Legacy-to-alternative shift of brominated flame retardants in the east china sea revealed by multimedia observations and coupled modeling.

With the phase-out of legacy brominated flame retardants (BFRs), particularly polybrominated diphenyl ethers (PBDEs), the use of novel brominated flame retardants (NBFRs) has increased steadily. This study investigated 42 PBDEs and 13 NBFRs in seawater, sediments, and atmospheric aerosols from the East China Sea (ECS). Regional investigations were integrated with a coupled dynamic material flow analysis-Level IV fugacity model and ecological risk assessment to characterize present contamination patterns and project long‑term trends over the coming decades. Legacy and novel BFRs co-occurred across all media, with lower-brominated congeners relatively enriched in seawater and highly brominated compounds dominating sediments and aerosols. Model results identified sediments as the major sink for BFRs, accounting for most of the ECS system inventory. PBDE concentrations peaked around 2007 and subsequently declined, whereas NBFRs increased rapidly after 2006 and are projected to gradually surpass PBDEs in aquatic and sedimentary environments under current emission trends. Most BFRs posed low average risks in seawater, but elevated risks occurred at nearshore sites, and sediment-associated risks were substantially higher. Our results reveal an ongoing shift from legacy PBDE contamination to NBFR-dominated pollution and highlight sediments as a long-term reservoir of BFR risk in the ECS.