Role of Environmental Weathering and Gastrointestinal Digestion on the Bioavailability and Toxicity of Microplastic and Cadmium Mixtures - A Platform for Undergraduate Interdisciplinary Training Ph 2

About This Grant

Project Summary Humans are continuously exposed to micro- and nanoplastics (MNPs) by accidental ingestion (e.g. cracked plastic utensils) or ingestion of food and water contaminated with MPs. Our recent findings (resulting from a multi-institutional effort) evidence that human tissues and organs including placenta, kidney, and brain in fact accumulate MNPs – the threat of MNPs to human health is a reality. However, the reactivity, bioaccumulation, and toxicity of MNPs after ingestion is largely unknown. In the 2022-2025 funding phase of our R15 AREA award, we recruited and mentored eight undergraduate students, retained one postbaccalaureate student for graduate school, supported two graduate students already enrolled in the Environmental Engineering and Chemistry graduate programs, and obtained a supplement to hire a postdoctoral fellow. Our key findings from the previous funding period indicate that 1) UV aging modifies the capacity of polyethylene (PE) and polyvinyl chloride (PVC) MPs to adsorb cadmium (Cd) and hydrophobic organic compounds; 2) PVC and PE MPs preserved their sorption capacity and decreased the available Cd in solution in an in vitro digestion system; 3) UV aging enhances the release of phthalates from PVC MPs into aqueous media; 4) MNPs attenuated the cytotoxicity and reduced the bioavailability of Cd, lindane, and (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), and 5) the toxicity increased in assays supplied with NPs. In this renewal application, we build on the findings from the previous funding phase to advance the key knowledge barrier of our understanding of the transformation that MNPs undergo in the digestive system. Our overall goal is to recruit and develop strong research skills in undergraduate researchers in an interdisciplinary environmental engineering and toxicology project that studies MNP transformation, bioavailability, and toxicity to encourage them to pursue a graduate degree and career in STEM. We propose to use the rainbow trout gut intestinal cells (RTgutGC) in vitro digestion system as it resembles the human digestion system. We hypothesize that MNPs will continue transforming during the digestion process and they will release plastic additives (e.g., phthalates and flame retardants) from the bulk plastic and contaminants sorbed onto their surface into the GI fluids; additionally, the compounds released into the GI fluids will affect bioavailability and induce toxic effects. To test these hypotheses we propose to: Specific Aim 1: Evaluate the release (leaching capacity) of plastic additives from MNPs into GI fluids; Specific Aim 2: Asses the desorption of chemicals previously sorbed onto MNPs into GI fluids; and Specific Aim 3: Evaluate the bioavailability and toxicity of MNPs leachates and pollutants desorbed from MNPs to RTgutGC following GI processes. Our results will bridge the knowledge gap between chemical transformations of MPs in the GI system and will serve as a platform for integrating undergraduate students into multidisciplinary research and will allow them to acquire multiple skills spanning from environmental chemistry to cell biology and toxicology.