Microplastic pollution in Nigeria: a review on environmental pathways, ecosystems, and human health implications

Microplastic pollution is increasingly documented in Nigeria; however, the evidence remains uneven across regions, ecosystems, and direct human-exposure matrices. This review synthesised Nigeria-specific evidence on microplastic sources, distribution, transport pathways, ecological effects, and human exposure using a structured qualitative evidence-synthesis approach guided by PRISMA 2020. Searches of Scopus, Web of Science, PubMed, ScienceDirect, and Google Scholar (2015–March 2026) identified 1856 records. After removing 248 duplicates, 1608 titles and abstracts were screened, 1572 records were excluded, and 36 Nigeria-focused studies were included. Of the 35 zone-specific studies, 22 were from the South-West, 6 from the South-South, 3 from the South-East, 2 each from the North-Central and North-West, and none from the North-East; one additional study covered all six geopolitical zones. Freshwater systems were the most studied, whereas terrestrial and atmospheric evidence remained sparse. Reported abundances (not directly comparable due to differing matrices and methods) ranged from 0.13 particles/g in branded table salt to 22,079 ± 134 particles/L in Osun River water. Fibres and fragments predominated, blue and transparent were the most recurrent colours, and polyethylene, polypropylene, and polystyrene were the dominant polymers. Nigerian studies confirmed exposure through bottled water, drinking-water systems, table salt, fish, and seafood, with intake generally higher in children than in adults. Current evidence indicates widespread exposure and emerging ecological concern; however, direct epidemiological evidence in humans remains lacking. Standardised methods, broader inland and northern coverage, atmospheric monitoring, and integrated exposure-effect studies are urgently needed.