The exposure to plastic debris and associated pollutants for wildlife is of urgent conc,but little attention has been paid on the transfer of plastic additives from plastic debris to organisms.In the present study,the leaching of incorporated flame retardants (FRs),including polybrominated diphenyl ethers (PBDEs),altative brominated FRs (AFRs),and phosphate flame retardants (PFRs),from different sizes of recycled acrylonitrile-butadiene-styrene (ABS) polymer were investigated in avian digestive fluids.The impact of co-ingested sediment on the leaching of additive-derived FRs in digestive fluids was also explored.In the recycled ABS,BDE 209 (715 μg/g) and 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE,1766 μg/g) had the highest concentrations among all target FRs.The leaching proportions of FRs were higher in finer sizes of ABS.The leaching proportions of FRs from recycled ABS increased with elevated logKow of FRs.In the tests with coexisted ABS and sediment,hexato deca-BDEs,BTBPE,and decabromodiphenyl ethane (DBDPE) migrated from ABS to sediment,which resulted in the less bioaccessible fractions of these FRs in gut fluids.More lipophilic chemicals tended to be adsorbed by sediment from ABS.The results suggest the migration of additive-derived FRs from plastics to other indigestible materials in digestive fluids.The findings in this study provide insights into the transfer of additive-derived FRs from plastics to birds,and indicate the significant contribution of FR-incorporated plastics to bioaccumulation of highly lipophilic FRs.