Proportional contributions to organic chemical mixture effects in groundwater and surface water

Semi-quantitative GC-MS and LC-MS measurements of organic chemicals in groundwater and surface waters were used to assess the overall magnitude and contribution of the most important substances to calculated mixture hazard. Here we use GC-MS and LC-MS measurements taken from two separate national monitoring programs for groundwater and surface water in England, in combination with chronic species sensitivity distribution (SSD) HC50 values published by Posthuma . (2019, 38, 905–917) to calculate individual substance hazard quotients and mixture effects using a concentration addition approach. The mixture analysis indicated that, as anticipated, there was an increased hazard from the presence of a cocktail of substances at sites compared to the hazard for any single chemical. The magnitude of the difference between the hazard attributed to the most important chemical and the overall mixture effect, however, was not large. Thus, the most toxic chemical contributed ≥ 20% of the calculated mixture effect in >99% of all measured groundwater and surface water samples. On the basis of this analysis, a 5 fold assessment factor placed on the risk identified for any single chemical would offer a high degree of in cases where implementation of a full mixture analysis was not possible. This finding is consistent with previous work that has assessed chemical mixture effects within field monitoring programs and as such provides essential underpinning for future policy and management decisions on how to effectively and proportionately manage mixture risks.

对地下水和地表水中有机化学品进行半定量气相色谱 - 质谱（GC - MS）和液相色谱 - 质谱（LC - MS）测量，用于评估最重要物质的总体量级以及它们对计算混合危害的贡献。在此，我们利用从英格兰针对地下水和地表水的两个独立的国家监测项目中获取的GC - MS和LC - MS测量结果，并结合波斯图马（Posthuma）发表的慢性物种敏感度分布（SSD）HC50值（2019年，38卷，905 - 917页），通过浓度相加法计算单个物质的危害商和混合效应。混合分析表明，正如预期的那样，与任何单一化学品的危害相比，场地中多种物质混合存在时危害增加。然而，最重要化学物质所致危害与总体混合效应之间的差异幅度并不大。因此，在超过99%的所有测量的地下水和地表水样本中，毒性最强的化学物质对计算的混合效应的贡献≥20%。基于此分析，在无法进行全面混合分析的情况下，对任何单一化学物质所确定的风险采用5倍的评估因子将提供高度的（保护）。这一发现与先前在实地监测项目中评估化学混合物效应的工作一致，因此为未来关于如何有效且适度地管理混合物风险的政策和管理决策提供了重要支撑。