Chlorinated hydrocarbon contaminants and metabolites in polar bears (Ursus maritimus) from Alaska, Canada, East Greenland, and Svalbard: 1996 2002

A suite of chlorinated hydrocarbon contaminants (CHCs) including organochlorine pesticides (OCPs) and by-products, polychlorinated biphenyls (PCBs), and methyl sulfone (MeSO2) PCB and p,pV-dichlorodiphenyldichloroethylene ( p,pV-DDE) metabolites were determined in adipose tissue of 107 adult and sub-adult polar bears, almost exclusively females, sampled between 1996 and 2002 from populations spanning Arctic and Subarctic regions of Alaska, Canada, East Greenland, and Svalbard. The East Greenland and Svalbard populations of polar bears were distinguished by higher proportions of dichlorodiphenyldichloroethane (DDT)-related compounds, nonachlors, oxychlordane, and higher-chlorinated and persistent PCB congeners (hepta- to nona-chlorinated). Conversely, Alaska, the westernmost population of the North American Arctic, was characterized by higher proportions of relatively volatile compounds such as hexachlorocyclohexanes (HCHs) and pentachlorobenzene (PnCBz), lower-chlorinated PCB congeners (tri- to penta-chlorinated), and lower proportions of oxychlordane. Geometric mean (GM) with 95% confidence limits (CL) AHCH concentrations were highest in Alaska male polar bear fat samples (GM 593; CL 363 909 ng g 1 lipid weight), ADDT concentration were highest in East Greenland female samples (GM 309; CL 249 490 ng g 1 l.w.), and A42PCB (GM 5972; CL 4637 9129 ng g 1 l.w.) and AMeSO2-PCB (GM 198; CL 162 279 ng g 1 l.w.) concentrations were highest in female samples collected from Svalbard. The distribution of A-chlordanerelated compounds (ACHL), ACBz, mirex, and dieldrin was relatively uniform among the populations of polar bears investigated. The present 1996 2002 data of female polar bear fat samples was compared to spatial assessments of female polar bear fat samples collected between 1989 and 1993 from comparable populations. The two-point temporal comparisons showed a general decrease for age-adjusted mean concentrations of ACHL, p,pV-DDE, A42PCB, AMeSO2-PCB and 3-MeSO2- p,pV-DDE over a period of approximately 10 years. However, concentrations of dieldrin were comparatively unchanged. Comparisons of present 2001 2002 concentrations in fat of female polar bears from Western Hudson Bay showed great consistency with temporal trends (1991 1999) previously reported for the same region, i.e. the apparent non-decreasing trend of ACHL, h-HCH, AHCH and dieldrin, and the apparent declining trend for APCB. However, present concentrations of a-HCH and ACBz were elevated, and ADDT was notably lower in Western Hudson Bay samples compared to the last measurements in fat samples collected in 1999, which was not in accord with reported temporal trends for this region. As a result of their relatively high degree of contamination, East Greenland and Svalbard polar bears are at higher health risk of contaminant exposure among Arctic and Subarctic populations. In addition to continued biomonitoring, further research on health and population status is needed to evaluate the impact from chronic exposure of polar bear populations to CHCs and their metabolites.