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

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. Environ Toxicol Chem 2015;34:1103–1112. © 2015 SETAC