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Formation of environmentally persistent free radicals on microplastics under UV irradiations
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This study found that UV light from the sun creates long-lasting free radicals on the surface of microplastics, with stronger UV producing more radicals faster. These environmentally persistent free radicals are chemically reactive and can damage cells and DNA. The finding is important because it means sunlight-weathered microplastics in the environment may be more harmful than fresh plastics, carrying these damaging free radicals into the body when ingested or inhaled.
Microplastics (MPs) are widely distributed in the environment due to breakdown of widespread plastic wastes through physicochemical and biological processes. Environmentally persistent free radicals (EPFRs) might be generated as intermediates when MPs are further fragmented and decomposed under ultraviolet (UV) radiation. Formation of EPFRs is highly depended upon the radiation energy level. This study was designed to establish the correlation between EPFRs concentrations and UV energy. Polystyrene (PS) and polyethylene (PE) were employed to investigate the generation of EPFRs under the irradiation of three ultraviolet light sources (long-wave UVA, medium-wave UVB and short-wave UVC). Electron paramagnetic resonance (EPR) spectroscopy revealed that free radical signals were detected on PS irradiated by UVC and UVB and PE irradiated by UVC, which may be due to the difference in the MPs structure and UV energy. The g-factor and ΔH of EPR suggested that three different types of EPFRs may be formed on PS while two types of EPFR may be formed on PE. Meanwhile, EPFRs were detected within shorter time under UVC radiation than UVB and UVA, indicating that UVC radiation could lead to faster generation of free radicals. Results of Fourier transform infrared spectroscopy (FTIR) and two-dimensional correlation spectroscopy revealed that tertiary alkyl radicals, peroxy radicals and tertiary alkoxy radicals were dominant in PS whereas alkoxy radicals and keto radicals for PE. The study provides insight to the mechanisms for EPFRs formation on ubiquitously found microplastic particles. Our finding is of great significance as EPFRs may not only play important roles in decomposition of MPs and abiotic reactions of MPs-bound pollutants, but also affect physicochemical properties of MPs and MPs toxicity to aquatic organisms, hence possessing broad impacts on MPs fate and transport in aquatic environmental systems.
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Formation of Environmentally Persistent Free Radicals on Microplastics under Light Irradiation
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Four types of virgin microplastics were aged under simulated solar irradiation and analyzed by electron paramagnetic resonance spectroscopy, finding that polystyrene and phenol-formaldehyde resin produced environmentally persistent free radicals (EPFRs) that decayed slowly, while polyethylene and PVC did not. The study identifies photoaged plastic surfaces as a previously unrecognized source of EPFRs—emerging contaminants with known health risks.
A Critical Review of an Environmental Risk Substance Induced by Aging Microplastics: Insights into Environmentally Persistent Free Radicals
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This review examines how microplastics generate long-lasting free radicals as they age in the environment through exposure to sunlight and chemical reactions. These environmentally persistent free radicals (EPFRs) on aged microplastics can cause oxidative stress and damage to living cells, adding a previously underappreciated layer of toxicity beyond the physical harm caused by the plastic particles themselves.
Environmentally persistent free radicals on photoaged microplastics from disposable plastic cups induce the oxidative stress-associated toxicity
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Researchers found that when disposable plastic cups break down under UV light, they generate persistent free radicals on their surfaces that cause toxic effects in living organisms. These sun-aged microplastics reduced movement, growth, and reproduction in nematode worms through oxidative stress at environmentally realistic concentrations. The study shows that weathered microplastics from everyday items like disposable cups may be more harmful than fresh plastics because of the reactive chemicals generated during breakdown.
The generation of environmentally persistent free radicals on photoaged microbeads from cosmetics enhances the toxicity via oxidative stress
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Researchers studied how sunlight aging affects microbeads from cosmetics and their potential toxicity. They found that UV exposure generates persistent free radicals on the plastic surface, which significantly increased harmful effects on the roundworm C. elegans, including reduced reproduction and elevated oxidative stress. The findings suggest that weathered microplastics from personal care products may be considerably more toxic than their freshly manufactured counterparts.
Environmentally persistent free radicals on photoaging microplastics shortens longevity via inducing oxidative stress in Caenorhabditis elegans
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Researchers found that microplastics aged by sunlight develop persistent free radicals on their surface that are more toxic than fresh microplastics. In experiments with a common laboratory worm, these sun-aged microplastics caused significant oxidative stress and shortened lifespan. This is important because most microplastics in the real world have been exposed to sunlight, meaning their actual health risks may be greater than studies using brand-new plastic particles would suggest.
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