Potential Release of Micro- and Nanoplastics from Stormwater Infrastructure.

Stormwater systems increasingly rely on polymer-based materials such as polyvinyl chloride (PVC), polyethylene (PE), high-density polyethylene (HDPE), and polypropylene (PP) due to their durability, low cost, and corrosion resistance. However, these materials are susceptible to photochemical, abiotic chemical (e.g., oxidation/chlorination from disinfectants and oxidants), biological (microbial/enzymatic), and mechanical degradation, resulting in the release of micro- and nanoplastics (MNPs) throughout their service life. This perspective critically examines the mechanisms underlying MNP formation in stormwater infrastructure - including ultraviolet (UV)/photoaging, chemical oxidation, hydraulic abrasion, and bed-load interactions - and evaluates laboratory methods used to study these processes. Standardized tools such as the Taber abrasion, Darmstadt rigs, circulating-loop systems, UV weathering, and chemical aging protocols are evaluated for their ability to simulate real-world conditions and quantify plastic particle release. Existing methods primarily quantify material durability but rarely capture or characterize released MNPs, leading to gaps in emission factor development and poor translation of laboratory results to stormwater environments. Analytical techniques such as μ-FTIR, Raman spectroscopy, SEM/EDX, and Py-GC/MS are reviewed for their complementary roles in particle identification and quantification. Key methodological gaps are identified, including inconsistent sampling protocols, limited detection of nanoplastics (NPs), unrealistic hydraulic simulations, and sparse comparisons between recycled and virgin pipe materials. To address these issues, this perspective proposes a hydraulically realistic circulating-loop platform capable of integrating stormwater-like hydraulics with UV and chemical aging, as well as analytical techniques to quantify MNP emissions from pipe materials under environmentally relevant conditions. This integrated framework supports the development of predictive models that link material degradation to MNP release, thereby advancing sustainable infrastructure design and plastic pollution mitigation in water systems.