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Co-exposure to UV-aged microplastics and cadmium induces intestinal toxicity and metabolic responses in earthworms
Summary
This study found that UV-aged microplastics (the kind that naturally degrade in sunlight) are more harmful than fresh microplastics when combined with the heavy metal cadmium in soil. Aging changed the microplastics' surface, making them better at absorbing cadmium and delivering it to earthworms, causing more gut damage and metabolic disruption. This highlights that weathered microplastics in the real environment may pose greater risks than lab studies using new plastic particles suggest.
Aged microplastics (MPs) alter the interaction with heavy metals due to changes in surface properties. However, the combined toxicological effects of aged MPs on heavy metals in soil remain poorly understood. In this study, earthworms were employed as model animals to investigate the effects of aged MPs on the biotoxicity of cadmium (Cd) by simulating the exposure patterns of original and UV-aged MPs (polylactic acid (PLA) and polyethylene (PE)) with Cd. The results showed that UV-aging decreased the zeta potential and increased the specific surface area of the MPs, which enhanced the bioaccumulation of Cd and caused more severe oxidative stress to earthworms. Meanwhile, the earthworm intestines exhibited increased tissue damage, including chloragogenous tissue congestion lesions, and typhlosole damage. Furthermore, the combined exposure to UV-aged MPs and Cd enhanced the complexity of the microbial network in the earthworm gut and interfered with endocrine disruption, membrane structure, and energy metabolic pathways in earthworms. The results emphasized the need to consider the degradation of MPs in the environment. Hence, we recommend that future toxicological studies use aged MPs that are more representative of the actual environmental conditions, with the results being important for the risk assessment and management of MPs.
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