INDEXES OF TCDD EXPOSURE AND TCDD BODY BURDEN IN VETERANS OF OPERATION RANCH HAND

Using responses from a questionnaire detailing herbicide exposure duri ng service in Vietnam and information on job classifications, we inves tigated the relationship between 2,3,7,8-tetrachlorodibenzo-p-dioxin ( TCDD) body burden and self-reported exposure in enlisted members of Op eration Ranch Hand, the United States Air Force herbicide spraying mis sion in Vietnam. We constructed three TCDD exposure indices from the q uestionnaire data: the number of days of skin exposure (DAYS), the per centage of skin area exposed (PCNT), and a combined index (SRI) which was the product of these and the concentration of TCDD in the herbicid e. A fourth index (AFI) based on gallons of herbicide sprayed and the number of men on the job was also studied. The regression model most p redictive of TCDD levels (R(2) = 0.61) included job classification (di vided into four categories), the number of days of skin exposure, perc ent body fat during the tour of duty, and relative change in body fat. A model with job classification alone had an R(2) of 0.60. The four e xposure indices were constructed to further explain TCDD exposure in t he job classifications with the highest potential for exposure: Ranch Hand flight engineers and ground crew. In these two groups, days of sk in exposure was the index most significantly