Results of a 30-day safety assessment in young mice orally exposed to polystyrene nanoparticles.

Polystyrene nanoparticles (PSNPs) are a newly emerging pollutant in the natural environment. However, due to the lack of sufficient toxicological studies in mammals, the potential effects of PSNPs on human health remain largely undefined. Therefore, in this study, young mice aged four weeks old were subjected to oral administration of 0, 0.2, 1, or 10 mg/kg PSNPs for 30 days. Our results demonstrated for the first time that oral exposure to PSNPs affected the expressions of mucus secretion-related genes and altered the community composition of intestinal microbiota, although this treatment did not cause behavioral impairments in young mice. No significant alterations in inflammatory or oxidative stress-related indicators were observed in the liver, lung, intestine, cortex or serum of PSNPs-treated animals. Moreover, exposure to PSNPs did not cause pathological changes in the liver, lung, or cortex tissues. Notably, although oral administration of PSNPs did not produce obvious toxic effects in the major organs of young mice, the possible toxicity of PSNPs remains unresolved and it may depend on the dose, exposure route and species. The potential hazardous effects of PSNPs still need to be systematically assessed, especially for children who are susceptible to exposure to nanoparticles.