Investigation of microplastics from granulated virgin and UV aged samples in artificial digestion system

The environmental concerns of microplastics (MPs) have attracted increasing attention due to their potential harm to human health. However, most of the MPs used in previous studies are from virgin materials through artificial granulation, as it is almost impossible to collect the natural MPs from nature and accurately identify their sources or ages. It is anticipated that the MPs after UV aging possess some major distinct characteristics similar as aged in nature, including variations in molecular weight, molecular weight distribution, surface chemicals. This study systematically investigated both virgin and UV aged samples derived from the most prevalent sources, including polyethylene (PE), polypropylene (PP), poly(ethylene terephthalate) (PET), polystyrene (PS), and poly(vinyl chloride) (PVC), focusing on the effects of the artificial digestion system on the MPs. Additionally, the study evaluated the impact of these MPs on health by examining their effects on probiotics within the digestive system. The results demonstrate that both the effect of digestion treatment MPs and the impact of MPs on intestinal microbiota are significantly different between virgin and aged MPs. While digestion processes were ineffective in degrading virgin MPs, primarily due to their chemical inertness, the surface changes in MPs were more pronounced after UV aging, though they remained largely unaffected by digestion. The surface chemical changes were significant during aging but not during digestion. On the other hand, certain MPs, particularly PVC, may disrupt the balance of intestinal microbiota, especially from aged samples.