Mitigating risk of tire wear particles in Daphnia pulex: In silico approaches

Tire wear particles (TWPs), commonly detected emerging contaminants in aquatic environments, have recently attracted global attention. Therefore, the toxicity and potential mitigation of TWPs in the experimental model species Daphnia pulex (D. pulex) were evaluated using molecular docking and molecular dynamic simulation methods. The binding energy of styrene-butadiene rubber, along with tire additives (i.e., antioxidants, flame retardants, heat stabilizers, light stabilizers and lubricants) and arginine kinase protein was used as an indicator of ecological risk of TWPs on D. pulex. Ninety-six proportioning schemes for styrene-butadiene rubber tire microplastics were generated, and Formulation No. 38 was identified as the one with the minimum ecological risk, corresponding to a binding energy value of -46.486 kJ/mol. Based on a full factorial design, the third-order interaction effect was determined to account for the most substantial proportion, relative to both the main effects and second-order interaction effects. Consequently, the competitive or synergistic effects governing the molecular docking of tire additives cannot be neglected in subsequent analyses. Furthermore, the applicability of the developed tire proportioning schemes was validated using the jumping frequency of D. pulex-a key ecotoxicological endpoint. This finding indicates that the tire formulations screened in the present study exhibit a certain degree of representativeness for mitigating risks to the aquatic ecological environment. This is a novel ecological risk evaluation method that can be effectively used to reduce the ecological risk of tire additives in aquatic environments.