Temporal trends (1986-2004) of organochlorines and brominated flame retardants in tawny owl eggs from northern Europe

Eggs (n = 139) from tawny owls (Strix aluco) were collected annually (1986-2004) in Central Norway and analyzed for organochlorines (OCs) and brominated flame retardants (BFRs). p,p'-DDE (2,2-bis(4-chlorophenyl)-1,1-dichloroethene) and polychlorinated biphenyls (PCBs) were the dominating contaminants (mean/median = 2.7/1.7 and 2.9/1.6,mu g/g, lipid weight [l.w.], respectively), comprising 90% of the contaminant burden. Other OCs (hexachlorobenzene [HCB], hexachlorocyclohexanes [HCHs], traps-nonachlor and oxychlordane) comprised less than 4% of the contaminant burden. Concentrations of OCs dropped 74-96% during the study period; p,p'-DDE, HCB, beta-HCH, oxychlordane, and PCBs decreased rapidly in the early (1986-1989) study period (23-34% per year; mean = 27.4%), but leveled off to less than 7% (mean = 3.6%) in the late period (2001-2004). The decrease in p,p'-DDE concentrations leveled off in the early 1990s, possibly due to an early ban on the use of DDT. alpha-HCH showed the strongest decline (always > 20% per year), while traps-nonachlor and gamma-HCH dropped at a constant rate of 9% per year. Toxaphene made up less than 0.6% of the measured contaminants (mean/median = 39/13 ng/ g, l.w.), and the concentrations of these compounds were lower in the late period compared to the early period, but not significant. BFRs, including hexabromocyclododecane (HBCD) and polybrominated diphenyl ethers (Sigma PBDE: mean/median = 182/ 85 ng/g, l.w.) made up about 3% of the measured contaminants. Sigma PBDE declined significantly over the study period (62%). Most PBDE congeners declined: significantly for BDE-47 (80% reduction) and BDE-153 (50% reduction), but the patterns differed; i.e., congeners associated with PentaBDE mixtures showed a rapid annual decline early (22-26%) and a slower decline late in the study period (6-12%), while the PBDEs associated with OctaBDE declined at a constant rate (1-4%). This may result from a larger reduction in the use of PentaBDE compared to other PBDE products in Europe.