Pennell Kelly G, Scammell Madeleine Kangsen, McClean Michael D, Ames Jennifer, Weldon Brittany, Friguglietti Leigh, Suuberg Eric M, Shen Rui, Indeglia Paul A, Heiger-Bernays Wendy J
University of Massachusetts-Dartmouth, Civil and Environmental Engineering Department, North Dartmouth MA 02747.
Ground Water Monit Remediat. 2013 Summer;33(3):119-126. doi: 10.1111/gwmr.12021.
The United States Environmental Protection Agency (USEPA) is finalizing its vapor intrusion guidelines. One of the important issues related to vapor intrusion is background concentrations of volatile organic chemicals (VOCs) in indoor air, typically attributed to consumer products and building materials. Background concentrations can exist even in the absence of vapor intrusion and are an important consideration when conducting site assessments. In addition, the development of accurate conceptual models that depict pathways for vapor entry into buildings is important during vapor intrusion site assessments. Sewer gas, either as a contributor to background concentrations or as part of the site conceptual model, is not routinely evaluated during vapor intrusion site assessments. The research described herein identifies an instance where vapors emanating directly from a sanitary sewer pipe within a residence were determined to be a source of tetrachloroethylene (PCE) detected in indoor air. Concentrations of PCE in the bathroom range from 2.1 to 190 ug/m and exceed typical indoor air concentrations by orders of magnitude resulting in human health risk classified as an "Imminent Hazard" condition. The results suggest that infiltration of sewer gas resulted in PCE concentrations in indoor air that were nearly two-orders of magnitude higher as compared to when infiltration of sewer gas was not known to be occurring. This previously understudied pathway whereby sewers serve as sources of PCE (and potentially other VOC) vapors is highlighted. Implications for vapor intrusion investigations are also discussed.
美国环境保护局（USEPA）正在敲定其蒸气侵入指南。与蒸气侵入相关的一个重要问题是室内空气中挥发性有机化合物（VOCs）的背景浓度，通常归因于消费品和建筑材料。即使在没有蒸气侵入的情况下，背景浓度也可能存在，并且在进行场地评估时是一个重要的考虑因素。此外，在蒸气侵入场地评估期间，建立准确的概念模型以描述蒸气进入建筑物的途径非常重要。在蒸气侵入场地评估中，通常不会对下水道气体进行评估，无论是作为背景浓度的贡献者还是作为场地概念模型的一部分。本文所述的研究确定了一个实例，即住宅内卫生下水道管道直接散发的蒸气被确定为室内空气中检测到的四氯乙烯（PCE）的来源。浴室中PCE的浓度范围为2.1至190微克/立方米，比典型的室内空气浓度高出几个数量级，导致人类健康风险被归类为“紧迫危险”状况。结果表明，与不知道发生下水道气体渗入时相比，下水道气体的渗入导致室内空气中PCE浓度高出近两个数量级。突出了这条以前研究较少的途径，即下水道作为PCE（以及潜在的其他VOC）蒸气的来源。还讨论了对蒸气侵入调查的影响。
