Seasonal and temporal trends in polychlorinated biphenyls and organochlorine pesticides in East Greenland polar bears (Ursus maritimus), 1990–2001

Persistent organochlorine (OC) contaminants (PCBs, DDTs, chlordanes (CHLs), dieldrin, hexachlorocyclohexanes (HCHs), chlorobenzenes (CBzs)) were determined in adipose tissue of 92 polar bears (Ursus maritimus) sampled between 1999 and 2001 in central East Greenland (698009N to 748009N).OC data were presented from subadults (S: females: =5 years and males: =6 years), adult females (F: =5 years) and adult males (M: =6 years).Summed chlorobiphenyl (SCBs) concentrations (41 congeners including co-eluters), SCHLs and SDDTs were the dominant classes of OCs. SCBs concentrations were found to be 6470, 8240 and 9100 ngyg lipid weight (lw) i subadults, adult females and adult males, respectively.The corresponding figures were: 2010 (S), 2220 (F) and 1710 (M) ngy g lw for SCHLs and 462 (S), 462 (F) and 559 (M) ngyg lw for SDDTs.The dominant CB congeners were CB153 (32.3%), CB180 (21.4%), CB170 (12.2%) and CB138 (11.0%).The metabolite p,p9-DDE (88.2%) dominated the SDDTs, while oxychlordane was the dominant (57.1%) CHL-related compound.Concentrations of SCBs, SCBzs, SDDTs, mirex and dieldrin were highest in adult males, whereas concentrations of SHCHs were lower than in adult females but not than those in subadults.Adult females had the lowest concentrations of SCBzs, mirex and dieldrin. Concentrations of SCHLs were lowest in adult males, intermediate in subadults and highest in adult females. SCB, SHCH and SCHL concentrations showed high seasonal variability in adult females but remained relatively constant in adult males and subadults.In general, the OC levels in females appeared to be highest in March and lowest in January or September.Concentrations of SCBzs and dieldrin showed seasonal variability in all three groups, with a maximum in March in adult females. SCBz concentrations in adult males and subadults of both sexes peaked in April–July, and dieldrin concentrations peaked in April–July in subadults, but not until August in adult males. SDDT concentrations increased from January to a maximum in April–July for subadults and in August for adults.T emporal trends within the last decade were examined by comparing the present data to the concentrations reported in samples from 1990 from the same region. SCB, p,p9-DDE and SHCH concentrations in 1999–2001 were 22.1%, 66.3% and 39.3% lower than the 1990 concentrations, respectively. in contrast, SCHL and dieldrin concentrations showed differences amongst sex and age groups in the temporal trends, where present concentrations are between 24.4% to 69.3% and 27.0% to 69.0% lower, respectively, relative to the 1990 levels. However, power analysis suggested that firm conclusions could not be drawn regarding the general time trend based on these two sampling periods.The range of half-lives of the various OC classes were estimated to lie between 4.5 and 20.6 years depending on the age and sex groups considered.