MECHANISMS OF SORPTION OF PHARMACEUTICAL AND PERSONAL CARE PRODUCTS TO MICROPLASTICS

Microplastics (MPs) are found in almost every ecosystem and in many commercially important seafood species. MPs have been found to be physically harmful to marine organisms, but also may act as vectors for organic pollutants and together have been shown to cause toxic effects in a variety of species. Wastewater effluent is a significant source of MPs to aquatic systems, as well as pharmaceutical and personal care product compounds (PPCPs). The first research contribution was to create a reference material for secondary fragment type microplastics of the polymer’s high-density polyethylene (HDPE) and polypropylene (PP) that is standardized by surface area (SA) for use in sorption and toxicity studies. Standardization for both polymers was successful, with a SA coefficient of variation of ~3%. PP MPs had greater SA due to it being a less crystalline polymer than HDPE. This reference material may act as a more realistic material than purchased powders or beads, as well as provide a more readily comparable material for fragment type MPs. The second research contribution used the reference material to create an extraction methodology for measuring semi-polar PPCPs associated with MPs. Acetone was chosen as the best solvent for extraction and extraction efficiency for both polymers was ~88% (first extraction). This methodology was then used to measure the equilibrium of the antimicrobial triclocarban with PP and PE of different MP particle sizes. Smaller particles with greater SA sorbed more triclocarban, rather than larger particles. PP had greater sorption of triclocarban than PE. This was due to PP MPs having greater SA due to being a less crystalline polymer. The third contribution created a framework for prioritizing study compounds based on environmental relevance for MP sorption using polyethylene as a model polymer, water solubility, and a correlation with the octanol water-distribution ratio, DOW, rather than the octanol-water partition coefficient, KOW. A possible threshold for polyethylene sorption was found for compounds with water solubility ~20-60mg/L and DOW ~3.7. This dissertation advances the understanding of MP reference materials, extraction methodology, sorption mechanisms, and modeling of sorption data of PPCPs

Investigating the Sorption of Pharmaceutical and Personal Care Products on High-Density Polyethylene and Polypropylene Microplastics

The term “microplastics” refers to plastic particles with a diameter of 5mm or less. Microplastics are capable of sorbing organic contaminants to concentrations magnitudes higher than the surrounding water. One such contaminants class is a group of pharmaceuticals and personal care products (PPCPs). As of now, very little information is known about the sorption behavior of PPCPs on microplastics; therefore, to better understand the interaction between PPCPs and microplastics, their sorption behavior must be studied. The goal of this project is to explore and evaluate the sorption behavior of polar and ionizable PPCPs onto microplastics. The PPCPs in this study were: diphenhydramine, an antihistamine, venlafaxine hydrochloride, an antidepressant, and N, N-diethylmeta-toluamide (DEET), which is an insect repellant.NSF, Sea Gran

Reporting Guidelines to Increase the Reproducibility and Comparability of Research on Microplastics

The ubiquitous pollution of the environment with microplastics - a diverse suite of contaminants - is of growing concern for science and currently receives considerable public, political, and academic attention. The potential impact of microplastics in the environment has prompted a great deal of research in recent years. Many diverse methods have been developed to answer different questions about microplastic pollution, from sources, transport, and fate in the environment, and about effects on humans and wildlife. These methods are often insufficiently described, making studies neither comparable nor reproducible. The proliferation of new microplastic investigations and cross-study syntheses to answer larger scale questions are hampered. We - a diverse group of 23 researchers - think these issues can begin to be overcome through the adoption of a set of reporting guidelines. This collaboration was created using an open science framework that we detail for future use. Here, we suggest harmonized reporting guidelines for microplastic studies in environmental and laboratory settings through all steps of a typical study, including best practices for reporting materials, quality assurance / quality control, data, field sampling, sample preparation, microplastic identification, microplastic categorization, microplastic quantification, and considerations for toxicology studies. We developed three easy to use documents - a detailed document, a checklist, and a mind map - that can be used to quickly reference the reporting guidelines. It is our intention that these reporting guidelines support the annotation, dissemination, interpretation, reviewing, and synthesis of microplastic research. Through open access licensing (CC BY 4.0), these documents aim to increase the validity, reproducibility, and comparability of studies in this field for the benefit of the global community