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Unraveling the impacts of photolysis-induced aging microplastics on enhanced immunotoxicity and nephrotoxicity
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Researchers compared the toxicity of pristine and sun-aged polyethylene and PET microplastics on kidney cells and immune cells and found that aged particles were up to 40 percent more toxic. The increased harm was attributed to environmentally persistent free radicals that form on plastic surfaces during UV exposure, which amplify oxidative stress inside cells. The study highlights that weathered microplastics in the real environment may pose greater health risks than the pristine particles typically used in laboratory studies.
Photolytically aged microplastics i.e. photoaged MPs in aquatic environments could potentially enter human body through ingestion with associated health risks. However, most studies have focused on pristine MPs, single polymer types with single-cell models, leaving critical gaps in achieving a comprehensive toxicological assessment of pristine and photoaged MPs exposure. This study examines the cytotoxic effects of photoaged, environmentally relevant polymers-polyethylene (PE) and polyethylene terephthalate (PET)-on human embryonic kidney cells (HEK-293T) and murine macrophages (RAW264.7). The toxic properties of MPs, including the formation of environmentally persistent free radicals (EPFRs), reactive oxygen species (ROS), and leaching organics from pristine and photoaged MPs, are comprehensively characterized using electron paramagnetic resonance spectroscopy and orbitrap liquid chromatography-mass spectrometry. By integrating viability, oxidative stress, and apoptosis analysis, we provide mechanistic insight into how polymer type and photolytic aging influence MP-induced toxicity. Results demonstrate that photoaged MPs induced significantly higher cytotoxicity than their pristine counterparts, with differences of up to 40 %. Furthermore, PET exhibited greater cytotoxic effects than PE, with differences reaching 30 %. These effects are attributed to the presence of stable EPFRs, which intensify intracellular ROS generation and subsequently trigger apoptosis, whereas the leachate-only test showed no significant cytotoxicity. Photoaged PET, containing carbon- and oxygen-centered EPFRs (g-factor > 2.00400), induce the highest ROS levels and apoptosis in both cell types (P < 0.01). These findings underscore the polymer- and cell type-dependent toxicity of photoaged MPs and provide a foundation for further in vitro co-culture studies.
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UVB-aged polystyrene microplastics induce enhanced stress responses in human proximal tubular cells
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Scientists exposed human kidney cells to microplastics that had been sun-weathered, similar to what happens to plastic waste outdoors. The aged plastic particles caused more cell stress and DNA damage than fresh plastic, suggesting that sunlight exposure may make microplastics more harmful to our kidneys. This matters because most safety testing uses unweathered plastic, potentially underestimating real-world risks.
Polyethylene, whose surface has been modified by UV irradiation, induces cytotoxicity: A comparison with microplastics found in beaches
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Researchers showed that polyethylene microplastics degraded by UV light, mimicking what happens to plastics in the environment, were toxic to immune and skin cells in lab tests. Fresh, undegraded plastic particles did not cause the same harm, meaning weathered microplastics found in nature are likely more dangerous than the pristine plastics typically used in lab studies. This suggests that real-world human exposure to environmentally aged microplastics may carry greater health risks than current research indicates.
UVB-Aged Microplastics and Cellular Damage: An in Vitro Study
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Researchers compared the cellular damage caused by UV-aged versus new microplastic particles using lab-grown human cells. They found that UV-aged microplastics caused significantly more DNA damage and oxidative stress than pristine particles, likely due to chemical changes on their surfaces during weathering. The findings suggest that environmentally weathered microplastics may pose greater health risks than freshly produced ones.
Photoaging of microplastics and nanoplastics: Physicochemical transformations, cellular responses, and toxicological implications
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When plastic waste breaks down in sunlight, it doesn't just become smaller pieces, it actually changes chemically in ways that can make it more toxic to cells, according to this review of existing research. Scientists found that sun-damaged microplastics and nanoplastics are often more harmful to cells than fresh, unweathered plastic particles, though how harmful depends on the plastic type and other conditions. This matters because most plastic pollution in the environment has been sitting in the sun for a while, so real-world exposure may pose greater health risks than lab studies using pristine plastic particles suggest.
New Insights into the Mechanisms of Toxicity of Aging Microplastics
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This study showed that UV-aged polypropylene microplastics are significantly more toxic than fresh ones, absorbing more chemicals and generating more harmful reactive oxygen species in seawater. The aged particles caused greater damage to cell membranes in mussels compared to pristine plastics. Since most microplastics in the ocean have been weathered by sunlight, real-world exposure risks may be higher than laboratory studies using new plastics suggest.
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