Possible influence of microplastic on the partitioning and bioavailability of 17α-ethinylestradiol in agricultural soil; a literature review using mass balance equations
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Global concern regarding microplastic (MP) pollution increases. MPs may function as a novel compartment for the partitioning of chemical pollutants, thereby altering their bioavailability. 17α-ethinylestradiol (EE2), a potent endocrine disruptor compound, enters soil via biosolid application. Limited literature about influenced partition of EE2 in soil due to the presence of MPs is available. This research aims to assess the distribution of EE2 in soil in the presence of MPs for the plastic types of polyethylene (PE), polyamide (PA) and thermoplastic polyurethane (TPU) in different environmental compartments using mass balance modelling, based on recent literature. Generally, EE2 was found to be majorly bound to soil, except for low values of partitioning of EE2 in soil, while high amounts PA MPs were present. Concluding, specific polymers in high concentrations present, may influence the distribution of EE2 in soils co-contaminated with MPs. The observed sorption order (PA> PE > TPU) differed from expectations based on literature. Combined effects of differences in crystallinity and strength of hydrogen bonds of PA possibly outweighs the difference in hydrophobic capacities between PA and PE. The observed concentrations of EE2 distributed in various compartments are not expected to show any adverse effects, based on the PNECwater. Also, less EE2 was taken up by biota in the presence of a higher plastic mass, so the presence of MPs may reduce bioavailability of EE2. However, this model does not adequately reflect real-life scenarios due to assumption made and the nature of the parameters. Nevertheless, it provides a rough estimate of EE2 partitioning in soil in the presence of MPs and highlights the lack of knowledge about toxicity of EE2 on soil organisms and the complexity of this matter. Follow-up research should focus on identifying partition values for EE2, for the variety of MPs and their degree of weathering found in soil. Additionally, trustworthy toxicity data is needed for accurate risk assessment.