Paint-derived particles are increasingly recognised as a major contributor to marine microplastic pollution, yet emissions from active vessels under routine operational conditions remain poorly characterised. We tested the hypothesis that exposed deck coatings on operational ships continuously generate and accumulate paint-derived micro- and meso-particles in the absence of maintenance activities. Samples were collected from accumulation zones adjacent to drainage points on three vessel types: an offshore support vessel, a container ship, and a liquefied natural gas carrier. Size-fractionated material was analysed using microscopy, FTIR/NIR spectroscopy, and multispectral imaging. Across vessels, more than 90% of classified particles were paint-derived fragments or iron oxide-rich corrosion products, while a minor fraction consisted of synthetic polymer fibres and fragments. Although the study design does not allow calculation of emission rates per unit area, the consistent presence and dominance of coating-derived debris across vessel types provide field-based evidence that routine weathering of deck coatings represents an ongoing and currently unregulated source of micro-sized particulate pollution. These findings identify exposed ship superstructures as a previously undercharacterised emission pathway and support the inclusion of coating degradation in ship-borne microplastic inventories and maritime sustainability frameworks.
