Southern California Coastal Water Research Project Authority, Costa Mesa, CA, USA, 92626.
Water Res. 2021 Jan 1;188:116510. doi: 10.1016/j.watres.2020.116510. Epub 2020 Oct 9.
Environmental risk assessment of complex chemical mixtures has increasingly been prioritized as a management goal, especially in the regulatory sector. Although fipronil and its three degradates (-sulfone, -sulfide and -desulfinyl) have been frequently quantified in waterways, little information is available about the likelihood and magnitude of ecological risk posed by these chemical mixtures - collectively known as fiproles - in surface water. In the present study, a probabilistic risk assessment of mixtures of fipronil and its three degradates was conducted for three effluent-dominated southern California rivers: Los Angeles River (LAR), San Gabriel River (SGR) and Santa Clara River (SCR), California, USA. The assessments, which used fiproles as an integrated proxy, were based on three levels of toxicity endpoints: median lethal concentration (LC50), half-maximal effective concentration (EC50), and lowest observed effect concentration (LOEC), to gain comprehensive assessment information. Probabilistic approaches based on species sensitivity distribution (SSD) and exposure concentration distribution (ECD) were developed with the log-logistic model by pooling the toxicity and occurrence data, respectively. The 5th percentile hazardous concentrations (HC5s) were calculated to be at low parts per billion levels, enabling these values to be used to estimate the chemical-specific benchmarks for components that lack ecotoxicity data. The single substance potentially affected fraction (ssPAF) of fiproles revealed risk levels for the three rivers in descending order: LAR ≥ SGR > SCR. The overall risk probability estimated from the joint probability curve (JPC) by Monte Carlo simulation was 1.13 ± 0.20% (LC50), 9.31 ± 1.46% (EC50), and 6.58 ± 1.43% (LOEC) for the three rivers collectively. These results derived from the fiproles indicates that fipronil and its degradates pose risks to the aquatic organisms in the surface water of the three rivers. The present study provides a methodology for the use of a proxy in the risk assessment of chemical mixtures.
环境风险评估复杂的化学混合物已日益被作为一个管理目标，特别是在监管部门。虽然氟虫腈及其三种降解产物（-砜、-硫醚和-去磺酰基）经常在水道中被定量，但关于这些化学混合物（统称为氟虫腈）在地表水中造成的生态风险的可能性和程度的信息很少。在本研究中，对美国加利福尼亚州三条以污水为主的河流（洛杉矶河、圣加布里埃尔河和圣克拉拉河）中的氟虫腈及其三种降解产物进行了混合物的概率风险评估。这些评估使用氟虫腈作为综合代理，基于三个毒性终点的水平：半数致死浓度（LC50）、半数有效浓度（EC50）和最低观察效应浓度（LOEC），以获得全面的评估信息。基于物种敏感性分布（SSD）和暴露浓度分布（ECD）的概率方法，分别使用对数逻辑模型对毒性和发生数据进行了汇总。计算了第 5 个百分位危险浓度（HC5s），以便在低部分/十亿水平下使用这些值来估计缺乏生态毒性数据的成分的化学特异性基准。氟虫腈单一物质潜在影响分数（ssPAF）显示了三条河流的风险水平按降序排列：LAR≥SGR>SCR。通过蒙特卡罗模拟从联合概率曲线（JPC）中估计的总体风险概率为 1.13±0.20%（LC50）、9.31±1.46%（EC50）和 6.58±1.43%（LOEC），用于三条河流的综合情况。这些源自氟虫腈的结果表明，氟虫腈及其降解产物对三条河流地表水的水生生物构成了风险。本研究提供了一种在化学混合物风险评估中使用代理的方法。
