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Secondary PVC microplastics are more toxic than primary PVC microplastics to Oryzias melastigma embryos
Summary
Researchers compared the toxicity of weathered secondary PVC microplastics to pristine primary particles using marine fish embryos. They found that the secondary microplastics caused earlier hatching, more developmental abnormalities, and greater oxidative stress than the primary ones. The study demonstrates that the irregular, partially degraded microplastics found in the ocean are likely more harmful to marine life than the smooth manufactured particles typically used in laboratory tests.
Irregular-shaped and partially degraded secondary microplastics (SMP) account for the majority of MPs in marine environments, yet little is known about their effects on marine organisms. In this study, we investigated the embryotoxicity of polyvinyl chloride SMP and primary microplastics (PMP) to the marine medaka Oryzias melastigma. This study aimed to determine the physical impacts of MPs and, for the first time, elucidate the underlying mechanisms of physical toxicity. SMP shortened hatching time and induced higher teratogenic effects on larvae relative to PMP, indicating a higher toxicity from SMP. Physical damage from SMP to the chorion surface appears to be the main toxicity mechanism, caused by their irregular shape and reduced aggregation relative to PMP. In contrast, real-time changes in oxygen demonstrated that hypoxia caused by greater PMP adsorption to the chorion surface contributes to the toxicological responses of this material relative to SMP. Modulation of genes involved in hypoxia-response, cardiac development and hatching confirmed the toxicity mechanisms of PMP and SMP. The chemical contribution to observed toxicity was negligible, confirming impacts derived from physical toxicity. Our findings highlight the negative effects of environmentally relevant SMP on the marine ecosystems.