Determination of no observable effect level of nanoplastics on intestinal flora

The risk of human exposure to nanoplastics (NPs) is increasing due to the incomplete decomposition and accumulation of plastic debris in the environment. Dietary intake is the most common way for human body to ingest NPs. NPs cannot degrade in vivo and will accumulate in multiple tissues, which result in various tissue damages. Although numerous studies have focused on evaluating the influences of exposure to NPs, the exposure amounts investigated were much higher than the actual exposure level in human daily life. Therefore, it is necessary to evaluate the hazards of exposure to low-dose NPs. Intestinal flora is a generally recognized sensitive indicator for NPs exposure, so determining a safe threshold to intestinal flora can represent the maximal no-effective dose for the human body of NPs exposure. Based on these information, mice were exposed to NPs at concentrations of 0, 0.001, 0.005, 0.01 and 0.1 mg kg^-1·BW, respectively. The composition changes of the intestinal flora were investigated after exposing 28 days. The obtained consequences indicated that 0.01 mg kg^-1·BW was the maximal no-effective dose to intestinal flora. This study provided a clear safe threshold for investigating the potential adverse effects of low-dose NPs exposures on human health.