Reducing uncertainty and confronting ignorance about the potential impacts of microplastic on animals: A critical review

Microplastics (MPs) pollution is omnipresent in the global environment, and its potential harm to animal health has aroused widespread concern. The primary pathways and influencing factors of MPs entering animals, the effects of MPs and other pollutants on the comprehensive toxicity of animals and the degradation of MPs by animals were reviewed. The literature review shows that MPs can cause immune reactions, liver and intestinal dysfunction, neurodevelopmental harm, reproductive and developmental toxicity in animals, and its toxicity is affected by the characteristics of MPs (such as polymer type, shape, size, etc.). Meanwhile, the combined toxic effects of MPs with co-existing pollutants on animal health include synergistic and antagonistic effects. Additionally, the process and internal mechanism of animal-mediated degradation of MPs is elucidated. Finally, we put forward the limitations into toxicity studies of MPs and their future development directions to better understand the exposure risk and potential health hazards of MPs. [Display omitted] •The primary pathways of the uptake of MPs by animals is reviewed.•The toxicity of MPs to animals is affected by different factors.•The combined effects of MPs with pollutants on animals are concluded.•The degradation processes and mechanisms of MPs by animals were outlined.•The future research directions of MPs toxicity to animals were proposed.