Neustonic microplastic pollution in the Persian Gulf

Unveiling the ecotoxicological impact of microplastics on organisms - the persistent organic pollutant (POP): A comprehensive review

Microplastics have been ubiquitous in our environment for decades, and numerous studies have revealed their extensive dispersion, reaching far beyond the surface of the land, soil, aquatic ecosystems. They have infiltrated the food-chain, the food web, even the air we breathe, as well as the water we drink. Microplastics have been detected in the food we consume, acting as vectors for hazardous chemicals that adhere to their hydrophobic surfaces. This can result in the transfer of these chemicals to the aquatic life, posing a threat to their well-being. The release of microplastics into different environmental settings can give rise to various eco-toxicological implications. The substantial body of literature has led scientists to the consensus that microplastic pollution is a global problem with the potential to impact virtually any type of ecosystem. This paper aims to discuss crucial information regarding the occurrence, accumulation, and ecological effects of microplastics on organisms. It also highlights the new and emerging disease named "Plasticosis" that is directly linked to microplastics and its toxicological effects like permanent scarring and long-term inflammation in the digestive system of the seabirds. By comprehending the behaviour of these microplastic pollutants in diverse habitats and evaluating their ecological consequences, it becomes possible to facilitate a better understanding of this toxicological issue.

Basin scale monitoring of microplastics and phthalates in sediments from the Persian Gulf and the Gulf of Makran using GIS-based algorithms: Insights towards spatial variation and potential risk assessment

Information on sedimentary microplastics and phthalates has been restricted to the coastal regions of the Persian Gulf and the Gulf of Makran. Our basin-wide study monitored their levels, spatial behaviors, and potential risks using GIS-based techniques. Microplastics and phthalates ranged from 5 to 75 particles/kg d.w and 0.004-1.219 μg g-1 d.w, respectively. Microplastics were in the size category of 100 μm to 3 mm, and black microfibers (< 1 mm) and high-density polymers were dominant. The total number of microplastics was between 356.333 × 1012 and 469.075 × 1012 particles in the surface sediments of the studied regions (confidence interval = 99 %). Diethylhexyl phthalate (DEHP) and Di-isobutyl phthalate contributed 88 % of detected phthalates. Significant correlations among microplastic abundance, total phthalates, and DEHP were distinguished (p < 0.05). Overall, the findings reiterated the widespread presence of microplastics and a potential link between phthalates and microplastics. Semi-variogram, cluster Voronoi polygons, and Trend analysis identified spatial outliers and major deposition sites of microplastics and phthalates and consequently outlined the localities where upcoming studies should be concentrated. A hotspot of potential risks was marked using Fuzzy logic and GIS-based algorithms in the Sea of Makran, covering an area equal to 342. 99 km2.

A Systematic Review on Microplastic Contamination in Fishes of Asia: Polymeric Risk Assessment and Future Prospectives

Microplastics (MPs) have attracted global concern because of their harmful effects on marine biota; their toxic properties can negatively impact aquatic ecosystems. Fish is an essential source of protein for humans, playing a crucial role in daily food intake. Until recently, MPs were addressed primarily as environmental pollutants, but they are now increasingly recognized as contaminants in the food supply. The present review has comprehended the current knowledge of MP contamination in freshwater and marine fishes of Asia, including 112 peer-reviewed sources from 2016 to 2023. The review recorded 422 Asian fishes (345 marine and 77 freshwater) to be contaminated with MPs. Clarias gariepinus and Selaroides leptolepi have shown maximum MP contamination in the freshwater and marine environments of Asia, respectively. Omnivorous and carnivorous fishes exhibited higher susceptibility to ingesting MPs. Benthopelagic, demersal, and reef-associated habitats were identified as more prone to MP accumulation. In both freshwater and marine environments, China has the highest number of contaminated species among all the countries. Pollution indices indicated high MP contamination in both freshwater and marine environments. A prevalence of fibers was recorded in all fishes. Black- and blue-colored MPs of <500 µm-1 mm size were found dominantly. Polyethylene terephthalate and polyethylene were recorded as the prevalent plastic polymers in freshwater and marine fish, respectively. Overall, the review served as a comprehensive understanding of MP concentrations and variations between species, between feeding habits, and between geographic locations, which can be pivotal for addressing pressing environmental challenges, protecting human health, and fostering global sustainability efforts in the face of escalating plastic pollution. Environ Toxicol Chem 2024;43:671-685. © 2024 SETAC.

Influence of the polymer type of a microplastic challenge on the reaction of murine cells

Due to global pollution derived from plastic waste, the research on microplastics is of increasing public interest. Until now, most studies addressing the effect of microplastic particles on vertebrate cells have primarily utilized polystyrene particles (PS). Other studies on polymer microparticles made, e.g., of polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), or poly (ethylene terephthalate) (PET), cannot easily be directly compared to these PS studies, since the used microparticles differ widely in size and surface features. Here, effects caused by pristine microparticles of a narrow size range between 1 - 4 µm from selected conventional polymers including PS, PE, and PVC, were compared to those of particles made of polymers derived from biological sources like polylactic acid (PLA), and cellulose acetate (CA). The microparticles were used to investigate cellular uptake and assess cytotoxic effects on murine macrophages and epithelial cells. Despite differences in the particles' properties (e.g. ζ-potential and surface morphology), macrophages were able to ingest all tested particles, whereas epithelial cells ingested only the PS-based particles, which had a strong negative ζ-potential. Most importantly, none of the used model polymer particles exhibited significant short-time cytotoxicity, although the general effect of environmentally relevant microplastic particles on organisms requires further investigation.

Analysis of microplastics in ships ballast water and its ecological risk assessment studies from the Persian Gulf

Transport of ballast water is considered a significant vector for dispersion of different pollutants, including microplastics (MPs), throughout the world's oceans. However, there is limited information on MPs in ballast water. Size distribution, polymer type, and ecological risks of MPs in ballast water were investigated for the first time in this study. The mean levels of MPs in ballast water and seawater samples were 12.53 and 11.80 items/L, respectively. MPs with a size category of 50-300 μm was the most abundant. Fiber, black, and polycarbonate (PC) were the predominant shape, color, and polymer type of identified MPs in ballast water and seawater, respectively. The pollution load index (PLI), hazard index (HI), and risk quotient (RQ) indicated high levels of MP pollution, potentially indicating an ecological risk. These findings increase our understanding of the major sources (such as ballast water), transportation routes, and related ecological risks of MPs to marine ecosystems.

Heavy metal and persistent organic pollutant profile of sediments from marine protected areas: the northern Persian Gulf

Marine protected areas (MPAs) are one of the policy tools to support marine biodiversity conservation and sustainable use of marine resources. The distribution, sources, and ecological risk assessment of persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbon (PAHs), total petroleum hydrocarbons (TPHs), polychlorinated biphenyls (PCBs), and heavy metals (HMs) in sediments of MPAs in the northern Persian Gulf, were evaluated for the first time in this study. The Σ16PAHs ranged from 4.65 to 20.86 μg/kg dry weight (dw). The molecular ratios and ring's pattern of PAHs suggested a mixed origin with a predominance of pyrogenic sources. The TPH concentration varied from 5.21 to 17.90 μg/g dw. Ecological risk assessment suggested that sediment samples in Bushehr Province's MPAs can be categorized as medium risk. The mean concentration of ∑18PCB was 0.345-0.419 ng/g dw, and the main components correspond to PCB-77, PCB-105, PCB-81, PCB-101, and PCB-114. The mean concentration of As, Co, Cr, Ni, V, Mg, Pb, Zn, Cu, Al, and Fe varied from 4.79 to 9.69, 2-12, 39-142, 18-90, 15-58, 184-425, 7-45.9, 6-42.4, 4-20 μg/g dw, 0.75-4.12%, and 0.35-1.62%, respectively. Multivariate analysis, such as principal component analysis (PCA) and cluster analysis (CA), coupled with correlation coefficient analysis, was used to analyze the analytical data and to identify possible pollution sources. The results of this study provided the background information on the extent of POP contamination in the sediment and highlighted the need to further control pollution in MPAs.

Microplastics as contaminants in the Brazilian environment: an updated review

Microplastics have long been present in marine and terrestrial environments and have emerged in recent decades as a global environmental concern. This pollutant has been detected with increasing frequency in Brazilian territory and herein primarily highlights current information and developments about the quantity, distribution, techniques of identification, origins, and sources of microplastics and related pollutants in the Brazilian environment. We evaluated 79 publications from 2018 to December 2022, and some aspects can be highlighted: 27% of studies were published in the Journal Marine Pollution Bulletin; 22% of all studies were conducted in São Paulo city; and 52% of all microplastics found were collected from biota followed by sediment samples. According to the findings given here, microplastics in Brazilian habitats, which can reach concentrations of 4367 to 25,794 items m-2 in sediments, are becoming a serious problem in the Anthropocene age, and some topics regarding the open questions in this area were pointed out in this review.

Abundance and characteristics of microplastic in some commercial species from the Persian Gulf, Iran

Global production of plastics has increased dramatically in recent decades and is considered a major threat to marine life and human health due to their stability, persistence, and potential to move through food chains. The study was conducted to detect, identify and quantify microplastics (MP) in the gastrointestinal tract (GI) of some commercial fish species in the North Persian Gulf in Bushehr Province: Psettodes erumei, Sphyraena jello, Sillago sihama, Metapenaeus affinis and Portunus segnis. A total of 216 plastic particles were collected from 102 individuals (72.68% of all sampled individuals; MP prevalence of 85.1% for M. affinis, 80% for P. segnis, 70% for P.erumei, 60.3% for S.sihama, 45.2% for S.jello). The average number of microplastics per organism was 2.26 ± 0.38 MP/ind (considering only species that ingested plastic, n = 102) and 1.51 ± 0.40 pieces/ind (considering all species studied, n = 140). Microfibers accounted for 58.49% of the total microplastics, followed by fragments (33.02%) and pellets (8.49%). The most common color of microplastic was black (52.83%), followed by blue (22.64%) and transparent (15.09%). The length of microplastic ranged from 100 to 5000 μm with an average of 854 ± 312 μm. Microplastics were significantly (p < 0.05) abundant in two shrimp studied: M. affinis and P. segnis (plastic in 80% of individuals studied) and to a lesser extent in the pelagic barracuda fish S. jello (plastic in 45% of individuals studied). The main synthetic polymers identified by Fourier transform infrared spectroscopy (FTIR) were polyethylene (38%), polypropylene (24%), polystyrene (17%), polyethylene terephthalate (11%) and polyamide (10%). The pollutant load index and lifetime accumulation index were calculated to identify the most polluted species and their toxicity to human health. The white shrimp M. affinis was identified as the most polluted and toxic species for MP based on PLI. The present study can provide valuable data for further research and a background for the control and monitoring of this pollutant in the coastal environment of Bushehr province.

Micro- and nanoplastics (MNPs) and their potential toxicological outcomes: State of science, knowledge gaps and research needs

Plastic waste has been produced at a rapidly growing rate over the past several decades. The environmental impacts of plastic waste on marine and terrestrial ecosystems have been recognized for years. Recently, researchers found that micro- and nanoplastics (MNPs), micron (100 nm - 5 mm) and nanometer (1 - 100 nm) scale particles and fibers produced by degradation and fragmentation of plastic waste in the environment, have become an important emerging environmental and food chain contaminant with uncertain consequences for human health. This review provides a comprehensive summary of recent findings from studies of potential toxicity and adverse health impacts of MNPs in terrestrial mammals, including studies in both in vitro cellular and in vivo mammalian models. Also reviewed here are recently released biomonitoring studies that have characterized the bioaccumulation, biodistribution, and excretion of MNPs in humans. The majority MNPs in the environment to which humans are most likely to be exposed, are of irregular shapes, varied sizes, and mixed compositions, and are defined as secondary MNPs. However, the MNPs used in most toxicity studies to date were commercially available primary MNPs of polystyrene (PS), polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and other polymers. The emerging in vitro and in vivo evidence reviewed here suggests that MNP toxicity and bioactivity are largely determined by MNP particle physico-chemical characteristics, including size, shape, polymer type, and surface properties. For human exposure, MNPs have been identified in human blood, urine, feces, and placenta, which pose potential health risks. The evidence to date suggests that the mechanisms underlying MNP toxicity at the cellular level are primarily driven by oxidative stress. Nonetheless, large knowledge gaps in our understanding of MNP toxicity and the potential health impacts of MNP exposures still exist and much further study is needed to bridge those gaps. This includes human population exposure studies to determine the environmentally relevant MNP polymers and exposure concentrations and durations for toxicity studies, as well as toxicity studies employing environmentally relevant MNPs, with surface chemistries and other physico-chemical properties consistent with MNP particles in the environment. It is especially important to obtain comprehensive toxicological data for these MNPs to understand the range and extent of potential adverse impacts of microplastic pollutants on humans and other organisms.

Occurrence and abundance of macro, meso and microplastics along the coasts of the Persian Gulf (case study: Bushehr Province coast)

One of the most critical emerging pollutants in aquatic environments is plastic waste. During this study, the presence and abundance of macro, meso, and microplastics at 17 stations on the coast of Bushehr province were investigated. The average abundances of macro-plastics and meso-plastics in coastal sediment were 41.0 and 121.8 items/m2, respectively. The mean abundance of microplastics at depths of 0-5 cm, 5-15 cm, 0-15 cm and the mean of two depth abundance were 226.2 ± 76.7 and 47.1 ± 16.1, 273.4 ± 78.8, and 136.7 ± 39.4 particles/kgd.w., respectively. Fibers with 55 %, black microplastics with 40 %, and microplastic size of <500 μm with 48 % had the highest abundance, respectively. According to the FTIR spectra, polyethylene, polystyrene, polyethylene terephthalate, and nylon were the most common types of polymers in plastics. Although plastics were observed at all stations, a comparison of our results, with other studies around the world shows that the region is moderately contaminated with plastics.

Risk assessment of microplastic pollution in an industrial region of Bangladesh

Despite the high potential for microplastics (MPs) pollution in Bangladesh, the presence of MPs in the industrial region has largely been unexplored in Bangladesh. So, this study was conducted to determine whether MP pollution is prevalent in the industrial soil of Bangladesh and the extent of its toxicity. To examine MPs, a total of 12 soil samples were collected from the industrial region of Narayanganj, and a stereoscopic microscope was used to visually identify the MPs. Prior to that the technique of density separation and sieving was applied to extract MPs from those 12 soil samples. Among the twelve investigated samples, a total of 151 MPs (Mean: 12.6 ± 7.9 particles kg^-1) were identified, which were mostly white and ranged in size from 0.5 to 1 mm. Different types of MPs according to their shapes such as fibers (60.3%), fragments (19.2%), films (10.6%), and foam (9.9%) have been detected. 7 MPs (Mean: 0.58 ± 0.79) have been found in 3 urban farmland sites, 15 MPs (Mean: 1.87 ± 1.81) in two near metropolitan areas, and 129 MPs (Mean: 4.6 ± 4.39) in 7 industrial locations. Five polymers were identified by μ-FTIR, among which Polyamide predominated, followed by Polypropylene. According to risk assessments, the region falls under hazard categories II and III, suggesting a moderate to high risk. This paper gives thorough information on the toxicity of MP in an industrial location; therefore, it may be useful in the development of effective methods to address environmental issues.

Occurrence and ecological risks of microplastics and phthalate esters in organic solid wastes: In a landfill located nearby the Persian Gulf

Landfill sites are the main source of plastic waste. Thus, municipal solid waste (MSW) in landfills may act as a reservior of microplastics (MPs) and related pollutants such as phthalate esters (PAEs) into surrounding environment. However, there is limited information on MPs and PAEs in landfill sites. Levels of MPs and PAEs in organic solid waste disposed in a landfill of Bushehr port were investigated for the first time in this study. The mean MPs and PAEs levels in organic MSW samples were 12.3 items/g and 7.99 μg/g, respectively, and the mean PAEs concentration in MPs was 87.5 μg/g. The highest number of MPs was related to the size classes of >1000 μm and <25 μm. The highest dominant type, color, and shape of MPs in organic MSW were nylon, white/transparent, and fragments, respectively. Di (2-ethylhexyl) phthalate (DEHP) and diisobutyl phthalate (DiBP) were the dominant compounds of PAEs in organic MSW. Based on the finding of present study, MPs showed a high hazard index (HI). DEHP, dioctyl phthalate (DOP), and DiBP demonstrated high-level hazards for sensitive organisms in water. This work illustrated considerable MPs and PAEs levels from an uncontrolled landfill without adequate protection, possibly contributing to their release into the environment. The sites of landfill located near marine environments, such as Bushehr port landfill adjacent to the Persian Gulf, may indicate critical threats to marine organisms and the food chain. Continuous landfills control and monitoring, especially the ones near the coastal area, is highly recommended to prevent further environmental pollution.

Microplastics as carriers of iron and copper nanoparticles in aqueous solution

In recent years, microplastics have attracted a lot of attention due to their excessive spread in the environment, especially in aquatic ecosystems. By sorbing metal nanoparticles on their surface, microplastics can act as carriers of these pollutants in aquatic environments and thus cause adverse effects on the health of living organisms and humans. This study, investigated the adsorption of iron and copper nanoparticles on three different microplastics i.e. polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS). In this regard, the effects of parameters such as; pH, duration of contact and initial concentration of nanoparticle solution were investigated. By using atomic absorption spectroscopic analysis, the amount of adsorption of metal nanoparticles by microplastics was measured. The maximum amount of adsorption occurred at pH = 11, after a duration time of 60 min and at the initial concentration of 50 mg L^-1. Scanning electron microscope (SEM) images showed that microplastics have different surface characteristics. The spectra obtained from Fourier transform infrared analysis (FTIR) before and after the adsorption of iron and copper nanoparticles on microplastics were not different, which showed that the adsorption of iron and copper nanoparticles on microplastics was physically and no new functional group was formed. X-ray energy diffraction spectroscopy (EDS) showed the adsorption of iron and copper nanoparticles on microplastics. By examining Langmuir and Freundlich adsorption isotherms and adsorption kinetics, it was found that the adsorption of iron and copper nanoparticles on microplastics is more consistent with the Freundlich adsorption isotherm. Also, pseudo-second-order kinetics is more suitable than pseudo-first-order kinetics. The adsorption ability of microplastics was as follows: PVC > PP > PS, and in general copper nanoparticles were adsorbed more than iron nanoparticles on microplastics.

Occurrence and risks of microplastics in the ecosystems of the Middle East and North Africa (MENA)

The ubiquitous nature of microplastics (MPs) in nature and the risks they pose on the environment and human health have led to an increased research interest in the topic. Despite being an area of high plastic production and consumption, studies on MPs in the Middle East and North Africa (MENA) region have been limited. However, the region witnessed a research surge in 2021 attributed to the COVID-19 pandemic. In this review, a total of 97 studies were analyzed based on their environmental compartments (marine, freshwater, air, and terrestrial) and matrices (sediments, water columns, biota, soil, etc.). Then, the MP concentrations and polymer types were utilized to conduct a risk assessment to provide a critical analysis of the data. The highest MP concentrations recorded in the marine water column and sediments were in the Mediterranean Sea in Tunisia with 400 items/m³ and 7960 items/kg of sediments, respectively. The number of MPs in biota ranged between 0 and 7525 per individual across all the aquatic compartments. For the air compartment, a school classroom had 56,000 items/g of dust in Iran due to the confined space. Very high risks in the sediment samples (Erⁱ > 1500) were recorded in the Caspian Sea and Arab/Persian Gulf due to their closed or semi-closed nature that promotes sedimentation. The risk factors obtained are sensitive to the reference concentration which calls for the development of more reliable risk assessment approaches. Finally, more studies are needed in understudied MENA environmental compartments such as groundwater, deserts, and estuaries.

Dynamic characteristics of microplastics under tidal influence and potential indirect monitoring methods

Rivers are an important channel for the transport of microplastics from inland areas to the ocean. It is of great significance to explore the dynamic changes in microplastic pollution characteristics under tidal fluctuations to understand the exchange of microplastics between rivers and oceans. In this study, the occurrence of microplastics in typical tidal channels in the lower reaches of the Dong River was investigated during the wet and dry weather seasons, and high frequency continuous dynamic monitoring of microplastics was carried out in a typical tidal cross section during a tidal cycle. The abundances of microplastics during wet and dry weather seasons were 3.97-102.87 ± 28.63 item/m³ and 5.43-56.43 ± 14.32 item/m³, respectively. The microplastics generally exhibited a fluctuating growth pattern, with low contents in the upstream area and high contents in the downstream area, and the abundance of microplastics differed greatly in the different functional zones. The dynamic monitoring results showed that the abundance of microplastics was clearly affected by the tides, in that it increased during the flood tide and decreased during the ebb tide, with abundances ranging from 11.15 to 95.26 item/m³. In addition, there was a significant linear relationship between the abundance of microplastics and flow in the typical tidal cross section. The relationship between the response of microplastic pollution characteristics and tides combined with local hydrometeorological factors may be a potentially effective real-time monitoring method for assessing microplastic pollution indirectly.

Marine debris and associated organic pollutants in surface waters of Chiloé in the Northern Chilean Patagonia (42°-44°S)

We report the occurrence of plastics and associated persistent organic pollutants (POPs) in surface waters from Northern Chilean Patagonia. A total of 200 particles were found during the conducted survey. The highest number of particles found was 0.6 item m^-3. We found that 53 % of the collected particles corresponded to plastic, with an average of 0.19 ± 0.18 item m^-3. Microplastics (68 %) were the dominant size found in the area, followed by macroplastics (18 %) and mesoplastics (14 %). Most plastic particles were white (55 %) while others were <10 % each. Black and light blue represented 9 %; red, dark blue, and other colors 7 %; and green 6 %. Fragments were the most frequent shape of plastic debris (38 %), followed by Styrofoam (30 %) and fiber (27 %). Higher PBDE levels were found in the central zone, and those were higher than DDT, PeCB, HCB, and PCB levels. This study is the first report on POP occurrence in marine plastic debris from Chiloé Sea in the Northern Chilean Patagonia.

Microplastics as Contaminants in Water Bodies and Their Threat to the Aquatic Animals: A Mini-Review

Microplastics (MPs), which are particles with a diameter of less than 5 mm, have been extensively studied due to their serious global pollution. Typically, MPs in water originate from terrestrial input. A number of studies have reported the presence of MPs as a stressor in water environments worldwide, and their potential threat to the aquatic animals, affecting the growth, oxidative stress responses, body composition, histopathology, intestinal flora, and immune and reproduction systems. During the plastic degradation process, a large variety of toxic substances are released. MPs have been proposed to be the carriers of toxic chemicals and harmful microorganisms. A study of the literature on MP pollution and stress on the aquatic animals associated with MPs was carried out.

Occurrence, seasonal distribution, and ecological risk assessment of microplastics and phthalate esters in leachates of a landfill site located near the marine environment: Bushehr port, Iran as a case

Plastic wastes are produced in a large amount everywhere, and are commonly disposed in landfills. So landfill leachate seems an obvious source of microplastics (MPs) and phthalate esters (PAEs) due to a huge usage as plastic additives and plasticizers. But this issue still lacks attention and the present study provides the first information on the levels of MPs and PAEs in the fresh landfill leachate of Bushehr port during different seasons. The mean levels of MPs and PAEs in the fresh leachate in all seasons were 79.16 items/L and 3.27 mg/L, respectively. Also, the mean levels of PAEs in MPs were 48.33 μg/g. A statistically significant difference was detected in the levels of MPs and PAEs among different seasons with the highest values in summer and fall. MPs with a size of >1000 μm had the highest abundance in all seasons. The most prominent shape, color, and type of MPs in the leachate were fibers black, and nylon, respectively. Dibutyl phthalate (DBP) and Di(2-ethylhexyl) phthalate (DEHP) were the most dominant PAEs present in the leachate samples. The results of this study revealed high hazard index (HI) and pollution load index (PLI) of MPs in all seasons. Dioctyl phthalate (DOP), DEHP, DBP, diisobutyl phthalate (DiBP), butyl benzyl phthalate (BBP), and diethyl phthalate (DEP) represented a high risk to the sensitive organisms. The results of this study showed that significant levels of MPs and PAEs may release into the surrounding environment from the landfill sites without sufficient protection. This issue is more critical when the landfill sites in particular are located near the marine environments like the Bushehr landfill that is located near the Persian Gulf, which can lead to serious environmental problems. Thus permanent control and monitor of landfills, especially in the coastal areas are highly needed to prevent further pollution.

Microplastic and oil pollution in oceans: Interactions and environmental impacts

Microplastics (MPs) have been found in oil-polluted oceans, but studies on MPs and oil were still focused on their respective transport, biodegradation, and bioaccumulation. The interactions between MPs and oil in the marine environment remain unknown. MPs would incorporate with oil to form MP-oil agglomerate (MOA), the behaviors of MOA were thus discussed in this study. It was found that the MOA formation resulted in the decreased oil dispersion efficacy and affect marine oil spill response operations. Moreover, oil biodegradation rate would be changed when oil existed as the form of MOA. The slow vertical transport of MOA might lead to wider ocean contamination. MOA would cause much worse impacts on phytoplankton, zooplankton, and high trophic species in the marine environment than MPs or oil individually. MOA assembling with phytoplankton in oceans may reduce carbon dioxide (CO₂) transport to deep seas. Exploring the interactions between MPs and oil in the marine environment opened a door for understanding MPs and oil as co-contaminants.

Detection and assessment of marine litter in an uninhabited island, Arabian Gulf: A case study with conventional and machine learning approaches

In 2018, the Ministry of Municipality and Environment, Qatar removed 90 t of marine litter (ML) from the Ras Rakan Island (RRI), a remote uninhabited island in the Arabian Gulf (hereinafter referred to as Gulf). To identify the sources of ML and understand the post-cleaning ML accumulation rate, a ML survey was conducted around RRI in 2019. A total of 1341 ML items were found around RRI with an average abundance of 3.4 items/m². In addition, a machine learning approach was applied to extract the quantity and types of ML from 10,400 images from the sampling sites (beaches) to make the ML clean-up process and monitoring effort more efficient. The image coordinates of ML objects were used to train an object detection algorithm 'You Only Look Once (YOLO-v5)' to automatically detect ML from video data. An image enhancement technique was performed to improve the quality of unclear images. The best performing YOLO-v5 model had 90% of mean Average Precision (mAP) while maintaining near real-time processing speeds at 2 ms/image. The abundance of ML around RRI was higher than that found on the coast of mainland Qatar. 61.5% of the sampling locations are considered as 'extremely dirty' based on Clean Coast Index. Windward beaches had higher ML concentrations (derived from neighbouring countries) than the leeward beaches. Like RRI, most of the uninhabited islands in the Arabian Gulf are home to many seabirds and sea turtles, and could act as major sinks for ML deposition. Therefore, implementation of this machine learning technique to all islands allows estimating and mitigating the load of ML for achieving a sustaining and a cleaner ocean.

Material flow analysis of plastic waste in the gulf co-operation countries (GCC) and the Arabian gulf: Focusing on Qatar

Global plastic waste production has increased dramatically in recent years, both globally and regionally, having a multitude of adverse effects on the environment and human health. However, little attention has been directed to this problem in the Arabian Gulf region. This study aims to delineate and map the status of the plastic waste problem in the Gulf Co-operation Countries (GCC), with a focus on Qatar. The study focuses on the plastic waste in the marine environment, depicting the different types, sizes and shapes of plastic particles found in the Arabian Gulf. To depict the flow of plastic waste, a generic material flow diagram was built using a material flow analysis software named STAN, in which transfer coefficients were assigned based on existing scientific literature and estimations built on data from local industries and recycling facilities. The recovery and recycling efforts that have been made by the different GCC countries, in efforts to reduce plastic waste and minimize the risk of plastic on the environment are analyzed, too. Our analyses indicate that approximately 11.9 Mt ± 595.395 Kt of plastic waste is produced annually in the GCC region, of which only 23 ± 15% is recycled, indicating that improvements are yet to be made in the recovery, recycling and treatment of plastics in the region. However, in Qatar, a higher percentage of plastics (40 ± 10%) is recovered-recycled with efforts to treat plastics and reuse it to generate energy.

Optimization of polypropylene microplastics removal using conventional coagulants in drinking water treatment plants via response surface methodology

Background and purpose

The ubiquitous presence of microplastics (MPs) in aquatic environments has been studied widely. Due to toxicological impacts of MPs and associated contaminants, it is crucial to understand the performance of MPs removal in drinking water treatment plants (DWTPs). Few studies have investigated removal characteristics of MPs via coagulation/flocculation processes, yet removal characterization of polypropylene microplastics (PPMPs) in this process is poorly understood. This study aims to optimize coagulation of virgin PPMPs in conventional DWTPs.

Methods

In this study, samples were synthesized through response surface methodology (RSM), polyaluminium chloride (PACl) was applied as a conventional coagulant to remove PPMPs in the coagulation/flocculation process, which has the least density among common polymers and is one of the most abundant manufactured polymers worldwide. A particle size analyzer (PSA) was used to measure floc size at different pH levels. Additionally, a zeta potential analyzer was used to measure stability of the flocs at different pH.

Results

Base on the experimental range in Design-Expert, results revealed that the optimum removal rate was predicted to be at pH 9, PACl concentration of 200 ppm, polyacrylamide (PAM) concentration of 21 ppm, and PPMPs size of d < 0.25 mm. According to the predicted optimum condition, actual and predicted removal rates were 18.00 ± 1.43% and 19.69%, respectively.

Conclusion

According to this study, PACl is not capable of efficiently removing virgin PPMPs in DWTPs, thereby exposing humans to eco-toxicological impacts of PPMPs through tap water.

Spatial distribution and risk assessments due to the microplastics pollution in sediments of Karnaphuli River Estuary, Bangladesh

Microplastics (MPs) have become an emerging global pollutant due to their widespread dispersion and potential threats to marine ecosystems. However, studies on MPs in estuarine and coastal ecosystems of Bangladesh are very limited. Here, we conducted the first study on abundance, distribution, characteristics, and risk assessment of microplastics in the sediment of Karnaphuli River estuary, Bangladesh. Microplastic particles were extracted from sediments of 30 stations along the estuary by density separation and then enumerated and characterized using a stereomicroscope and Fourier Transform Infrared (FT-IR) spectroscopy. In the collected sediment of the Karnaphuli River estuary, the number of MPs varied from 22.29 to 59.5 items kg^-1 of dry weight. The mean abundance was higher in the downstream and left banks of the estuary, whereas the predominant shape, colour, and size of MPs were films (35%), and white (19%), and 1-5 mm (30.38%), respectively. Major polymer types were polyethylene terephthalate, polystyrene, polyethylene, cellulose, and nylon. MPs were found to pose risks (low to high) in the sediment of the estuary, with the highest risk occurring at one station near a sewage outlet, according to the results of risk analyses using the pollution risk index, polymer risk index (H), contamination factors, and pollution load index (PLI). The single value index, PLI, clearly demonstrated that all sampling sites were considerably polluted with microplastics (PLI > 1). H values showed toxic polymers, even in lower proportions, possess higher polymeric hazard scores and vice versa. This investigation uncovered new insights on the status of MPs in the sediments of the Karnaphuli River estuary, laying the groundwork for future research and control of microplastic pollution and management.

Distribution and environmental risk assessment of microplastics in continental shelf sediments in the southern East China Sea: A high-spatial-resolution survey

We report a high-spatial-resolution study on the distributions, characteristics, and environmental risks of microplastics in surface sediments of the southern East China Sea. Microplastics were omnipresent in the sediments (concentration range: 53.3-246.7; mean: 138.4 particles/kg dry-weight sediment) and enriched in nearshore areas close to urban centers relative to lower offshore concentrations. The microplastics identified were dominated by polyethylene (41.2%) and polyethylene terephthalate (19.9%) in polymer type, fibers (45.8%) and fragments (40.3%) in shape, 0.1-0.5 mm (61.0%) in size, and black (52.0%) in color. The benthic environment experienced low to moderate microplastic pollution, with polyvinylchloride exhibiting the highest ecological risk index. The high-resolution sampling revealed highly diverse polymer types and strongly patchy distributions of microplastic abundance and pollution indices in sediments. Results from this study imply that complex physical, biological, and topographic interactions control the distribution of microplastics and the associated environmental risks in coastal sediments.

Current status of microplastics pollution in the aquatic environment, interaction with other pollutants, and effects on aquatic organisms

Microplastics, as emerging pollutants, have received great attention in the past few decades due to its adverse effects on the environment. Microplastics are ubiquitous in the atmosphere, soil, and water bodies, and mostly reported in aqueous environment. This paper summarizes the abundance and types of microplastics in different aqueous environments and discusses the interactions of microplastics with other contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), antibiotics, and heavy metals. The toxicity of microplastics to aquatic organisms and microorganisms is addressed. Particularly, the combined toxic effects of microplastics and other pollutants are discussed, demonstrating either synergetic or antagonistic effects. Future prospectives should be focused on the characterization of different types and shapes of microplastics, the standardization of microplastic units, exploring the interaction and toxicity of microplastics with other pollutants, and the degradation of microplastics, for a better understanding of the ecological risks of microplastics.

Assessing the relationship between the abundance of microplastics in sediments, surface waters, and fish in the Iran southern shores

The purpose of this study was to investigate the microplastic (MP) pollution in sediments, surface waters, and four fish species in the northern coast of the Persian Gulf. Sampling was conducted in seven important regions during December 2019. The abundance of MPs was respectively 190 ± 35.5 items/kg dry weight for sediments, 9.28 ± 2.1 items/km² for surface waters, and 0.33 ± 0.05 items/individual for fish. There was no correlation between MP abundance in surface water, sediment, and fish samples. Except for Cynoglossus arel, abundance of isolated MPs did not show significant relationships with body weight, body length, and gastrointestinal tract weight (P > 0.05). MPs were ranged from 0.3 to 5 mm in size and were prevailed by fiber in shape; black, red, and blue in color; and polypropylene and polyethylene in polymer. This study may help in increasing our knowledge regarding MP pollution in marine water systems and biota.

Occurrence of microplastics and phthalate esters in urban runoff: A focus on the Persian Gulf coastline

Urban runoff seems an obvious pathway for the transfer of microplastics (MPs) and phthalate acid esters (PAEs) from land-based sources to the marine environment; an issue that still lacks attention. This study presents the first results on MP and PAE levels in the urban runoff into the northern part of the Persian Gulf during the dry season. Average concentrations of MPs and PAEs in the urban runoff of eight selected sampling sites (N = 72) along the Bushehr coast were 1.86 items/L and 53.57 μg/L, respectively. MPs with a size range of 500-1000 μm had the highest abundance, and the mean levels of PAEs in MPs were 99.77 μg/g. The results of this study show that urban runoff is a main source of MP and PAE contaminants that are discharged into the Persian Gulf. Therefore, to decrease these pollutants from entering the aquatic environment, decision-makers in the area should consider this problem and stop the direct discharging of urban runoff into water bodies.

Micro-Nano Plastic in the Aquatic Environment: Methodological Problems and Challenges

Microplastic research has become a buzz word. It is seen as one of the most pressing issues of Anthropocene contamination. There is certainly no doubt about the ubiquitous presence of microplastic (MP) in almost all environmental matrices. However, the validity of considering them as a vector for contaminants needs some reconsideration, there are other more potent pathways. Their effect on marine biota also calls for some realistic experiments with environmental concentrations of MP and nanoplastic (NP). It has been observed that in most published literature, polymer characterization is performed. Is it necessary to do, or will merely finding and confirming the particle as plastic suffice for environmental research? Harmonization of protocols is necessary, and there is likely a need for some inter-laboratory comparison exercises in order to produce comparable data and reliable assessments across regions. Samples collected from the same area using different techniques show an order of magnitude difference in MP concentration. The issue of nanoplastic is more contentious; are we technologically ready to identify NP in environmental samples?

Non-Negligible Effects of UV Irradiation on Transformation and Environmental Risks of Microplastics in the Water Environment

Microplastics (MPs) are ubiquitous in environmental media, and their harmful effects on MPs on the ecosystem have attracted more and more attention. Once released into the environment, MPs can trigger oxidative degradation through ultraviolet (UV) to cause photoaging. Photoaging significantly affects the properties of MPs, which leads to changing their environmental behaviors and increasing environmental risks. In this review, the generation of MPs under UV irradiation and the influence of environmental factors on the photoaging of MPs were discussed. Photoaging of MPs is an important process affecting the migration, transformation and interaction of pollutants in water and soil. In order to fully predict the fate and environmental interaction of MPs, more researches are needed in the future to explore the photoaging behavior of different types of MPs under natural environmental conditions.

Subchronic toxicity of dietary sulfamethazine and nanoplastics in marine medaka (Oryzias melastigma): Insights from the gut microbiota and intestinal oxidative status

Antibiotics and nanoplastics are two prevalent pollutants in oceans, posing a great threat to marine ecosystems. As antibiotics and nanoplastics are highly bioconcentrated in lower trophic levels, evaluating their impacts on marine organisms via dietary exposure route is of great importance. In this study, the individual and joint effects of dietborne sulfamethazine (SMZ) and nanoplastic fragments (polystyrene, PS) in marine medaka (Oryzias melastigma) were investigated. After 30 days of dietary exposure, 4.62 mg/g SMZ decreased the Chao1 index (60.86% for females and 26.85% for males) and the Shannon index (68.95% for females and 65.05% for males) and significantly altered the structure of gut microbial communities in both sexes. The female fish exposed to 4.62 mg/g SMZ exhibited higher intestinal sod (43.5%), cat (38.5%) and gpx (39.6%) transcripts, indicating oxidative stress in the gut. PS alone at 3.45 mg/g slightly altered the composition of the gut microbiota. Interestingly, the mixture of SMZ and PS caused more modest effects on the gut microbiota and intestinal antioxidant physiology than the SMZ alone, suggesting that the presence of PS might alleviate the intestinal toxicity of SMZ in a scenario of dietary co-exposure. This study helps better understand the risk of antibiotics and nanoplastics to marine ecosystems.

An inverted in vitro triple culture model of the healthy and inflamed intestine: Adverse effects of polyethylene particles

As environmental pollution with plastic waste is increasing, numerous reports show the contamination of natural habitats, food and drinking water with plastic particles in the micro- and nanometer range. Since oral exposure to these particles is virtually unavoidable, health concerns towards the general population have been expressed and risk assessment regarding ingested plastic particles is of great interest. To study the intestinal effects of polymeric particles with a density of <1 g/cm³ in vitro, we spatially inverted a triple culture transwell model of the healthy and inflamed intestine (Caco-2/HT29-MTX-E12/THP-1), which allows contact between buoyant particles and cells. We validated the inverted model against the original model using the enterotoxic, non-steroidal anti-inflammatory drug diclofenac and subsequently assessed the cytotoxic and pro-inflammatory effects of polyethylene (PE) microparticles. The results show that the inverted model exhibits the same distinct features as the original model in terms of barrier development and inflammatory parameters. Treatment with 2 mM diclofenac causes severe cytotoxicity, DNA damage and complete barrier disruption in both models. PE particles induced cytotoxicity and pro-inflammatory effects in the inverted model, which would have remained undetected in conventional in vitro approaches, as no effect was observed in non-inverted control cultures.

Investigation of microplastics in edible wild mussels from İzmir Bay (Aegean Sea, Western Turkey): A risk assessment for the consumers

The presence of microplastics (MPs) was determined in Mediterranean mussel (Mytilus galloprovincialis Lamarck, 1819) and grooved carpet shell (Ruditapes decussatus Linnaeus, 1758) together with water samples from in İzmir Bay (Aegean Sea, Western Turkey). A total of 895 MPs from Karşıyaka (Station 1), and 787 MPs from Gülbahçe (Station 2) were detected in 60 mussel samples, giving a total content of 1682 MPs. In water samples, a total of 545 MPs were detected in samples from Station 1 and 1287 MPs in samples from Station 2 (1832 MPs total). The amount of MPs in water samples was less in Station 1 than in Station 2. This difference is probably caused by Çiğli Wastewater Treatment Plant (WWTP) located near Station 1. Public health risk assessment on the consumption of the species M. galloprovincialis revealed that 70.82 items person^-1 year^-1 MPs through this species could enter consumers' digestive systems.

Occurrence, abundance and characteristics of microplastics in some commercial fish of northern coasts of the Persian Gulf

This study assessed the abundance of microplastics (MPs) in muscle, liver, gill, and gastrointestinal tissues of 14 fish species from the Persian Gulf. The quality control showed no significant difference in MPs abundance between blank samples and muscle and liver tissues. The mean abundance of MPs accumulated in gill and gut was 2.85 ± 1.57 and 2.46 ± 1.46 pa/individual, respectively. The maximum mean abundance of MPs was observed in the gill (5.71 pa/ind) of the fish Thunnus tonggol and gut tissue (5.67 pa/ind) of the fish Sphyraena putnamiae. Fiber, black color and size of 23-75 μm were the predominant form of MPs. There was a significant positive correlation between the total fish length and the abundance of MPs. MPs were more abundant in pelagic fish (5.79 ± 5.98) than demersal fish species (3.89 ± 3.53). The level of fish contamination with MPs was low to moderate in comparison to the ranges reported in the literature.

Microplastic pollution in inshore and offshore surface waters of the southern Caspian Sea

In this study, as the first comprehensive monitoring, the occurrence of microplastics (MPs) in inshore and offshore surface waters of the southern Caspian Sea was investigated. Our data indicated that MPs, which were detected in all the samples, were widely distributed in the thirteen studied stations. Non-normally distribution of the MPs was observed among the studied stations (p<0.05). The average concentration of microplastics in the selected stations was 0.246 ± 0.020 MP/m³. In most of the transects, negative gradients of MPs from coastal waters to deeper waters were observed. The dominant size and color of MPs in the inshore and offshore water samples was 1000-5000 μm and white-transparent, respectively. Films and fibers constituted about 50% and 40% of the total number of MPs of the water samples, respectively. Also, polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) were the three main polymer types of microplastics in the inshore and offshore surface waters. Our data provide valuable evidence for the comparative assessing of future data regarding decreases or increases of MPs in the southern Caspian Sea.

Microplastic pollution in Southern Atlantic marine waters: Review of current trends, sources, and perspectives

Microplastics (MPs) are emerging and ubiquitous contaminants which have been gaining prominence since the last decade to nowadays. This is due to their possible adverse effects in aquatic ecosystems as well as the huge amount of plastic waste exponentially generated around the globe. Plastics may be introduced either directly to water bodies or indirectly to the aquatic systems by being carried by the wind, from emissions of contaminated effluents, and soil leaching, among other processes. In turn, these debris may interact with organic and inorganic contaminants, such as polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs) and trace constituents, and with microorganisms. Although the abundance of microplastics from South Atlantic waters is among the highest found worldwide, the number of studies in these marine waters regarding MP contamination is still scarce. Additionally, there still are no consensus on the best sampling conditions, which may be underestimating MPs. In this way, adequate MPs studies regarding their distribution, exposure levels, chemical and biological interactions are highly suggested in order to better understand both environmental and human health potential risks. This review assessed advances in sampling, analytical methodologies, characterization and understanding of MP sources in these marine waters in comparison to data from other regions around the globe.

First evidence of microplastics occurrence in mixed surface and treated wastewater from two major Saudi Arabian cities and assessment of their ecological risk

In this study, water of the channels and ponds that conduct residual water in two most important cities of Saudi Arabia were assessed to ascertain the influence of the population on the occurrence and pollution characteristics of microplastics (MPs) (> 20 µm in size). Riyadh has 7.6 million inhabitants and is an urban city even though also have industry while Al-Jubail has only 0.78 and is the biggest industrial city. MPs showed an average of 3.2 items/L in Riyadh and 0.2 items/L in Al-Jubail showing a statistically significant difference between both cities. Sampling with a Turton Tow Net of 20 µm mesh, fibers were dominant in all sites (60%). MPs size was mainly distributed between 80 and 250 µm (60%), and their major colors were white (40%), red (25%) and blue (20%). Infrared spectral analysis revealed that most of the selected particles were identified as MPs of polypropylene and polyethylene (48.3%). The risk assessment was carried out using both the hazard index (HI) and the pollution load index (PLI). The results showed that, in this case, the decisive index is the PLI since the main difference in the MPs characteristics between the two cities is their concentration.

Spatial distribution of microplastics in sandy beach and inshore-offshore sediments of the southern Caspian Sea

The occurrence of microplastics (MPs) in nearshore zones of the southern Caspian coasts is well documented; however, no data are available on MP occurrence in offshore sediments. In this study, six sandy beach stations and 18 inshore-offshore stations (six transects) were surveyed. MPs were detected in all sediment samples. The mean abundances of MPs in the beach and inshore-offshore stations were 196.67 ± 11.58 and 103.15 ± 7.21 MPs/kg, respectively. Fibers constituted the most common shape of MPs. Polystyrene (PS) and polyethylene terephthalate (PET) were the major polymer types found in the beach and inshore-offshore sediments, respectively. In most transects, negative MP gradients were observed from nearshore to offshore, which showed that coastal fishing, tourism, and rivers were the main sources of MPs in this area. These results will improve our understanding on MPs pollution in the marine ecosystem. We recommend further MP studies in different parts of the Caspian Sea to develop appropriate management programs.

Multiple endpoints of polylactic acid biomicroplastic toxicity in adult zebrafish (Danio rerio)

Although the toxicity of conventional microplastic types (i.e., petroleum derivatives) in different organisms is already known, knowledge about the effects of alternative biopolymers on aquatic vertebrates remains incipient. Thus, the aim of the present study is to test the hypothesis that the exposure of adult Danio rerio individuals to this pollutant for 30 days is enough to cause polylactic acid biomicroplastics (BioMPs of PLA) accumulation in their bodies, which leads to behavioral/neurotoxic, biochemical, and morphological changes. Based on our results, PLA BioMPs at concentrations of 2.5 and 5 mg/L accumulated in the liver, brain, gills and carcass of the assessed animals. However, such an accumulation was not able to cause locomotor damages or to trigger anxiety-like behavior in them. On the other hand, it was enough to cause behavioral changes (in shoal) predictive of co-specific social interaction and anti-predatory defensive response deficit likely related to cholinergic changes inferred by increased acetylcholinesterase activity and REDOX imbalance. This imbalance was featured by increased production of reactive species. We observed that the treatments have affected animals' pigmentation pattern. Therefore, our study highlights the toxicological potential of the herein assessed biopolymer, and this finding puts in check the innocuousness of this material, as well as expands our knowledge about how PLA BioMPs can affect the ichthyofauna in freshwater environments.

Occurrence and characterization of microplastics in white shrimp, Metapenaeus affinis, living in a habitat highly affected by anthropogenic pressures, northwest Persian Gulf

Microplastics (MPs) are a modern societal concern and recognized as a growing environmental hazard by careless disposal. This study aimed to assess the MPs content in white shrimp (Metapenaeus affinis) inhabiting in a natural habitat affected by high anthropogenic pressures, and recognize if the shrimp could be a suitable bioindicator for MPs pollution. To assess spatial changes of MPs presence in shrimps, sampling was carried out by a trawl net from 13 stations across the entire Musa Bay. Tissues of shrimps were examined for MPs following floatation, digestion, microscopic observation and identified by Confocal Raman Spectroscopy. MPs were observed in the shrimps of all stations. The average MPs abundance was 1.02 items/g of digestive tissues. About 37% of recorded MPs in M. affinis samples exceeding 500 μm that could be related to surface area and stickiness as notable controls beyond ingestion. The dominant shape of MPs was fiber, followed by film. Five different colors were recorded in tissues of M. affinis samples, and the white/transparent MPs were the most abundant, followed by blue and black. In addition, a wide range of recorded colors of MPs in the study area could suggest a variety of sources of MPs. Confocal Raman Spectroscopy confirmed that polyethylene terephthalate (46%), polypropylene (27%) and polystyrene (27%) were dominant polymers. As the average annually consumption of shrimp in the region is 2.3 g/person/day, therefore each person could consume 857 MPs per year. In conclusion, the results of this research provide a detailed and useful information for a better understanding of MPs contamination in the region and suggest Jinga shrimp as a suitable species for monitoring MPs in marine ecosystems.

Paint particles in the marine environment: An overlooked component of microplastics

Because paint particles consist of a resin (polymer) combined with one or more additives, they bear compositional similarities with microplastics. Despite these shared characteristics, however, paint particles are often undetected, deliberately overlooked or evade classification in the pool of micro-debris (all synthetic debris of < 5 mm in size), and in particular in the marine setting where an extensive body of microplastic literature exists. Accordingly, the present paper provides a critical insight into the physico-chemical properties, sources, distributions, behaviour and toxicity of paint particles in the marine environment. Paint particles contain a greater proportion of additives than plastics and, consequently, are more brittle, angular, opaque, dense, heterogeneous and layered than microplastics of equivalent dimensions. Land-based sources of paint particles, including deteriorating or disturbed coatings on roads and building, are transported to the ocean with other microplastics via urban runoff, water treatment facilities and the atmosphere. However, inputs of paint particles are enhanced significantly and more directly by the disturbance, erosion and weathering of coatings on coastal structures, boats and ships. Estimates of paint particle emissions to the marine environment vary widely, with calculated contributions to the total synthetic micro-debris input as high as 35%. Upper estimates are consistent with available (albeit limited) quantitative information on the relative abundance of paint particles amongst synthetic material captured by sea surface trawls and ingested by marine animals. Of greatest environmental concern is the high chemical toxicity of paint particles compared with similarly-sized microplastics and other synthetic debris. This results from the contemporary and historical use of high concentrations of hazardous inorganic additives in marine antifouling and land-based paints, and the relatively ready mobilisation of harmful ions, like Cu⁺/Cu²⁺, TBT⁺, Pb²⁺ and CrO₄ ^2-, from the matrix. Recommendations arising from this review include greater use of particulate capturing devices, waste collection systems and recycling facilities during paint disturbance, raising awareness of the potential impacts of discarded paint amongst users, and alerting the microplastic community to the significance of paint particles and developing means by which they are isolated from environmental samples.

Disparities in Methods Used to Determine Microplastics in the Aquatic Environment: A Review of Legislation, Sampling Process and Instrumental Analysis

Plastic particles smaller than 5 mm, i.e., microplastics, have been detected in a number of environments. The number of studies on microplastics in marine environments, fresh water, wastewater, the atmosphere, and the human body are increasing along with a rise in the amounts of plastic materials introduced into the environment every year, all contributing to a range of health and environmental issues. Although the use of primary microplastics has been gradually reduced by recent legislation in many countries, new knowledge and data on these problems are needed to understand the overall lifecycle of secondary microplastics in particular. The aim of this review is to provide unified information on the pathways of microplastics into the environment, their degradation, and related legislation, with a special focus on the methods of their sampling, determination, and instrumental analysis. To deal with the health and environmental issues associated with the abundance of microplastics in the environment, researchers should focus on agreeing on a uniform methodology to determine the gravity of the problem through obtaining comparable data, thus leading to new and stricter legislation enforcing more sustainable plastic production and recycling, and hopefully contributing to reversing the trend of high amounts of microplastics worldwide.

Source and risk assessment of heavy metals and microplastics in bivalves and coastal sediments of the Northern Persian Gulf, Hormogzan Province

The objectives of the current study are to investigate the concentration, biological risks, chemical speciation, and mobility of of heavy metals and also the determination of their distribution, physicochemical characteristics, and abundance of microplastics in coastal sediments and edible bivalves in the Persian Gulf, the coastal area of Hormozgan Province. Sampling points were selected considering the location of industrial, urban and Hara forest protected areas. In November 2017, a total of 18 sediment samples from coastal sediments (top 0-10 cm) and the most consumed bivalve species in the region were collected from two stations, Lengeh and Bandar Abbas Ports. The average concentration of heavy metals (except for Ni and Cd) in the sediments were lower than their average shale and the upper continental crust. Enrichment factors revealed significant enrichment of Ni, Mn, Cr, Cd and As. The fractionation of heavy metals using the Community Bureau of Reference (BCR) sequential extraction scheme indicated the high bioavailability of Zn, As, Mn, and Co. In general, the highest concentration of Mo, Cd, Pb, Zn, Cr, Cu, Mn, Hg, and Sb was detected in areas with frequent human activities including Shahid Rajaee Port, Shahid Bahonar Port, and Tavanir station. Shahid Rajaee and Shahid Bahonar Ports are the most important ports on the coast of Hormozgan province. The Risk Assessment Code calculated for the study elements indicates that As, Co, Zn, and Cu pose a moderate environmental risk a threat to the aquatic biota. Health risks of most heavy metals arising from bivalves consumption were safe, except for As which is associated with the high target cancer risk values. With reference to the type of microplastics found, they were mainly fibeours with lengths ranging between 100 and 250 μm in sediments and bivalves. Most of the microfibers found in the sediments were made of polyethylene terephthalate (PET) and polypropylene (PP), and the fibers found in the bivalves were made of PP.

Microplastics decrease the toxicity of triphenyl phosphate (TPhP) in the marine medaka (Oryzias melastigma) larvae

Plastics have been recognized as a serious threat to the environment. Besides their own toxicity, microplastics can interact with other environmental pollutants, acting as carriers and potentially modulating their toxicity. In this study, the toxicity of polystyrene (PS) microplastic fragments (plain PS; carboxylated PS, PS-COOH and aminated PS, PS-NH₂) and triphenyl phosphate (TPhP) (an emerging organophosphate flame retardant) at the environmentally relevant concentrations to the marine medaka (Oryzias melastigma) larvae was investigated. Larvae were exposed to 20 μg/L of microplastic fragments or 20 and 100 μg/L of TPhP or a combination of both for 7 days. The results showed that the three microplastics did not affect the larval locomotor activity. For TPhP, the larval moving duration and distance moved were significantly decreased by the TPhP exposure, with a maximum decrease of 43.5% and 59.4% respectively. Exposure to 100 μg/L TPhP respectively down-regulated the expression levels of sine oculis homeobox homologue 3 (six3) and short wavelength-sensitive type 2 (sws2) by 19.1% and 41.7%, suggesting that TPhP might disturb eye development and photoreception and consequently the low locomotor activity in the larvae. Interestingly, during the binary mixture exposure, the presence of PS, PS-COOH or PS-NH₂ reversed the low locomotor activity induced by 100 μg/L TPhP to the normal level. Relative to the larvae from the 100 μg/L TPhP group, the movement duration and distance moved were increased by approximately 60% and 100%, respectively, in the larvae from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH₂ groups. However, the gene expression profiles were distinct among the fish from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH₂ groups, implying different mechanisms underlying the reversal of the locomotor activity. The findings in this study challenge the general view that microplastics aggravate the toxicity of the adsorbed pollutants, and help better understand the environmental risk of microplastic pollution.

Microplastics accumulation in sediments and Periophthalmus waltoni fish, mangrove forests in southern Iran

This investigation was aimed to identify microplastics in the sediment and mudskipper fish (Periophthalmus waltoni) in mangrove forests in southern Iran. Sediments and mudskipper samples were collected at high, mid, and low tidal points of five stations. A total of 2657 plastic particles in different size, color, shape, and genera were identified from sediment samples and 15 microplastic were isolated from mudskippers. The highest and lowest abundance of isolated microplastics from sediments was observed in mangrove forests of Bidkhoun (urban area) and Bordkhon, respectively while no microplastics were found in the fish tissue in those stations. The black (60%) and white (7%) color microplastics in the mudskipper had the highest and the lowest frequency. The highest and lowest polymers in mangrove forest sediments were corresponded to polystyrene (26%) and polycarbonate (3%), respectively. Raman and Fourier transform infrared spectroscopy (FT-IR) techniques were used to identify the type of the polymer. Most of the microplastics found were made of polystyrene, polypropylene, and polyethylene terephthalate. The type of studied area and texture of sediment separately affected the frequency of microplastic and mesoplastic (P-value <0.05) in the sediment samples. The abundance of microplastics in the sediment samples of the Bidkhoun mangrove forest was higher than other studied stations due to proximity to urban and industrial areas. The findings of this study raised concerns about microplastic pollution in the mangrove forests of southern Iran, a threat to the ecosystem and public health, which requires careful actions to prevent and diminish its adverse effects.

Emerging contaminants in the water bodies of the Middle East and North Africa (MENA): A critical review

Many emerging contaminants (ECs) are not currently removed by conventional water treatment methods and consequently, often reach the aquatic environment. In the absence of proper management strategies, ECs can accumulate in water bodies, which poses potential environmental and health risks. This paper critically reviews, for the first time, the reported occurrence and treatment of ECs in the Middle Eastern and North Africa (MENA) region. The paper also provides recommendations to properly manage EC risks. In the MENA region, pharmaceuticals and personal care products (PPCPs) have been detected in surface water, seawater, groundwater, and wastewater treatment plants. A focus on surface water in the published literature suggests that studies are skewed towards worldwide trends, whereas studies on ECs in seawater are of great importance in the study region. The types of PPCPs detected in the MENA region vary, but anti-inflammatories and antibiotics dominate. In comparison, microplastics have mainly been studied in surface waters and seawater with much less focus on drinking water. The majority of microplastics in the region are secondary types resulting from the degradation of larger plastic debris; polyethylene (PE) and polypropylene (PP) fibers are the most frequently detected polymers, which are indicative of local anthropogenic sources. Research progress on ECs varies between countries, having received more attention in Iran and Tunisia. Most MENA countries have now begun monitoring water bodies for ECs; however, studies are still lacking in some countries including Sudan, Djibouti, Syria, Ethiopia, and Bahrain. Based on this review, critical knowledge gaps and research needs are identified. Countries in the MENA region require further research on a broader range of EC types. Overall, water pollution due to the use and release of ECs can be tackled by improving public awareness, public campaigns, government intervention, and advanced monitoring and treatment methods.

Scientific studies on microplastics pollution in Iran: An in-depth review of the published articles

This literature review was conducted to collect present data on microplastics pollution in Iran's ecosystems. Most of the studies performed in aquatic environment were conducted in Persian Gulf & Oman Sea (70%). The Persian Gulf, along with the beaches of Bushehr and Hormozgan Provinces, are the most studied areas. Moreover, most of the studies were conducted in aquatic environments and only four studies were conducted in terrestrial environment (4/42). One study has assessed microplastics in commercial salt and another study has reported the microplastics presence in Iranian bottled mineral water brands. The investigation of microplastics associated with biota was highlighted, customarily for fish species. Microplastics were also present in urban wastewater samples in Sari and Bandar Abbas cities. Three studies were performed in freshwater ecosystems until now (Haraz River, Anzali wetland, and Taleqan dam). The need for further studies in this field still exists, especially in terrestrial and freshwater compartments.

Microplastic's story

The problem of microplastic pollution is now the order of the day in front of everyone's eyes affecting the environment and the health of leaving creature. This work aims to retrace the history of microplastics in a critical way through a substantial bibliographic collection, defining the points still unresolved and those that can be resolved. Presence of marine litter in different environments is reviewed on a global scale, focusing in particular on micro and macro plastics definition, classification and characterization techniques.

Micro and Nano-Plastics in the Environment: Research Priorities for the Near Future

Plastic litter dispersed in the different environmental compartments represents one of the most concerning problems associated with human activities. Specifically, plastic particles in the micro and nano size scale are ubiquitous and represent a threat to human health and the environment. In the last few decades, a huge amount of research has been devoted to evaluate several aspects of micro/nano-plastic contamination: origin and emissions, presence in different compartments, environmental fate, effects on human health and the environment, transfer in the food web and the role of associated chemicals and microorganisms. Nevertheless, despite the bulk of information produced, several knowledge gaps still exist. The objective of this paper is to highlight the most important of these knowledge gaps and to provide suggestions for the main research needs required to describe and understand the most controversial points to better orient the research efforts for the near future. Some of the major issues that need further efforts to improve our knowledge on the exposure, effects and risk of micro/nano-plastics are: harmonization of sampling procedures; development of more accurate, less expensive and less time-consuming analytical methods; assessment of degradation patterns and environmental fate of fragments; evaluating the capabilities for bioaccumulation and transfer to the food web; and evaluating the fate and the impact of chemicals and microorganisms associated with micro/nano-plastics. The major gaps in all sectors of our knowledge, from exposure to potentially harmful effects, refer to small size microplastics and, particularly, to the occurrence, fate and effects of nanoplastics.