AbstractThe occurrence, spatial and seasonal concentration variations in air and seawater and the air–seawater exchange of polybrominated diphenyl ethers (PBDEs), alternate brominated flame retardants (BFRs) and Dechlorane Plus (DP) were studied in the German part of the North Sea in 2010. BDE–209 and DP were found to be the dominating compounds, both in the atmosphere and in seawater. Sum PBDEs (∑10PBDEs) ranged from 0.31 to 10.7 pg m−3 in the atmosphere and from not detected (n.d.) to 10.5 pg L−1 in seawater, respectively. DP ranged from 0.13 to 22.3 pg m−3 and from 0.10 to 17.7 pg L−1 in air and seawater, respectively. Besides, four other BFRs including hexabromobenzene (HBB) and pentabromobenzene (PBBz) were detected. Elevated atmospheric concentrations were observed in continentally influenced air masses while highest seawater concentrations were observed at sampling stations close to the coast influenced by riverine discharge. The ratio of the two DP stereoisomers both in air and water was found to be close to the technical mixture at high concentrations but changed at lower concentrations giving first evidence for the alteration within the aquatic environment. Both dry air-seawater gas exchange and dry deposition are input pathways of BFRs and DP in the North Sea besides riverine discharge.