Alvarez Olga Alda, Jager Tjalling, Colao Beatriz Nuñez, Kammenga Jan E
Laboratory of Nematology, Wageningen University, Binnenhaven 5, 6709 PD Wageningen, The Netherlands.
Environ Sci Technol. 2006 Apr 1;40(7):2478-84. doi: 10.1021/es052260s.
In effect assessment the comparability and applicability of LCx and ECx values, which are calculated at single points in time during exposure, relies on the ability to perform a valid extrapolation to other time points of interest. The behavior of LCx in time has been extensively studied, and the behavior of ECx in time is expected to follow similar dynamics, as it is considered that the LCx is just a specific case of ECxs. However, most models have focused on validating the dynamics of LCx, and hardly anything is known about the time dependence of ECx for other endpoints or whether it is comparable to that of LCxs. We have created four scenarios where we study the dynamics of the ECx for different endpoints and how it is affected by the characteristics of two different compounds (carbendazim and pentachlorobenzene) and of two different life history strategies (hermaphroditic and sexually reproducing strains of Caenorhabditis elegans). The observed patterns of behavior in time of the ECx for body size and for reproduction showed unexpected dynamics that deviate considerably from that of the LCx. It was demonstrated that the temporal dynamics of ECx were very different for each particular endpoint. The shape of the ECx-time curves depends on the intrinsic characteristics of the endpoint of study, as well as on the characteristics of the compound and life history strategy of the organism. This makes extrapolation in time or between endpoints difficult and hampers the comparability of results based on this summary statistic. The interpretation of the results from toxicity tests can be improved through process-based modeling, as demonstrated on the current data set.
在效应评估中，暴露期间在单个时间点计算的LCx和ECx值的可比性和适用性，依赖于对其他感兴趣的时间点进行有效外推的能力。LCx随时间的变化行为已得到广泛研究，预计ECx随时间的变化行为遵循类似的动态，因为LCx被认为只是ECxs的一个特定情况。然而，大多数模型都集中于验证LCx的动态，对于其他终点的ECx的时间依赖性或它是否与LCxs的时间依赖性可比，几乎一无所知。我们创建了四种情景，研究不同终点的ECx动态，以及它如何受到两种不同化合物（多菌灵和五氯苯）和两种不同生活史策略（秀丽隐杆线虫的雌雄同体和有性繁殖菌株）特征的影响。观察到的ECx在体型和繁殖方面随时间的行为模式显示出意想不到的动态，与LCx的动态有很大偏差。结果表明，每个特定终点的ECx时间动态非常不同。ECx-时间曲线的形状取决于所研究终点的内在特征，以及化合物的特征和生物体的生活史策略。这使得时间外推或不同终点之间的外推变得困难，并妨碍了基于此汇总统计量的结果的可比性。如当前数据集所示，通过基于过程的建模可以改进毒性测试结果的解释。
