Scientists from City University of Hong Kong have documented how nanoplastics—plastic fragments smaller than 1 micrometer—enter zebrafish, cross biological barriers, and accumulate in vital organs. The study, published in Environmental Chemistry and Ecotoxicology, found these particles can be ingested through both waterborne exposure and dietary exposure, then rapidly enter the circulatory system within 24 hours.
The research identified the gills and intestines as primary absorption points, with the intestines also serving as the main excretion organ. Despite this excretion pathway, a portion of nanoplastics remains trapped in the body long-term. Once absorbed, particles translocate to and accumulate in multiple organs including the blood, brain, gills, liver, intestines, gonads, and muscles, reaching stable levels within days.
This widespread accumulation poses significant risks to aquatic organisms. The buildup of nanoplastics in organs can have harmful effects, with severe cases potentially stunting growth and reproduction in fish. Of particular concern is accumulation in critical tissues like the brain and reproductive organs, which could lead to disorders in nervous and reproductive systems.
The researchers developed a computer model that successfully predicts how nanoplastics accumulate, travel, and are cleared from different organs, whether ingested from water or food. This model provides a valuable reference for predicting how nanoplastics might behave in mammals, including 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).
Corresponding author Wen-Xiong Wang noted the broader implications: "This alarming journey may also occur in other animals, and even in humans." The findings build on previous field studies that found plastic fragments inside fish, mostly within the digestive system, with evidence of plastics entering circulatory systems such as fragments found in hearts.
The complete research is available at https://doi.org/10.1016/j.enceco.2025.10.002. For business leaders and technology professionals, this research highlights emerging environmental challenges with potential regulatory, supply chain, and product development implications across industries that produce or use plastic materials.
