The toxic unit and additive index approaches were used to understand how 2 pesticides, 3‐trifluoromethyl‐4‐nitrophenol (TFM) and 2,5‐dichloro‐4‐nitrosalicylanilide (niclosamide; Nic), interact in mixtures. Our first objective was to determine whether the interaction was strictly additive or greater than additive at doses comparable to those used to control invasive sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes, and our second was to compare the utility of the toxic unit and additive index models for determining how TFM and Nic interacted. Typically, TFM is mixed with Nic (1–2%, w/v) to increase its potency and reduce TFM use. However, there is little information on how the 2 chemicals interact. Using a well‐studied, resident nontarget fish, the rainbow trout (Oncorhynchus mykiss), we conducted toxicity tests with TFM, Nic, and TFM:Nic (100:1, w/v; TFM/1% Nic) mixtures over 12 h to determine if the interaction was strictly additive, less than additive (antagonistic), or greater than additive (synergistic). The toxic unit and additive index approaches indicated synergistic interactions at environmentally relevant concentrations, suggesting that both are valid approaches for predicting how TFM and Nic interact. The toxic unit approach was simpler to conceptualize and to calculate, and we recommend that it be used when describing how TFM and Nic, and other similar organic compounds, interact with each other in aquatic ecosystems. Environ Toxicol Chem 2021;40:1419–1430. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

中文翻译：

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了解虹鳟鱼中 2 种杀鱼剂、3-三氟甲基-4-硝基苯酚和氯硝柳胺相互作用的毒性单位和添加剂指数方法

毒性单位和添加剂指数方法用于了解 2 种农药，3-三氟甲基-4-硝基苯酚 (TFM) 和 2,5-二氯-4-硝基水杨酰苯胺（氯硝柳胺；Nic）如何在混合物中相互作用。我们的第一个目标是确定在与用于控制劳伦大湖中入侵海七鳃鳗（Petromyzon marinus）的剂量相当的剂量下，相互作用是严格相加还是大于相加，第二个目的是比较有毒单位和用于确定 TFM 和 Nic 如何相互作用的附加指数模型。通常，TFM 与 Nic（1–2%，w/v）混合以增加其效力并减少 TFM 的使用。然而，关于这两种化学物质如何相互作用的信息很少。使用经过充分研究的非目标鱼，虹鳟鱼（Oncorhynchus mykiss)，我们对 TFM、Nic 和 TFM:Nic (100:1, w/v; TFM/1% Nic) 混合物进行了 12 小时的毒性测试，以确定相互作用是否严格相加，小于相加（拮抗），或大于加性（协同）。毒性单位和添加剂指数方法表明在环境相关浓度下的协同相互作用，表明两者都是预测 TFM 和 Nic 如何相互作用的有效方法。有毒单位方法更易于概念化和计算，我们建议在描述 TFM 和 Nic 以及其他类似有机化合物如何在水生生态系统中相互作用时使用它。环境毒理学化学2021；40：1419-1430。© 2021 作者。环境毒理学和化学 由 Wiley Periodicals LLC 代表 SETAC 出版。