Cellulose-based wet wipes undergo limited degradation in river environments.

The environmental fate of cellulose-based "biodegradable" wet wipes in freshwater ecosystems remains poorly understood, despite growing market demand and legislative shifts banning plastic-containing alternatives. This study evaluated the degradation behaviour of two commercially available biodegradable wet wipe brands in upland stream mesocosms mimicking real-world river conditions. Using tensile strength loss (TSL) as the primary degradation metric, wipe degradation was compared across varied pH, temperature, nutrient, and light regimes, alongside cotton strip controls. Results revealed that although degradation rates varied by material and environmental context, both wet wipe brands persisted in river systems for 5 weeks, with Brand A degrading ∼50 % faster than Brand B and nearly twice as fast as cotton controls. Degradation was significantly influenced by pH, temperature, and total dissolved solids, but not by wipe positioning in the water column (hyporheic, submerged, surface) or microbial biomass alone. Temperature-adjusted TSL (% per degree day) emerged as the most robust degradation metric, suggesting initial physical disintegration preceded microbial breakdown. These findings challenge current biodegradability claims and highlight the need for regulatory testing under environmentally relevant freshwater conditions to ensure truly biodegradable wet wipe products.