Project 5 - Bioavailability as a Central Concept in Determining Remediation Goals and Strategies for PCDD/F-Contaminated Superfund Sites

由于其极低的水溶性，多氯二苯并二恶英和呋喃(PCDD/FS) 强烈和广泛地结合在沉积物和土壤的固体颗粒上，尤其是类木炭的热源 碳质物质(PCM，[1])、无定形有机物(AOM)和粘土矿物。美国 美国环境保护局(USEPA)保守地假设，100%与土壤结合的PCDD/F是 哺乳动物，包括人类的生物可利用性[2]，而在真实土壤中测量的二恶英和二恶英的生物利用度远远不够。 下部[3-13]。哺乳动物的真实生物利用度知之甚少，但我们最近推动了这项科学的发展 通过将土壤中PCDD/F的生物有效性与单个颗粒类型的属性相关联：我们已经展示了 与AOM、粘土矿物或多孔二氧化硅颗粒结合的PCDDs确实是100%生物可利用的 (相对于玉米油)[14-18]。相反，我们展示了PCDs与一种特殊的PCM结合，称为 活性碳(AC)对小鼠[19，20]的生物利用度为零，保护了哺乳动物的健康。我们最近 工作提供了两个假设，为多氯二苯并二恶英/氟污染的风险评估和补救战略提供信息 地点：1)低水平的PCM普遍存在于土壤和沉积物中，因此PCM中的AC样结构域可能是 对降低真实土壤中PCDD/FS在哺乳动物中的生物利用度负责，以及2)我们对 土壤颗粒类型充分简化了土壤的复杂性，以至于我们可以直接和机械地测试 AC对二恶英/氟污染土壤的改良有可能通过以下方式保护人类和生态系统的健康 将哺乳动物的生物利用度降至最低。很久以前就提出了使用AC修正案的补救措施，因为它是 比将受污染的土壤移至危险废物填埋场要便宜得多，对环境的破坏也小得多， 但监管机构不能将空调作为一种补救措施，因为没有人证明空调修正案真正具有保护作用 对哺乳动物和人类健康的影响。我们提出了一系列旨在严格检验这一假说的实验 与AC修正案绑定的多氯二苯并二恶英不再对哺乳动物有生物利用价值，因此有助于美国环保局和 州监管机构严格评估了这一有望修复受PCDD/F污染的超级基金的方法 现场：添加AC后，我们将跟踪土壤中PCDDs的全部质量平衡，然后对其进行管理 给小鼠灌胃土壤，并测量小鼠体内的二恶英生物利用度和质量平衡。第一次，我们将 直接测量多氯二苯并二恶英在AC改进剂中的累积动力学并与测量结果进行比较 土壤动力学-多氯二苯并二恶英哺乳动物的生物利用度。这项工作将通过提供以下六项数据来为风险评估提供信息 环保局使用[21]来选择超级基金补救措施的实用标准，包括是否有可能修改AC 为了保护人类和生态系统的健康，它们的短期生物利用度降低的动力学，以及较长时间的- PCDD-AC络合物形成后的项稳定性。总而言之，项目5将与 中心将把AC修正案作为监管决策的实验基础转化为潜力 多氯二苯并二恶英/氟污染超级基金场地的低成本补救处理。

Due to their exceptionally low water solubilities, polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) are strongly and extensively bound to the solid particles of sediments and soils, especially charcoal-like pyrogenic carbonaceous matter (PCM, [1]), amorphous organic matter (AOM), and clay minerals. The United States Environmental Protection Agency (USEPA) conservatively assumes that 100% of soil-bound PCDD/Fs are bioavailable to mammals, including humans [2], while measured bioavailabilities of PCDD/Fs in real soils are far lower [3-13]. Real mammalian bioavailabilities are poorly understood, but we have recently advanced the science of PCDD/F bioavailability from soils by relating it to the properties of individual particle types: We have shown that PCDDs that are bound to AOM, clay minerals, or porous-silica particles are indeed 100% bioavailable (relative to those in corn oil) [14-18]. In contrast, we showed that PCDDs bound to a special kind of PCM called activated carbon (AC) had bioavailabilities of zero to mice [19, 20] and protected mammalian health. Our recent work provides two hypotheses to inform risk assessment and remediation strategies for PCDD/F-contaminated sites: 1) Low levels of PCM are ubiquitous in soils and sediments, so AC-like domains in PCM may be responsible for lowering the mammalian bioavailabilities of PCDD/Fs in real soils, and 2) Our understanding of soil particle types simplifies the complexity of soils enough that we can directly and mechanistically test whether AC amendment of PCDD/F-contaminated soils has potential to be protective of human and ecosystem health by minimizing mammalian bioavailability. Remediation using AC amendment was proposed long ago, because it is far cheaper and less environmentally disruptive than removing contaminated soils to hazardous-waste landfills, but regulators cannot adopt AC as a remedy because no one has shown that AC amendments are truly protective of mammalian and human health. We propose a set of experiments designed to rigorously test the hypothesis that PCDDs bound to AC amendments are no longer bioavailable to mammals, and thereby help USEPA and state regulators critically assess this promising treatment for remediation of PCDD/F-contaminated Superfund sites: We will track the full mass balance of PCDDs in soils after AC has been added, and then administer these soils orally to mice and measure PCDD bioavailability and mass balance in the mice. For the first time, we will directly measure the kinetics of PCDD accumulation in AC amendments and compare these with measured kinetics of soil-PCDD mammalian bioavailability. This work will inform risk assessment by supplying data for six practical criteria that EPA uses [21] to select Superfund remedies, including whether AC amendments are likely to protect human and ecosystem health, the kinetics of their short-term bioavailability reduction, and the longer- term stabilities of PCDD-AC complexes once they form. In sum, Project 5 will collaborate with the rest of the Center to transform the experimental basis for regulatory decision-making about AC amendment as a potential low-cost remediation treatment for PCDD/F-contaminated Superfund sites.