AbstractMarine boundary layer air and seawater samples taken during a polar expedition cruise from East China Sea to the Arctic were analyzed in order to compare the occurrence, distribution, and fate of the banned polybrominated diphenyl ethers (PBDEs) with their brominated alternatives as well as the chlorinated Dechloranes. The sum of PBDEs (∑10PBDEs) in the atmosphere ranged from 0.07 to 8.1 pg m–3 with BDE–209 being the dominating congener and from not detected (n.d.) to 0.6 pg L–1 in seawater. Alternate brominated flame retardants (BFRs), especially hexabromobenzene (HBB), (2,3–dibromopropyl–2,4,6–tribromophenyl ether (DPTE), pentabromotoluene (PBT), 2–ethylhexyl 2,3,4,5–tetrabromobenzoate (EHTBB), bis–(2–ethylhexyl)–tetrabromophthalate (TBPH), were detected in higher concentrations than PBDEs, even in the high Arctic (0.6 to 15.4 pg m–3 for sum of alternate BFRs), indicating the change of PBDEs toward alternate BFRs in the environmental predominance. In addition, Dechlorane Plus (DP) as well as Dechlorane 602, 603, and 604 were detected both in the atmosphere and in seawater. The highest concentrations as well as the highest compound variability were observed in East Asian samples suggesting the Asian continent as source of these compounds in the marine environment. The air–seawater exchange indicates strong deposition, especially of alternate BFRs, as well as dry particle–bound deposition of BDE–209 into the ocean.