Halogenated dibenzofurans are found worldwide as environmental pollutants. Structurally related to other halogenated aromatic xenobiotics, their toxicity and disposition seem to vary with the degree and position of halogenation. This work has established that 2,3,7,8,-tetrachlorodibenzofuran (TCDF), an extremely toxic isomer, is excreted only after metabolism and toxicity is inversely related to metabolic capability. The distribution to the fetus was examined after maternal exposure. The role of body composition on the disposition of 2,3,7,8-tetrachlorodibenzodioxin (TCDD), the most toxic man-made compound known, has been examined in congenic mouse strains which are sensitive or resistant to TCDD toxicity and shown to be a major determinant of disposition. The disposition of octachlorodibenzodioxin (OCDD) was also studied in rats. Studies with 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF) have begun in rats and monkeys.
