1,2,3,4,7,8,9-HEPTACHLORODIBENZOFURAN 1,2,3,4,7,8,9-Heptachlorodibenzofuran [Dioxin and dioxin-like compounds] 55673-89-7 Dibenzofuran, 1,2,3,4,7,8,9-heptachloro- F 134