Study Finds No Clear Evidence Of Long-Term Health Effects Among Veterans
An Institute of Medicine study finds no clear evidence specific long-term health effects are associated with participation in a series of tests during the 1960s known as the Shipboard Hazard and Defense Project.
The IOM study compared the health of veterans who participated in SHAD with the health of a similar group of veterans who did not take part. A greater number of SHAD veterans have died of heart disease, but overall mortality rates among both groups of veterans were similar. Moreover, the differences in the rates of medical symptoms and conditions experienced by each group were slight for the most part, and the study authors found no consistent, specific patterns of ill health among SHAD veterans.
Because of limitations in the study response rates and the size of the study, the authors cautioned that their findings should not be misconstrued as clear evidence that there are no possible long-term health effects related to SHAD involvement. Also, there have been very few hypotheses about specific health problems that could be related to the materials used in the SHAD tests to serve as a starting point for further investigation.
Project SHAD was a series of tests conducted by the U.S. Department of Defense during the 1960s to determine how well service members aboard military ships could detect and respond to chemical and biological attacks. Many of the agents used in the tests were presumably innocuous simulants such as Bacillus globigii and zinc cadmium sulfide, but some tests involved active agents such as the toxic nerve gases sarin and VX, and infectious bacteria. Although many of the roughly 5,500 veterans who took part were aware of the tests, some were involved without their knowledge.
The IOM study compared mortality rates and causes among deceased SHAD participants and control group veterans by reviewing death certificates and other records. To compare health status among living veterans, the study authors relied on data provided by the former service members in an extensive questionnaire. About 61 percent of SHAD participants and 47 percent of the control group veterans responded.
Overall death rates among SHAD participants were comparable to those among control group veterans. However, SHAD participants had a somewhat higher rate of mortality from heart disease. The study cannot speak to whether exposure to the agents used in SHAD tests is linked to increased risk for heart disease because data on veterans' exposure levels are limited. Also, the study authors did not have information on other possible risk factors, such as whether the deceased veterans were overweight, how much they exercised, or whether they had a family history of cardiovascular ailments.
Cancer deaths were higher among a subset of SHAD veterans who were potentially exposed only to trioctyl phosphate -- a nontoxic simulant for VX used during the tests. Again, a lack of exposure data and information on other risk factors prevented the authors from being able to intepret this finding.
In response to the survey sent by the study authors, living SHAD veterans as a group reported experiencing medical symptoms and poorer health at higher rates than the control veterans did. However, most of the differences in health status scores calculated from the responses of the two groups were relatively small. Veterans who were potentially exposed to trioctyl phosphate only or to multiple simulants did report moderately higher rates of psychological, psychosocial, and behavioral problems. The subset of SHAD participants who were potentially exposed to active agents such as sarin and Q-fever reported medical symptoms and conditions at rates no greater than the control veterans. There were no notable differences in rates of hospitalization reported by either group of veterans.
The study authors noted some interesting findings that extended beyond their comparison of the SHAD participants and control group veterans. Among the subset of SHAD veterans potentially exposed only to trioctyl phosphate, former Marines had higher mortality rates than their former Navy counterparts, a finding the authors believe might warrant further investigation. Both groups of veterans reported poorer health than national norms, but their self-reported health status was better than that of a sample group of Veterans Health Administration outpatients.