Half-lives of tetra-, penta-, hexa-, hepta-, and octachlorodibenzo-p-dioxin in rats, monkeys, and humans -: a critical review

The elimination half-lives (t(1/2)) in Sprague-Dawley rats for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 1,2, 3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (HxCDD), 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) and 1,2,3,4,6,7,8,9-octachlorodibetizo-p-dioxin (OCDD) were estimated in long-term studies by Schlatter, Poiger and others. Furthermore, there are some published half-lives of TCDD in adult humans. The average half-life of TCDD in adult humans is approximately 2840 days, while in Sprague-Dawley rats the average t(1/2) of TCDD is 19 days. The t(1/2) of TCDD in humans is about 150 times that of rats. This factor was used to calculate the t(1/2) values of the other polychlorinated dibenzo-p-dioxins (PCDDs) in humans from the rat data. Furthermore, the terminal t(1/2) Values Of PCDDs in adult humans were calculated from the regression equation: log t(1/2H) = 1.34 log t(1/2R) + 1.25 which was recently established for 50 xenobiotics (t(1/2H) = terminal half-lives in days for humans, t(1/2R) = terminal half-lives in days for rats). The following terminal half-lives in adult humans were obtained: 12.6 years for 1,2,3,7,8-PeCDD, 26-45 years for 1,2,3,4,7,8-HxCDD, 80 102 years for 1,2,3,4,6,7,8-HpCDD and ca. 112-132 years for OCDD. These half-lives of PCDDs are critically compared with measured t(1/2) values of PCDDs and other persistent organic pollutants in rats, monkeys and humans. (C) 2002 Elsevier Science Ltd. All rights reserved.