Waste-water treatment plants are implicated as an important source of flame retardants in insectivorous tree swallows (Tachicyneta bicolor).

Wastewater treatment plants (WWTPs) are an important source of anthropogenic chemicals, including organic flame retardants (FRs). Limited studies indicate birds can be exposed to FRs by feeding from waters receiving WWTP effluent or in fields receiving biosolids. Expanding on our earlier study, 47 legacy and 18 new FR contaminants were characterized in the eggs of insectivorous tree swallows (Tachycineta bicolor) feeding in water bodies receiving effluent from two WWTPs and compared to those from a reference site 19 km downstream of the nearest WWTP. Of the FRs measured, polybrominated diphenyl ethers (PBDEs) dominated the FR profile, specifically BDE-47, -99, -100, -153, -154, with considerably lower concentrations of hexabromocyclododecane (HBCDD), BDE-183 and BDE-209; each detected in 96-100% of the eggs overall except HBCDD (83%). FR concentrations were usually significantly greater in eggs from the secondary WWTP versus the tertiary WWTP and/or reference site. Despite low detection rates, concentrations of new FRs, specifically pentabromobenzyl acrylate (PBBA), 1,2,-bis-(2,4,6-tribromophenoxy)ethane (BTBPE), bis(2-ethylhexyl)-tetrabromophthalate (BEHTBP), tetrabromo-o-chlorotoluene (TBCT), hexabromobenzene (HBB), α- and β-1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (DBE-DBCH), were greater than HBCDD or BDE-209. Additional evidence that WWTPs are an important source of exposure to new FR contaminants for birds utilizing associated water bodies is that only the WTTP eggs, not the reference eggs, had measureable concentrations of PBBA, TBCT, BEHTBP, HBB, α-DBE-DBCH, 2,2',4,5,5'-pentabromobiphenyl (BB-101), pentabromoethyl benzene (PBEB), 2,4,6-tribromophenyl allyl ether (TBPAE), and tetrabromo-p-xylene (pTBX). Our study suggests that WWTPs are an important source of legacy and new FR contaminants for birds consuming prey that are associated with WWTP out-flows.