In this study, we investigate whether the influence of natural organic matter (NOM) on the aquatic ecotoxicity of engineered nanoparticles (ENPs) can be described quantitatively for the purpose of risk assessments based on existing ecotoxicity studies. A review of the literature studying the aquatic ecotoxicity of ENPs in the presence of NOM identified 66 studies in total, covering the metal and metal oxide ENPs most commonly used in consumer products. It was found that 80% of the studies show a reduction in ENP ecotoxicity in the presence of NOM. Analyses of ecotoxicity data based on 50% effect/inhibition/lethal concentrations (collectively referred to as XC50) were conducted. Correlations of XC50 values with the concentrations of NOM were investigated through Spearman's rank correlation coefficient as well as linear, power law, polynomial, exponential and logarithmic correlations. Furthermore, multiple linear regression (MLR) analyses, including also the pH in the reviewed ecotoxicity test systems (mainly in the range pH 7.0–8.5), were conducted. While none of these statistical approaches provided strong empirical correlations between XC50 values, NOM concentration and pH, an empirical rule of thumb was discovered for the ratio between XC50 values with and without NOM over an environmentally realistic concentration range for NOM (0.1–10 mg/L): XC50 values obtained in experiments with NOM present tended to be a factor of 1–10 higher than those without NOM. Until more accurate correlations are provided, a pragmatic approach for environmental risk assessments of ENPs might therefore be to use observed XC50 values from experiments without NOM present as reasonably conservative proxies for XC50 values with NOM present. Further studies are needed to confirm or falsify this rule of thumb for different ENPs, environmental conditions and metrics.

中文翻译：

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天然有机物对工程纳米粒子水生生态毒性的影响：环境风险评估建议

在这项研究中，我们调查了天然有机物 (NOM) 对工程纳米粒子 (ENP) 的水生生态毒性的影响是否可以定量描述，以便基于现有的生态毒性研究进行风险评估。对研究在 NOM 存在下 ENP 的水生生态毒性的文献进行的回顾确定了总共 66 项研究，涵盖了消费品中最常用的金属和金属氧化物 ENP。发现 80% 的研究表明，在 NOM 存在下，ENP 生态毒性降低。对基于 50% 效应/抑制/致死浓度（统称为 XC50）的生态毒性数据进行了分析。XC50 值与 NOM 浓度的相关性通过 Spearman 秩相关系数以及线性、幂律、多项式、指数和对数相关。此外，还进行了多元线性回归 (MLR) 分析，包括审查的生态毒性测试系统中的 pH 值（主要在 pH 值 7.0-8.5 范围内）。虽然这些统计方法都没有提供 XC50 值、NOM 浓度和 pH 值之间的强经验相关性，但发现了经验法则，用于在 NOM 的环境现实浓度范围内（0.1-10 毫克/ L)：在有 NOM 的实验中获得的 XC50 值往往比没有 NOM 的实验高 1-10 倍。在提供更准确的相关性之前，因此，ENP 环境风险评估的一种实用方法可能是使用从没有 NOM 的实验中观察到的 XC50 值，作为存在 NOM 的 XC50 值的合理保守代理。需要进一步的研究来确认或证伪不同 ENP、环境条件和指标的经验法则。