Fig. 8.

Schematic diagram of the present study. When microplastics are in the environment, more undetected nanoplastics are around. The current “microplastic exposure” is in fact the mixture of micro- and nanoplastic exposures. The PS micro- and nanoplastics affect the intestinal permeability in a size-dependent manner and change their biodistribution. More importantly, we found a combined toxicity of PS micro- and nanoplastics on the intestine. This manifested as the mixture of PS micro- and nanoplastics causing more severe intestinal barrier dysfunction, compared with the micro- or nanoplastics alone. Considering that most existing studies on PS micro- and nanoplastics have been conducted using a single particle size, the health risk of exposure to PS micro- and nanoplastics on organisms could be underestimated and in need of reevaluation accounting for the biological interaction between varying sizes of PS micro- and nanoplastics