Visual Similarity Does Not Imply Equivalent Microplastic and Nanoplastic Burden: Optical Differentiation of Tap and Filtered Water

Microplastics and nanoplastics (MNPs) are now recognized as widespread contaminants in drinking water, yet many samples appear visually indistinguishable from clean water. This study used simple top-down optical imaging to compare tap water, Lifestraw-filtered water, and double-filtered (Lifestraw + Aquatru) water. Despite all samples appearing similarly clear to the naked eye, consistent differences in background haze, spatial uniformity, and subtle optical structure were observed across conditions. These findings demonstrate that visual similarity does not imply equivalent microplastic and nanoplastic burden. The results support the development of accessible, interaction-based optical methods capable of revealing hidden differences in water quality that conventional visual inspection or basic turbidity measurements cannot detect.Representative photo included within the report.