Microplastics, synthetic polymers of less than 5 mm in diameter, are emerging environmental contaminants, appearing in different water matrices including storm, waste, and drinking water. While the number of studies on microplastic observations have increased, analyzing and comparing studies has grown more challenging due to the use of various techniques for sampling, extraction, and identification. This study aims to understand trends in research methods and how they affect microplastic observations reported in samples. As part of WRF Project 5088, 142 peer-reviewed articles and government reports were compiled into a database, documenting over 4000 samples and their quantitative and qualitative information such as sampling volume, microplastic concentrations, particle sizes, and polymer types. The database can be used by researchers to find similar projects (water matrix, country, project scope, etc.) for cross-study comparison. Results from analyzing the database indicate (1) few researchers use sample volume sizes recommended by the ASTM 8332, a standard practice for collecting water samples for microplastic identification and quantification, (2) microplastic concentrations (particles per volume) increase with decreasing particle sizes, (3) most researchers used vibrational spectroscopy techniques with a wide range of sub sample sizes, and (4) many studies reported contamination, using blanks but not matrix spikes. Results presented will also compare morphology units and polymer types found through different extraction and identification techniques. Microplastics will also be compared on a global scale, highlighting differences between countries and water matrices. Lessons learned in the development of the database will be presented along with recommendations for standardizing microplastic methodologies to maximize the accuracy of the microplastic collection and concentration.
