Uptake, distribution, depletion, and in ovo transfer of isomers of hexabromocyclododecane flame retardant in diet-exposed American kestrels (Falco sparverius)

Abstract

Hexabromocyclododecane (HBCDD) is a flame retardant and a global contaminant, yet the toxicokinetics of HBCDD diastereoisomers remains unknown in wildlife species. The present study examined in captive American kestrels (Falco sparverius) (diastereo) isomer-specific HBCDD uptake, depletion, tissue distribution, and transfer to eggs in a dietary dosing study with an HBCDD technical mixture (HBCDD-TM). Adult tissue and plasma collections were from separate cohorts of unpaired individual males (n = 10) and females (n = 10) exposed for 21 d to 800 ng/g wet weight of HBCDD-TM (in safflower oil and injected into their cockerel [brain] diet), followed by a 25-d depuration period. A separate cohort of 12 males only was used for control adult tissue and plasma collections. For egg collections, separate cohorts of 11 control pairs (n = 22 birds) and 20 HBCDD-exposed pairs (n = 40 birds) were allowed to breed, and their eggs were collected (n = 19 exposed eggs and n = 10 control eggs). The sum (Σ) HBCDD concentrations were near or below detection (<0.01-0.1 ng/g wet wt) in all control samples but quantifiable in all samples from exposed birds (no differences [p > 0.05] between males and females). Arithmetic mean ΣHBCDD concentrations were highest in fat >> eggs > liver > plasma. The mean ΣHBCDD depletion rate in plasma between the uptake and depuration periods was estimated to be 0.22 ng/g/d with a half-life of approximately 15 d. The γ-HBCDD diastereoisomer was >60% of the ΣHBCDD in plasma after the uptake period and similar to the HBCDD-TM (∼80%). After the depuration period, α-HBCDD was >70% of the HBCDD in plasma, fat, liver, and eggs; and this α-HBCDD domination indicated isomer-specific accumulation as a result of selective metabolism, uptake, protein binding, and/or in ovo transport.

Keywords: American kestrel; Diet-exposed; Flame retardant; Hexabromocyclododecane diastereoisomer; Uptake and distribution.