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Review

A Review of Microplastics Research in the Shipbuilding and Maritime Transport Industry

by
Ivana Lučin
1,
Ante Sikirica
1,*,
Bože Lučin
2 and
Marta Alvir
1
1
Faculty of Engineering, University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia
2
Flowtech d.o.o., Milutina Barača 15/2, 51000 Rijeka, Croatia
*
Author to whom correspondence should be addressed.
J. Mar. Sci. Eng. 2026, 14(1), 73; https://doi.org/10.3390/jmse14010073 (registering DOI)
Submission received: 2 December 2025 / Revised: 23 December 2025 / Accepted: 26 December 2025 / Published: 30 December 2025
(This article belongs to the Section Marine Pollution)
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Abstract

Microplastics are contaminants of increasing environmental concern, particularly in marine ecosystems where they can be easily ingested by marine organisms, causing adverse health problems in animals and, through trophic transfer, in humans. While numerous studies have examined microplastic pollution in marine environments, most focus on water, sediment, or biota, thereby only measuring cumulative effects from multiple pollution sources in one area. This review aims to assess existing research on microplastic pollution originating from shipyards and maritime transport activities, with the goal of identifying current knowledge, methodological approaches, and existing research gaps. A review of the scientific literature was conducted, focusing on studies that investigated microplastic pollution associated with shipyards and maritime transport. Priority was given to peer-reviewed publications that included quantitative or qualitative measurements of microplastics. The reviewed literature reveals a limited number of studies explicitly addressing microplastic emissions from shipyards and maritime transport. Available studies employ diverse sampling strategies and analytical methods, making direct comparisons challenging. This review highlights significant gaps in current knowledge regarding microplastic sources and pathways linked to maritime industries. By synthesizing existing data, the paper provides a foundation for future targeted research and supports the development of more effective pollution reduction strategies.

1. Introduction

Marine pollution is a growing concern, so regulations addressing this issue have been developed over the years. The United Nations Convention on the Law of the Sea (UNCLOS), adopted in 1982, establishes rules for ocean usage and the management of marine resources. It includes provisions for preventing the pollution of the marine environment. It has been ratified by 171 parties, which include almost all major maritime and coastal states, excluding the United States. The International Convention for the Prevention of Pollution from Ships (MARPOL), drafted by the United Nations agency the International Maritime Organization (IMO) and adopted in 1973, is the main international convention addressing marine pollution from ships resulting from operational and accidental causes. It sets regulations and standards to control pollution from various sources, including oil, garbage, air emissions, wastewater, harmful substances, etc. Many countries have also formulated additional directives and regulations addressing this matter; for example, in the EU, there is Directive 2005/35/EC on ship-source pollution and penalties for infringements [1] and Directive (EU) 2019/883 on port facilities for reception of waste from ships [2]. The EU is continuously adjusting its legislation, with a more recent maritime safety package adopted in 2024 that amends the relevant directives on ship-source pollution.
It is typically reported that around 80% of pollution in water bodies originates from land-based sources, which can enter marine environments via untreated wastewater systems, wastewater treatment plants, combined sewer overflows, and stormwater systems [3,4]. The remaining 20% originates from sea-based sources, including shipping activities, offshore industries, and maritime operations such as fishing. Fishing vessels can produce microplastic (MP) particles from their fishing gear during operation [5], while lost or discarded fishing gear has been identified as a significant contributor to plastic pollution [6,7]. Plastic pellets, also considered as MP, have been identified as a hazardous substance that can be released as lost cargo during sea transport [7,8]. This issue has been recognized worldwide and has been addressed by the European Commission’s proposal for a regulation to prevent plastic pellet losses and thereby reduce MP pollution [9].
MP is considered an emerging pollutant, prompting growing concern about its adverse effects on the environment and living organisms. Due to their size and shape, MP particles can be easily ingested by aquatic organisms, causing adverse effects [10]. Subsequently, they become part of the food chain and can ultimately be ingested by humans, potentially causing adverse health effects [11]. The surfaces of MP particles are hydrophobic and have a high surface-area-to-volume ratio, making them suitable for microbial colonization and biofilm formation. In aquatic environments, these biofilms can harbor harmful substances, including toxic chemicals, plastic additives, and pathogens [12]. However, due to many research gaps that need to be explored to fully understand the impacts of MP pollution, there are currently no established measurement or estimation strategies, and there is no legal framework imposing regulations for MP pollution in the shipbuilding sector.
The growing concern regarding MP pollution is evident in the proliferation of studies that conduct measurements in water bodies, including lakes, rivers, and seas. However, these measurements capture the cumulative effect of various MP pollution sources rather than isolating individual contributors. Harbors, often located in shallow, semi-enclosed areas with limited water exchange, are significant contributors to localized MP pollution through their operational activities. Graca et al. [13] investigated MP in marine and beach sediments of the Southern Baltic Sea and found elevated concentrations of polymers commonly used in shipbuilding, suggesting marine transport activities as an important contributor. Two recent reviews synthesized current knowledge on MP pollution in maritime environments. Belioka et al. [14] conducted an extensive review of studies examining MP pollution in marine and harbor settings, identifying port activities as the second most significant MP pollution source, greater than fishing activities, industrial facilities, shipping operation, etc. Supe et al. [15] focused specifically on ports and revealed substantial geographic imbalance in research coverage; half of the reviewed studies examined Asian ports, 17% focused on European locations, and the remainder covered the Americas, Oceania, and Africa. They concluded that MP research in port environments remains in its early stages, with a particular need for studies addressing spatio-temporal distribution patterns.
Shipping routes have also been investigated as locations with MP pollution, though to a lesser extent. Zhou et al. [16] measured MP concentration in the sea surface microlayer in Osaka Bay, Japan. Three locations were chosen in the coastal area, as well as four along shipping routes and one in the center of the bay. Measurements were conducted from September 2021 until June 2023. The authors noted that measurements were conducted under varying conditions, including tides, currents, and different weather patterns. A greater number of MP particles were found along shipping routes, and the polymer type used in the antifouling paints was observed, indicating that the shipping activities are a source of MP pollution. In work by Yang et al. [17], MP concentration was measured at surface and subsurface levels (5 m depth) along the shipping route, with the primary focus on observing differences between surface and subsurface levels. Rivas et al. [18] conducted a citizen science study where volunteers gathered traffic data for three estuaries along the Cantabrian coast (Spain) from December 2023 to February 2024. Water samples were taken from eight sites for each estuary, and the study reported that there is a direct relationship between maritime traffic and the amount of microplastics. These studies, however, are scarce, so it is difficult to draw general conclusions about contributions to MP pollution from specific shipping and marine activities; therefore, targeted research is needed.
Shipyards were identified as MP pollution sources in the study by Sparks and Awe [19], where sediment was analyzed in the marina of a small urban town in False Bay, Cape Town, South Africa. The uniqueness of the investigated location lies in minimal anthropogenic inputs (e.g., no major riverine input, no major industrial activities, and low commercial maritime activities), enabling pollution attribution to localized sources (naval harbour, marina, and shipyard), as reported by the authors. The greatest concentration of MP in the form of antifouling paint particles (APPs) was observed at the slipway of a shipyard. Islas et al. [20] measured paint MPs in sediment of high maritime traffic and maintenance areas in the port of Mar del Plata, Argentina and a high concentration of paint-related MPs was associated with places dedicated to vessel maintenance. Other researchers have also measured paint fragments in sediment or seawater, and some have linked them to ship paints, as reported in Thuan et al. [21]. However, these studies cannot definitively distinguish whether these particles originate from vessel operation, maintenance, or production activities conducted in shipyards. Therefore, research on MP pollution from specific shipyard activities is needed.
The presented papers suggest maritime transport and shipbuilding activities as potential sources of MP pollution but without identifying and quantifying pollution contributions from specific activities. Wastewater from cleaning and maintenance operations in shipyards has been analyzed for various pollutants [22,23,24,25,26,27]; however, due to the complex composition of marine coatings, most studies focus on metal concentrations, with MP particle analysis only recently emerging as a research focus. Therefore, to establish appropriate mitigation or prevention strategies, it is necessary that specific contributors are identified and quantified. Given the increasing concern regarding MP pollution, review papers focusing on specific aspects of MP pollution are emerging. For example, Belioka et Achilias [14] reviewed MP pollution in harbor environments by synthesizing MP measurements in seawater; Oertel et al. [28] examined ship paints as MP pollutants along the supply chain; and Naik et al. [29] reviewed papers detailing the fate of MPs in ballast water and their consequences for the environment and human health. To the best of the authors’ knowledge, however, there are no review papers providing a systematized overview of research conducting MP measurements for specific activities in shipbuilding and maritime transport. In light of this gap in the existing literature, this paper aims to present a review of relevant studies examining MP pollution generation associated with shipbuilding and maritime transport activities. Following a presentation of the methodology and a contextual overview of MP measurements and modelling strategies in marine environments, this review systematically evaluates four key pollution sources and vectors: antifouling paints, manufacturing operations, gray water, and ballast water. Research gaps are identified, and possible future research directions are presented.

2. Materials and Methods

To identify the most relevant topics in the previous literature, a bibliometric analysis was conducted using keyword co-occurrence in VOSviewer 1.6.20 [30]. Such analyses offer a comprehensive understanding of major focus areas, current research status, and emerging topics for future investigation. A diagram of the literature overview procedure is presented in Figure 1. The Web of Science and Scopus databases were queried using the following search terms: (“microplastic*” OR “micro-plastic*”) AND (“shipbuilding*” OR “shipyard*” OR “maritime*” OR “shipping*” OR “gray water” OR “graywater” OR “ballast water” OR “antifouling paint particle*”). For both databases, a search was conducted based on article title, abstract and keywords. To ensure comprehensive coverage, various term forms were used; for instance, both “shipping” and “maritime transport” were considered. The query identified 232 articles in Web of Science and 283 in the Scopus database. Given the larger number of results, the Scopus database was taken for keyword co-occurrence analysis, while a literature review was conducted for both databases, i.e., search results were compared to include literature identified by at least one database. Notably, only 7 studies addressed both microplastics and shipbuilding, while 11 examined microplastics and shipyards in the Scopus database, indicating limited research in this area. Among the 3314 identified keywords, 130 appeared at least 10 times and were included in the co-occurrence analysis, as shown in Figure 2. It can be observed that beyond “microplastic,” the most frequently occurring keywords included “plastic”, “water pollutant”, “environmental modelling”, “marine pollution”. The color of keywords indicates the average publication year, indicating that topics such as ships, paint, and risk assessments have received increased attention in recent years. Overall, the analysis encompasses research articles, book chapters, and conference papers published from 2006 to November 2025.
An overview of the locations in the world that have conducted research on this topic is presented in Figure 3. A map is created for the affiliations appearing in the list of articles according to the Scopus database that was previously created. It can be observed that the highest numbers of affiliations are from China, the United States of America, Italy, the United Kingdom, and India.
All identified papers were screened based on their titles and abstracts. Studies reporting MP measurements related to shipbuilding or maritime transport were subsequently subjected to a full-text review. Only a limited number of papers were found to conduct MP measurements relevant to these activities. In an attempt to further expand the literature base, review papers on marine microplastic pollution were examined to identify references addressing microplastics in shipbuilding or maritime transport activities. These papers and their cited works were analyzed and included when relevant. Additionally, forward citation searches of papers conducting MP measurements in shipbuilding and maritime transport were conducted via Google Scholar. The aim was to identify if there are subsequent thematically related studies. This approach resulted in the identification of a small number of additional papers, which were included in the review.
The authors acknowledge that this methodology does not provide an exhaustive literature review. Relevant studies may exist beyond those identified through the applied search methods. This reflects the early and underdeveloped state of research in the field. Notably, even papers published in high-impact journals report minimal or no prior research on this topic and cite few relevant sources, reinforcing the conclusion that little established work exists in this area. Despite these constraints, the review captures the vast majority of the existing literature and identifies key findings and future research directions.

3. Measurement and Modeling of Microplastic Pollution in the Sea

Based on size, plastic debris can be divided into four categories—macroplastic, mesoplastic, microplastic, and nanoplastic—with reported size ranges varying between studies [31]. Microplastic particles are typically defined as plastic particles with a size below 5 mm [32]; however, some researchers suggest that this threshold should be reduced to a smaller value (e.g., 1 mm) [33]. In most of the research, particles larger than 2.5 cm are called macroplastics, while mesoplastics are particles in the range between 2.5 cm and 5 mm. Nanoplastic is usually defined as particles smaller than 0.001 mm. MP can be divided into primary MP, produced at microscopic sizes, and secondary MP, resulting from the breakdown of larger particles. Depending on their origin, MP particles have various properties and can vary in size, shape, polymer composition, density, etc. These characteristics influence particle transport and deposition processes in marine environments. Environmental factors such as wind, waves, tides, and currents influence microplastic transport and deposition, while biochemical processes, including degradation and biofouling, can alter particle properties over time. For more details regarding the characteristics, pathways, and potential impacts of MP pollution, readers are referred to review papers [10,34,35,36]. Although the number of MP papers is rapidly increasing, there are still considerable gaps in our understanding of MP pollution sources and pathways.
Understanding the spatial distribution of MP particles in global waters is crucial for assessing pollution patterns and transport pathways. Researchers have synthesized existing data through review papers examining MP pollution in the Indian Ocean [37], Mediterranean Sea [38], and globally [39,40]. However, these reviews consistently highlight the need for standardized methods in sample collection, particle separation, and identification. Samples for MP characterization can be collected from sediment, water, and biota using various techniques. For water sampling, two primary methods are employed: manta trawl and grab sampling. Manta trawls use nets with specific mesh sizes to filter large volumes of surface water, capturing only particles larger than the mesh openings. Grab sampling, by contrast, collects predefined water volumes and can be used to detect smaller MP particles depending on subsequent filtration and analytical methods. Poli et al. [41] conducted in situ comparison of these techniques, demonstrating the advantages of each and ultimately recommending that both methods be combined for optimal reliability. However, the choice of sampling method is only part of the standardization challenge in MP research. MP concentrations vary naturally with sampling depth, yet studies addressing this variability employ different sampling depths, mesh sizes, reporting units, and laboratory preparation protocols. These combined methodological differences make direct comparison across studies problematic [42]. To address these standardization challenges, Stock et al. [42] provided a comprehensive review of MP measurement strategies in marine environments with specific recommendations for methodological standardization.
Coastal areas typically receive MP from multiple sources, but concentration measurements alone cannot distinguish between them or quantify individual source contributions. To address this limitation, studies typically analyze particle characteristics such as type, composition, shape, and color, alongside size and quantity. MP particles can subsequently be classified into distinct morphologies: fragments, foams, pellets, films, and fibers [43]. While these characteristics can suggest probable sources, current analytical techniques cannot definitively identify pollution sources. For example, fiber particles mainly originate from clothing, but due to a lack of consistent methodologies for polymer identification, the true source cannot be unambiguously determined [44]. Therefore, authors may report textiles as the most probable pollution source while noting other possible sources, such as fishing nets, ropes, or shipping activities [45].
Field measurements capture MP concentration or abundance at specific locations and time points, making them impractical to characterize dynamic spatio-temporal behavior across large areas due to the time and cost constraints of extensive sampling campaigns. Numerical modeling offers a complementary approach for understanding MP transport pathways and distribution patterns over broader spatial and temporal scales. The paper by Moodley et al. [46] provides a comprehensive review of mathematical modeling approaches for MP transport in aquatic environments, categorizing methodologies into five primary types: hydrodynamic, process-based, statistical, mass-balance, and machine learning models. Hydrodynamic models simulate fluid motion driven by wind, waves, and tides using platforms such as MIKE or the Regional Ocean Modeling System (ROMS). Process-based models incorporate biological and physical processes affecting MPs, including degradation, biofouling, settling, and resuspension. Statistical models apply probabilistic techniques to characterize MP distributions, while mass-balance models track inflows, outflows, and concentration changes via conservation equations. Machine learning models identify underlying patterns and correlations from observational data. The authors [46] reviewed 61 modeling studies from 2012 to 2022 and emphasized that model calibration and validation require substantial experimental data collected using standardized units that report both mass and particle counts. Senathirajah et al. [47] recently conducted a more focused review on MP transport in bay systems, where complex land–ocean–atmosphere interactions occur. They similarly highlighted the critical need for standardized sampling protocols and harmonized datasets for model validation. Such simulations offer a framework for assessing MP transport and fate; however, their reliability is dependent on the specification of initial conditions. Accurate quantification of MP inputs from distinct pollution sources is required; therefore, in subsequent sections, research on specific MP pollution contributors and vectors in maritime transport and shipbuilding are presented.

4. Sources and Vectors of MP-Related Pollution in Maritime Transport

During vessel operation, paint particles can be released into the marine environment through self-polishing or mechanical erosion, contributing to MP pollution. Additional MP pollution sources include gray water from wastewater discharge generated by human activities onboard, which becomes more significant on cruise ships with larger passenger numbers. Ballast water is also of interest in the context of MP pollution, as it can act as a vector for the transport of MP particles. More detail regarding these pollution sources and vectors is provided in subsequent sections.

4.1. Paint Erosion During Vessel Operation

Antifouling coatings are commonly applied to prevent the growth of aquatic organisms, but these paints are now becoming recognized as a significant source of marine pollution [21,48,49,50]. In a policy brief by Tamburri et al. [51], five scenarios causing MP release from commercial ship coatings were identified: application, vessel operation, in-water cleaning, routine maintenance, and end-of-life processes (coating removal or ship decommissioning).
Turner [49] emphasized that the high chemical toxicity of paint particles poses a greater environmental threat than similarly-sized MPs from other sources. A review paper by Diana et al. [50] suggests that paint from both terrestrial and marine sources may represent one of the largest, potentially even the greatest, sources of MPs globally. However, this problem remains inadequately addressed due to the complex composition of paints, limitations in measurement procedures, and the failure to classify paint particles as plastic. Recent studies have revealed that antifouling paints on research vessels or sampling equipment are significant and occasionally dominant sources of measured MP particles [49]. For instance, Leistenschneider et al. [52] investigated MPs in the Weddell Sea, Antarctica, finding that 45.5% of all detected MPs originated from the research vessel itself. Due to these issues, various sampling, processing, and characterization strategies have received considerable research attention, as noted by Forero-López et al. [53].
Self-polishing paints used in the maritime sector present a considerable problem since they are designed to erode over time, consequently intentionally releasing MP particles directly into the marine environment. Bork et al. [54] evaluated particle release from self-polishing yacht coatings under controlled simulated low-speed sailing conditions in artificial seawater. Authors noted the absence of prior literature describing polymer particle release during self-polishing coating erosion. While the methodology shows promise for comparing emissions across different coatings, authors acknowledge that several limitations must be addressed before accurate predictions of MP release can be made. Such investigations, combined with the development of novel low-impact antifouling approaches [55], would provide valuable insights and support the development of more sustainable solutions.
To gain insight into the relationship between maritime transport and the amount of microplastics, more focus should be on correlating the results of microplastic measurements at shipping lanes and off-route locations. Ship monitoring could be carried out using new technologies, including AI-powered tracking, drone-based monitoring [18], and satellite remote sensing such as synthetic aperture radar [56].

4.2. Gray Water

Gray water on ships includes wastewater from sinks and showers, laundry facilities, kitchen areas, etc. Cruise ships can be a considerable source of pollution, given the large number of passengers. If a ship is in port, gray water is disposed of at a wastewater facility. However, if that is not possible, it is directly disposed of at sea. Various studies have focused on the assessment of contaminants in gray waters, including industrial chemicals, pharmaceuticals, personal care products, various metals, etc. [57,58,59]. Studies on gray water are scarce, with even fewer focusing on MP pollution, and this knowledge gap is compounded by the absence of legal instruments addressing gray water pollution [58]. With increasing understanding of MP pollution sources and pathways, gray water has been recognized as an MP pollution source. Since it is known that households are a considerable source of MP pollution, mainly due to laundry washing and cosmetics, it is reasonable to assume that ships are also contributors to MP pollution through similar pathways [60]. Wastewater from cruise ships as a source of MP pollution was explored for the first time, as noted by the authors in Folbert et al. [61]. Pathways were identified based on previous research on MP sources and pathways, the literature on cruise operations and wastewater management, and questionnaire data from cruise lines; however, no quantification was performed. A review of papers investigating gray water as a potential source of MP pollution is presented in the study by Ma et al. [62], with only a few papers reporting MP measurements.
Kalnina et al. [63] measured MP levels in five transport ships, and Jang et al. [64] measured MP levels in gray water from a research vessel, while the remaining literature covered in the review relies on various estimations. In their work, Kalnina et al. [63] conducted measurements of MP particles for both gray water and post-treatment sewage samples, where results indicated that fewer than 30% of microparticles were captured by the sewage treatment equipment of the transport ships analyzed. Jang et al. [64] measured MP concentration and characteristics on a research vessel equipped with three separate tanks for the galley, cabins, and laundry, enabling specific measurements of each type of gray water. The results showed the greatest concentration of MP particles from laundry, followed by cabins and the galley. More recently, Lu et al. [65] investigated 33 sewage samples from transport ships, comprising gray water samples, black water samples, and mixed black and gray water effluent. The results indicated that the average MP concentration in gray water is significantly higher than in black water and mixed effluent and that MP particles are more diverse. However, it must be noted that only three samples of gray water were collected out of the total number of samples. The authors reported greater concentrations in wastewater from passenger ships than oil tankers, which indicates that usually, larger number of crew members and passengers on passenger ships result in a higher volume of domestic sewage and consequently a greater amount of MP particles. Furthermore, 26 samples were processed, while seven remained unprocessed. The processed samples contained fewer MP particles, indicating that various treatment procedures can help remove MP particles. All three papers note that untreated gray water discharge into the marine environment is a potential contributor to MP pollution. An overview of the MP concentrations reported in studies is presented in Table 1.
A study by Jang et al. [64] provided valuable insight into specific MP contributors in gray water due to a unique research vessel design with three separate tanks not typically found on other ships. Both Kalnina et al. [63] and Lu et al. [65] observed that treated wastewater contained fewer MP particles than untreated wastewater. Kalnina et al. [63] compared treated and untreated samples from the same vessels, while Lu et al. [65] analyzed single samples (either treated or untreated) from 33 different vessels. Lu et al. [65] noted that the existing literature identified retention and sedimentation as mechanisms that can remove MP particles. Further wastewater measurements before and after various treatment procedures could help to identify effective strategies for MP reduction. It must be noted that existing studies have covered a narrow range of vessel types. Kalnina et al. [63] investigated only 5 passenger ships (17–23 passengers each), Jang et al. [64] examined a single vessel (33 passengers), and Lu et al. [65] studied 33 vessels, including passenger ships, cargo vessels, and oil tankers, though passenger numbers were not reported. Table 2 provides an overview of the presented studies with indicated contributions and limitations.

4.3. Ballast Water

The amount of ballast water is adjusted based on ship load and can be discharged into marine environments that differ from those from which it was taken. This has been recognized as a serious ecological hazard since non-native aquatic organisms can be transferred to new marine environments via ballast water. As a result, a regulatory framework was established at the Ballast Water Management Convention in 2004, which came into force in 2017. The two primary regulations are D-1, which defines ballast water exchange and the volume of water to be replaced and prohibits ballast water exchange within 200 nautical miles of shore, and D-2, which requires ballast water treatment systems. Concerns remain regarding the transport of sediment, which can contain contaminants such as toxins, pharmaceuticals, heavy metals, and disinfection by-products [66].
MP particle measurements in ballast waters were first presented in a brief report by Matiddi et al. [67]. Within the project Ballast Water Management System For Adriatic Sea Protection (BALMAS), a large number of MP particles were observed in ballast water samples collected from nine cargo vessels that arrived at the port of Bari, Italy. This prompted further research; the first review paper on ballast water as a possible vector for MPs was published by Naik et al. [29]. The review presented the role of MP in ballast water as a vector for the transport of harmful chemicals, metals, bacterial pathogens, invasive species, etc. Research by Zendehboudi et al. [68] followed, where MP concentrations in seawater and ballast water were measured in the Persian Gulf with 6 and 30 samples, respectively. In both seawater and ballast water, MP particles were identified, with no significant difference in concentration between the two. Su et al. [45] measured MP in ship ballast water in ports around the Liaodong Peninsula, China, where 13 transport vessels were investigated at 5 different sampling sites. They also measured MP concentrations and, compared with [67,68], found intermediate values in ballast water. However, differences in measurement procedures must be taken into account, particularly differences in the mesh aperture diameter and pore size used in these studies. Most recently, Kalnina et Andze [69] investigated MP concentrations in ballast water from five tankers. In their work, they reported an average of 26 different complex MP particles in 1 liter of the ship’s BW, but note that observed values vary between the vessels due to different geographical locations where the vessel conducts the ballasting operation and difference in ballasting treatment. Authors did not provide a comparison of MP concentrations with the previous literature but presented a novel technical solution for ballast water treatment; however, they did not report its efficiency. Table 3 provides an overview of the reported MP concentrations in different studies.
It can be observed that research on MP in ballast water remains limited. Matiddi et al. [67] first considered MP analysis in ballast waters but provided only a brief review without in-depth data analysis. Zendehboudi et al. [68] offered more valuable insights by comparing MP abundance in ballast water with baseline measurements of local seawater. Although the authors reported the origin of ballast water for their 30 samples, they did not explore the relationship between ballast water origin and MP abundance. Su et al. [45] analyzed ballast water from 13 vessels on international (3 vessels) and domestic (10 vessels) routes, with 6 using brackish water and 7 using seawater as ballast. Given the small sample size and variety of factors, drawing strong conclusions about the drivers of MP abundance was challenging, which the authors acknowledged. Table 4 provides an overview of the contributions and limitations of studies measuring MP concentrations in ballast water. Despite limited data, these studies confirm the presence of MP in ballast water, revealing both a pollution pathway and a potential opportunity. For example, Naik et al. [70] proposed a filtration technique to remove MP particles from ballast waters. This is further supported by a recent paper by Kalnina and Andze [69] presenting a novel technical solution for ballast water treatment. While water treatment procedures are already implemented on ships, they do not target MP particles. Appropriate ballast water filtration techniques could capture MP during routine ballast exchange operations. This approach could shift the paradigm from ships as pollution contributors to ships as pollution mitigation tools.

5. Sources of MP-Related Pollution in Shipyards

Industrial processes in shipyards generate a wide range of contaminants, including heavy metals, particulate matter, volatile organic compounds, oil, grease, solvents, etc. Activities conducted in wet docks can produce particles that are deposited into the surrounding waters. Working on a dry dock requires cleaning practices to be followed [71]; however, these measures cannot completely prevent the dispersion of pollutants, particularly the atmospheric transport of particles generated during manufacturing. Recent studies have begun to investigate particle emissions from shipyard activities and their environmental pathways. In work by Lopez et al. [72], ultrafine particle emissions were measured in a workshop and a shipyard during maintenance activities. It was noted that, despite cleaning procedures, deposited dust can still reach surface waters. Considering that atmospheric transport can be a pathway for MP particles to reach remote regions [73], activities in shipyards conducted in the immediate vicinity of water bodies can create a significant risk of MP pollution. This is particularly true for paint particles [49]. The interaction between airborne MP and water presents a complex system that needs further investigation [74]. In the following subsections, the literature investigating MP pollution from two shipyard activities, antifouling paint work and plastic pipe cutting and fabrication, is presented.

5.1. Antifouling Paint

Antifouling coatings typically last five years, after which old paint must be removed before reapplication. Various removal techniques, such as in-water cleaning, hydroblasting, and sandblasting, have been identified as sources of seawater pollution. Soon et al. [23] collected 10 wastewater effluent samples from hydroblasting operations at ship repair yards, focusing primarily on dissolved metal release. Subsequent studies analyzed contamination from in-water cleaning conducted by divers using brushing techniques [24] and using remotely operated vehicles (ROVs) [25]. While none of these studies directly measured MP particles, Soon et al. [75] later used emission data from the latter two studies to estimate MP pollution from these activities. The authors acknowledged that factors such as cleaning efficiency, coating degradation, and interactions with environmental contaminants and organisms introduce uncertainty into these estimates. Kim et al. [76] analyzed effluent generated during hydroblasting of a 99.8 m ocean-going vessel. This is the first time researchers analyzed MPs during this procedure and, based on the results, authors estimated that approximately 5% of all marine paint-derived microplastics could be attributed to hydroblasting. However, the authors also noted this estimate is based on a single case study, and MP particles in hydroblasting effluents remain largely unquantified in the literature. Table 5 provides an overview of estimated plastic emissions from maintenance activities. It must be noted that Soon et al. [75] only provided plastic emission estimations, while Kim et al. [76] provided both plastic and MP estimation. In comparison, Bork et al. [54] reported that during their simulated low-sailing experiment, around 46–88% of the coating was released as particles, while Kim et al. [76] reported that 9.1% of paint was removed during hydroblasting. However, both studies are based only on a single case.
Wastewater from cleaning and maintenance operations has been extensively investigated as a pollution source in the literature [22,23,24,25,26,27]. However, due to the complex composition of marine coatings, most studies focus on metal concentrations, with MP particle characterization only recently emerging as a research focus. The limited number of studies can be explained by the fact that paints have been considered as microplastics only recently [49,50] and that identification of APP presents a methodological challenge that requires the development of analytical techniques [77]. It also indicates significant potential for further research, particularly given the variety of techniques employed in painting and maintenance operations. Ideally, MP pollution contributions should be investigated across different vessel types, antifouling coating types, and maintenance procedures. Table 6 provides an overview of the studies quantifying APP MP particles with contributions and limitations also indicated.

5.2. Plastic Piping Fabrication Debris

Ships require extensive networks of plastic piping for various onboard systems. These typically include potable water distribution, technical water, wastewater, and drainage systems, with the specific configuration varying by vessel type and size. The fabrication and installation of these systems occur directly onboard during construction or retrofit, generating plastic debris through cutting, threading, and fitting operations. This debris can be transported through multiple pathways: workers may carry fragments on clothing or footwear, particles may become airborne during processing, or waste may be deposited directly into surrounding waters. Beyond environmental concerns, airborne plastic particles create occupational health risks, particularly in confined shipboard spaces where workers already face documented respiratory hazards [78].
Recognizing plastic pipe fabrication as a pollution source, Lučin et al. [79] proposed design strategies to minimize debris-generating operations during pipe system assembly. Despite this, research remains extremely limited. To date, only [80] has quantified MP generation during PVC pipe cutting. Critical knowledge gaps persist regarding particle release during pipe processing operations. Comprehensive studies measuring both particle quantities and characteristics across all fabrication activities are needed to assess the full scope of MP pollution from shipboard plastic pipe installation.

6. Discussion

Research on marine plastic pollution has evolved from focusing on larger debris to increasingly prioritizing microplastics. In 2015, the United Nations (UN) recognized plastic pollution as a global concern through Sustainable Development Goal 14 (Life Below Water), with Target 14.1 aiming to prevent and reduce marine pollution, including plastic debris density. IMO adopted the 2025 Action Plan to Address Marine Plastic Litter from Ships, which encourages Member States to conduct research on ship-related microplastics and their contribution to marine litter. The urgency of the issue is further reflected in initiatives under the OceanLitter Programme. Limited understanding of MP pollution sources has hindered regulatory development in most jurisdictions. However, policy frameworks are beginning to emerge. For example, intentionally added MPs, especially microbeads, are being regulated, with varying legal strength and coverage of application, depending on the country. Additionally, in 2022, the UN adopted a resolution to develop an international legally binding instrument on plastic pollution, including in the marine environment. As of late 2025, a consensus has not yet been reached, and negotiations remain ongoing. As legislative frameworks are expected to expand to other sectors and industries while also becoming increasingly stringent, researchers play a critical role in providing insights into MP pollution sources and transport.
The scientific research covered in the initial screening had authors dominantly from China, the United States, Europe, and India (Figure 3). This is mostly consistent with previous observations in the literature; for example, in the study by Diana et al. [50], it has been reported that paint microplastic sampling locations have been concentrated in Europe and, to a lesser extent, East Asia. Furthermore, in Sumaway et al. [81]’s analysis of research on perceptions of microplastics, it was noted that most publications were from European countries, followed by China, Australia, and the US. Lack of published research was observed from developing countries, with the authors noting that socio-economic contexts contribute to research gaps in the field. When only studies that measure microplastics (MP) in specific activities are considered, namely, papers presented in Table 1, Table 2 and Table 3, it becomes apparent that such research is carried out by scientists from a limited number of countries: China, the Republic of Korea, Latvia, Iran, Italy, and the United States. It is also noteworthy that several studies were conducted by the same research groups. In particular, one group from China and one from Latvia performed MP measurements in both ballast water and gray water, while a single research group from the Republic of Korea investigated MP concentrations in gray water as well as MP emissions from hydroblasting. This shows that an already limited number of studies are further concentrated among only a few research groups focusing on MP pollution in relation to shipbuilding and maritime transport activities. This is likely influenced by funding constraints, especially if extensive investigations are needed.
The limited research in this area can also be partially attributed to access constraints. Sample collection requires permissions from shipyards and vessel operators, who may lack the incentive to participate in studies that could identify them as pollution sources. Shipyards already face increasingly stringent environmental regulations requiring substantial investments, such as those addressing carbon dioxide emissions and ballast water treatment. Many operators are reluctant to support research that may impose additional regulatory burdens. Greater industry participation is needed to obtain data across various vessel types and operational contexts. Research could be facilitated through government support or collaborative projects that aim to investigate and develop solutions to MP pollution mitigation.
Scientific research clearly demonstrates that MP pollution is increasing and must be reduced, yet economic considerations dominate decisions. Environmental solutions require substantial investment and carry financial risks, with novel approaches increasing costs and production time, directly impacting shipyard competitiveness. Research such as Oertel et al. [28], which examinated ship paint microplastic pollution along the supply chain, is therefore essential for understanding industry perspectives and the barriers they face. The authors noted concerns such as reluctance to adopt unproven novel solutions and paints, potential quality reduction due to worker inexperience with new procedures, inadequate adaptation of solutions to specific operational needs, and legislative inconsistencies across countries that create competitive disadvantages. Given the low profit margins in shipbuilding, only legislation is likely to compel shipyards and shipowners to implement green solutions.
Addressing MP pollution from maritime industries requires collaboration across multiple disciplines. Standardized methods for sample collection, preparation, and analysis must be established to generate reliable data. Authors note that there is no standard for water collection on ships; therefore, some studies follow United States Environmental Protection Agency (US EPA) sampling advice [63,69]. For ballast water, studies [68,69] collected 10 L samples, while [45] collected 5 L, with all studies using 1 L subsamples. For gray water, samples of 20 L were collected in [64], whereas studies [63,65] collected 1 L samples. This standardization challenge is further amplified when experimental data are scarce. For instance, Jang et al. [64] had only one prior empirical study on MP in gray water available for comparison, leading to assumptions in their research. Similarly, the first investigation of MP abundance in engine cooling systems was only recently published [82]. More studies are necessary to establish meaningful baselines and enable valid comparisons. Understanding how air and water interact, including the effects of wind, currents, waves, and particle movement, is necessary to trace MP sources and pathways. Knowledge of maritime operations is also essential to develop effective measurement strategies. This includes selecting representative vessels by type and size and tracking relevant factors such as ballast water origin and passenger numbers. Progress in reducing MP pollution depends on understanding shipbuilding and maritime transport processes well enough to design practical mitigation solutions.

7. Conclusions

Based on the conducted literature review, it is observed that targeted measurements in the field of shipbuilding and maritime transport are in their infancy. Our main observations are as follows:
  • Graywater treatment procedures demonstrate significant potential to reduce the release of MP particles into the marine environment. The available evidence indicates that passenger ships require particular attention due to their comparatively higher MP emissions.
  • Reported MP concentrations in ballast water vary substantially across studies. Due to the lack of information on ballast water origin and the limited number of studies, no general conclusions can currently be drawn. Nevertheless, emerging treatment approaches show promise for capturing MP particles.
  • Existing estimates of plastic and MP releases from vessel operation and maintenance activities indicate potentially concerning emission levels; however, direct measurements remain limited, highlighting the need for more comprehensive investigation.
Several key future research directions are identified:
  • Manufacturing procedures that minimize plastic debris generation should be investigated, alongside operational strategies to prevent debris from entering marine environments.
  • Gray water research should encompass a wider variety of vessels with varying passenger capacities to determine true MP contributions. A comprehensive analysis of both treated and untreated wastewater samples is needed to identify effective treatment strategies for MP reduction.
  • Studies investigating ballast water should explore how the geographic source of ballast water influences MP contamination, using larger sample sizes to establish reliable trends.
  • Standardized methodologies for quantifying MP emissions from different maintenance operations should be established to enable accurate assessment based on the maintenance operation.
  • Standardized methodologies for measuring MP concentrations are needed to enable reliable assessment and comparison of emerging filtration techniques and other treatment technologies for MP removal.
A deeper understanding of specific pollution sources is essential for identifying the main contributors to MP pollution in both coastal areas and open seas. Characterizing these sources should facilitate the development of targeted mitigation solutions and improve MP modeling capabilities, which can provide valuable insights and guide future action on marine MP pollution. Significant knowledge gaps remain regarding MP pollution from shipbuilding and maritime transport activities. Only by addressing these gaps can the industry be effectively incentivized to implement meaningful MP reduction solutions.

Author Contributions

Conceptualization, I.L., B.L. and M.A.; methodology, I.L., A.S. and M.A.; investigation, I.L. and M.A.; writing—original draft preparation, I.L.; writing—review and editing, all authors; visualization, M.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the University of Rijeka, grant number uniri-mladi-tehnic-23-49.

Data Availability Statement

No new data were created or analyzed in this study.

Conflicts of Interest

Author Bože Lučin was employed by the company Flowtech d.o.o. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. Flowchart of the literature overview.
Figure 1. Flowchart of the literature overview.
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Figure 2. Visualization of keyword co-occurrence using an overlay map.
Figure 2. Visualization of keyword co-occurrence using an overlay map.
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Figure 3. World map showing the countries of institutional affiliation of authors identified through Scopus queries related to microplastic research in shipbuilding and maritime transport, with countries colored by the number of affiliations.
Figure 3. World map showing the countries of institutional affiliation of authors identified through Scopus queries related to microplastic research in shipbuilding and maritime transport, with countries colored by the number of affiliations.
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Table 1. Average MP concentrations in wastewaters reported in studies.
Table 1. Average MP concentrations in wastewaters reported in studies.
ReferenceSewage TypeAverage Concentration (n/L)Pore Size ( μ m)
Kalnina et al. [63]Gray water710.7
Treated gray and black water51
Jang et al. [64]Laundry gray water17710
Cabins gray water133
Galley gray water75
Lu et al. [65]Gray water1670.7
Black water36.96
Mixed domestic sewage46.57
Passanger ships57.2
Oil tankers44.4
Unprocessed domestic sewage87.43
Processed domestic sewage40.96
Average value50.82
Table 2. Gray water as a microplastic pollution source in maritime transport: contributions and limitations of reviewed studies.
Table 2. Gray water as a microplastic pollution source in maritime transport: contributions and limitations of reviewed studies.
SourceRef.FocusContributionLimitation
Gray water[63]50 gray water and treated sewage samples from 5 transport shipsQuantified MP treatment reductionLimited vessel count
[64]Galley, cabin, laundry tanks on research vesselMP quantification by source typeSingle-vessel study
[65]Gray and black water from 33 vesselsCompared treated vs untreated water across vessel typesUnbalanced sampling
Table 3. Average MP concentrations in ballast water reported in studies.
Table 3. Average MP concentrations in ballast water reported in studies.
ReferenceNumber and Type of VesselAverage Concentration (n/L)Filtration
Matiddi et al. [67]9 cargo ships0.651 ± 0.16050 μ m (mesh aperture diameter)
Zendehboudi et al. [68]30 ships12.53 ± 4.850.45 μ m (pore size)
Su et al. [45]13 transport ships6.07 ± 1.30.7 μ m (pore size)
Kalnina and Andze [69]5 tankers260.7 μ m (pore size)
Table 4. Ballast water as a microplastic pollution vector in maritime transport: contributions and limitations of reviewed studies.
Table 4. Ballast water as a microplastic pollution vector in maritime transport: contributions and limitations of reviewed studies.
VectorRef.FocusContributionLimitation
Ballast water[67]MP in ballast water of 9 cargo vesselsFirst ballast water MP studyNo size/polymer data
[68]6 seawater and 30 ballast water samples from vesselsBaseline comparisonSource impact unclear
[45]13 transport vessels at 5 sitesConsidered vessels on international and domestic routesSmall subgroup sizes
[69]5 tankers with samples collected in different regionsProposed novel technical solutionEfficiency not evaluated
Table 5. Estimated plastic and MP emissions from hull cleaning activities.
Table 5. Estimated plastic and MP emissions from hull cleaning activities.
Ref.ActivityGlobal Plastic Fleet Emission Estimation (Tons/Year)Pore Size ( μ m)
Soon et al. [75]Manual in-water cleaning by divers2319 to 13,4810.2
ROV-based system without capture295 to 1183
ROV-based system with capture and debris processing68 to 302
Kim et al. [76]Hydroblasting665.6 (MP 550.2)10
Table 6. Microplastic pollution sources in APP: contributions and limitations of reviewed studies.
Table 6. Microplastic pollution sources in APP: contributions and limitations of reviewed studies.
SourceRef.FocusContributionLimitation
APP[54]MP emissions during simulated low-sailing conditionsMeasured MP release from commercial coatingSingle coating, reported methodological limits
[75]MP emissions from diver and ROV brushingCompared 2 cleaning techniquesMP estimation based on total suspended solids
[76]MP from hydroblastingQuantification and characterizationSingle case study
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MDPI and ACS Style

Lučin, I.; Sikirica, A.; Lučin, B.; Alvir, M. A Review of Microplastics Research in the Shipbuilding and Maritime Transport Industry. J. Mar. Sci. Eng. 2026, 14, 73. https://doi.org/10.3390/jmse14010073

AMA Style

Lučin I, Sikirica A, Lučin B, Alvir M. A Review of Microplastics Research in the Shipbuilding and Maritime Transport Industry. Journal of Marine Science and Engineering. 2026; 14(1):73. https://doi.org/10.3390/jmse14010073

Chicago/Turabian Style

Lučin, Ivana, Ante Sikirica, Bože Lučin, and Marta Alvir. 2026. "A Review of Microplastics Research in the Shipbuilding and Maritime Transport Industry" Journal of Marine Science and Engineering 14, no. 1: 73. https://doi.org/10.3390/jmse14010073

APA Style

Lučin, I., Sikirica, A., Lučin, B., & Alvir, M. (2026). A Review of Microplastics Research in the Shipbuilding and Maritime Transport Industry. Journal of Marine Science and Engineering, 14(1), 73. https://doi.org/10.3390/jmse14010073

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