Comparative assessment of microplastics contamination in settled dust and source identification near plastic-related anthropogenic activities in South-Western Nigeria

This study investigated the prevalence, characteristics, and relative pollution intensity of microplastics (MPs) present in settled dust from selected cities in South-Western Nigeria. Samples of settled dust were gathered using an anti-static wooden brush and aluminum foil. MPs were quantified based on their shape, polymer type, and color through stereomicroscopy and Fourier-transform infrared (FTIR) spectroscopy. The 100–500 µm fraction was found to be the most prevalent, while the respirable fraction (<10 µm) accounted for approximately 5.0%. Regions with high population density and considerable human activity displayed higher concentrations of MPs. The distribution of MPs varied significantly across different locations, with Lagos (46.00 ± 1.00 particles/100 g) and Ibadan (39.33 ± 3.78 particles/100 g) recording the highest and second-highest concentrations, respectively, whereas Ondo (2.33 ± 0.57 particles/100 g) had the lowest. Fibers and fragments were the most common types, with polyamide (PA), polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) being among the frequently detected polymers. The Pollution Load Index (PLI) values increased from Ondo (1.0) to Ibadan (2.1), Ilesha (2.2), and Lagos (2.4), indicating a clear spatial gradient in pollution intensity. These results provide baseline evidence of MP accumulation in settled dust and highlight the influence of urbanization, plastic-related activities, traffic, and waste management practices on spatial contamination patterns.