Comparative Analysis of Polychlorinated Dibenzo-p-dioxin and Dibenzofuran Congeners in Great Lakes Fish Extracts by Gas Chromatography-Mass Spectrometry and In Vitro Enzyme Induction Activities

The high-resolution gas chromatographic-mass spectrometric analysis of 25 Great Lakes fish extracts confirmed the identities of several 2, 3, 7, 8-tetrasubstituted polychlorinated dibenzofurans (PCDFs) and dibenzo-pdioxins (PCDDs). The dominant congener in extracts from Lake Michigan, Lake Erie, Lake St. Clair, Lake Huron, and Lake Superior fish was 2, 3, 7, 8-tetrachlorodibenzofuran (TCDF). The fish extracts from Lake Ontario showed significant levels of 2, 3, 7, 8-tetrachlorobenzo-p-dioxin (TCDD) besides containing considerable amounts of PCDFs. The “2, 3, 7, 8-TCDD equivalents” in these extracts were determined by their activities as inducers of aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) in rat hepatoma H-4-II E cells in culture. For most of these samples, there was less than a 2-fold difference in the bioassay-estimated 2, 3, 7, 8-TCDD equivalents and the total PCDDs plus PCDFs as determined by GC-MS, The bioassay-derived values were significantly (>2-fold) higher for the Lake Erie and Lake Ontario fish extracts. This difference may be due to several factors including synergistic interactive effects of the congeners in the bioassay induction response or the presence of “bioassay-active” components that are not detected by GC-MS analysis.