Degradation of cellulose-based wet wipes marketed as 'biodegradable' in their receiving urban rivers.

The environmental degradation and fate of cellulose-based 'biodegradable' wet wipes under real-world conditions remain underexplored, particularly in urban freshwater systems where they are frequently discharged via toilet flushing. Building on previous mesocosm-based experiment, this study quantified in-situ degradation of two commercially available cellulose-based wipes labelled 'biodegradable' across ten urban rivers and streams and identified key environmental drivers of degradation. Tensile strength loss was used as a proxy measurement for wipe degradation alongside cotton strip bioassays as ecological benchmarks. Wipes rich in natural cellulose degraded substantially faster (Brand A: 6.69 ± 3.19 % per day) than those dominated by regenerated cellulose (Brand B: 3.12 ± 1.93 % per day) or cotton bioassay controls (2.22 ± 1.00 % per day). Degradation rates were shaped by microbial biomass, total dissolved solids, temperature, and river-level fluctuations, although exposure duration had the largest effect - suggesting complex interactions between physical and biological processes. Despite early-stage degradation, most wipes persisted after five weeks, challenging their biodegradability claims. These findings highlight potential ecological risks from persistent textile fibre pollution, emphasising the need for updated labelling and biodegradability standards that appropriately reflect real-world freshwater conditions, as well as greater scrutiny of plastic-free alternative products and their environmental fates in general.