Microplastics are increasingly present in the environment, including drinking water. However, data on microplastic contamination in packaged water and the effects of sunlight exposure remain limited, hindering assessment of potential health risks. Sunlight and heat can accelerate leaching of toxic chemicals, while deterioration of polythene packaging may allow microbial contamination. This study investigated the effect of sunlight on microplastic levels in bottled and sachet water sold in Ilorin Metropolis, Nigeria. Fifteen samples (nine bottled and six sachet) were collected from two major markets and analysed using vacuum filtration, Nile red staining, stereomicroscopy, and FTIR spectroscopy. The results showed that microplastic concentrations ranged from 5 to 18 particles L⁻¹, with sachet water exhibiting higher contamination levels than bottled water. The smallest particles measured 22.5 µm, while the largest reached 32.5 µm, indicating high bioavailability and ingestion risk. Sample L (sachet water) recorded the highest concentration (18 particles L⁻¹), whereas bottled samples A, C, and F had the lowest (5 particles L⁻¹). The Microplastics Pollution Index (MPI) ranged from 0 to 100 %, classifying bottled water mostly as low-risk (MPI 0–23 %), while sachet water ranged from moderate (23–46 %) to very high (100 %). One-sample t and Wilcoxon tests (p < 0.05) revealed that the average MPI exceeded acceptable safety thresholds, indicating potential health risks from microplastic ingestion. The findings reveal sunlight-induced degradation of packaging as a key driver of contamination. It concludes that sachet water poses a greater microplastic exposure risk and recommends improved storage, stricter regulation, and public awareness to ensure safer drinking water in Nigeria.
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