Ship engine room-related marine pollution: current status, impact mechanisms, and prevention strategies

This review provides a multi-dimensional and systems-oriented assessment of pollution originating from engine room operations, integrating waste typologies, dispersion mechanisms, ecological and human health impacts, regulatory frameworks, and technological mitigation strategies. Following the PRISMA 2020 framework, 267 records were identified in Scopus and Web of Science, 61 duplicates were removed, 206 records were screened, 64 full-text articles were assessed for eligibility, and 50 studies were included in the final synthesis. Key pollution sources, including oily bilge water, fuel leaks, spent lubricants, and cooling system discharges, are examined in relation to direct discharge events, accidental spills, inadequate maintenance, and insufficient treatment performance. The study critically evaluates international and regional regulatory frameworks, with particular attention to MARPOL Annex I and the operational conditions governing machinery-space bilge-water discharge. Technological and managerial countermeasures, such as multi-stage bilge treatment systems, oil-content monitor (OCM), automatic stopping or diversion arrangements, digital log integration, satellite-supported surveillance, structured waste management plans, and competency-based crew training, are analyzed within a performance-based governance framework. The synthesis indicates that treatment performance is strongly influenced by stable emulsions, surfactant loading, maintenance, calibration, and source segregation, while compliant discharge depends on the combined reliability of treatment, monitoring, record keeping, and shore reception arrangements.Abbreviations: AIS: Automatic Identification System; API: Application Programming Interface; BOD: Biological Oxygen Demand; COD: Chemical Oxygen Demand; EC: Electrocoagulation; EGCS: Exhaust Gas Cleaning System; IMO: International Maritime Organization; IoT: Internet of Things; MEPC: Marine Environment Protection Committee; NF: Nanofiltration; OCM: Oil-Content Monitor; OWS: Oil–Water Separator; PAHs: Polycyclic Aromatic Hydrocarbons; PRF: Port Reception Facility; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses; PSC: Port State Control; RO: Recognized Organization; SAR: Synthetic Aperture Radar; SLR: Systematic Literature Review; STCW: Standards of Training, Certification and Watchkeeping for Seafarers; STW: Seatrack Web; TDS: Total Dissolved Solids; UF: Ultrafiltration; VMS: Vessel Monitoring System; VR: Virtual Reality; WLO: Waste Lubricating Oil.