1.1 本规程涵盖了估算胖头鱼的程序( 黑头呆鱼 )96小时LC50的非活性（即无不饱和残基的共价键合）和非电溶性（即，需要强有力的试剂来促进取代、添加、替换反应，并且在水溶液中是非离子的、非解离的）有机化学品，仅通过麻醉起作用，也称为Meyer Overton毒性关系。 2. 1.2 该程序适用于因麻醉而有毒且非反应性和非电解性的有机化学品。合适的化学品的例子有:醇、酮、醚、简单卤化脂肪族、芳香族和脂肪族取代芳香族。它不适用于其结构包括潜在毒性载体的化学品（已鉴定为显示哺乳动物毒性的化学分子的结构成分，例如已知CN对酶的失活负责，NO 2. 用于氧化磷酸化的去耦，两者都导致哺乳动物毒性）。不适用于这一做法的化学品有:氨基甲酸酯、有机磷酸酯、酚类、β-γ-不饱和醇、亲电试剂和季铵盐。 1.3 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 5.1 该程序可用于限制在进行非反应性和非电解性化学品对胖头鱼的LC50估算试验之前进行筛选试验的需要。通过取消筛选测试，需要测试的鱼类更少。还可以节省准备和执行筛选测试所用的时间。 本程序中获得的值可作为全尺寸试验中LC50的初步估算值。 5.2 估计值可用于设置非反应性和非电解化学品组的测试优先级。 5.3 如果估计值超过实验值的0.3倍，则作用机制可能是麻醉。如果较小，则认为效应浓度反映了不同的作用机制。 5.4 该实践估计最大LC50，即非反应性和非电解性化学品的毒性至少与实践预测的一样，但如果通过更具体的机制起作用，则可能具有更低的LC50。由于测试材料的溶解度有限，表明毒性低于预测值的化学品数据应被视为可疑或人为因素。

1.1 This practice covers a procedure for estimating the fathead minnow ( Pimephales promelas ) 96-h LC50 of nonreactive (that is, covalently bonded without unsaturated residues) and nonelectrolytic (that is, require vigorous reagents to facilitate substitution, addition, replacement reactions and are non-ionic, non-dissociating in aqueous solutions) organic chemicals acting solely by narcosis, also referred to as Meyer-Overton toxicity relationship. 2 1.2 This procedure is accurate for organic chemicals that are toxic due to narcosis and are non-reactive and non-electrolytic. Examples of appropriate chemicals are: alcohols, ketones, ethers, simple halogenated aliphatics, aromatics, and aliphatic substituted aromatics. It is not appropriate for chemicals whose structures include a potential toxiphore (that structural component of a chemical molecule that has been identified to show mammalian toxicity, for example CN is known to be reponsible for inactivation of enzymes, NO 2 for decoupling of oxidative phosphorylation, both leading to mammalian toxicity). Examples of chemicals inappropriate for this practice are: carbamates, organophosphates, phenols, beta-gamma unsaturated alcohols, electrophiles, and quaternary ammonium salts. 1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 This procedure can be used to limit the need for screening tests prior to performing a test for estimating the LC50 of a non-reactive and non-electrolytic chemical to the fathead minnow. By eliminating the screening test, fewer fish need be tested. The time used for preparing and performing the screening test can also be saved. The value obtained in this procedure can be used as the preliminary estimate of the LC50 in a full-scale test. 5.2 Estimates can be used to set testing priority of groups of non-reactive and non-electrolytic chemicals. 5.3 If the estimated value is more than 0.3 times the experimental value, the mechanism of action is probably narcosis. If less, the effect concentration is considered to reflect a different mechanism of action. 5.4 This practice estimates a maximum LC50, that is, non-reactive and non-electrolytic chemicals are at least as toxic as the practice predicts, but may have a lower LC50 if acting by a more specific mechanism. Data on a chemical indicating a lower toxicity than predicted should be considered suspect or an artifact because of limited solubility of the test material.