Loading of BACs on PES membrane. Due to the cost and the large number of PES pieces required for the acute toxicity test, a roll of PES membrane (300 mm × 3 m, 0.1 μm pore size) purchased from GVS (Bologna, Italy), which has similar mechanical properties and the same pore size as the PES membranes used for the sorption experiments, was cut into pieces and used as passive dosing reservoirs for the following tests. For loading of BACs onto the membranes, six cleaned PES pieces of 3.5 × 3.5 cm 2 each were immersed in a 20% (v/v) methanol/water mixture with defined concentrations of a single chemical in a glass beaker at 25°C. After 24 h of shaking, water was added to each beaker to enhance the loading efficiency, yielding a total loading volume of 10 mL and a final fraction of methanol in the solution of 13.33% (v/v). The loading beakers were shaken horizontally at 150 rpm for 4 days. After loading, the PES membranes were rinsed in excess water to remove adhered loading solution and then dried in the fume hood for at least 4 h to ensure that all methanol evaporated before transfer to the clean glass beakers for the desorption and ecotoxicity tests described below. PES membrane extraction was conducted for checking the loading efficiency of C14-, C16-and C18-BACs (further details in Section S3, SI).