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Permeable pavement systems for microplastic mitigation: Critical insights on transport, retention, detection and removal efficiency
Summary
This review of 28 studies finds that special "permeable pavements" — designed to let rainwater soak through instead of running off streets into rivers — can trap 89-99% of tiny plastic particles (microplastics) in the short term, which matters because these particles wash off roads and eventually make their way into waterways, soil, and potentially our food and water supply. However, scientists still don't know if these pavements keep working well over years of use, or whether the trapped plastic particles could eventually break free again, so more long-term testing is needed before we can call this a lasting solution.
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 (<100 µm) are most frequently detected in effluent. Emerging design innovations, including drinking water treatment sludge, cured carbon fibres, recycled e-polycarbonate aggregates, and tyre- or plastic-derived materials, show potential for enhancing retention and hydraulic or mechanical performance. Nevertheless, their long-term durability, remobilisation potential, secondary MP generation, and life-cycle implications remain largely unresolved. Overall, current evidence provides stronger support for short-term MP interception than sustained environmental risk reduction. Future research should prioritise harmonised monitoring and analytical protocols, long-term field validation, improved detection of tyre wear particles, mass-balance assessment, and evaluation of MP remobilisation under realistic hydraulic, climatic, and maintenance conditions to strengthen confidence in PPS as sustainable stormwater treatment technologies.