CAN WE SEE SMALLER? QUANTIFYING less than 100 MICRON MICROPLASTICS WITH PHOTOMICROGRAPHS

Microplastic contamination has become an environmental and public health concern as the use of plastics increases. Full accounting of the abundance of microplastics in the environment is limited, in part, due to inconsistent methodology, poor detection of PVC and rubber particles, and detection limits that often overlook sub-100 micron particles. We present the results of a methodological study that employs a double-dye technique to quantify a wide range of microplastic particles at a detection limit of <100 micron using optical microscopy. Polyethylene terephthalate (PTE), High-Density Polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene (PP), and polystyrene (PS), and rubber tire particles grouped by size (<63 µm, 63-500 µm, and 500-1000 µm), were imaged using a Leica photomicrograph system following treatment with 1) Nile Red and 2) a non-polar UV dye. Particles were characterized by mean pixel intensity. The application of a second dye improved detection limits for non-polar plastics including PVC and rubber tire shreds but there may be practical limitations for employing this method.