Examination of the short- and long-term effects of microplastics in mammals using a mouse model, An

The United Nations has recognized plastic pollution as the second most concerning environmental problem after climate change. Photo-oxidation and other natural processes can fragment plastics into smaller particles, giving rise to another problem: microplastics. Despite many studies showing that humans are exposed to microplastics, their toxic effects are uncertain. The aim of this study was to contribute to the understanding of microplastic health impacts on mammals, using a mouse model. For the manuscript 1 study, we exposed female mice to two different shapes of microplastics (microbeads, microfibers) for up to four weeks. Although microbead and microfiber-treated groups showed a slightly altered food consumption, body weight was not affected in both groups. Microbeads, but not microfibers, were able to translocate from gut lumen to the liver, however no histopathological changes were observed. The expression levels of genes associated with inflammation (Apcs, Crp, Cfb) and tissue injury repair (Ccn1) did not show a statistically significant difference after exposure to microbeads and microfibers. For the manuscript 2 study, we exposed female and male mice to microbeads for up to sixteen weeks, followed by a four-week recovery period. Although microbeads translocated to deeper organs in both female and male mice, only females showed significant changes in gene expression. Overall, longer exposure caused more aggravated effects than short exposure; some of these effects were reversed after the recovery period, while others showed a delayed manifestation. Biological response to microplastic exposure has proven complex, depending on time of exposure and showing remarkable sex differences.