Nanoplastics Rapidly Invade Zebrafish Organs, Raising Human Health Concerns

Scientists from the City University of Hong Kong have documented how nanoplastics—plastic particles smaller than 1 micrometer—rapidly enter zebrafish bodies through both water and food exposure, accumulating in vital organs within 24 hours. The study, published in Environmental Chemistry and Ecotoxicology, found these particles cross biological barriers to reach the bloodstream, then translocate to the brain, gills, liver, intestines, gonads, and muscles, with accumulation stabilizing within days. This widespread distribution raises concerns about potential disorders in nervous and reproductive systems.

Zebrafish, commonly used in toxicology research due to physiological similarities with humans, were exposed to nanoplastics in controlled experiments. Researchers discovered the gills and intestines serve as primary absorption points, while the intestines also function as the main excretion organ. However, a significant portion of nanoplastics remained trapped in the body long-term. "Our study demonstrates that nanoplastics can cross biological barriers, enter the circulatory system of fish, and spread throughout their bodies," said corresponding author Wen-Xiong Wang. "This alarming journey may also occur in other animals, and even in humans."

The research addresses a key question in environmental toxicology: how plastic fragments found in field studies enter circulatory systems and travel through organisms. Previous observations documented plastics in fish digestive systems and even hearts, but the mechanisms remained unclear. This study provides experimental evidence of rapid translocation via multiple pathways. The full findings are available in the journal article accessible through https://doi.org/10.1016/j.enceco.2025.10.002.

Beyond laboratory findings, the researchers developed a computer model simulating nanoplastic accumulation, travel, and clearance in fish organs. This model successfully predicted behaviors for both waterborne and dietary exposure routes. According to the study, this computational approach provides valuable reference for predicting nanoplastic behavior in mammals, potentially informing future research on human exposure risks. The research was supported by the National Science Foundation of China and Hong Kong Research Grants Council.

The implications extend beyond aquatic ecosystems. Since plastic waste continuously breaks down into smaller fragments in the environment, nanoplastics represent a persistent contaminant. Their ability to cross biological barriers and accumulate in organs—particularly reproductive tissues and the brain—suggests potential impacts on growth, reproduction, and neurological function. As Wang noted, the translocation patterns observed in zebrafish likely occur in other animals, highlighting the need for further investigation into human health risks from environmental plastic pollution.