Hazard assessment of microplastic is challenging because standard toxicity testing is targeting soluble (at least partially) chemicals. Adverse effects can occur when test organisms are exposed to turbid environments in the presence of various particulate matter (PM), both natural, such as clay and cellulose, and anthropogenic, such as microplastic. It is, therefore, relevant to compare responses to PM exposure between the microplastic and other suspended solids present at ecologically relevant concentrations. This comparison is possible when reference materials are included in the testing of microplastic hazard potential. Here, we evaluated growth inhibition in unicellular alga Raphidocelis subcapitata exposed to different PM (microplastic, kaolin, and cellulose; 10, 100, and 1,000 mg/L); algae without added solids were used as a control. Also, aggregate formation in the exposure systems was analyzed using particle size distribution (PSD) data. At 10–100 mg/L, no adverse growth effects were observed in any treatments; moreover, algal growth was significantly stimulated in kaolin and cellulose treatments compared to the control. However, at 1,000 mg/L, all tested materials exerted growth inhibition, with no significant differences among the materials. Comparing PSD s across the treatments showed that both PM concentration and size of the particle aggregates were significant growth predictors for all materials tested. Therefore, at high concentrations, both natural and anthropogenic materials have a similar capacity to cause growth inhibition. Linking effects in unicellular organisms to microplastic fragments remains a challenge since plastics incorporate chemicals that may leach and elicit specific effects relative to the particulates. The use of reference materials in hazard assessment of plastic litter is needed to delineate these effects.

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悬浮固体环境相关浓度下的藻类生长：对微塑料危害评估的影响

微塑料的危害评估具有挑战性，因为标准毒性测试针对的是可溶性（至少部分）化学品。当测试生物体暴露于混浊环境中并存在各种颗粒物 (PM) 时，可能会发生不利影响，这些颗粒物包括天然颗粒物（如粘土和纤维素）和人为颗粒物（如微塑料）。因此，有必要比较微塑料和其他以生​​态相关浓度存在的悬浮固体对 PM 暴露的反应。当微塑料潜在危害测试中包含参考材料时，这种比较是可能的。在这里，我们评估了暴露于不同 PM（微塑料、高岭土和纤维素；10、100 和 1,000 mg/L）的单细胞藻类 Raphidocelis subcapitata 的生长抑制；未添加固体的藻类用作对照。还，使用粒度分布 (PSD) 数据分析暴露系统中的聚集体形成。在 10-100 mg/L 时，任何处理均未观察到不利的生长影响；此外，与对照相比，高岭土和纤维素处理显着刺激了藻类生长。然而，在 1,000 mg/L 时，所有测试材料都发挥了生长抑制作用，材料之间没有显着差异。比较不同处理的 PSD 表明，PM 浓度和颗粒聚集体的大小都是所有测试材料的重要生长预测因子。因此，在高浓度下，天然和人为材料都具有相似的抑制生长的能力。将单细胞生物中的影响与微塑料碎片联系起来仍然是一个挑战，因为塑料中含有化学物质，这些化学物质可能会浸出并引起与颗粒相关的特定影响。需要在塑料垃圾危害评估中使用参考材料来描述这些影响。