In-water ship hull cleaning: an unregulated source of hazardous organic contaminants to marine environments

In-water hull cleaning (IWC) is a recognized source of paint-derived contaminant release to marine environments, yet the dissolved organic chemical fraction of IWC effluents remains poorly characterized. Here, we investigated IWC effluents from four vessels, two container vessels (Ship A and B), a research vessel (Ship C), and a RO-RO ship (Ship D), at three major South Korean ports (Busan, Gwangyang, and Jangmok) to characterize hull-cleaning-associated dissolved organic contaminants. Non-targeted screening using ultra-performance liquid chromatography coupled with high-resolution mass spectrometry was followed by targeted quantification using triple quadrupole mass spectrometry. Data acquisition in both ionization modes yielded 21 compounds; 14 were confirmed at Level 1 confidence using authentic standards and prioritized as hull coating-derived contaminants. Prioritized analyte concentrations ranged from 6.2 to 4829 ng/mL, with coating additives dominating the quantitative profile. Nine compounds were detected in all vessel effluents, whereas five showed vessel-specific patterns, including the booster biocides tralopyril and quinoclamine, each detected exclusively in single-vessel effluents. Chemical fingerprints were highly similar among the three commercial vessels (r 2 = 0.793–0.916), supporting a ship-coating formulation source rather than site-specific contamination, whereas Ship C showed a distinct profile likely reflecting coating-formulation differences. Risk quotient assessment indicated potential ecological risks (RQ > 1) for most compounds, while global emission modeling estimated annual releases of approximately 142.84 tons. These findings demonstrate the dissolved organic fraction of IWC effluents as a chemically important and ecologically relevant component of hull-cleaning contamination, highlighting the need for improved monitoring, treatment, and regulatory control of organic chemical releases from IWC operations.