Adsorption Behavior of Nonylphenol on Polystyrene Microplastics and Their Cytotoxicity in Human Caco-2 Cells

As two environmental pollutants of great concern, polystyrene microplastics (PS-MPs) and nonylphenol (NP) often coexist in the environment and cause combined pollution. Batch adsorption experiments were carried by varying parameters such as pH, particle sizes of PS-MPs, initial concentration of NP and metal ions. Results showed that particle size of PS-MPs in the range tested (0.1, 1, 10, 50, and 100 μm) had significant effect on their NP adsorption capacity. NP adsorption process of PS-MPs was best described by the pseudo-second-order kinetic model and the Langmuir isotherm model, while the intraparticle diffusion and Bangham model were also involved as to the NP adsorption process of 0.1 μm PS-MPs. Both PS-MPs and NP significantly affected cell proliferation, which had been confirmed by reduced cell viability, blocked cell cycle G1 phase and elevated apoptosis by affecting the basic cell functions. Especially, the negative effects of 0.1 μm PS-MPs on cell proliferation and function were aggravated after the adsorption of NP. Further research on the potential health risks of PS-MPs combined with NP or other environmental contaminants is needed