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Size-dependent translocation of polystyrene nanoplastics across biological barriers in mammals
Summary
This study tracked radiolabeled nanoplastic particles in rats and found that smaller 20-nanometer particles could cross biological barriers that larger 100-nanometer particles could not, including reaching the brain. Both sizes were transferred from mothers to offspring, but through different pathways, revealing that nanoplastic size plays a critical role in determining which organs and tissues are exposed.
Nanoplastics (NPs) pose health concerns worldwide. However, robust quantitative data on their absorption, distribution, and excretion in mammals remain scarce. Here, we provide a comprehensive assessment of polystyrene (PS) NP biodistribution and elimination in rats using C-radiolabeling, the most accurate and quantitative method available. Pregnant rats were exposed to C-labeled 20 nm or 100 nm PS NPs (PS or PS) via oral gavage, intratracheal aerosolization, or intravenous injection, and tissue distribution and excretion were determined by radioactivity measurements. We found that PS NPs were exclusively excreted through faeces, irrespective of the exposure routes, without urinary elimination. Both PS and PS crossed multiple biological barriers, yet only PS reached the brain. Maternal transfer of PS occurred through both placenta and milk, while PS transferred solely via milk. A physiologically based toxicokinetic model further simulated accumulation kinetics across tissues. This study establishes the most comprehensive and reliable quantitative profile of PS NP biodistribution in mammals to date, revealing distinct size-dependent translocation patterns that provide a robust foundation for evaluating their health impacts.