Efficient and Scalable Detection of Microplastics in Drinking Water Using Fluorescence High-Content Imaging

The increasing production and inadequate disposal of plastics have led to widespread microplastic presence in the environment, posing potential health risks. However, existing microplastic detection techniques often face challenges in resolution, sensitivity, speed, and complexity of extraction and microplastic identification. In this study, a rapid, high-throughput approach based on fluorescence microscopy is developed and validated to investigate the prevalence of microplastics in bottled drinking water. By utilizing Nile Red (NR) staining for fluorescence imaging, imaging the entire filtered area, machine learning for automated classification, and thermal treatment to remove false positives, microplastic concentrations up to 1.52 × 10⁵ particles/liter and mineral microparticle concentrations up to 4.93 × 10⁵ particles/liter are detected. Over 90% of the detected microplastics are within the smallest 1-5 µm size range, a size fraction overlooked by the Delegated Drinking Water Act (DDWA) 2024, which focuses on particles larger than 20 µm. With fewer than 1% of microplastic particles in bottled water exceeding 20 µm, these findings highlight the urgent need for more rigorous regulatory frameworks and advanced detection methods, such as the fluorescence-based approach, to ensure the safety of drinking water.