Permeable pavement systems for microplastic mitigation: Critical insights on transport, retention, detection and removal efficiency

Microplastics (MPs) in urban stormwater are emerging contaminants of increasing concern due to their persistence, mobility, and potential impacts on ecosystems and human health. Permeable pavement systems (PPS) have gained attention as stormwater control measures capable of intercepting MPs; however, their long-term performance and associated uncertainties remain poorly understood. This paper synthesises current evidence on MP transport, retention, detection, and removal in PPS based on twenty-eight peer-reviewed studies published between 2000 and May 2026. The evidence indicates a rapidly emerging field, with most studies published during the past six years and annual output peaking in 2025. Reported short-term MP retention efficiencies range from 89% to 99.6% under controlled and field conditions. However, meaningful comparison among studies is constrained by substantial variation in pavement configurations, hydraulic loading, MP characteristics, and analytical methodology. Retention occurs predominantly within surfaces, joints, bedding, and geotextile layers, whereas fragment-shaped MPs (