The majority of pharmaceuticals and personal health-care products are ionisable molecules at environmentally relevant pHs. The ionization state of these molecules in freshwater ecosystems may influence their toxicity potential to aquatic organisms. In this study we evaluated to what extent varying pH conditions may influence the toxicity of the antibiotic enrofloxacin (ENR) and the personal care product ingredient triclosan (TCS) to three freshwater invertebrates: the ephemeropteran Cloeon dipterum, the amphipod Gammarus pulex and the snail Physella acuta. Acute toxicity tests were performed by adjusting the water pH to four nominal levels: 6.5, 7.0, 7.5 and 8.0. Furthermore, we tested the efficiency of three toxicity models with different assumptions regarding the uptake and toxicity potential of ionisable chemicals with the experimental data produced in this study. The results of the toxicity tests indicate that pH fluctuations of only 1.5 units can influence EC50-48 h and EC50-96 h values by a factor of 1.4-2.7. Overall, the model that only focuses on the fraction of neutral chemical and the model that takes into account ion-trapping of the test molecules showed the best performance, although present limitations to perform risk assessments across a wide pH range (i.e., well above or below the substance pKa). Under such conditions, the model that takes into account the toxicity of the neutral and the ionized chemical form is preferred. The results of this study show that pH fluctuations can have a considerable influence on toxicity thresholds, and should therefore be taken into account for the risk assessment of ionisable pharmaceuticals and personal health-care products. Based on our results, an assessment factor of at least three should be used to account for toxicity differences between standard laboratory and field pH conditions. The models evaluated here can be used to perform refined risk assessments by taking into account the influence of temporal and spatial pH fluctuations on aquatic toxicity.

中文翻译：

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pH值对可离子化药物和个人护理产品对淡水无脊椎动物毒性的影响。

大多数药品和个人保健产品在环境相关的pH值下都是可电离的分子。这些分子在淡水生态系统中的电离状态可能会影响其对水生生物的潜在毒性。在这项研究中，我们评估了不同的pH条件在多大程度上会影响抗生素恩诺沙星（ENR）和个人护理产品成分三氯生（TCS）对三种淡水无脊椎动物的发育：表翅opter科克隆，两栖类Gammarus pulex和蜗牛Physella阿库塔。通过将水的pH值调节至四个标称水平（6.5、7.0、7.5和8.0），进行了急性毒性试验。此外，我们使用本研究产生的实验数据，对可离子化化学物质的吸收和潜在毒性的不同假设，测试了三种毒性模型的效率。毒性测试的结果表明，pH波动仅1.5个单位即可影响EC50-48 h和EC50-96 h值1.4-2.7。总体而言，尽管目前存在局限性，无法在较宽的pH范围内进行风险评估，但仅关注中性化学成分的模型和考虑了测试分子离子捕获的模型均表现出最佳性能。低于物质pKa）。在这种条件下，考虑到中性和电离化学形式的毒性的模型是优选的。这项研究的结果表明，pH波动可能会对毒性阈值产生重大影响，因此在可电离药物和个人保健产品的风险评估中应考虑到这一点。根据我们的结果，至少应使用三个评估因子来解释标准实验室和现场pH条件之间的毒性差异。考虑到时间和空间pH波动对水生毒性的影响，此处评估的模型可用于进行精细的风险评估。至少应使用三个评估因子来说明标准实验室和现场pH条件之间的毒性差异。考虑到时间和空间pH波动对水生毒性的影响，此处评估的模型可用于执行精细的风险评估。至少应使用三个评估因子来说明标准实验室和现场pH条件之间的毒性差异。考虑到时间和空间pH波动对水生毒性的影响，此处评估的模型可用于进行精细的风险评估。