• • Total PBDE concentrations in Dalian coastal seawater ranged from not detected to 511.96 pg·L−1 (mean 163.96 pg·L−1), indicating widespread but low-level contamination; this baseline is critical for regulatory trend monitoring.
• • BDE-209 dominated the congener profile, accounting for 24.1% of ∑PBDEs, reflecting ongoing sources from commercial deca-BDE mixtures despite restrictions; this informs source apportionment and risk prioritization.
• • Spatial analysis revealed elevated highly brominated PBDEs near sewage outlets, confirming sewage discharge as a major anthropogenic input pathway; this identifies targeted intervention points for pollution control.
• • Ecological risk quotients were extremely low (max 0.013 for BDE-17), suggesting negligible acute risk; however, chronic effects and bioaccumulation potential warrant long-term surveillance.