Scientists from the City University of Hong Kong have demonstrated that nanoplastics can enter zebrafish via waterborne and dietary exposure, cross biological barriers, and accumulate in various organs including the blood, brain, gills, liver, intestines, gonads, and muscles. The findings, published in Environmental Chemistry and Ecotoxicology, highlight the gills and intestines as primary absorption organs, with the intestines also serving as the main excretion route.
Plastic waste degrades into smaller fragments, with nanoplastics measuring less than 1 micrometer. Aquatic animals inadvertently ingest these particles from water or contaminated food. Due to their ultra-small size, nanoplastics can cross biological barriers, translocate to different organs, and potentially cause harmful effects, including stunted growth and reproduction in fish. Previous field studies found plastic fragments in fish digestive systems and even in the heart, prompting researchers to investigate how these particles enter the bloodstream and travel through the body.
Zebrafish, commonly used in toxicology due to their physiological and genetic similarities to humans, were exposed to nanoplastics in the study. Within 24 hours of ingestion, nanoplastics entered the bloodstream and spread throughout the body, accumulating rapidly in organs and reaching stable levels within days. Particles were detected in critical tissues such as the brain, gills, liver, intestine, gonads, and muscle, suggesting potential disorders in nervous and reproductive systems. The researchers also found that most nanoplastics entered through gills and intestine, with primary excretion via the intestine, though some particles remained trapped in the body for extended periods.
Based on experimental results, the team developed a computer model simulating nanoplastic accumulation, travel, and clearance in fish organs. This model successfully predicted behavior whether particles were ingested from water or food, providing a reference for predicting nanoplastic behavior in mammals. Corresponding author Wen-Xiong Wang stated, "Our study demonstrates that nanoplastics can cross biological barriers, enter the circulatory system of fish, and spread throughout their bodies. This alarming journey may also occur in other animals, and even in humans."
The study was supported by the National Science Foundation of China (42430709, 22276157) and the General Research Fund of Hong Kong Research Grants Council (11104225). Wang was supported by a Senior Research Fellowship from the Hong Kong Research Grants Council (SRFS2425-1S06).
