Detection and occurrence of microplastics in the stomach of commercial fish species from a municipal water supply lake in southwestern Nigeria

Microplastic dynamics and risk projections in West African coastal areas: Developing a vulnerability index, adverse ecological pathways, and mitigation framework using remote-sensed oceanographic profiles

Microplastic pollution presents a serious risk to marine ecosystems worldwide, with West Africa being especially susceptible. This study sought to identify the key factors driving microplastic dynamics in the region. Using NASA's Giovanni system, we analyzed environmental data from 2019 to 2024. Results showed uniform offshore air temperatures due to turbulence (25.22-45.62 K) with significant variations nearshore. Salinity levels remained largely stable (4 PSU) but slightly decreased in southern Nigeria. Surface wind speeds rose from 4.206-5.026 m/s in Nigeria to over 5.848 m/s off Mauritania, while eastward stress hotspots were prominent in Nigeria and from Sierra Leone to Senegal. Photosynthetically available radiation (PAR) beam values peaked off Mauritania and dipped from Nigeria to Sierra Leone, with the inverse pattern observed for diffuse PAR. Hotspots of high absorption, particulate backscattering, elevated aerosol optical depth, and remote sensing reflectance all pointed to substantial particulate matter concentrations. The Microplastic Vulnerability Index (MVI) identifies the coastal stretch from Nigeria to Guinea-Bissau as highly vulnerable to microplastic accumulation due to conditions that favor buildup. In contrast, moderate vulnerability was observed from Guinea-Bissau to Senegal and in Mauritania, where conditions were less extreme, such as higher offshore temperatures that could promote widespread microplastic suspension and cooler nearshore temperatures that favor sedimentation. Increased turbulence and temperatures in coastal areas of Senegal and Mauritania may enhance microplastic transport and impact marine life. In Nigeria, stable coastal conditions-characterized by consistent temperatures, low turbulence, and uniform salinity-may lead to increased persistence and accumulation of microplastics in sensitive habitats like mangroves and coral reefs. These findings highlight the need for region-specific management strategies to address microplastic pollution and effectively protect marine ecosystems.

Microplastic and associated emerging contaminants in marine fish from the South China Sea: Exposure and human risks

Microplastics can act as vectors of chemical contaminants in aquatic environments, but the extent to which this phenomenon contributes to chemical exposure in marine organisms remains poorly understood. We investigated the occurrence of microplastics and emerging contaminants (ECs), including antibiotics and per- and polyfluoroalkyl substances (PFAS) in 14 marine fish species. Microplastics were detected in all marine fish species, mainly in the gastrointestinal tract. Fluoroquinolones and tetracyclines were the dominant antibiotics in fish muscles with maximum concentrations of 24.84 and 26.95 ng g-1 ww, while perfluorooctanesulfonic acid (PFOS, 0.039-0.95 ng g-1 ww) was the dominant component in the PFAS profile. Fish with more microplastics had significantly higher concentrations of fluoroquinolones and perfluoroalkyl acids than fish with less microplastics (p < 0.05), but the correlation was not observed in other chemicals. Structural equation modeling revealed the contribution of microplastics in fish on the level of ECs contamination. The health quotient value indicated the low health risk of single compounds via fish consumption to humans; however, the combined risk of microplastics and ECs still needs to be considered. This work highlights the link between microplastics with associated ECs ingested by aquatic organisms and the human health risk of consuming polluted seafood.

A review of the ecotoxicological status of microplastic pollution in African freshwater systems

Microplastics (MPs) have found extensive application globally due to their low cost, flexibility and light weight. Microplastic pollution is a growing environmental concern that poses significant threats to aquatic ecosystems worldwide, including African freshwater systems. Nevertheless, although Africa houses some of the deepest and largest freshwater rivers and lakes in the world such as Lake Tanganyika and Victoria, River Congo and the Nile, there is limited information available regarding the presence of MPs in these inland waters. Selected published data on MPs in African freshwater systems, including sediments, biota, rivers, and lakes, were incorporated in this review. The study discovered that the sampling technique employed has a major impact on the morphological characteristics and abundance of MPs in African freshwater systems. Fibers and fragments were the most common shapes; black, white, and transparent were the most prevalent colors; and polyethene terephthalate, polystyrene, and polypropylene were the frequently dominant polymers. As the distance between the sampling sites increased geographically, the polymer similarities declined. MPs have been found to translocate into body cells and tissues where they are capable of causing genetic mutations, cytotoxicity, oxidative stress and neurotoxicity. In Africa, MPs are poorly managed and monitored, and there has been insufficient research done on the possibility that they could be present in drinking water. Considering the fact that humans in the continent are exposed to freshwater and aquatic organisms, the risk assessment routes are currently unvalidated, therefore it was recommended that African nations should strengthen their capacity for plastic management and environmental monitoring. This review provides up to date information on the occurrence, prevalence, ecotoxicity and management of MPs across African freshwater systems.

Occurrence of microplastics in commercial fish species from the Ethiopian rift valley's Lake Hawassa, Ethiopia

Microplastics (MPs) have recently been detected as emergent pollutants in the Ethiopian rift valley lakes located close to rapidly expanding towns. We provide the first study of MPs ingestion of commercial fish species from Lake Hawassa, Ethiopia: Catfish (Clarias gariepinus) and Nile Tilapia (Oreochromis niloticus). A total of 60 individual fish species was collected from three sampling sites of lake Hawassa in October 2020. Across all sampling sites, there was a significant difference in ingested MPs between benthic omnivore catfish and pelagic phytoplanktivorous Tilapia (χ2 = 15.864, p < 0.001). The most common size of ingested MPs (84.6%) was 0.5-1 mm, with fragments (59.5%) dominating, followed by fibers (25.4%). On average, 4.03 ± 1.33 MPs with sizes ranging between 60 μm and 10.53 mm were detected per individual. White and yellow MPs were particularly numerous, accounting for 36.8% and 26.4% of the total, respectively. Because Lake Hawassa's fishery is so significant, the potential impact of MP pollution on the lake biota in general, and economically valuable fish species in particular, deserves attention, additional research, and, if possible, early mitigation.

Assessment of fishes, sediment and water from some inland rivers across the six geopolitical zones in Nigeria for microplastics

In Nigeria, limited research has been conducted on Microplastics (MPs) in inland rivers, necessitating a comprehensive assessment to understand the extent of contamination. This study aimed to assess the abundance, distribution, and composition of MPs in fishes, sediment, and water from inland rivers across Nigeria's six geopolitical zones. Samples were collected from selected rivers in each geopolitical zone (Rivers Yauri, Benue, Argungu, Jamare, Ogun, Ethiope and Orashi). MPs were isolated using a combination of filtration, density separation, and visual identification. MPs abundance, distribution, shapes, colors, and chemical composition were determined using microscopy and Fourier-transform infrared spectroscopy. The study presents the first report of MPs in six in land rivers in Nigeria and found that MPs were present in all the fishes, sediments and river waters studied across all the rivers. The abundance and composition of MPs varied among the different sample types, with fibers being the most abundant shape in both water and fish samples. PET, PP, and PE were the most prevalent types of plastics found in fish samples, while PE/PA/Nylon, PVA, and PVC were predominant in water samples. PA/Nylon, PUR, PVC, and PET were the most common in sediment samples. Source analysis by Principal component analysis (PCA) and Hierarchical Cluster Analysis (HCA) indicated that the presence of MPs was mainly influenced by local anthropogenic activities. However, estimated daily intakes are generally low, indicating that daily consumption of the samples is not likely to be harmful. The widespread presence of MPs in inland rivers across Nigeria highlights the urgent need for effective waste management strategies and environmental conservation efforts to mitigate plastic pollution.

Evidence of microplastics accumulation in the gills and gastrointestinal tract of fishes from an estuarine system in Ghana

The contamination of aquatic environments by microplastics (MPs) and their subsequent ingestion by fish continues to be a universal ecological challenge. Although numerous studies have been conducted on the accumulation of MPs by fishes globally, not much work has been done within the major estuaries along the Atlantic Coast. This study explored and characterized microplastics in the gills and gastrointestinal tract in 98 specimens of 10 fish taxa (Sarotherodon melanotheron, Pseudotolithus senegalensis, Gobionellus occidentalis, Ethmalosa fimbriata, Chrysichthys nigrodigitalus, Elops lacerta, Mugil bananesis, Cynoglossus senegalensis, Apsilus fuscus and Galeoides decadactylus) from the Pra Estuary, Ghana. The gastrointestinal contents of the fish were extracted, analysed and characterized using a stereomicroscope fitted with an Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR). A total of 529 MP particles were found in the fishes. C. nigrodigitalus recorded the highest MP levels in the gills with an average of 4.83 ± 2.08 items/individual whiles S. melanotheron recorded the highest in the gastrointestinal tract at 9.83 ± 4.63 items/individual. Within the fish, transparent fibrous MPs of size <0.5 mm were the dominate types found. A vertical prevalence of MPs was observed across the feeding and habitat preference of the species suggesting a possible linkage with the ecological niche of fishes. Our findings further demonstrate the need for advance studies on the impacts and level of threat microplastic accumulation pose to the sampled fishes and potential consumers.

The first evidence of microplastic presence in the River Nile in Khartoum, Sudan: Using Nile Tilapia fish as a bio-indicator

The extent of microplastics in African freshwater systems remains less investigated. In Sudan, there is no single study reporting microplastics in water bodies. This scoping study aimed to investigate the presence and characteristics of microplastics (MPs) in Nile Tilapia fish from the River Nile in Khartoum, Sudan. The digestive tracts of the fish were digested using 10% potassium hydroxide, and microplastic particles were extracted by density separation using sodium iodide. 567 particles of different sizes (0.04-4.94 mm), shapes (fibers, fragments, films, foams, and pellets), and colours (mostly green, black, blue, and grey) were identified as microplastics. The average abundance of microplastics was 72.02 ± 62.06 particles/kg, and the average intensity was 18.90 ± 9.17 MPs/fish. Small-sized (<1 mm), fibrous-shaped, and coloured microplastics were most abundant in all samples, representing 56%, 85%, and 84%, respectively. Surface examination by SEM showed signs of fragmentation such as cracks, pits, and pores. Two polymer types (high-density polyethylene and polypropylene) were identified by Raman spectroscopy. The predominance of fibers and fragments (94.5%) over pellets (0.35%) and the apparent signs of fragmentation may indicate that MPs are mostly secondary MPs. Wastewater effluent, domestic discharge, and recreational activities are the potential sources. This scoping investigation provided the first data on microplastic presence in the River Nile in Khartoum, and it could be used to guide future studies to fill research gaps in the region.

Microplastics contamination in two species of gobies and their estuarine habitat of Indian Sundarbans

Sundarbans, a Ramsar site of India is contaminated with heterogeneous microplastic wastes. Boddart's goggle eye mudskipper and Rubicundus eelgoby, were common gobies of Sundarbans estuary which accumulated microplastics during their normal biological activities. We estimated the abundance of microplastics in water, sediment; skin, gills, bucco-opercular cavity and gastrointestinal tract of these two goby fishes. Microplastic load estimated in gobies were 0.84 and 2.62 particles per fish species with a dominance of transparent, fibrous microplastics with 100-300 μm in length. ATR-FTIR and Raman spectroscopy revealed polyethylene as prevalent polymer. Surface degradations and adsorption of contaminants on microplastic surface were investigated by SEM-EDX analysis. Presence of hazardous polymers influenced high polymer hazard index and potential ecological risk index which indicated acute environmental threat to Sundarbans estuary and its resident organisms. Current study will provide a new information base on the abundance of microplastics and its ecological hazard in this biosphere reserve.

Impacts of microplastic on fisheries and seafood security - Global analysis and synthesis

This review paper collected, collated, analysed, interpreted, synthesised, and documented the research investigations conducted on microplastic (MPs) pollution impacts on seafood organisms (including fish, sharks, shrimps, lobsters, crabs, oysters, mussels, and seaweeds) during the last ten years (2012-2022) covering fifty-seven locations/countries in the world. MPs contaminated 926 seafood species comprising 895 finfish, 09 crustaceans, 20 molluscs and 02 seaweeds. Seafood from Asia was found to be most contaminated with MPs. High MP contamination/ingestion was revealed in several seafood organisms. The ingestion of MPs can reduce fish growth and fish fitness, leading to reduced yield/fish production. Fish and seafood play a significant role in supporting the economy, employment, food sources, and livelihoods of people across the globe, which can be threatened due to the contamination of seafood organisms with MPs. MPs have bioaccumulated in fish skin, gills, stomachs, liver, intestine, and muscles as well as dry fish and canned fish. Hence, the consumption of MP-contaminated fresh fish, whole fish, dried fish or canned fish poses risks as it may be a pathway of MP transfer to humans. MPs can increase the health risks to seafood fish consumers since there is a probability that high risks pollutants adsorbed on MPs (heavy metals, pesticides, and oil compounds) can transfer to humans via the food chain. Several of the chemicals (heavy metals, DDT, PAHs) adsorbed onto MPs are carcinogenic. MPs have also been detected in fish meals, therefore, farmed livestock such as aquaculture fish and chicken fed to fish meals can be exposed to MPs and ultimately to humans. Preventive and safety measures are suggested to reduce the exposure of MPs to humans. In addition, several policy strategies are recommended to reduce the impacts of plastic waste and plastic pollution on the environment, aquatic biota, wildlife, seafood and human health.

Plastics in an endemic fish species (Alburnus sellal) and its parasite (Ligula intestinalis) in the Upper Tigris River, Türkiye

Occurrence of micro-, meso- and macroplastics in Alburnus sellal and its parasite Ligula intestinalis is reported for the first time in the Tigris River, one of the two large rivers that defines Mesopotamia. Plastic occurrence was assessed from museum fish materials collected in the upper Tigris River between 2007 and 2021. Plastics were found in 57 % of A. sellal specimens (536 individuals) and in 74 % of L. intestinalis specimens (57 individuals). Mean plastic ingestion was 1.27 ± 1.30 items. fish-1 and 1.77 ± 1.79 items. parasite-1 considering all the fish and parasites analysed. Fibres were the most common types of plastics, comprising 96.2 % and 81 % of plastics in A. sellal and L. intestinalis, respectively. Black was the most common colour of plastics found in both fish (37 %) and parasite specimens (58 %). Microplastics comprised 95.5 % and 100 % of plastics found in A. sellal and L. intestinalis, respectively. In both specimens acrylic (PAN) was the most common polymer as confirmed by FTIR spectroscopy. Differences in plastic ingestion were not significantly over time and among regions. No significant correlation was found between plastics ingestion by fish and by parasites. The present assessment shows that native fish species of the Tigris River have been contaminated by plastics by more than a decade. Our results contribute to a better understanding of the status of plastic pollution in fish and parasites, provide plastic pollution baseline data for the Tigris River and highlight the urgent need to elucidate on the distribution and fate of plastics in freshwater environments and their effects on the ecosystem and humans.

A standard analytical approach and establishing criteria for microplastic concentrations in wastewater, drinking water and tap water

The ubiquitous presence of microplastics (MPs) in natural water bodies reflects the global issue regarding these micropollutants. The main problem of MPs lies on the difficulty of removing these particles from water during wastewater and drinking water treatments. The release of MPs to the environment in treated wastewater contributed to the dispersion of these micropollutants, which enhances the harmful effect of MPs on fauna and flora. In addition, their presence in tap water entails a potential risk to human health since MPs can be directly consumed. The first step is being able to quantify and characterise these microparticles accurately. In this work, a comprehensive analysis on the presence of MPs in wastewater, drinking water and tap water has been conducted with emphasis on sampling methods, pre-treatment, MP size and analytical methods. Based on literature data, a standard experimental procedure has been proposed with the objective of recommending a methodology that allows the homogenisation of MP analysis in water samples. Finally, reported MP concentrations for influents and effluents of drinking and wastewater treatment plants and tap water have been analysed, in terms of abundance, ranges and average values, and a tentative classification of different waters based on their MP concentrations is proposed.

A study on managing plastic waste to tackle the worldwide plastic contamination and environmental remediation

Over the past 50 years, the emergence of plastic waste as one of the most urgent environmental problems in the world has given rise to several proposals to address the rising levels of contaminants associated with plastic debris. Worldwide plastic production has increased significantly over the last 70 years, reaching a record high of 359 million tonnes in 2020. China is currently the world's largest plastic producer, with a share of 17.5%. Of the total marine waste, microplastics account for 75%, while land-based pollution accounts for responsible for 80-90%, and ocean-based pollution 10-20% only in overall pollution problems. Even at small dosages (10 μg/mL), microplastics have been found to cause toxic effects on human and animal health. This review examines the sources of microplastic contamination, the prevalent reaches of microplastics, their impacts, and the remediation methods for microplastic contamination. This review explains the relationship between the community composition and the presence of microplastic particulate matter in aquatic ecosystems. The interaction between microplastics and emerging pollutants, including heavy metals, has been linked to enhanced toxicity. The review article provided a comprehensive overview of microplastic, including its fate, environmental toxicity, and possible remediation strategies. The results of our study are of great value as they illustrate a current perspective and provide an in-depth analysis of the current status of microplastics in development, their test requirements, and remediation technologies suitable for various environments.

Feeding behavior and species interactions increase the bioavailability of microplastics to benthic food webs

Plastics are pervasive in aquatic ecosystems, in which they circulate in the water column, accumulate in sediments, and are taken up, retained, and exchanged with their biotic environment via trophic and non-trophic activities. Identifying and comparing organismal interactions are a necessary step to improve monitoring and risk assessments of microplastics. We use a community module to test how abiotic and biotic interactions determine the fate of microplastics in a benthic food web. Using single-exposure trials on a trio of interacting freshwater animals (the quagga mussel Dreissena bugensis, a filter feeder; the gammarid amphipod Gammarus fasciatus, a deposit feeder; and the round goby Neogobius melanostomus, a benthivorous fish), we quantify the (1) uptake of microplastics from environmental routes (water, sediment) under six exposure concentrations, (2) the depuration capacities over 72 h, and (3) the transfer of microbeads via trophic (predator-prey) and behavioral interactions (commensalism, intraspecific facilitation). Under 24 h exposures, each animal of our module acquired beads from both environmental routes. The body burden of filter-feeders was higher when they were exposed to particles in suspension, whereas detritivores had similar uptake from either route. Mussels transferred microbeads to amphipods, and both invertebrates transferred beads to their mutual predator, the round goby. Round gobies generally displayed low contamination from all routes (suspension, sedimented, trophic transfer) with a higher microbead load from preying on contaminated mussels. Higher mussel abundance (10-15 mussel per aquaria, i.e., ~200-300 mussels·m2) did not increase individual mussel burdens during exposure, and neither did it increase the transfer of beads from mussels to gammarids via biodeposition. Our community module approach revealed that the feeding behavior of animals allows microplastic uptake from multiple environmental routes, whereas trophic and non-trophic species interactions increased their burden within their food web community.

Face masks: a COVID-19 protector or environmental contaminant?

Face masks, a prime component of personal protective equipment (PPE) items, have become an integral part of human beings to survive under the ongoing COVID-19 pandemic situation. The global population requires an estimated 130 billion face masks and 64 billion gloves/month, while the COVID-19 pandemic has led to the daily disposal of approximately 3.5 billion single-use face masks, resulting in a staggering 14,245,230.63 kg of face mask waste. The improper disposal of face mask wastes followed by its mismanagement is a challenge to the scientists as the wastes create pollution leading to environmental degradation, especially plastic pollution (macro/meso/micro/nano). Each year, an estimated 0.15-0.39 million tons of COVID-19 face mask waste, along with 173,000 microfibers released daily from discarded surgical masks, could enter the marine environment, while used masks have a significantly higher microplastic release capacity (1246.62 ± 403.50 particles/piece) compared to new masks (183.00 ± 78.42 particles/piece). Surgical face masks emit around 59 g CO2-eq greenhouse gas emissions per single use, cloth face masks emit approximately 60 g CO2-eq/single mask, and inhaling or ingesting microplastics (MPs) caused adverse health problems including chronic inflammation, granulomas or fibrosis, DNA damage, cellular damage, oxidative stress, and cytokine secretion. The present review critically addresses the role of face masks in reducing COVID-19 infections, their distribution pattern in diverse environments, the volume of waste produced, degradation in the natural environment, and adverse impacts on different environmental segments, and proposes sustainable remediation options to tackle environmental challenges posed by disposable COVID-19 face masks.

Coupling of microplastic contamination in organisms and the environment: Evidence from the tidal flat ecosystem of Hangzhou Bay, China

Microplastics are a new type of contaminant, widely defined as fragmented plastics with the longest dimension or diameter less than 5 mm, that are widely distributed, difficult to degrade, and easily adsorb other pollutants. Estuaries are key habitats where terrestrial microplastics flow in water runoff and import into the ocean. The ubiquitous use of plastics has resulted in a massive amount of plastic waste that is released and accumulated in bay ecosystems, posing serious ecological impacts. The study of microplastic contamination in Hangzhou Bay, the estuary of the Qiantang River, has important theoretical value in ecology and environmental science. Microplastic contamination in the tidal flats and organisms of Hangzhou Bay is serious and microplastic characteristics (type, size, and polymer type) in organisms were significantly correlated with those in the environmental media. Spatial autocorrelation was found in the abundance of microplastics in marine and tidal flat sediments of Hangzhou Bay, China, but no spatial autocorrelation was found in the sediment environment as a whole. The microplastic abundance in each organism in this study was not statistically correlated by weight or by individual count with its corresponding trophic level (P = 0.239 > 0.05; P = 0.492 > 0.05, respectively). Our study suggests a coupling relationship of microplastic contamination between organisms and the environment and can provide essential data and a scientific foundation for the study of microplastics pollution in Hangzhou Bay, as well as provide important evidence for the ecological and health risk assessment of microplastics.

Plastic occurrence in fish caught in the highly industrialized Gulf of İzmit (Eastern Sea of Marmara, Türkiye)

Occurrence of micro- (<5 mm) and mesoplastics (5-25 mm) in twelve fish species caught off Gulf of İzmit in the Sea of Marmara was investigated. Plastics were found in the gastrointestinal tracks of all the analysed species: Trachurus mediterraneus, Chelon auratus, Merlangius merlangus, Mullus barbatus, Symphodus cinereus, Gobius niger, Chelidonichthys lastoviza, Chelidonichthys lucerna, Trachinus draco, Scorpaena porcus, Scorpaena porcus, Pegusa lascaris, Platichthys flesus. From a total of 374 individuals examined plastics were found in 147 individuals (39%). The average plastic ingestion was 1.14 ± 1.03 MP. fish^-1 (considering all the analysed fish) and 1.77 ± 0.95 MP. fish^-1 (considering only the fish with plastic). Fibres were the primary plastic types found in GITs (74%), followed by films (18%) and fragments (7%), no foams and microbeads were found. A total of ten different colours of plastics were found with blue (62%) being the most common colour. Length of plastics ranged from 0.13 to 11.76 mm with an average of 1.82 ± 1.59 mm. A total of 95.5% of plastics were microplastics, and 4.5% as mesoplastics. The mean frequency of plastic occurrence was higher in pelagic fish species (42%), followed by demersal (38%) and bentho-pelagic species (10%). Fourier-transform infrared spectroscopy confirmed that 75% of polymers were synthetic with polyethylene terephthalate being the most common polymer. Our results indicated that carnivore species with a preference for fish and decapods were the highest impacted trophic group in the area. Fish species in the Gulf of İzmit are contaminated with plastics, representing a potential risk to ecosystem and human health. Further research is needed to understand the effects of plastic ingestion on biota and possible pathways. Results of this study also provide baseline data for the implementation of the Marine Strategy Framework Directive Descriptor 10 in the Sea of Marmara.

Exploring microplastic pollution in a Mediterranean river: The role of introduced species as bioindicators

Studies of plastic contamination in freshwater ecosystems and their biota remain scarce, despite the fact that the vast majority of plastic waste initially passes through lotic ecosystems. Biomonitoring provides valuable information regarding plastic pollution and microplastic threats to biota and human health. The aim of this study was to explore the potential use of a non-indigenous fish species as a bioindicator of microplastic pollution in an Eastern Mediterranean River. Our study area is located in a heavily modified and vastly impacted urban river which flows through the largest part of the Metropolitan area of Athens, Greece. We used an introduced chub species (Squalius vardarensis) to assess microplastic ingestion in the river. The results indicated moderate occurrence and abundance of microplastics in the fish gastrointestinal tracts; one-third of specimens (35%) contained microplastics, although the average number of microplastics per specimen was relatively low (1.7 ± 0.2). Overall, the abundance of microplastics in the water confirmed the moderate level of microplastics contamination in our study area. The major polymer types of microplastics identified by FT-IR analysis were: polyethylene (PE), polyvinyl alcohol (PVA) and polypropylene (PP); reflecting the fragmentation of larger litter from industrial packaging and/or household goods. Surface runoff of the urban environment, via motorways and major road networks, could be the contributing factor to the reported microplastics. Our results suggest that generalist's non-indigenous species such as chubs could be used as bioindicators of microplastics in inland waters. Introduced fishes can be a feasible, nondestructive, and cost-effective option for the assessment of microplastics in freshwater ecosystems, while freshwater chubs' high abundance and omnipresence in European rivers further serve this scope. However, it is worth noting that the suitability of any particular species as a bioindicator of microplastics may depend on a variety of factors, including their feeding behavior, habitat, and exposure to microplastics in their environment.

Microplastics in the Surface Water and Gastrointestinal Tract of Salmo trutta from the Mahodand Lake, Kalam Swat in Pakistan

Microplastic pollution is becoming an increasingly severe environmental problem. As compared to the marine ecosystem, freshwater ecosystems at high-altitude, remote regions are less studied and lag far behind. Thus, the present study aims to highlight this issue and fill the gap in this regard. The presence of microplastics (MPs) in the surface water and the gastrointestinal tracts (GITs) of brown trout (Salmo trutta) from Lake Mahodand, Kalam Swat, Pakistan, at a high altitude of 2865 m above sea level was investigated. For microplastic extraction, samples were digested with H2O2, NaCl solution was added for density separation, and then samples were filtered with a cellulose nitrate filter (pore size 0.45 µ). After this, visual observation and polymer detection with Fourier transform infrared spectroscopy, microplastics were characterized by their shapes, sizes, colors, and polymer types. In the surface water sample, MP particles were found in the range of 0−5 MPs/L, where the mean concentration of MPs was 2.3 ± 1.52 MPs/L and 1.7 ± 1.05 MPs/gastrointestinal tract (GIT) isolated from the GIT of brown trout. Particles of relatively larger size (500−300 µm) were more abundant than other ranges of particles (300−150 and 150−50 µm) in the surface water and fish samples. The fiber was the most abundant shape of MP particles, followed by sheets and fragments in surface water and fish samples (fibers > sheets > fragments). Four types of polymer viz. low-density polyethylene (LDPE) (44.4%), polypropylene homopolymer (PPH) (19.4%), polyvinyl chloride (PVC) (30.5%), and high-density polyethylene (HDPE) (5.5%) were detected by FTIR spectroscopy. The findings of the present study showed that MPs reached into higher altitudes in remote areas due to tourism activities.

Impact of “sachet water” microplastic on agricultural soil physicochemistry, antibiotics resistance, bacteria diversity and function

Nigeria's most consumed potable water plastic wastes are indiscriminately dumped into agricultural soil despite their ability to become microplastics. The study evaluates the potential impacts of these microplastics on soil physico-chemical parameters, soil bacterial diversity and functions as well as antibiotic resistance. Soil sample was collected using a sterile hand-held auger and its physico-chemical parameters evaluated. Baseline microplastic concentration was determined via the flotation method while microbial isolates were obtained from the test (enriched with microplastics) and control samples using cultural technique and metagenomics. Metagenomic next-generation sequencing (mNGS) was done using the Illumina Miseq platform. The cluster of orthologous genes (COG) tool was used in the prediction of bacterial functional roles. Replicate readings were analysed using analysis of variance (ANOVA) and means compared using the student’s t test. Observed baseline microplastic concentration was 0.08 particles/g of soil. The addition of the microplastics to the soil sample decreased the concentrations of some metals (iron, zinc, lead and nickel) while cobalt concentration, pH level and microbial counts increased. Microbial count and pH clustered together while iron, magnesium, nitrate, nitrite, chromium, cobalt, total organic carbon, zinc, lead, and nickel showed positive loading values suggesting that the addition of microplastics could alter them. Dominant taxa were proteobacteria, unknown, firmicutes at the phyla level. At the level of species, Pseudomonas species dominated microplastics incubated soil while potential pathogenic species such as Klebsiella dominated the control sample. A higher level of multi-drug resistance and altered metabolisms was observed in the test sample. Sachet water microplastics could have serious implications for public health and food security.

Occurrence of Microplastics in the Gastrointestinal Tracts of Edible Fishes from South Indian Rivers

Microplastics (MPs) in the gastrointestinal (GI) tracts of the five fish species from the Kollidam and Vellar rivers of Tamil Nadu, Southern India were evaluated. A total of 315 MPs were isolated from GI tracts of 23 fishes (Chanos chanos, Chanda nama, Chelon macrolepis, Carangoides malabaricus and Gerrus filamentosus) sampled from both rivers. MPs ranged from 109 to 129 μm (119 ± 79.7) and 181 to 284 μm (122 ± 92.6) in size, with fibres (85.7%) and fragments (14.3%) being the most common ones in the fishes from Kollidam and Vellar river, respectively. The colour pattern of ingested MPs was dominated by blue, transparent, red, yellow and black in collected fishes from both rivers. In this study, MPs were higher in fishes with omnivore feeding habits due to their broad diet habits. Moreover, urban wastes, fishing and agricultural activities are the possible primary sources of MPs in both rivers.

Microplastics accumulation in gastrointestinal tracts of Mullus barbatus and Merluccius merluccius is associated with increased cytokine production and signaling

There is clear evidence that different marine species can be impacted by microplastic (MP) ingestion accumulating such MPs mainly in the gastrointestinal tract. However, there is still limited knowledge on the consequences of MPs' accumulation in the gut. The present study aims to assess MPs and their potential immunotoxic effects in the digestive tract of two species showing different ecological traits: the red mullet (Mullus barbatus) and the European hake (Merluccius merluccius). Infrared spectroscopy (FTIR-ATR), micro-Raman and electron scanning microscope (SEM) were used to accurately identify the main plastic polymers detected in gut contents. In addition, we investigated the association between MP uptake and intestinal inflammation by evaluating expression and secretion of proinflammatory cytokines. MP abundance ranged from 1 to 20 items/individual in red mullet and from 2 to 15 items/individual in European hake. The majority of ingested MPs were fibers, while the dominant colors were black and blue in both species. Chemical characterization indicated polyethylene and polypropylene as the most common polymer types. Moreover, it was observed that MP abundance was highly positive correlated to cytokines (i.e. interleukin-1β, 10, and interferon) and antioxidant enzyme (i.e. catalase and superoxide dismutase) transcript levels suggesting ROS generation and an infiltration of immune cells in the gut. Our findings provide evidence that the induction of cytokine-dependent signaling pathways is one aspect of the complex mechanism by which MPs affect the gut system in fish.

Effect of biological and environmental factors on microplastic ingestion of commercial fish species

Marine litter is an emerging pollution all over the world. In addition to the macro sized plastics, ongoing scientific efforts revealed risks of micro and nano sized plastic particles in marine environment. In the past decades, an increasing number of studies have been carried out to understand the dynamics of this pollution. The aim of the present study was to investigate the microplastic (MPs) ingestion in commercially important fish species and to evaluate biological and environmental factors influencing the ingestion status. Gastrointestinal tract content of a total of 2222 individuals belonging to 17 species were examined for MPs existence. Out of 17 species evaluated, 13 of them was detected to ingest MPs. Our results showed that 18.1% of investigated fishes ingested MPs and the average length of the detected particles was 1.26 ± 1.38 (±SD) mm. The most dominant MP type was fiber (90.1%), while the most common particle colours were black (46.9%) and blue (29.4%). Polypropylene (85%) was the most common polymer type detected. Our evaluations indicated that the exposure of fish distributed in coastal areas to microplastic pollution is corelated to physical (precipitation and distance to nearest shore) and biological (functional trophic group, habitat of the species) factors. In order to design a more effective control mechanism, these impacts should be included in the assessments in future practices to reveal the effects of microplastic pollution on biota.

Microplastics Risk into a Three-Link Food Chain Inside European Hake

Microplastics (MPs) are increasing in the marine environment as well as inside marine organisms, having an important effect on biological diversity. The trophic transfer of MPs was demonstrated under laboratory conditions, but this study is based on the analysis of preys found in stomach contents. MPs from Merluccius merluccius individuals caught in the Cantabrian Sea and preys inside their guts (blue whiting, and northern krill inside blue whiting) were analyzed. MPs with different chemical composition occurred inside every hake and their preys, with different damages, from aquatic life hazards with long lasting effects, to allergic skin reactions and respiratory irritation, not only for aquatic species and fishing resources, but also for humans through hake consumption. The similarity of MPs profiles from gills and seawater samples would support seawater as the main source of gill microplastics. The MPs profile of hake GIT was similar to that of hake preys inside. Despite the small sample size, the presence of MPs in all the tissues analyzed of hakes and their preys, together with the evidence of hazard compositions of some of them, highlights the need for policies and actions to reduce plastic and microplastic production and consumption.

Effects of ingestion of polyethylene microplastics on survival rate, opercular respiration rate and swimming performance of African catfish (Clarias gariepinus)

The study evaluated the impact of ingestion of microplastics on accumulation, survival, opercular respiratory rate (ORR), and swimming performance of Clarias gariepinus, the African freshwater catfish exposed to polyethylene microplastics. Juveniles were exposed for 4 days to 50-500 µm low-density polyethylene (LDPE) microplastics at four different concentrations (0.5, 1.0, 1.5, and 2.0 g/L). After 4 days of exposure, the concentration of microplastics in the gastrointestinal tract (GIT) of the fish increased with increasing concentrations of microplastics. Mean weights of microplastics in the GIT of the fish ranged from 0.0025 ± 0.001 g to 0.054 ± 0.01 g, suggesting that the fish were unable to detect and avoid ingesting the microplastics. No mortality was observed in all the treatment concentrations except in the highest concentration (2 g/L) where 10% mortality was observed. The results showed that ORR increased in a concentration and time-dependent manner. Compared with the control group, the swimming speed, travel distance and movement patterns of the fish exposed to microplastics were significantly reduced (p < 0.05). Therefore, this study helps understand the environmental impact of microplastics on C. gariepinus in freshwater environments.

Potential microplastics impacts on African fishing resources

Microplastic (MP) pollution is increasing worldwide and affecting aquatic fauna in different ways, which endangers current aquatic resources in a still unknown extent. MP-induced threats to marine fauna are critical for developing countries, where waste treatment may be not optimal and coastal communities rely heavily on marine resources for dietary protein. In this study, we assess the importance of MP pollution for African fishing resources. A new meta-database was created from published studies, containing 156 samples with more than 6200 individuals analysed for microplastic content from African and adjacent waters. A combination of research landscape analysis and rank analysis served to identify main research targets and to determine regional fishing resources especially affected by MP. A network of relevant terms showed fish health as a concern in Mediterranean waters, environmental pollution in freshwater and an emphasis on plastic items in South Africa. MP contents in fishing resources from Nile countries and the Gulf of Guinea, followed by Tunisia, are significantly higher than in other regions. Some of the most exploited species are among the most polluted ones, highlighting the threat of MP pollution in valuable but already compromised African fishing resources. Large geographic gaps with almost absent data about MP in aquatic fauna were revealed, especially in freshwater and in East African coasts. These results emphasize the importance of increasing the coverage of MP pollution in African fishing resources, and improving plastic waste management in the continent.

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?

Microplastic distribution, abundance, and composition in the sediments, water, and fishes of the Red and Mediterranean seas, Egypt

This study records the extent of microplastics (MPs) in the surface water, sediments, and fishes of the Mediterranean and Red seas in Egypt. In sediment and water samples, the Ras Gharib station in the Red sea and Damietta and Port Said stations in the Mediterranean sea exhibited the highest microplastic abundance, while the lowest concentration was found in the Ain Sukhna station in the Red Sea and Marsa Matruh station in the Mediterranean sea. Rayon and polyethylene terephthalate were the most frequently found polymers in fishes. The results highlighted the abundant existence of microplastics in sediments, water, and fishes of the Mediterranean and Red seas, thereby improving our understanding of the environmental risks posed by microplastics to fisheries and marine ecosystems and the need for measures to diminish the flux of plastics to the marine settings.

A Review of Chemical Contaminants in Marine and Fresh Water Fish in Nigeria

Pollutants in aquatic food are a major global concern for food safety and are a challenge to both national and international regulatory bodies. In the present work, we have reviewed available data on the concentrations of polycyclic aromatic hydrocarbons (PAH), persistent organic pollutants, metals, and microplastics in freshwater and marine fish in Nigeria with reference to international maximum levels for contaminants in food and the potential risk to human health. While most of the contaminant levels reported for fish do not imply any health issues, iron and lead may represent potentially toxic levels in fish from specific areas. Studies on PAHs in marine fish are scarce in Nigeria, and the main focus is on the environmental pollution caused by PAHs rather than on their presence in food. The findings suggest that the consumption of smoked Ethmalosa fimbriata poses a higher potential carcinogenic risk than the other fish species that were investigated. Most of the other studies on PAHs in smoked fish are focused on the smoking method, and little information is available on the initial level of PAHs prior to the smoking process. Metal contamination in fish appeared to be affected by mineral deposits in the environment and industrial effluents. In general, heavy metal levels in fish are below the maximum levels, while there is limited data available on POPs of relevance to food safety in fish from Nigeria, particularly in terms of dioxins, brominated flame retardants, and fluorinated compounds. Furthermore, there is currently limited information on the levels of microplastics in fish from Nigerian waters. This work revealed the need for a more systematic sampling strategy for fish in order to identify the most vulnerable species, the hot spots of contaminants, and applicable food safety control measures for fish produced and consumed in Nigeria.

Do Freshwater Fish Eat Microplastics? A Review with A Focus on Effects on Fish Health and Predictive Traits of MPs Ingestion

Microplastics (MPs) have received increasing attention in the last decade and are now considered among the most concerning emerging pollutants in natural environments. Here, the current knowledge on microplastic ingestion by wild freshwater fish is reviewed with a focus on the identification of possible factors leading to the ingestion of MPs and the consequences on fish health. Within the literature, 257 species of freshwater fishes from 32 countries have been documented to ingest MPs. MPs ingestion was found to increase with rising level of urbanization, although a direct correlation with MPs concentration in the surrounding water has not been identified. MPs ingestion was detected in all the published articles, with MPs presence in more than 50% of the specimens analyzed in one study out of two. Together with the digestive tract, MPs were also found in the gills, and there is evidence that MPs can translocate to different tissues of the organism. Strong evidence, therefore, exists that MPs may represent a serious risk for ecosystems, and are a direct danger for human health. Moreover, toxicological effects have also been highlighted in wild catches, demonstrating the importance of this problem and suggesting the need for laboratory experiments more representative of the environmental situation.

Face masks: protecting the wearer but neglecting the aquatic environment? - A perspective from Bangladesh

In Bangladesh, as with many countries, the spread of COVID-19 made the wearing of single-use face masks, a non-pharmaceutical intervention to reduce viral transmission, surge in popularity amongst the general population. Consequently, irresponsible discarding of used masks into the environment, and mismanagement of the waste they produce, is potentially placing a large pollution burden on aquatic ecosystems in the country. Slow degradation of mask-derived polypropylene and polyethylene fibres creates large reservoirs of microplastic pollutants and these have acute and chronic effects on aquatic organism physiology. Using literature reviews, extrapolation of published data, and field observations, we present an emerging issue of pollution from COVID-19 personal protective equipment such as face masks in Bangladesh. We have estimated the volume of waste generated and document the potential consequences of its improper disposal, and subsequent degradation, in aquaculture ponds within country. In a field survey of 30 ponds in the Muktagacha upazilla, 76.7% were found to have plastics in contact with the water, or within 1m of the pond, and there was an average of 63 pieces of macro-plastic pollution per 5m2. This included floating discarded face masks. Bangladesh has a rich freshwater and marine resource which it depends upon for export trade, nutrition of the population, and jobs. To mitigate potential acute and chronic impacts on aquaculture and the environment, recommendations are made that, if adopted, would reduce entry of microplastics into the aquatic environments via face mask waste mismanagement.

Emerging pollutants in Nigeria: A systematic review

Emerging pollutants represent a group of synthetic or naturally occurring compounds that are not normally monitored within the environment but can enter into the environment and cause different adverse ecological and health effects. This systematic review identified the various emerging pollutants in Nigeria. The following databases, ScienceDirect, PubMed, Google Scholar, and African Journals OnLine (AJOL) were searched to identify studies on pollutants of emerging concerns in Nigeria. A total of 933 articles were identified out of which 30 articles were selected to be eligible for the study. Over 250 emerging pollutants were identified and divided into 9 major groups which are personal care products, pharmaceuticals, industrial chemicals, polycyclic aromatic hydrocarbons, volatile organic compounds, pesticides, mycotoxins, radionuclides and electromagnetic radiations (Gamma radiation) and other pollutants of emerging concerns such as microbes, microplastics, and particulate matter. These pollutants are found in water bodies and underground waters, soils and sediments, biological systems, and ambient air at different concentrations with seasonal variations. Some of these pollutants act as endocrine disruptors, β-adrenergic receptors agonist blockers, oxidative stress inducers and can cause genetic alterations in DNA and epigenetic reprogramming through global DNA methylation, gene-specific CpG methylation and microRNA expression. Emerging pollutants of public health concern in Nigeria are on the increase and are threat to both ecological and human health.

Microplastic pollution in African countries' water systems: a review on findings, applied methods, characteristics, impacts, and managements

ABSTRACT

Owed to their simplicity, flexibility, lightweight, and low cost, plastics have become highly demanded in Africa as well as worldwide. However, the management of plastic wastes, particularly in African countries, is inadequate and most of the plastic debris is gatewayed into the water bodies. Nowadays, environmentalists, organizations, and governments are aware of microplastic pollution in the marine and terrestrial environment. Thus, addressing a compressive literature review in one referenced paper, as they draw up the articles, is essential to propose new research directions, to synthesize the existing theories among the existing studies. The abundance of microplastics is variable depending on the sampling and identification techniques. In this review, the available publications on microplastic pollution in African countries' water systems were retrieved. Investigations found that microplastic pollution levels in the studied water bodies were reported in high concentrations. It was observed that different sampling and analytical methods were applied for the detection of microplastics, and suggestions were raised at it may affect the reliability of the results. Most of the detected and quantified microplastics were confirmed as they are from secondary sources. Most of the microplastic pollution research was conducted dominantly in South Africa, and secondly Nigeria, although other countries should also start conducting in their water systems. Surface water and sediment samples were dominantly carried out, but are limited with biota samples; hence, the risk assessment of microplastics is not yet determined. Some of the African countries have regulations on the prevention of macroplastic wastes, but the implementations are unsuccessful and most have not yet been established resulting in a threat of microplastics pollution. Thus, the research priorities on microplastic detection should be identified, and the African countries' governments should be more proactive in eradicating macroplastic, which ends up as microplastics, pollutions in the water environments.

GRAPHIC ABSTRACT

ARTICLE HIGHLIGHTS

Researches on microplastic pollution in African countries water system is limited .A high microplastics abundance is found in African countries water system.Sampling methods and used analytical techniques for microplastic detection were included.Harmonized standard methods for microplastic pollution research should be established.Combined analytical tools at once should be adopted to detect reliable microplastics.

Microplastics and associated contaminants in the aquatic environment: A review on their ecotoxicological effects, trophic transfer, and potential impacts to human health

The microplastic pollution and related ecological impacts in the aquatic environment have attracted global attention over the past decade. Microplastics can be ingested by aquatic organisms from different trophic levels either directly or indirectly, and transferred along aquatic food chains, causing different impacts on life activities of aquatic organisms. In addition, microplastics can adsorb various environmental chemical contaminants and release toxic plastic additives, thereby serving as a sink and source of these associated chemical contaminants and potentially changing their toxicity, bioavailability, and fate. However, knowledge regarding the potential risks of microplastics and associated chemical contaminants (e.g., hydrophobic organic contaminants, heavy metals, plastic additives) on diverse organisms, especially top predators, remains to be explored. Herein, this review describes the effects of microplastics on typical aquatic organisms from different trophic levels, and systematically summarizes the combined effects of microplastics and associated contaminants on aquatic biota. Furthermore, we highlight the research progress on trophic transfer of microplastics and associated contaminants along aquatic food chain. Finally, potential human health concerns about microplastics via the food chain and dietary exposure are discussed. This work is expected to provide a meaningful perspective for better understanding the potential impacts of microplastics and associated contaminants on aquatic ecology and human health.

Effects of microplastic exposure on the blood biochemical parameters in the pond turtle (Emys orbicularis)

The accumulation of microplastics (MPs) is a growing problem in aquatic ecosystems. Despite increased research on MPs in the last decade, their potential threat to freshwater ecosystems remains an open question. In the present study, the negative impacts of MPs were investigated on blood biochemical parameters in the European pond turtle (Emys orbicularis). Pond turtles were distributed into three experimental groups (n = 9 for each group) and were fed diets containing 250, 500, and 1000 mg MPs (PE100 polyethylene) per kg of food for 30 days, and a control group fed with a standard uncontaminated diet. The results indicated that exposure to 500 and 1000 mg kg^-1 MPs caused a significant increase in the activities of alanine and aspartate aminotransferases, and in the levels of cholesterol, glucose, creatinine, urea, and calcium (Ca⁺²) compared with the control group. On the contrary, the activity of gamma-glutamyl transferase and the levels of total protein, albumin, total immunoglobulins, and phosphorus were significantly reduced in E. orbicularis exposed to 500 and 1000 mg kg^-1 MPs when compared with the controls. In all the MP-exposed groups, the activity of lactate dehydrogenase and globulin and magnesium (Mg⁺²) levels were significantly reduced; while creatine phosphokinase and alkaline phosphatase activities were increased with respect to the control turtles. A significant decrease in triglyceride levels was reported in E. orbicularis exposed to 1000 mg kg^-1 MPs. MPs intake induced notable alterations in blood biochemical parameters of E. orbicularis. These results suggest that changes in the blood biochemical parameters could be an appropriate bio-indicator to evidence the existence of tissue damage in E. orbicularis.

Plastic pollution threat in Africa: current status and implications for aquatic ecosystem health

Rapid population growth and poor waste management practice are among the main drivers of plastic pollution in modern times, thus making Africa a hotspot for plastic pollution both now and in the future. This study is a review of plastic pollution reports from the African aquatic environment with regard to causes, current status, toxicological implications and implications for ecosystem services. A total of 59 plastic pollution studies from 1987 to September 2020 were reviewed. They comprised 15 from North Africa (NA) (Algeria, Egypt, Morocco and Tunisia), six from East Africa (EA) (Ethiopia, Kenya, Tanzania and Uganda), 13 from West Africa (WA) (Ghana, Guinea-Bissau, Mauritania and Nigeria), and 25 studies from Southern Africa (SA) (South Africa). This shows that plastic pollution studies in Africa, according to the sub-regions, are in the order: SA > NA > WA > EA. High human population in the basins of African large aquatic systems is identified as the greatest driver enhancing plastic surge in the aquatic environment. The occurrence of plastics was mostly reported in the estuarine/marine environment (42 studies) compared to the freshwater environment (only 17 studies). Plastics have also been reported in the three compartments of the aquatic environment: water column, benthic sediment and animals. Zooplankton, annelids, molluscs, insects, fishes and birds were reported as bioindicators of plastic ingestion in the inland and coastal waters of Africa. Polyethylene, polyethylene terephthalate (polyester) and polypropylene were the common plastic polymers observed in the African aquatic environment. In situ toxicological implications of the ingested plastic polymers were not reported in any of the studies. However, reports from laboratory-controlled experiments showed that these polymers are deleterious to aquatic animal health. More research efforts need to delineate the plastic pollution status of the East, West and North of Africa. Furthermore, such studies are required to identify the plastic polymers and in situ ecotoxicological impacts of plastics on both animal and human health.