Pharmacokinetics of tcdd in veterans of operation ranch hand: 15-year follow-up

Using multiple measurements from serum collected over 15 yr (in 1982, 1987, 1992, and 1997), the half-life of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCD D) in 97 veterans of Operation Ranch Hand, the Air Force unit responsible f or the aerial spraying of Agent Orange in Vietnam, was estimated. The poten tial influences of age, percent body fat, and changes in percent body fat o n the half-life estimate were also examined. The elimination rate of TCDD f or these veterans was 0.0915 per year with 95% confidence interval 0.0844 t o 0.0986 per year; the corresponding half-life estimate was 7.6 yr with 95% confidence interval 7.0 to 8.2 yr. The elimination rate decreased signific antly with increasing body fat, but not with age or relative changes in per cent body fat.