1,2,3,4,7,8,9-Heptachlorodibenzofuran

1,2,3,4,7,8,9-Heptachlorodibenzofuran is a dioxin-like polychlorinated dibenzofuran (PCDF).¹ It induces the expression of the genes encoding the cytochrome P450 (CYP) isoforms CYP1A1 and CYP1B1, as well as the aryl drocarbon receptor repressor (AhRR) in primary human peripheral blood lymphocytes and increases ethoxyresorufin-O-deetlase (EROD) activity, a marker of CYP1A1 activity, in isolated human peripheral blood lymphocytes in a concentration-dependent manner. 1,2,3,4,7,8,9-Heptachlorodibenzofuran decreases the number of splenic plaque-forming cells, indicating immunosuppression, and increases hepatic microsomal aryl drocarbon droxylase (AHH) activity in mice induced with sheep red blood cells (ED₅₀s = 12 and 700 nmol/kg, respectively).² It has been found in human breastmilk and in the air near municipal waste incinerators.^3,4