Effects of Microplastics on Human Physiology: Mechanisms of Toxicity and Health Risks

This systematic review aimed to analyze the effects of microplastics on human physiology, emphasizing toxicity mechanisms and health risks. The search was conducted in the PubMed, Scopus, Web of Science, Embase, and SciELO databases, covering studies published between 2000 and 2025. Forty-eight studies were included that addressed the presence of microplastics in human tissues and fluids, their pathophysiological mechanisms, and possible clinical outcomes. The results showed that microplastics are present in blood, placenta, and reproductive tissue samples, demonstrating their ability to cross biological barriers and interact with cells and organelles. The most consistent mechanisms described involve oxidative stress, systemic inflammation, mitochondrial dysfunction, endocrine dysregulation, and reproductive changes. In vitro and in vivo assays indicated increased production of reactive oxygen species, activation of inflammatory cytokines, and DNA damage. Recent evidence also suggests effects on the gut microbiota and fetal development, with a higher microplastic load observed in placentas from premature births. Despite advances in research, there are significant methodological limitations, such as a lack of standardization in detection techniques, control of environmental contamination, and a scarcity of longitudinal studies evaluating the dose-response relationship. It is concluded that microplastics represent an emerging contaminant with potential systemic and multi-organ impact, posing a growing concern for public health. More stringent environmental policies, population biomonitoring, and the development of standardized analytical methodologies are needed to more accurately assess the biological effects of these particles. Understanding of the risks associated with microplastics must be expanded through interdisciplinary approaches that integrate toxicology, cell biology, epidemiology, and environmental health.