Exponent Inc., 1331 17th Street, Suite 515, Denver, CO 80202, USA.
Exponent Inc., 1331 17th Street, Suite 515, Denver, CO 80202, USA.
Sci Total Environ. 2018 Sep 15;636:1382-1395. doi: 10.1016/j.scitotenv.2018.04.335. Epub 2018 May 5.
D4 (octamethylcyclotetrasiloxane) is a high-production-volume cyclic volatile methyl siloxane with a wide range of industrial and consumer applications. This study conducted a robust ecological risk evaluation for D4 using exposure data collected under a nation-wide environmental monitoring program facilitated under the Toxic Substances Control Act (TSCA). This ecological risk evaluation was conducted consistent with the principles outlined in the U.S. Environmental Protection Agency's (EPA's) Guidance to Assist Interested Persons in Developing and Submitting Draft Risk Evaluations under TSCA (U.S. EPA 2017a). The evaluation examined multiple lines of evidence (LoEs) to determine the potential risks from D4 to aquatic receptors in rivers and streams in the United States from municipal wastewater treatment plant (WWTP) discharges and discharges from manufacturing, processing, and/or formulating (MPF) facilities after onsite wastewater treatment. The LoEs consisted of comparing D4 concentrations measured in water and sediment to toxicity thresholds derived from laboratory studies; comparing D4 concentrations measured in biota tissue to critical target lipid body burdens (CTLBBs); comparing fugacity-based chemical activities between toxicity thresholds and measured environmental concentrations; and assessing benthic macroinvertebrate community structure and habitat suitability. The approach taken moves beyond a standard deterministic hazard quotient approach to incorporate more advanced methods for risk prediction, using distributions rather than conservative point estimates of exposure to obtain a realistic view of the probability of harm, consistent with EPA's stated intent to "strive to utilize probabilistic approaches for exposure assessments included in a risk evaluation" (U.S. EPA 2017b). The risk evaluation concluded there is negligible risk to water column and sediment receptors from D4 discharged from MPF facilities after onsite wastewater treatment or from municipal WWTPs that may treat a mix of industrial and consumer wastewater.
D4（八甲基环四硅氧烷）是一种高产量的环状挥发性甲基硅氧烷，具有广泛的工业和消费应用。本研究使用在《有毒物质控制法》（TSCA）下的全国性环境监测计划收集的暴露数据，对 D4 进行了稳健的生态风险评估。该生态风险评估是根据美国环境保护署（EPA）的《协助有关人员根据 TSCA 制定和提交风险评估草案的指南》（美国 EPA，2017a）中概述的原则进行的。该评估审查了多个证据线（LoE），以确定来自市政污水处理厂（WWTP）排放和经过现场废水处理的制造、加工和/或配方（MPF）设施排放的 D4 对美国河流和溪流中水生受体的潜在风险。证据线包括将水中和沉积物中测量的 D4 浓度与实验室研究得出的毒性阈值进行比较；将生物组织中测量的 D4 浓度与关键目标脂质体负担（CTLBB）进行比较；将基于逸度的化学活性与毒性阈值和测量的环境浓度进行比较；并评估底栖大型无脊椎动物群落结构和栖息地适宜性。所采用的方法超越了标准的确定性危害商方法，采用更先进的风险预测方法，使用分布而不是保守的暴露点估计值，以获得对伤害可能性的现实看法，这与 EPA 的声明意图一致，即“努力利用风险评估中包括的暴露评估的概率方法”（美国 EPA，2017b）。风险评估的结论是，经过现场废水处理的 MPF 设施或可能处理工业和消费废水混合物的市政 WWTP 排放的 D4 对水柱和沉积物受体的风险可以忽略不计。
