Enhanced reproductive toxicity of photodegraded polylactic acid microplastics in zebrafish

Microplastics are widely used due to their numerous advantages. However, they can have detrimental effects on marine ecosystems. When microplastics enter the ocean, they can be absorbed by marine organisms, leading to toxic effects. Additionally, the transformation of microplastics during natural degradation can alter their toxicity, necessitating further investigation. Polylactic acid (PLA) biodegradable plastics are commonly used, yet research on their toxicity, particularly their reproductive effects on aquatic organisms, remains limited. In this study, we conducted photodegradation of PLA using potassium persulfate as a catalyst to simulate natural degradation conditions. Our objective was to assess the reproductive toxicity of photodegraded PLA microplastics on zebrafish. The results revealed that photodegraded PLA exhibited elevated reproductive toxicity, resulting in abnormal oocyte differentiation, disruption of sexual hormone levels, and alterations in ovarian tissue metabolism. Metabolomics analysis indicated that both unphotodegraded PLA (UPLA) and photodegraded PLA (DPLA) disrupted oxidative stress homeostasis in zebrafish ovarian tissue by influencing pathways such as purine metabolism, phenylalanine metabolism, glutathione metabolism, and riboflavin metabolism. Furthermore, the DPLA treatment induced abnormal biosynthesis of taurocholic acid, which was not observed in the UPLA treatment group. Importantly, the DPLA treatment group exhibited more pronounced effects on offspring development compared to the UPLA treatment group, characterized by higher mortality rates, inhibition of embryo hatching, accelerated heart rates, and reduced larval body length. These findings underscore the varying levels of toxicity to zebrafish ovaries before and after PLA photodegradation, along with evidence of intergenerational toxicity.