PHARMACOKINETICS OF TCDD IN VETERANS OF OPERATION RANCH HAND - 10-YEAR FOLLOW-UP

Using multiple measurements from serum collected over 10 yr (1982, 198 7, and 1992), we estimated the half-life of 2,3,7,8-tetrachlorodibenzo -p-dioxin (TCDD) in 213 veterans of Operation Ranch Hand the Air Force unit responsible for the aerial spraying of Agent Orange in Vietnam. The potential influences of age, percent body fat, and changes in perc ent body fat on the half-life estimate were also examined. The mean de cay rate of TCDD for these veterans is 0.0797 per year with 95% confid ence interval 0.0727 to 0.0868 per year; the corresponding half-life e stimate is 8.7 yr with 95% confidence interval 8.0-9.5 yr. Half-life i ncreased significantly with increasing body fat, but not with age or r elative changes in percent body fat.