age-related incidence. In addition, a high priority should be placed on clarifying the role of genetic factors, in particular the role of aryl-hydrocarbon receptor (AhR) polymorphisms, in determining individual susceptibility to disease.

Air Force Health Study

The Air Force Health Study (AFHS) is an epidemiologic study whose purpose is to determine whether exposure to the herbicides used in Vietnam might underlie any adverse health conditions observed in a cohort of Air Force personnel who conducted aerial spray missions (Operation Ranch Hand). A baseline morbidity study and a matched comparison cohort study were initiated in 1982, with follow-up assessments in 1985, 1987, 1992, and 1997. In accordance with the study protocol, one additional assessment was completed in 2003, and a final report will be issued in May, 2005 (personal communication, Joel Michalek, Brooks Air Force Base, September 24, 2004).

The AFHS is one of the few primary sources of information on the health of Vietnam veterans known to have been exposed to Agent Orange and other herbicides, and the study is coming to its scheduled end. A congressionally-mandated Institute of Medicine (IOM) committee has been recently formed to evaluate the future of the AFHS. That IOM committee is charged with evaluating the scientific merit of maintaining the records and samples, and how those specimens could be made available for independent researchers. That committee also will evaluate the merit of extending that study beyond its scheduled end and, if extended, what oversight would be most appropriate. Previous VAO committees have recommended extending the AFHS, and this committee encourages the newly appointed AFHS review committee to consider those recommendations in the course of its deliberation.

Army Chemical Corps Study

Members of the Army Chemical Corps constitute the largest cohort of Vietnam veterans exposed directly to herbicides and TCDD. They were involved in the handling and distribution of the compounds in Vietnam. Preliminary studies of this cohort by scientists in the Department of Veterans Affairs have demonstrated increased TCDD concentrations in Chemical Corps veterans who reported spraying herbicides as part of their duties. Information on health outcomes from that cohort is expected to provide insight into the effects of the chemicals of interest on the entire population of Vietnam veteran. The committee has long awaited publication of more data from this study, and reasons why it has not been forthcoming are not apparent. Issues concerning continuation similar to those being evaluated by the IOM committee reviewing the AFHS should be assessed as well for the study of the Army Chemical Corps veterans.

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