Nonpolar narcosis, also known as baseline toxicity, has been described as the minimal toxicity that an organic chemical may elicit based on its lipophilicity. Although lethal effects of narcosis-inducing chemicals (NICs) have been thoroughly investigated, knowledge of sublethal effects is still very limited. We investigated the effects of 3 well-known NICs (phenanthrene, 1,3,5-trichlorobenzene, and pentachlorobenzene) on a variety of organismal endpoints (malformations, swim bladder inflation, respiration, heart rate, swimming activity, and turning angles), which can be plausibly linked to narcosis in zebrafish embryos. Baseline toxicity recorded as mortality is typically observed in similar exposure ranges in a wide variety of species including fish, corresponding to a chemical activity range between 0.01 and 0.1. In the present study, we found that sublethal effects occurred at concentrations approximately 5 times below lethal concentrations. Altered swimming activity and impaired swim bladder inflation were the most sensitive endpoints occurring at exposure levels below the generally accepted threshold for baseline toxicity for 2 out of 3 compounds. Overall, most effective exposure levels across the sublethal endpoints and compounds did fall within the range typically associated with baseline toxicity, and deviations were generally limited to a factor 10. Although there could be benefit in adding sublethal endpoints to toxicity tests, such as the fish embryo acute toxicity (FET) test, based on the present sublethal endpoints and available evidence from our and other studies, the underestimation of toxicity as a result of the sole assessment of mortality as an endpoint in an FET test may be limited for narcosis. Environ Toxicol Chem 2021;40:2802–2812. © 2021 SETAC

中文翻译：

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斑马鱼胚胎中非极性麻醉的亚致死效应浓度

非极性麻醉，也称为基线毒性，已被描述为有机化学品基于其亲脂性可能引起的最小毒性。尽管已经彻底研究了麻醉诱导化学品 (NIC) 的致死作用，但对亚致死作用的了解仍然非常有限。我们研究了 3 种众所周知的 NIC（菲、1,3,5-三氯苯和五氯苯）对各种生物体终点（畸形、鱼鳔膨胀、呼吸、心率、游泳活动和转角）的影响，这可能与斑马鱼胚胎中的麻醉有关。记录为死亡率的基线毒性通常在包括鱼类在内的多种物种的相似暴露范围内观察到，对应于 0.01 和 0.1 之间的化学活性范围。在目前的研究中，我们发现亚致死效应发生在低于致死浓度约 5 倍的浓度下。游泳活动改变和鱼鳔膨胀受损是最敏感的终点，发生在暴露水平低于普遍接受的 3 种化合物中 2 种的基线毒性阈值时。总体而言，亚致死终点和化合物中最有效的暴露水平确实落在通常与基线毒性相关的范围内，偏差通常限制在 10 倍以内。尽管在毒性试验中增加亚致死终点可能会有好处，例如鱼胚胎急性毒性 (FET) 测试，基于目前的亚致死终点和我们和其他研究的可用证据，环境毒物化学2021；40:2802–2812。© 2021 SETAC