Center for Health and Environmental Risk Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki, 305-8506, Japan.
Center for Health and Environmental Risk Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki, 305-8506, Japan.
Environ Pollut. 2020 Oct;265(Pt A):115059. doi: 10.1016/j.envpol.2020.115059. Epub 2020 Jun 20.
Field survey-based ecological risk assessments for trace metals are conducted to examine the necessity and/or effectiveness of management intervention, such as setting of environmental quality standards. Observational datasets often involve confounders that may bias estimation of the effects of intervention (e.g., reduction of trace-metal concentrations through regulation). The field of ecotoxicology lags behind some other research fields in understanding proper analytical procedures for causal inference from observational datasets; there are only a few field survey-based ecotoxicological studies that have explicitly controlled for confounders in their statistical analyses. In the present study, we estimated the effect of intervention in nickel concentrations on Ephemeroptera, Plecoptera, and Trichoptera richness in rivers in Japan. We also provide detailed explanations for the backgrounds of spurious associations derived from confounders and on proper analytical procedures for obtaining an unbiased estimate of the targeted intervention effect by using regression analysis. We constructed a multiple regression model based on a causal diagram for aquatic insects and environmental factors, and on "the backdoor criterion," that enabled us to determine the set of covariates required to obtain an unbiased estimate of the targeted intervention effect from regression coefficients. We found that management intervention in nickel concentrations may be ineffective compared to intervention in organic pollution, and that analysis ignoring the confounders overestimated the effect of intervention in nickel concentrations. Our results highlight the fact that confounders can lead to misjudging the necessity for management of anthropogenic chemical substances. Confounders should be explicitly specified and statistically controlled to achieve a comprehensive assessment of ecological risks for various substances.
基于实地调查的痕量金属生态风险评估旨在检验管理干预（例如设定环境质量标准）的必要性和/或有效性。观测数据集通常涉及混杂因素，这些因素可能会影响干预效果的估计（例如，通过监管减少痕量金属浓度）。与其他一些研究领域相比，生态毒理学在理解从观测数据集进行因果推断的适当分析程序方面还有所欠缺；只有少数基于实地调查的生态毒理学研究在其统计分析中明确控制了混杂因素。在本研究中，我们估计了日本河流中镍浓度干预对蜉蝣目、襀翅目和毛翅目丰富度的影响。我们还详细解释了混杂因素导致的虚假关联的背景，以及通过回归分析获得目标干预效果无偏估计的适当分析程序。我们基于水生昆虫和环境因素的因果关系图以及“后门准则”构建了一个多元回归模型，这使我们能够确定从回归系数中获得目标干预效果无偏估计所需的协变量集。我们发现，与有机污染干预相比，镍浓度管理干预可能无效，并且忽略混杂因素的分析高估了镍浓度干预的效果。我们的研究结果强调了这样一个事实，即混杂因素可能导致对人为化学物质管理必要性的错误判断。为了全面评估各种物质的生态风险，应明确指定并进行统计控制混杂因素。
