Masten L W, Boeri R L, Walker J D
Toxicology and Regulatory Compliance, ARCO Chemical Company, Newtown Square, Pennsylvania 19073.
Ecotoxicol Environ Saf. 1994 Apr;27(3):335-48. doi: 10.1006/eesa.1994.1027.
Studies are described in which ethyl benzene (EB) was tested to determine its acute toxicity to three marine organisms, Atlantic silversides (Menidia menidia), mysid shrimp (Mysidopsis bahia), and diatoms (Skeletonema costatum), and to one freshwater algae (Selenastrum capricornutum). The respective 96-hr median lethal concentration (LC50) values and 95% confidence intervals for EB in the flow-through studies with fish and mysid shrimp were 5.1 (4.4-5.7) mg/liter and 2.6 (2.0-3.3) mg/liter. While the 96-hr median effective concentrations (EC50's) for growth inhibition and 95% confidence intervals for the static studies with diatoms and algae were 7.7 (5.9-10.0) mg/liter and 3.6 (1.7-7.6) mg/liter, respectively. Problems were encountered in all four studies as a result of the high volatility and poor water solubility of EB in water and an apparent "salting out" effect noted in seawater. This effect was found particularly true in the diatom and algae studies where the salinity was increased with the addition of culture medium. Measures are described which were used to overcome this stability problem with EB. These included sealing the test systems tight without any air spaces to prevent the collection of EB vapors. Also, increased mixing of EB in the test solutions was found to be essential in the flow-through studies to maintain stable levels. In the case of the diatom and algal studies, since current EPA test guidelines were judged to be inadequate to overcome EB volatility from the test medium, a new closed test system had to be developed and employed, after validation with a nonvolatile reference toxicant in the new and conventional static test systems. The results of these studies indicate that previous reports underestimated the potential acute aquatic toxicity of EB by at least one order of magnitude. The implications of these findings are discussed in relation to the potential environmental impact of EB and the resultant regulatory actions.
所描述的研究中，对乙苯（EB）进行了测试，以确定其对三种海洋生物（大西洋银汉鱼（Menidia menidia）、糠虾（Mysidopsis bahia）和硅藻（Skeletonema costatum））以及一种淡水藻类（羊角月牙藻（Selenastrum capricornutum））的急性毒性。在对鱼类和糠虾的流水试验中，EB的96小时半数致死浓度（LC50）值及95%置信区间分别为5.1（4.4 - 5.7）毫克/升和2.6（2.0 - 3.3）毫克/升。而在对硅藻和藻类的静态试验中，生长抑制的96小时半数有效浓度（EC50）值及95%置信区间分别为7.7（5.9 - 10.0）毫克/升和3.6（1.7 - 7.6）毫克/升。在所有四项研究中都遇到了问题，这是由于EB在水中挥发性高、水溶性差，以及在海水中明显存在“盐析”效应。这种效应在硅藻和藻类研究中尤为明显，因为添加培养基后盐度增加。文中描述了用于克服EB稳定性问题的措施。这些措施包括将测试系统密封严密，不留任何空气间隙以防止EB蒸汽积聚。此外，在流水试验中发现增加EB在测试溶液中的混合对于维持稳定水平至关重要。在硅藻和藻类研究中，由于现行美国环境保护局（EPA）测试指南被认为不足以克服测试介质中EB的挥发性，因此在新的和传统的静态测试系统中用一种非挥发性参考毒物进行验证后，必须开发并采用一种新的封闭测试系统。这些研究结果表明，先前的报告至少低估了EB潜在的急性水生毒性一个数量级。结合EB潜在的环境影响和由此产生的监管行动，对这些发现的影响进行了讨论。
