US Army Chemical Corps Vietnam veterans health study: preliminary results

Spirometric Pulmonary Restriction in Herbicide-Exposed U.S. Vietnam War Veterans

Spirometric restriction in herbicide-exposed U.S. Army Chemical Corps Vietnam War veterans was examined because no published research on this topic in Vietnam War veterans exists. Spirometry was conducted on 468 veterans who served in chemical operations in a 2013 study assessing the association between chronic obstructive pulmonary disease (COPD) and herbicide exposure. Exposure was verified based on blood serum values of 2,3,7,8-tetrachlorodibenzo-p-dioxin. Further, the association between herbicide exposure and spirometry restriction (forced expiratory volume in one second (FEV₁)/forced vital capacity (FVC) ≥ lower limit of normal (LLN) and FVC < LLN) was tested after adjustment for military characteristics, selected anthropometrics, and other predictors using multivariable regression. Spirometric restriction in herbicide sprayers (15.7%, 95% CI: 10.6, 20.9) was almost twice that of nonsprayers (9.91%, 95% CI: 5.9, 13.9) (p = 0.081). While spirometric restriction was not significantly associated with herbicide exposure (adjusted odds ratio (aOR) = 1.64, 95% CI: 0.82, 3.29) despite the greater prevalence of restriction in sprayers versus nonsprayers, spirometric restriction was significantly associated with race/ethnicity (aOR = 3.04, 95% CI: 1.36, 6.79) and waist circumference (aOR = 2.46, 95% CI: 1.25, 4.85). Because restrictive pulmonary disease may result from chemically-induced inflammation or sensitivity, research on chemical exposures and restriction in veterans should continue. Future study should include full pulmonary function testing, targeted research designs, and a wider set of explanatory variables in analysis, such as other determinants of health.

Skin diseases associated with Agent Orange and other organochlorine exposures

Organochlorine exposure is an important cause of cutaneous and systemic toxicity. Exposure has been associated with industrial accidents, intentional poisoning, and the use of defoliants, such as Agent Orange in the Vietnam War. Although long-term health effects are systematically reviewed by the Institute of Medicine, skin diseases are not comprehensively assessed. This represents an important practice gap as patients can present with cutaneous findings. This article provides a systematic review of the cutaneous manifestations of known mass organochlorine exposures in military and industrial settings with the goal of providing clinically useful recommendations for dermatologists seeing patients inquiring about organochlorine effects. Patients with a new diagnosis of chloracne, porphyria cutanea tarda, cutaneous lymphomas (non-Hodgkin lymphoma), and soft-tissue sarcomas including dermatofibrosarcoma protuberans and leiomyosarcomas should be screened for a history of Vietnam service or industrial exposure. Inconclusive evidence exists for an increased risk of other skin diseases in Vietnam veterans exposed to Agent Orange including benign fatty tumors, melanomas, nonmelanoma skin cancers, milia, eczema, dyschromias, disturbance of skin sensation, and rashes not otherwise specified. Affected veterans should be informed of the uncertain data in those cases. Referral to Department of Veterans Affairs for disability assessment is indicated for conditions with established associations.

Military service and lung disease

OBJECTIVE

Lung diseases associated with military service are often a reflection of the conditions seen in the local civilian population, and with a few notable exceptions, are often related to unique environmental and occupational exposures.

METHODS

This article reviews important pulmonary diseases that have been associated with military service in the past 100 years in a question-and-answer format.

RESULTS

Traditionally, bacterial and viral pneumonias were the most common sources of military morbidity and mortality. With improved preventive medicine and antimicrobial therapy, other diseases related to battlefield injuries or inhalational exposures have assumed greater importance.

CONCLUSIONS

The etiology of military morbidity and mortality has evolved over the past century. Many of the discoveries related to vaccine efficacy, trauma resuscitation, interstitial lung disease, and even carcinomas have a strong military association.

A critical review of the epidemiology of Agent Orange/TCDD and prostate cancer

To inform risk assessment and regulatory decision-making, the relationship between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and prostate cancer requires clarification. This article systematically and critically reviews the epidemiologic evidence on the association between exposure to TCDD or Agent Orange, a TCDD-contaminated herbicide used during the Vietnam War, and prostate cancer risk. Articles evaluated include 11 studies of three cohorts, four case-control or cross-sectional studies, and three case-only studies of military veterans with information on estimated Agent Orange or TCDD exposure; 13 studies of seven cohorts, one case-control study, and eight proportionate morbidity or mortality studies of Vietnam veterans without information on Agent Orange exposure; 11 cohort studies of workers with occupational exposure to TCDD; and two studies of one community cohort with environmental exposure to TCDD. The most informative studies, including those of Vietnam veterans involved in Agent Orange spraying or other handling, herbicide manufacturing or spraying workers with occupational TCDD exposure, and community members exposed to TCDD through an industrial accident, consistently reported no significant increase in prostate cancer incidence or mortality. Only some potentially confounded studies of Vietnam veterans compared with the general population, studies with unreliable estimates of Agent Orange exposure, and analyses of selected subgroups of Vietnam veterans reported positive associations. Overall, epidemiologic research offers no consistent or convincing evidence of a causal relationship between exposure to Agent Orange or TCDD and prostate cancer. More accurate exposure assessment is needed in large epidemiologic studies to rule out a causal association more conclusively.

Health status of Army Chemical Corps Vietnam veterans who sprayed defoliant in Vietnam

BACKGROUND

U.S. Army Chemical Corps veterans handled and sprayed herbicides in Vietnam resulting in exposure to Agent Orange and its contaminant 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin). This study examined the long-term health effects associated with herbicide exposure among these Vietnam veterans.

METHODS

A health survey of these 1,499 Vietnam veterans and a group of 1,428 non-Vietnam veterans assigned to chemical operations jobs was conducted using a computer-assisted telephone interview (CATI) system. Exposure to herbicides was assessed by analyzing serum specimens from a sample of 897 veterans for dioxin. Logistic regression analyses were used to estimate the risk of selected medical outcomes associated with herbicide exposure.

RESULTS

Odds ratios for diabetes, heart disease, hypertension, and chronic respiratory disease were elevated, but not significantly (P>0.05) for those who served in Vietnam. However, they were significantly elevated among those Vietnam veterans who sprayed herbicides: diabetes, odds ratio (OR)=1.50 (95% confidence interval [95%CI]=1.15-1.95); heart disease, OR=1.52 (1.18-1.94); hypertension, OR=1.32 (1.08-1.61); and chronic respiratory condition, OR=1.62 (1.28-2.05). Hepatitis was associated with Vietnam service, but not with herbicide application.

CONCLUSIONS

Vietnam veterans who were occupationally exposed to herbicide experienced a higher risk of several chronic medical conditions relative to other non-Vietnam veterans. A potential selection bias is of concern. However, there were relatively high participation rates in both the Vietnam and non-Vietnam veteran groups, and the prevalence rates of some of these medical conditions among non-Vietnam veterans were comparable to general populations. Therefore, self-selection factors are considered unlikely to have biased the study results.

Vietnam military service history and prostate cancer

Background

Three decades after US and Australian forces withdrew from Vietnam, there has been much public interest in the health consequences of service in Vietnam. One controversial question is whether the risk of prostate cancer amongst Vietnam veterans is increased. This paper examines relationships between military history, family history and risk of prostate cancer in a population-based case control study.

Methods

Cases were selected from the Cancer Registry of Western Australia as incident cases of histologically-confirmed prostate cancer, and controls were age-matched and selected from the Western Australian electoral roll. Study participants were asked to report any military service history and details about that service.

Results

Between January 2001 and September 2002, 606 cases and 471 controls aged between 40–75 years were recruited. An increased prostate cancer risk was observed in men reporting they were deployed in Vietnam although this was not statistically significant (OR = 2.12; 95% CI 0.88–5.06). An increased risk was also observed in men reporting prostate cancer in fathers (OR = 1.90; 95% CI 1.20–3.00) or brothers (OR = 2.05; 95% CI 1.20–3.50) diagnosed with prostate cancer.

Conclusion

These findings support a positive association between prostate cancer and military service history in the Vietnam war and a first degree relative family history of prostate cancer.

Association between Agent Orange and birth defects: systematic review and meta-analysis

BACKGROUND

The association between parental exposure to Agent Orange or dioxin and birth defects is controversial, due to inconsistent findings in the literature. The principal aim of this study was to conduct a meta-analysis of relevant epidemiological studies that examined this association and to assess the heterogeneity among studies.

METHODS

Relevant studies were identified through a computerized literature search of Medline and Embase from 1966 to 2002; reviewing the reference list of retrieved articles and conference proceedings; and contacting researchers for unpublished studies. A specified protocol was followed to extract data on study details and outcomes. Both fixed-effects and random-effects models were used to synthesize the results of individual studies. The Cochrane Q test and index of heterogeneity (I2) were used to evaluate heterogeneity, and a funnel plot and Egger's test were used to evaluate publication bias.

RESULTS

In total, 22 studies including 13 Vietnamese and nine non-Vietnamese studies were identified. The summary relative risk (RR) of birth defects associated with exposure to Agent Orange was 1.95 [95% confidence interval (95% CI) 1.59-2.39], with substantial heterogeneity across studies. Vietnamese studies showed a higher summary RR (RR = 3.00; 95% CI 2.19-4.12) than non-Vietnamese studies (RR = 1.29; 95% CI 1.04-1.59). Sub-group analyses found that the magnitude of association tended to increase with greater degrees of exposure to Agent Orange, rated on intensity and duration of exposure and dioxin concentrations measured in affected populations.

CONCLUSION

Parental exposure to Agent Orange appears to be associated with an increased risk of birth defects.

Does long term residency near industry have an impact on the body burden of polychlorinated dibenzo-p-dioxins, furans, and polychlorinated biphenyls in older women?

BACKGROUND

For the retrospective study of environment and health linkages biomarkers of exposure are required. Polychlorinated dibenzo-dioxins and furans (PCDD/F) and polychlorinated biphenyls (PCBs) have been useful markers in some settings. This is the first study of PCDD/F body burden in a population based sample from the UK.

AIMS AND METHODS

The authors aimed to investigate whether long term residents close to a heavy chemical industrial complex (Teesside, UK) had a higher body burden and distinct pattern of PCDD/F and PCBs. We measured current levels of PCDD/F and PCBs in a population based sample of older women (mean 64 years, range 42-79 years). Forty women were recruited, 20 living near (zone A: 0.1-2.7 km) and 20 distant (zone C: 5-40 km) from industry during 2000-03. The authors ascertained occupational exposure to lung carcinogens, residential history, consumption of local produce, breast feeding, diet, and height and weight.

RESULTS

The mean body burden measured on lipid basis in ng/kg for the whole sample was: WHO-TEQ (PCDD/Fs): 29.9, 2378TCDD: 4.0, PCB 118:16200, PCB156: 13100. Body burdens were similar to others reported from industrialised countries, except that mean 2378TCDD was slightly higher. Mean ages, body mass index, and lifelong dietary patterns were similar in both zones. The authors found no significant difference in mean body burden levels between zones A and C before or after adjustment for covariates. All congener patterns were consistent with an urban background pattern, and there was no significant difference between congener compositions in the two zones. The TCDD body burden increased with age with accelerated increments above age 70.

CONCLUSION

Long term residency near heavy and chemical industry did not have an effect on women's body burden of PCDD/Fs and PCBs on Teesside, UK. The body burden of PCDD/F and PCBs was not a suitable biomarker for chronic, non-occupational exposure to industrial air pollution.

Dioxin risks in perspective: past, present, and future

The United States Environmental Protection Agency (USEPA) and other U.S. and international agencies have focused extensive efforts on the evaluation of the potential health risks of exposures to chlorinated dioxins (PCDDs), furans (PCDFs), and related dioxin-like polychlorinated biphenyls (PCBs). Extensive regulatory efforts over the past 20 years have also been made to control emissions of these compounds and thus to reduce exposures in the general population. This paper reviews the available information on temporal trends in emissions, environmental levels, intake levels through foods, and human body burdens of dioxins. This paper also provides an overview and comparison of recent hazard assessments for dioxins from U.S. and international agencies. Available data on emissions, environmental and food levels, and human body burdens of dioxins in the general population indicate a several-fold reduction in exposures and body burdens in the general population over the three decades from 1970 to 2000. U.S. and international hazard assessments concur on certain aspects, but disagree on fundamental issues including the likelihood of a threshold for carcinogenic dose-response and the degree of safety factors needed in deriving a protective exposure limit. These disagreements have significant consequences for interpreting the potential health risks of current background dioxin exposure levels. However, whatever the degree of health risk that may be associated with current background exposures, the general population is experiencing several-fold lower exposures, and, therefore, lower health risks, currently compared to 30 years ago. In light of the dramatic declines in exposure already observed, further efforts to reduce exposures through attempts to control emissions or food levels should be carefully evaluated to understand the likely efficacy of the efforts and the relative costs and benefits.

Temporal trends in human TCDD body burden: decreases over three decades and implications for exposure levels

Data on lipid levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the general population in the United States, Canada, Germany, and France over the past 30 years were compiled from the literature. Mean lipid levels of TCDD exhibited a steady decrease by nearly a factor of 10 over this time period, with lipid-adjusted TCDD levels in 2000 about 2 parts per trillion (ppt). Pharmacokinetic modeling using a one-compartment model indicated that absorbed intake levels of TCDD must have decreased by more than 95% from levels in 1972 to result in the observed decrease in human lipid levels, with the bulk of this decrease occurring before 1980. Based on this modeling and the pharmacokinetic properties of TCDD in humans, we conclude that mean levels of TCDD in the general population are likely to decrease further over the next 15 years, to between 0.5 and 1 ppt, even if intake levels do not decrease further. Fewer data over a shorter time period are available for other dioxin and furan congeners in human lipid, but these data indicate substantial decreases as well, with general population TEQ lipid levels currently at least fourfold lower than in 1970 and still decreasing. Food sampling data are limited, but support these trends.