Unveiling the Invisible: A Low-Cost Student Methodology for Microplastic Monitoring

Microplastics in drinking water and food chains pose a growing threat to human health. Students (ages 12–15) at Ciência Viva STEM Club (D. Maria II School, Portugal) implemented a low-cost methodology to detect and quantify microplastics in bottled and tap water, raising awareness of underlying risks.The methodology relied on Nile Red staining (4 µg/mL for 60 minutes) to enable microscopic inspection under UV light. Samples underwent density separation with saline solution and vacuum filtration through 0.45 µm membranes. Identification used a microscope coupled with a mobile device for real-time visualization and image capture, allowing potential AI-based analysisResults confirmed the presence of significant quantities of microplastics in both tap and bottled water, with clearly measurable dimensions, compatible with PVC (polyvinyl chloride) and PE (polyethylene), likely originating from the supply network, plumbing materials, or taps. In bottled water samples, fragments were predominantly compatible with PET (polyethylene terephthalate).Key findings revealed that extreme pH level, both acidic and basic samples, contained higher amounts of microplastics, likely due to the higher degradative or "leaching" effect on the plastic containers. Experimental sunlight exposure significantly increased microplastic counts, though particles were smaller than in unexposed samples. This suggests contamination occurs primarily during storage and transport, with solar exposure and extreme pH levels significantly exacerbating the processThis low-cost technique serves as an effective pedagogical tool, fostering concrete understanding of the microplastics crisis. The initiative successfully increased awareness of global environmental risks through hands-on investigation, bridging the gap between classroom learning and urgent ecological challenges.