National Institute for Advanced Industrial Science and Technology, Research Institute of Science for Safety and Sustainability, 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan.
Ecotoxicol Environ Saf. 2019 Nov 15;183:109494. doi: 10.1016/j.ecoenv.2019.109494. Epub 2019 Jul 31.
In ecological risk assessment, the Predicted No Effect Concentration (PNEC) of a substance is generally derived by one of two methods: either by applying an Assessment Factor (AF) or by using a Species Sensitivity Distribution (SSD). With the AF method, which is the conventional way, the PNEC is determined by dividing the lowest No Observed Effect Concentration (NOEC) by an AF of a certain fixed magnitude. With the SSD method, which is becoming increasingly used in the European Union and the United States, an HC5 value (Hazardous Concentration for 5% of species) is estimated from the NOEC and then divided by an AF to derive the PNEC. This study aimed to explore the most appropriate AF and the most effective application of each method. The performances of the SSD and AF methods were compared on the assumption that the better method is that in which more PNECs are lower than HC5. We concluded that the performance of these methods depends on sample size and variation in species sensitivity. As the sample size increases (i.e., if there are more toxicity data), the performance of each method increases. The performance of the AF method is better when variation in species sensitivity is small (i.e., all species tend to have a similar NOEC), but it declines as variation in sensitivity rises, implying that persisting with either of the methods may misrepresent the ecological risk. Our results suggest that the variation in sensitivity is an important factor affecting the ecological risk and more effort should be paid to understanding why the variation varies depending on chemical substances.
在生态风险评估中，物质的预测无效应浓度 (PNEC) 通常通过以下两种方法之一得出：应用评估因子 (AF) 或使用物种敏感性分布 (SSD)。在传统的 AF 方法中，PNEC 通过将最低无观察效应浓度 (NOEC) 除以一定大小的 AF 来确定。在 SSD 方法中，越来越多的欧盟和美国在使用该方法，从 NOEC 估算出 HC5 值（5%物种的有害浓度），然后除以 AF 得出 PNEC。本研究旨在探讨最合适的 AF 和每种方法的最有效应用。假设更好的方法是有更多的 PNEC 低于 HC5 的方法，比较了 SSD 和 AF 方法的性能。我们得出的结论是，这些方法的性能取决于样本量和物种敏感性的变化。随着样本量的增加（即，如果有更多的毒性数据），每种方法的性能都会提高。当物种敏感性变化较小时（即所有物种的 NOEC 趋于相似），AF 方法的性能更好，但随着敏感性的变化，其性能会下降，这意味着坚持使用这两种方法之一可能会错误地表示生态风险。我们的结果表明，敏感性的变化是影响生态风险的一个重要因素，应更加努力理解为什么敏感性的变化取决于化学物质。
