ABSTRACT
OBJECTIVES: In an epidemiologic study on the health impact of Agent Orange exposure, the valid estimation of exposure level is the most important step. Based on recent studies, we examined the correlation between exposure levels categorized by personal exposure estimates and serum 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD, Dioxin), exploring the possibility of utilizing the exposure level as a surrogate for the estimate of exposure to agent orange. METHODS: During the study period (Jan 1996-Feb 1996), blood specimens of 745 subjects taken randomly among 1,329 persons and kept frozen, were analyzed for 2,3,7,8-TCDD and six other dioxin congeners. The serum dioxin and congeners were measured in 1998 by CDC ,adjusted for serum lipids. We categorized the total exposure scores into five groups based on Agent Orange exposure data collected by interview and military records. Pearson and Spearman's correlation coefficients & multiple regression analysis were used to identify the relationship of the exposure level categorized with serum concentration of 2,3,7,8-TCDD, and six other dioxin congeners. RESULTS: Dioxin and the other congeners, except 1,2,4,6,7,8-HpCDD, showed significant correlations to exposure categories (p<0.005); 2,3,7,8-TCDD and OCDD showed positive correlations, whereas the other congeners did negative. The values of 2,3,7,8-TCDD differed according to exposure category and proportionally increased from the low exposure group to the high, a dose-response relationship, even after other possible confounding variables were adjusted for. In multiple regression analysis, age(beta=0.033), dioxin(beta=0.433), 1,2,3,7,8-PeCDD(beta=0.998), 1,2,3,4,7,8-HxCDD(beta=0.773), 1,2,3,6,7,8-HxCDD(beta=0.255), 1,2,3,7,8,9-HxCDD(beta=3.468), 1,2,3,4,6,7,8-HpCDD(beta=0.109) were found to be significantly related to the total exposure score(p<0.005). CONCLUSION: This study demonstrated that the use of such categorizations as a surrogate measure of agent orange exposure in identifying exposure degrees in a health impact study is valid.