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Sci Total Environ. 2014 Jan 1;466-467:586-97. doi: 10.1016/j.scitotenv.2013.07.065. Epub 2013 Aug 15.
Over the last several decades, dioxin releases have decreased >90%, leading to a corresponding decrease in human body burdens. In addition, the weight-of-evidence indicates that soil exposures have little impact on human body burdens of dioxin-like compounds (DLCs), with dietary sources being the greatest contributor. In spite of this, USEPA recently proposed substantially lower preliminary remediation goals (PRGs) for soil based on their new oral reference dose (RfD) for dioxin. As such, it is important to understand how these lower soil PRGs compare to background concentrations in urban/suburban and rural soils. The objective of this evaluation was to conduct a comprehensive review of available data concerning background levels of DLCs in U.S. soils. There was substantial variability in how the soil dioxin data were presented (e.g., raw vs. summary data, congener vs. toxic equivalency [TEQ] concentration, number of DLC congeners reported, etc.). In cases where TEQ estimates were based on outdated TEFs and congener-specific data was provided, TEQ concentrations were recalculated using the current WHO2006 TEFs. The data available for rural soils were generally more robust than for urban/suburban soils. Not surprisingly, background levels of DLCs in urban/suburban soils were higher and more variable than in rural soils: 0.1-186 vs. 0.1-22.9 ng/kg TEQ, respectively. In several cases, incomplete soil DLC data were available (e.g., DL-PCBs not included) and, as such, calculated TEQ concentrations likely underestimate actual background levels. Though the current data are somewhat limited, these findings indicate that background DLC concentrations in urban/suburban soils may exceed the USEPA's updated PRGs based on the oral RfD, and are expected to substantially exceed future PRGs to be developed based on the forthcoming dioxin cancer slope factor. This demonstrates a need to characterize anthropogenic background DLCs in non-rural areas across the US to avoid establishing soil screening levels and PRGs that are lower than background concentrations.
在过去几十年中，二恶英的排放量减少了超过 90%，导致人体负荷相应减少。此外，大量证据表明，土壤暴露对二恶英类化合物（DLCs）的人体负荷影响很小，饮食来源是最大的贡献者。尽管如此，美国环保署（USEPA）最近还是基于其新的二恶英口服参考剂量（RfD），提议大幅降低土壤的初步修复目标（PRG）。因此，了解这些较低的土壤 PRG 与城市/郊区和农村土壤的背景浓度相比如何非常重要。这项评估的目的是全面审查有关美国土壤中二恶英类化合物背景水平的现有数据。土壤中二恶英数据的呈现方式存在很大差异（例如，原始数据与汇总数据、同系物与毒性等效浓度、报告的 DLC 同系物数量等）。在基于过时的毒性等效因子（TEF）估算 TEQ 浓度且提供了同系物特异性数据的情况下，使用当前的世界卫生组织（WHO）2006 年 TEF 重新计算了 TEQ 浓度。农村土壤的数据通常比城市/郊区土壤的数据更可靠。毫不奇怪，城市/郊区土壤中二恶英类化合物的背景水平较高且更具变异性：分别为 0.1-186 和 0.1-22.9ng/kg TEQ。在某些情况下，土壤中二恶英类化合物的数据不完整（例如，未包括 DL-PCBs），因此，计算出的 TEQ 浓度可能低估了实际的背景水平。尽管目前的数据有些有限，但这些发现表明，城市/郊区土壤中二恶英类化合物的背景浓度可能超过美国环保署（USEPA）基于口服 RfD 更新的 PRG，并且预计将大大超过未来基于即将发布的二恶英致癌斜率因子制定的 PRG。这表明需要对美国非农村地区的人为背景 DLC 进行特征描述，以避免制定低于背景浓度的土壤筛选水平和 PRG。
