Department of Civil and Environmental Engineering, University of Alberta, 9211-116 St. NW, Edmonton, Alberta T6G 1H9, Canada.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
Environ Sci Technol. 2020 Oct 6;54(19):12383-12392. doi: 10.1021/acs.est.0c03939. Epub 2020 Sep 24.
Exposure assessment of pesticides has substantially improved over time, with methods that now include a combination of advanced analytical techniques and fate/transport models to evaluate their spatiotemporal distribution. However, the current regulatory environmental risk assessment considers thresholds from laboratory studies completed under standardized conditions that do not reflect environmental dynamics. Using the General Unified Threshold model for Survival (GUTS) model framework, we predicted the impact of time-varying pesticide exposures on the survival of gammarids in a small agricultural stream. The LP values were used as an additional metric for assessing risks (defined in GUTS as a multiplication factor applied to the concentration time series to induce 50% mortality by the end of exposure). Although real-case exposures to individual pesticides were predicted to produce little to no impact on survival, the LP values indicate acute (LP ≤ 100) and/or chronic (LP ≤ 10) toxicities for azoxystrobin, chlorpyrifos, diazinon, and imidacloprid, while risk to propiconazole exposure was considered very low (LP ≫ 100). Finally, the model was extended to reflect mixture toxicity via concentration addition. It predicted risks under acute and chronic exposures to organophosphates and neonicotinoids. Given that gammarids are simultaneously exposed to multiple chemicals and other stressors throughout their lifetime, a decline in survival probabilities due to chemical stress can likely influence their overall fitness. We recognize that some assumptions require validation, but our work included a level of realism that can assist risk managers when evaluating the cumulative consequences of chemical exposure.
随着时间的推移，农药暴露评估有了很大的改进，现在的方法包括先进的分析技术和归宿/传输模型的组合，以评估它们的时空分布。然而，目前的监管环境风险评估考虑的是在标准化条件下完成的实验室研究的阈值，这些阈值并不能反映环境动态。我们使用通用统一生存阈值模型（GUTS）模型框架，预测了时间变化的农药暴露对小型农业溪流中桡足类生存的影响。LP 值被用作评估风险的附加指标（在 GUTS 中定义为应用于浓度时间序列的倍增因子，以在暴露结束时引起 50%的死亡率）。虽然预测到个别农药的实际暴露对生存几乎没有影响，但 LP 值表明唑菌胺酯、毒死蜱、二嗪磷和吡虫啉具有急性（LP ≤ 100）和/或慢性（LP ≤ 10）毒性，而丙环唑暴露的风险被认为非常低（LP ≫ 100）。最后，该模型通过浓度加和扩展到反映混合物毒性。它预测了在急性和慢性接触有机磷和新烟碱类杀虫剂时的风险。鉴于桡足类在其整个生命周期中同时暴露于多种化学物质和其他胁迫因素，由于化学胁迫导致的生存概率下降可能会影响它们的整体适应性。我们认识到一些假设需要验证，但我们的工作包含了一定程度的现实性，可以帮助风险管理者在评估化学暴露的累积后果时提供参考。
