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

Abstract

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 (69°00′N to 74°00′N). 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 (ΣCBs) concentrations (41 congeners including co-eluters), ΣCHLs and ΣDDTs were the dominant classes of OCs. ΣCBs concentrations were found to be 6470, 8240 and 9100 ng/g lipid weight (lw) i subadults, adult females and adult males, respectively. The corresponding figures were: 2010 (S), 2220 (F) and 1710 (M) ng/g lw for ΣCHLs and 462 (S), 462 (F) and 559 (M) ng/g lw for ΣDDTs. The dominant CB congeners were CB153 (32.3%), CB180 (21.4%), CB170 (12.2%) and CB138 (11.0%). The metabolite p, p′-DDE (88.2%) dominated the ΣDDTs, while oxychlordane was the dominant (57.1%) CHL-related compound. Concentrations of ΣCBs, ΣCBzs, ΣDDTs, mirex and dieldrin were highest in adult males, whereas concentrations of ΣHCHs were lower than in adult females but not than those in subadults. Adult females had the lowest concentrations of ΣCBzs, mirex and dieldrin. Concentrations of ΣCHLs were lowest in adult males, intermediate in subadults and highest in adult females. ΣCB, ΣHCH and ΣCHL 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 ΣCBzs and dieldrin showed seasonal variability in all three groups, with a maximum in March in adult females. ΣCBz 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. ΣDDT concentrations increased from January to a maximum in April–July for subadults and in August for adults. Temporal trends within the last decade were examined by comparing the present data to the concentrations reported in samples from 1990 from the same region. ΣCB, p,p′-DDE and ΣHCH concentrations in 1999–2001 were 22.1%, 66.3% and 39.3% lower than the 1990 concentrations, respectively. in contrast, ΣCHL 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.