Unveiling the Enigma: Decoding Chemical Additives in Shoe Soles for Recognition and Ecological Risk Insights

Although rubber shoes have been extensively produced and used for the past century, the chemical additives released from shoe soles, as well as the aquatic ecological risks, have been overlooked. Using nontargeted analysis, this study detected 106 and 70 chemicals in shoe soles and leachates, respectively. The total concentrations were in the range of 203 to 3.21 × 103 μg/g for shoe soles and 247 to 5.32 × 104 μg/L for leachates. The detected chemicals were distributed in 10 groups, among which phthalate esters were the dominant chemical additives. Chemical concentrations and compositions varied significantly among different shoes, with polyvinyl chloride shoe sole (3.21 × 104 μg/g) and leachate (5.32 × 104 μg/L) having concentrations 158 and 215 times higher, respectively, than that of polyurethane (shoe sole, 203 μg/g; leachate, 247 μg/L). Risk quotient analysis indicated low ecological risks of shoe sole abrasions to aquatic ecosystems (9.64 × 10–4 to 0.09). The predicted high binding affinities between the detected chemicals and hormone receptors of Oryzias melastigma suggested their potential endocrine-disrupting effects. This study emphasizes the screening results of chemical additives in shoe soles and proposes continuous monitoring of the potential environmental risks associated with global shoe products.