 9141 defoliation missions, including detailed coordinates of US Air Force Ranch Hand aircraft flight paths, along with chemical agent and gallonage sprayed. Two classes of models for use in epidemiological and environmental studies that utilize the HERBS data for estimating relative exposure opportunity indices are presented: a discrete "hits" model that counts instances of proximity in time and space to known herbicide applications, and a continuous exposure opportunity index, E4, that takes into account type and amount of herbicide sprayed, distance from spray application, and time interval when exposure may have occurred. Both direct spraying and indirect exposure to herbicide (or dioxin) that may have remained in the local environment are considered, using a conservative first-order model for environmental disappearance. A correction factor for dermal versus respiratory routes of entry has been incorporated. E4 has a log-normal distribution that spans six orders of magnitude, thus providing a substantial amount of discrimination between sprayed and unsprayed areas. The models improve on earlier ones by making full use of the geometry of the HERBS spray flight paths of Ranch Hand aircraft. To the extent possible so many decades after the War, the models have been qualitatively validated by comparison with recent dioxin soil and biota samples from heavily contaminated areas of Vietnam, and quantitatively validated against adipose dioxin obtained in epidemiological studies of Vietnamese. These models are incorporated within a geographic information system (GIS) that may be used, as one would expect, to identify locations such as hamlets, villages, and military installations sprayed by herbicide. In a novel application, the GIS also facilitates quantitative risk assessment in epidemiological and ecological studies by applying the models within a framework of historical reconstruction of exposure history of individuals based upon their location histories.

Agent orange and the risk of gestational trophoblastic disease in Vietnam

There have been claims of an increased risk for gestational trophoblastic disease (i.e., hydatidiform mole and choriocarcinoma) in Vietnam since the period of Agent Orange sprayings. In 1990, we conducted a case-control study in Ho Chi Minh City to investigate risk factors for gestational trophoblastic disease in Vietnam. Eighty-seven married women, all of whom had a recent pathologic diagnosis of gestational trophoblastic disease, identified in the Obstetrical and Gynecological Hospital, were included in the study. Eighty-seven married women who were admitted mainly in the surgery departments of the same hospital were the controls, and they were matched to cases for age and area of residence. Odds ratios (ORs), adjusted for matching variables and other potential confounders, were estimated with unconditional logistic regression. A statistically significant trend in risk was observed with previous live births (p = .01). Cases were found to eat less meat per wk (OR = 0.4, 95% confidence interval [95% CI] = 0.2-0.9 for > or = five meat dishes) and to own fewer consumer goods than controls. An increase in risk was associated with the breeding of pigs (OR = 5.7, 95% CI = 1.2-27.6 for raising three or more pigs). A cumulative Agent Orange exposure index was constructed, using the patient's complete residence history. No significant difference was found between cases and controls for this index (OR = 0.7, 95% CI = 0.2-1.8 for high-exposure category), nor was such a difference noted for the agricultural use of pesticides.

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans: the risks to human health. A review

1 PCDDs and PCDFs are ubiquitous and persistent in the environment. They are to be found in body tissues of both humans and animals. 2 The most extensively studied PCDD is 2,3,7,8-TCDD. It has been shown to produce a wide range of effects and is considered to be a (non-genotoxic) carcinogen in animals. 3 Studies into the mechanisms of toxicity so far reveal that there is involvement of a specific receptor (Ah), however further work is required to elucidate the mechanisms of the various effects. 4 Reports on a number of human exposures to PCDDs and PCDFs are described. Results from human epidemiological studies are difficult to interpret: there have been problems in methodology; there has been inadequate information on intake, and exposures have often been to mixtures of PCDDs and/or PCDFs together with other related compounds. 5 Many regulatory authorities faced with the problem of providing an index of risk from exposure to mixtures of PCDDs and PCDFs have employed the concept of 'TCDD equivalents'. 6 Whether or not PCDDs and PCDFs pose a significant human health risk at current levels of exposure they remain of considerable interest to the toxicologist.