National Council for Air and Stream Improvement, Inc., 402 SW 140th Terrace, Newberry, Florida 32669, USA.
Environ Toxicol. 2012 Dec;27(12):671-84. doi: 10.1002/tox.20686. Epub 2011 Mar 7.
Because many herbicides selectively control specific species or types of vegetation, they are often applied as mixtures to achieve better control over undesirable vegetation. When herbicides are applied in forest ecosystems, streams, ponds, and other bodies of water are typically protected by buffer zones in which no herbicide is applied. However, in some landscapes, small wetlands and streams are difficult to see and avoid, thus the potential acute toxicity of herbicide mixtures to aquatic organisms is of interest, yet it has not been well-studied. We examined the acute toxicity of 23 different herbicide mixtures to Ceriodaphnia dubia and fathead minnows (Pimephales promelas) at environmentally relevant concentrations, and, where possible, characterized mixture interactions using Marking's Additive Index. Maximum exposure concentrations were equivalent to applying the maximum allowable rate for each component directly to the surface of a 6-in. deep pond with no dissipation following application. Under the conditions of this study, herbicide formulations containing Accord Concentrate (glyphosate), Arsenal AC (imazapyr), Chopper (imazapyr), Escort (metsulfuron methyl), Oust XP (sulfometuron methyl), and Velpar L (hexazinone) were not associated with appreciable acute toxicity to fathead minnows or C. dubia when used alone or in mixtures with each other and various surfactants and adjuvants. Herbicide mixtures for which Additive Indexes could be calculated exhibited primarily antagonistic or simple additive toxicity. In the few cases where synergistic toxicity was observed, the degree of synergism was slight, never exceeding approximately twice the effect estimated based on additive toxicity. Based on the results of this study, neither acute toxicity nor enhanced acute aquatic toxicity due to synergistic mixture effects appears to be a significant concern for applications of the herbicide mixtures most commonly used in forestry.
由于许多除草剂能够有选择性地控制特定的物种或类型的植被，因此它们通常被混合使用，以更好地控制不需要的植被。当除草剂应用于森林生态系统时，溪流、池塘和其他水体通常通过缓冲区来保护，在缓冲区中不应用除草剂。然而，在一些景观中，小湿地和溪流很难被看到和避免，因此，除草剂混合物对水生生物的潜在急性毒性引起了人们的兴趣，但尚未得到很好的研究。我们研究了 23 种不同除草剂混合物对大型溞（Ceriodaphnia dubia）和褐翻车鱼（Pimephales promelas）的急性毒性，在环境相关浓度下，并尽可能使用标记的加性指数来描述混合物的相互作用。最大暴露浓度相当于将每种成分的最大允许剂量直接施用到 6 英寸深的池塘表面，施药后无消散。在本研究的条件下，当单独使用或与其他各种表面活性剂和助剂混合使用时，含有 Accord Concentrate（草甘膦）、Arsenal AC（咪草烟）、Chopper（咪草烟）、Escort（甲磺隆甲酯）、Oust XP（甲磺隆）和 Velpar L（六嗪酮）的除草剂制剂对褐翻车鱼或大型溞没有明显的急性毒性。可以计算加性指数的除草剂混合物表现出主要的拮抗或简单的加性毒性。在少数观察到协同毒性的情况下，协同作用的程度很小，从未超过基于加性毒性估计的效果的两倍左右。根据本研究的结果，由于协同混合物效应导致的急性毒性或增强的急性水生毒性似乎不是林业中最常用的除草剂混合物应用的一个重要问题。
