Microplastic Biomonitoring: Global Distribution, Matrix Selection, and Intrinsic and Extrinsic Effects

Due to their widespread distribution, persistence, and potential to release additives and adsorb environmental pollutants, microplastics pose complex risks to ecosystems and human health. Bioindicators can reflect microplastic pollution levels in specific environments, as well as reveal microplastic bioavailability, food chain transfer potential, and associated ecological risks, thereby providing key evidence for early warning systems and ecological health impact assessments. However, current biomonitoring studies have not yet provided a comprehensive synthesis of bioindicator distribution, monitoring matrix selection, intrinsic physiological traits, and extrinsic environmental influences. This review systematically analyzes these key aspects, with the following major findings: current research is unevenly distributed (primarily concentrated in Europe, Asia, and water environment; indicator species include fish and bivalves; and the biological substrate is mainly the digestive tract). By integrating factors including monitoring duration, quantitative accuracy, and ethical constraints, we established a research-objective-oriented decision tree for sample matrix selection. Further demonstrates that the correlation between biological traits and microplastic burden is species- and metric-dependent, and highlights the urgent need to establish a multi-indicator integrated assessment system and a novel toxicological framework.