Nanoplastics Invade Fish Organs, Raising Human Health Alarms

In a groundbreaking study published in Environmental Chemistry and Ecotoxicology, scientists from City University of Hong Kong have uncovered alarming pathways through which nanoplastics infiltrate living organisms. Led by corresponding author Wen-Xiong Wang, the research team exposed zebrafish to these microscopic plastic particles measuring less than 1 micrometer and discovered they enter through both waterborne and dietary exposure. Within just 24 hours of ingestion, nanoplastics crossed biological barriers to enter the circulatory system, then spread throughout the body and accumulated in critical organs including the brain, gills, liver, intestines, gonads, and muscles. The study, supported by the National Science Foundation of China and Hong Kong Research Grants Council, reveals that gills and intestines serve as primary absorption points while intestines function as the main excretion organ, though some particles remain trapped in the body long-term.

The research provides crucial insights into how plastic waste breakdown in the environment creates nanoplastics that aquatic animals inadvertently ingest through contaminated water or food. Unlike larger plastic fragments previously found mostly in digestive systems, these ultra-small particles can penetrate biological barriers and travel throughout organisms' bodies. The scientists developed a sophisticated computer model that successfully predicts how nanoplastics accumulate, travel, and clear from different organs, whether ingested from water or food. This model offers valuable reference points for understanding how nanoplastics might behave in mammals and potentially humans, given zebrafish share many physiological and genetic similarities with people.

Wang emphasizes the study's broader implications, noting "this alarming journey may also occur in other animals, and even in humans." The accumulation of nanoplastics in organs could potentially lead to disorders in critical systems like the nervous and reproductive systems, with severe cases potentially stunting growth and reproduction. The research findings, accessible through the DOI 10.1016/j.enceco.2025.10.002, represent a significant advancement in understanding environmental contamination's biological impacts. While the study focused on zebrafish commonly used in toxicology research, its implications extend to global ecosystems and human health, highlighting the urgent need to address plastic pollution at its microscopic level.