CAEE Department, College of Engineering, Drexel University, 3141 Chestnut St., Philadelphia, PA 19104, USA.
Int J Environ Res Public Health. 2018 Apr 11;15(4):727. doi: 10.3390/ijerph15040727.
Identifying sources of concern and risk from shale gas development, particularly from the hydraulic fracturing process, is an important step in better understanding sources of uncertainty within the industry. In this study, a risk assessment of residential exposure pathways to contaminated drinking water is carried out. In this model, it is assumed that a drinking water source is contaminated by a spill of flowback water; probability distributions of spill size and constituent concentrations are fit to historical datasets and Monte Carlo simulation was used to calculate a distribution of risk values for two scenarios: (1) use of a contaminated reservoir for residential drinking water supply and (2) swimming in a contaminated pond. The swimming scenario did not produce risks of concern from a single exposure of 1 h duration, but 11 such 1-h exposures did produce risks of 10 due to radionuclide exposure. The drinking water scenario over a 30-year exposure duration produced cancer risk values exceeding 10 for arsenic, benzene, benzo(a)pyrene, heptachlor, heptachlor epoxide, pentachlorophenol, and vinyl chloride. However, this extended exposure duration is probably not realistic for exposure by a spill event. Radionuclides produced risks in the residential drinking water scenario of 10 in just 8 h, a much more realistic timeline for continual exposure due to a spill event. In general, for contaminants for which inhalation exposure was applicable, this pathway produced the highest risks with exposure from ingestion posing the next greatest risk to human health followed by dermal absorption (or body emersion for radionuclides). Considering non-carcinogenic effects, only barium and thallium exceed target limits, where the ingestion pathway seems to be of greater concern than dermal exposure. Exposure to radionuclides in flowback water, particularly through the inhalation route, poses a greater threat to human health than other contaminants examined in this assessment and should be the focus of risk assessment and risk mitigation efforts.
识别页岩气开发（尤其是水力压裂过程）带来的关切和风险源，是更好地了解该行业不确定性来源的重要步骤。在本研究中，对受污染饮用水的住宅暴露途径进行了风险评估。在该模型中，假设饮用水源受到回流水泄漏的污染；泄漏规模和成分浓度的概率分布拟合历史数据集，并使用蒙特卡罗模拟计算了两种情况下的风险值分布：（1）使用受污染的水库作为住宅饮用水供应，（2）在受污染的池塘中游泳。游泳场景在单次 1 小时暴露的情况下不会产生令人担忧的风险，但 11 次这样的 1 小时暴露会因放射性核素暴露而产生 10 的风险。在 30 年的暴露时间内，饮用水情景下的砷、苯、苯并(a)芘、七氯、七氯环氧化物、五氯苯酚和氯乙烯的致癌风险值超过 10。然而，这种延长的暴露时间对于因泄漏事件而产生的暴露可能不太现实。放射性核素在住宅饮用水情景下仅 8 小时就产生了 10 的风险，这对于因泄漏事件而持续暴露来说是一个更现实的时间线。一般来说，对于可吸入暴露的污染物，这种途径产生的风险最高，其次是经口摄入对人类健康的风险最大，其次是皮肤吸收（或放射性核素的身体浸入）。考虑到非致癌效应，只有钡和铊超过目标限值，其中经口摄入途径似乎比皮肤暴露更令人担忧。回流水中放射性核素的暴露，特别是通过吸入途径，对人类健康构成的威胁大于本评估中检查的其他污染物，应成为风险评估和风险缓解努力的重点。
