Geographical distribution and identification of methyl sulphone PCB and DDE metabolites in pooled polar bear (Ursus maritimus) adipose tissue from western hemisphere Arctic and Subarctic regions

The geographical distribution of methyl sulphone (MeSO2-) PCB and DDE metabolites is unknown for any species in any region. In this study, pooled male polar bear (Ursus maritimus) adipose samples from 12 arctic and subarctic regions from the Bering Sea to the Greenland Sea were analyzed for PCBs, DDE, and their MeSO2-metabolites. Each adipose pool contained from three to 27 lipid extracts prepared on an equal fat basis. The total (S-) MeSO2-PCB and MeSO2-DDE levels were generally higher in the east (Greenland) and south (Hudson Bay) and ranged from 145 to 633 ng/g lipid and 0.8–11 ng/g lipid, respectively. Five new MeSO2- compounds were identified and/or quantitated, 3M-DDE, 4M-CB64, 3M- and 4M-CB70, and 3M-CB149. The congeners 3M- and 4M-CB101 and 3M- and 4M-CB87 consistently accounted for ca. 50% of theS-MeSO2-PCBs. The MeSO2-PCB congener pattern was independent of geographic variation among the regions, implying that the pattern of atmospheric input and subsequent biomagnification of precursor PCBs is homogeneous in the western hemisphere. The ratio ofS-MeSO2-PCBs to accumulating PCBs decreased very gradually (average value of 0.56 ± 0.11) from west to east reflecting the proportion of higher chlorinated PCBs that are not major precursors of MeSO2-PCBs. The 3-MeSO2- DDE/DDE ratio fluctuated among regions with an average value of 0.33 ± 0.016.