School of Environment, Tsinghua University, Beijing 100084, China.
Department of Civil and Environmental Engineering, William & Cloy Codiga Resource Recovery Center, Stanford University, Stanford, California 94305-4020, United States.
Environ Sci Technol. 2024 Nov 12;58(45):20147-20159. doi: 10.1021/acs.est.4c05504. Epub 2024 Oct 28.
In this study, we show that low-density polyethylene films, a prevalent choice for food packaging in everyday life, generated high numbers of microplastics (MPs) and hundreds to thousands of plastic-derived dissolved organic matter (DOM) substances under simulated food preparation and storage conditions. Specifically, the plastic film generated 66-2034 MPs/cm (size range 10-5000 μm) under simulated aging conditions involving microwave irradiation, heating, steaming, UV irradiation, refrigeration, freezing, and freeze-thaw cycling alongside contact with water, which were 15-453 times that of the control (plastic film immersed in water without aging). We also noticed a substantial release of plastic-derived DOM. Using ultrahigh-resolution mass spectrometry, we identified 321-1414 analytes with molecular weights ranging from 200 to 800 Da, representing plastic-derived DOM containing C, H, and O. The DOM substances included both degradation products of polyethylene (including oxidized forms of oligomers) and toxic plastic additives. Interestingly, although no apparent oxidation was observed for the plastic film under aging conditions, plastic-derived DOM was more oxidized (average O/C increased by 27-46%) following aging with a higher state of carbon saturation and higher polarity. These findings highlight the future need to assess risks associated with MP and DOM release from plastic wraps.
在这项研究中，我们表明，低密度聚乙烯薄膜是日常生活中食品包装的常见选择，在模拟食品制备和储存条件下，会产生大量的微塑料（MPs）和数百到数千种源自塑料的溶解有机物（DOM）物质。具体来说，在涉及微波辐射、加热、蒸煮、紫外线辐射、冷藏、冷冻和冻融循环以及与水接触的模拟老化条件下，塑料薄膜产生了 66-2034 MPs/cm（尺寸范围为 10-5000μm）的 MPs，是对照（未老化的浸入水中的塑料薄膜）的 15-453 倍。我们还注意到大量源自塑料的 DOM 物质的释放。使用超高分辨率质谱，我们鉴定出分子量在 200 到 800Da 之间的 321-1414 种分析物，代表含有 C、H 和 O 的源自塑料的 DOM。这些 DOM 物质包括聚乙烯的降解产物（包括低聚物的氧化形式）和有毒的塑料添加剂。有趣的是，尽管在老化条件下塑料薄膜没有明显的氧化，但源自塑料的 DOM 在老化后更易氧化（平均 O/C 增加了 27-46%），具有更高的碳饱和度和更高的极性。这些发现强调了未来需要评估塑料包装中 MPs 和 DOM 释放相关风险的必要性。
