Zero Hunger (SDG 2), Good Health & Well-being (SDG 3)
Microplastics and toxic contaminants in the Volta Lake: Implications for human health and food security Pennante Bruce-Vanderpuije*, Ruby Asmah, Yaa Asabea Agadzi, Ishmael Cudjoe Norvimagbe Council for Scientific and Industrial Research-Water Research Institute (CSIR-WRI) Synthetic plastic polymers, though beneficial to man, have resulted in the generation of waste macro, micro, and nano plastic contaminants considered as emerging environmental hazards that are persistent, bioaccumulative and toxic to aquatic ecosystem and human. Ghana, one of the top plastic users in western sub-saharan Africa, is yet to implement initiatives that enforce partial/total plastic bans/ restrictions. To date, microplastic (MP) research in Ghana has amassed 10 research publications (2020- 2022). However, a 70 % dominance in the use of fluorescent staining and visual identification techniques for MPs results in limitations of misidentification/biases in the absence of polymer characterization techniques, in a developing country such as Ghana. Despite the growing evidence of MPs in fish in Ghana, a quantitative comparison of MPs ingested by fish species from aquaculture, and wild environments on the Volta Lake- one of the largest man-made reservoirs, is yet to be completed. In this study, the abundance, types, and spatial distribution of MPs in sediment, surface water, 23 species of caged and wild fish from the lower Volta basin, and potential risks to human from fish consumption, is investigated for the first time. Laser Direct Infrared (LDIR) spectroscopy was utilized to characterize and quantify small MPs (10-500 µm). Larger microplastic particles of size range >500 µm were analysed using the Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) for confirmation, after a thorough sample extraction using an optimized method. Microplastic particle types identified in the gut and gills included fragments, fibers, films, and foams. The dominant plastic polymer types identified in fish were acrylates, polyurethane, and varnish (APV, 58.21 %), polyvinylchloride (PVC, 27.81 %), and polyethylene terephthalate (PET, 6.51 %). Other polymer types included polyethylene (PE, high density, and low density), polypropylene (PP) and polystyrene (PS). More than 30 % of the particles ranged between 100- 200 µm. Mean microplastic concentrations in sediments on the lower Volta basin (upstream, midstream, and downstream) followed the order- Ada Sogakope (2.55±1.73-2.70±1.47 MP items/g (60 g of fish)) > Asikuma (1.60±5.79-2.12±9.02 MP items/g) > Kpong (0.56±2.46 MP items/g). The estimated human exposure assessment (Estimated Annual Intake) from consumption of microplastic-contaminated whole fish/gills for an average of 23 species ranged from 2.73 MP items/year (for a 1 year old child) to 265.76 MP items/year (for an adult). Principal component analysis was explored to outline findings based on the seasonal variations, fish species, types, sizes and shapes of MPs, and their influcence on the fate and transport within the lower Volta basin. The results demonstrated that the degree of microplastic pollution in the lower Volta basin varied within the length of the basin. However, the data did inidcate fish contaminated with microplastics, an indication of risks to fish consumers in Ghana. This study serves an important reference to understand the seasonal variation for microplastics within the lower Volta basin- a part of the Volta River Basin, a transboundary basin shared by six riparian West African countries. Similar trends/data gaps identified in this study may serve as a background for other users of the Volta River Basin.
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© The Author(s), 2023
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