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Electron bridges and electron sinks: Molecular regulation of PVC aging by aromatic plastic additives in an nZVI-driven electron-donor system
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Chemicals added to plastics (like BPA and flame retardants) aren't just harmless extras — they actually change how fast microplastics break down in the environment, with some speeding up degradation and others slowing it down. This matters because it means the mix of additives in a plastic product could affect how long microplastics persist and how they release chlorine-based byproducts, which could influence human exposure to these particles and their chemical fragments over time.
Additives are usually required to be chemically inert and non-reactive with plastics, leading to their role in plastic aging being largely overlooked. However, their electronic structure may play a far more than expected role in regulating reactions. This study demonstrates that aromatic plastic additives can modulate the degradation pathways of polyvinyl chloride (PVC) at the molecular scale by acting as electron bridges or forming electron sinks. In anaerobic systems mediated by nanoscale zero-valent iron (nZVI), bisphenol A (BPA) and bisphenol B (BPB) promote electron transfer from nZVI to PVC via orbital delocalized, accelerating dechlorination and chain scission. In contrast, decabromodiphenyl ether (BDE209), with its high electron affinity, preferentially scavenges electrons and blocks the reaction chain, significantly suppressing aging. Similar phenomena have also been observed in other types of microplastics (MPs), not just limited to PVC. Under aerobic conditions, dissolved oxygen competes for electrons, accelerates nZVI passivation, and induces the formation of radicals, thereby shifting the reaction pathway from reductive dechlorination to additives degradation. In addition, the formation of phenolic intermediates, which further weaken the electron tranfer of additives and consequently suppress PVC dechlorination. Based on electrochemical, spectroscopic, and theoretical analyses, we propose a mechanistic centered on electron bridging-electron sinking, showing that additives are not passive background components but active regulators in MPs aging. This work helps to clarify the role of electron-driven processes and plastic additives aging of MPs.
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This review examines how the aging and weathering of microplastics in the environment causes chemical additives like plasticizers, flame retardants, and antioxidants to leach out. As microplastics age through UV exposure, heat, and biological activity, they release these additives more readily, increasing the toxic risk to organisms. The findings are important because they show that older, weathered microplastics found in the real world may be more chemically hazardous than fresh plastics used in most lab studies.
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This review examined how environmental aging processes affect the leaching behavior and toxicity of plastic additives from microplastics. Researchers found that UV exposure, weathering, and biological degradation alter the physicochemical properties of microplastics, increasing the release of harmful chemical additives and potentially amplifying their toxic effects on organisms in the environment.
Complex release dynamics of microplastic additives: An interplay of additive degradation and microplastic aging
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This study investigated how microplastics release their chemical additives -- including phthalates, bisphenol A, and flame retardants -- into water, especially under UV sunlight. The process is more complicated than simple leaching: sunlight both breaks down the additives and ages the plastic itself, which changes how fast chemicals are released. These findings matter because the toxic additives that leach from microplastics may pose a greater health risk than the plastic particles themselves.
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This review examines how the built-in properties of plastics — their chemical structure, additives, and molecular weight — determine how quickly they break down in the environment and what happens when they do. As microplastics degrade, they fragment into even smaller particles that may be more harmful because they can more easily enter living organisms. Understanding these degradation pathways is essential for predicting the long-term environmental and health risks of plastic pollution.
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This review found that environmental aging transforms microplastic surface properties through abrasion, chemical oxidation, UV irradiation, and biodegradation, altering their environmental behavior and ecological risk. Aging also triggers the release of toxic plastic additives, but significant gaps remain between laboratory aging simulations and real-world conditions.
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