Advancing Evaluation of Microplastics Thresholds to Inform Water Treatment Needs and Risks

Abstract

Although human health impacts of microplastics are not well understood, concern regarding chemical contaminants retained on or within them is growing. Drinking water providers are increasingly asked about these risks, but strategies for evaluating them and the extent of treatment needed to manage them are currently lacking. Microplastics can potentially induce health effects if the concentration of contaminants adsorbed to them exceeds predetermined drinking water guidelines (e.g., Maximum Contaminant Levels). The risk posed by microplastics due to adsorbed contaminants is difficult to determine, but a worst-case scenario can be evaluated by using adsorption capacity. Here, a "Threshold Microplastics Concentration" (TMC) framework is developed to evaluate whether waterborne microplastic concentrations can potentially result in the intake of regulated contaminants on/in microplastics at levels of human health concern and identify treatment targets for managing associated health risk. Exceeding the TMC does not indicate an immediate health risk; it informs the need for detailed risk assessment or further treatment evaluation to ensure particle removal targets are achieved. Thus, the TMC concept and framework provide an updateable, science-based screening tool to determine if there is a need for detailed risk assessment or treatment modification due to waterborne microplastics in supplies used for potable water production.

Framework to Quantify Uncertainty in Microplastic Concentrations in Wastewaters and Sludges Incorporating Analytical Recovery Information into Data Analysis

“…The recovery of labeled MPs in replicate samples has also been found to be nonconstant, leading to further uncertainty in concentration estimates. Therefore, understanding the intrinsic errors associated with the analytical procedure and quantifying the uncertainty in MP concentration estimates arising from these errors are crucial for enhancing the accuracy and reliability of MP enumeration in wastewater and sludge samples as well as simpler sample matrices …”

Development of “Threshold Microplastics Concentration” Concept and Framework in Drinking Water

“…Global attention on microplastics has increased because of their ubiquity in water, air, soil, and organisms. − Knowledge of the sources, occurrences, behaviors, and health risks of microplastics is quite limited. − Nevertheless, developing comprehensive health-based thresholds and regulatory guidelines for microplastics in water is impossible because of the limitations and complexity of determining their health effects. Writing in Environment & Health , Chowdhury et al reported a “Threshold Microplastics Concentration” (TMC) concept and framework . The TMC framework was used to identify microplastic concentrations that may result in the intake of regulated contaminants on/in microplastics at levels of human health concern and treatment targets for managing those potential risks …”

“…Writing in Environment & Health , Chowdhury et al reported a “Threshold Microplastics Concentration” (TMC) concept and framework . The TMC framework was used to identify microplastic concentrations that may result in the intake of regulated contaminants on/in microplastics at levels of human health concern and treatment targets for managing those potential risks …”

“…Chowdhury et al proposed a conservative approach using currently available data to identify the TMC. There are six primary types of microplastics detected in drinking water or wastewater, including Polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polypropylene (PP), and polycarbonate (PC). − So they were selected in the TMC framework development . The authors chose six key data sets to evaluate the TMC: microplastic size, microplastic shape, microplastic polymer type, health guidelines defined by MCLs or MACs, contaminant adsorption capacity on plastics, and the extent of microplastic removal during drinking water treatment .…”

“…TMC was calculated using three equations . In eq , TMC ijpx is the concentration of microplastics with size i , shape j , and type p that can carry an amount of contaminant x equal to the MCL/MAC ( H x ).…”