Dibenzofurans a greater global pollutant than dioxins ? : Evidence from analyses of open ocean killer whale

Three specimens of killer whales (Orcinus orca), an open ocean carnivore, were analysed for extremely toxic polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) to understand their long-range distribution patterns. Several PCDF congeners, including the highly toxic 2,3,7,8-tetra- and 2,3,4,7,8-penta-CDFs were identified in the blubber of those specimens. The PCDF isomeric pattern in killer whale is more complex than the reported patterns in humans and birds, indicating the weaker metabolic potency of killer whales for these toxic compounds. High levels of PCBs (about 400 mg kg⁻¹) have also been detected in those specimens. The 2,3,7,8-substituted PCDF congeners identified in commercial PCBs were also found in killer whale, indicating PCBs as the possible source. Isomer-specific and trace level determinations of PCDD in killer whale, revealed no detectable quantities. The detection of comparatively high levels ( > 300 ng kg⁻¹) of PCDFs and undetection of PCDDs in open ocean killer whales suggest that PCDFs are more ubiquitous than PCDDs.