Nationwide occurrence, distribution drivers, and source apportionment of steroids in China's coastal wetlands: An urgent priority for 4-androstene-3,17-dione and progesterone

Steroids are potent endocrine-disrupting compounds, yet their environmental behavior in coastal wetlands remains poorly understood. This first nationwide assessment of steroids along approximately 5000 km China's coastline analyzed 21 steroids across 136 water and 139 sediment samples from 10 regions. Eight and eleven steroids were identified in water and sediment, at total concentrations of not detected (ND) to 23 ng/L and ND to 32 ng/g, respectively, with spatial distributions showing significant heterogeneity. Sediments constitute the dominant reservoir, storing 97 % of the ~19-ton national steroid inventory, pinpointing them as a critical compartment for long-term monitoring. Steroid occurrence was primarily driven by socioeconomic inputs (livestock, aquaculture, and sewage), while their fate and partitioning were subsequently modulated by coastal environmental conditions (salinity, chlorophyll- a , temperature, total organic carbon). Source apportionment further demonstrated that water and sediment record pollution across different timescales: water reflects current wastewater inputs (64.3 % from wastewater treatment plants), whereas sediment preserves a legacy of historical domestic and livestock sources (96.6 %). Critically, risk-based prioritization showed that exposure potential outweighs intrinsic hazard, though steroid stanozolol exhibited the highest hazard, the most exposed steroids—4-androstene-3,17-dione and progesterone—were identified as high-priority contaminants. Our findings translated data into actionable management strategies, offering a scientific framework for targeted source control, optimized monitoring, and effective risk mitigation of steroid pollution in coastal ecosystems. • First nationwide assessment of steroids in China's coastal wetlands was conducted. • Sediment stored 97 % of total steroids, acting as the primary reservoir. • Environmental and socio-eco factors significantly drive steroid distribution. • 4-Androstene-3,17-dione and progesterone were high-priority steroids in water.