Urban Pavements as Sources and Conduits of Microbial, Microplastic, and Emerging Contaminants in Water Systems: A Critical Review of Mechanisms, Pathways, and Mitigation

Urban pavements act as reactive environmental interfaces, generating, retaining, and mobilizing pollutants, including microbial communities, microplastics, and emerging chemical contaminants. This critical review synthesizes 107 studies (2020–March 2026), providing a system-level analysis of pollutant generation, transport, transformation, and mitigation. Tire and pavement wear are dominant sources, contributing 23–38% of stormwater microplastic loads, often accompanied by copper, zinc, lead, and polycyclic aromatic hydrocarbons (PAHs) exceeding water quality guidelines. The toxic tire transformation product 6PPD-quinone (6PPD-Q) is frequently detected in urban stormwater (0.002–0.29 µg L⁻¹), posing acute risks to sensitive aquatic species. Direct characterization of microbial communities on active pavements remains a key knowledge gap, as current evidence relies on building facades or permeable subgrades. Stormwater runoff and combined sewer overflows transport pollutants at 1.6–29.6 microplastic particles L⁻¹ . Permeable pavements and green infrastructure achieve high removal efficiencies for particulate contaminants (89–99.6% for microplastics; 73–99% for heavy metals), but removal of sub-20 µm particles and dissolved contaminants (PFAS, 6PPD-Q) is limited, and long-term performance under clogging is uncertain. A quantitative framework conceptualizes pavements as reactive nodes in urban water systems. Future research should elucidate biofilm-mediated transformations, sub-20 µm particle fate, toxicity of complex mixtures, and establish standardized monitoring, emphasizing multi-barrier treatment strategies over single interventions to improve urban water quality.