Strong Disparities in Projected Ecotoxicological Risks from Pharmaceuticals in German Rivers: Implications for the 2050 EU’s Zero Pollution Ambition

The European Union’s zero-pollution ambition targets a toxic-free environment by 2050, but an aging population and a warming climate increase disease prevalence and pharmaceutical use, leaving future pollution levels and the route to this goal uncertain. Using a node-link model informed by Representative Concentration Pathways (RCP) and Shared Socioeconomic Pathway (SSP) scenarios, we projected concentrations of five pharmaceuticals and their ecological risks to three aquatic species in 1 km river stretches across Saxony, Germany, by the 2050s. Signal-to-noise ratios ranged from 4.49 ± 1.30 (carbamazepine) to 7.68 ± 2.22 (ciprofloxacin), showing an agreement across 15 climate models. Under SSP5–8.5, median pharmaceutical concentrations varied from −98% (sulfamethoxazole) to 192% (gabapentin) without policy intervention in pharmaceutical prescribing, and from −60% (carbamazepine) to −23% (metformin) with stringent intervention, relative to the 2010s baseline. Rivers under at-risk toxicity from pharmaceutical mixtures increased by 7.7% (algae) to 12.4% (daphnia) without intervention, but decreased by 6.5% (daphnia) to 6.8% (fish) with intervention. To reach no-harm targets for the ecosystem from pharmaceutical mixtures at the moderate-risk, 21% (with intervention) to 33% (without intervention) of wastewater treatment plants require full upgrades for all pharmaceuticals. This study consolidates knowledge on the gaps to EU’s zero-pollution goals amid socioeconomic and hydroclimatic changes.