A QA/QC screening framework to assess studies reporting microplastic presence in human organs, tissues, and bodily fluids

Quality Assurance and -control (QA/QC) tools are essential to evaluate the reliability of data on nano- and microplastic particles measured in the human body for use in risk assessment. Currently, no such criteria exist for human samples. To support human health risk assessment related to internal exposure to these particles, we developed a QA/QC screening protocol with fourteen criteria across three categories: sampling methods, particle characterization, and contamination mitigation. We applied this tool to evaluate 133 datasets from 101 studies reporting measurements of microplastics in human organs, tissues, and bodily fluids. None of the studies nor datasets met all essential QA/QC criteria, indicating their current value lies primarily in pioneering exploratory research. Common gaps were found in sample representativeness, the use of positive controls, and documentation of blank procedures. Data were also sparse for organs critical to toxicokinetic processes and physiologically-based kinetic modelling, highlighting a significant knowledge gap. Even in studies with relatively strong QA/QC performance, some findings warrant careful evaluation of biological plausibility. We recommend that future studies not only improve QA/QC practices but also explicitly reflect on the plausibility of their results to avoid misinterpretation and miscommunication.