Quantification of microplastics by count, size and morphology in beverage containers using Nile Red and ImageJ

Abundant evidence of microplastics (MP) found in the environment, and its toxicity effect in animals calls for human-related research. However, well-established quantitative controlled studies on the potential route of human exposure to MP are still sparse. MP count, size and morphology in 15 polylactic acid (PLA)-lined plastic cups and 15 PLA-lined paper cups were examined using Nile Red fluorescence tagging, microscopic photography, and morphology assessment and quantification based on ImageJ. In the plastic cups, the count and area of MP fibers were found to be significantly higher compared with blanks (p < 0.05), but not MP particles or total MP. In paper cups, count or area was not significantly different in terms of MP particle, MP fibers or total MP. No interesting trend was observed in the distribution regarding the size of MP particles or fibers. These results indicate that selected paper cups and plastic cups could be considered as safe beverage containers, but further research on the toxicological effects of MPs in different morphologies released from plastic cups on human health is needed.