Effects of microplastics and nanoplastics on the brain and behavior: Evidence from rodent and human studies

: Microplastics (MPs) and nanoplastics (NPs) pose serious environmental and health risks and have made plastic pollution a major concern worldwide. They have been detected in terrestrial and aquatic species, including humans, and have been linked to increased risks of cardiovascular, respiratory and metabolic diseases. However, a critical question remains regarding whether plastic pollution also affects brain function and behavior. This review summarizes the current state of knowledge on the neurotoxic effects of MPs and NPs (MNPs) in the brain and their impact on behavior in both humans and rodents. We analyzed recent studies across multiple experimental approaches, including in vitro assays, animal models, human biomonitoring, and emerging technologies (i.e., brain organoids) to provide a comprehensive overview of MNP-induced effects. Findings are organized and discussed in terms of their influence on behavior, brain neurotransmission and function, and mechanistic pathways underlying neurotoxicity. We conclude that clarifying how MNPs affect neural systems and behavior, and exploring strategies to prevent or reverse their neurotoxic effects, will be crucial for safeguarding brain health in an increasingly plastic-contaminated world.