The use of hydraulic fracturing (HF) to extract oil and natural gas has increased, along with intensive discussions on the associated risks to human health. Three technical processes should be differentiated when evaluating human health risks, namely (1) drilling of the borehole, (2) hydraulic stimulation, and (3) gas or oil production. During the drilling phase, emissions such as NOx, NMVOCs (non-methane volatile organic compounds) as precursors for tropospheric ozone formation, and SOx have been shown to be higher compared to the subsequent phases. In relation to hydraulic stimulation, the toxicity of frac fluids is of relevance. More than 1100 compounds have been identified as components. A trend is to use fewer, less hazardous and more biodegradable substances; however, the use of hydrocarbons, such as kerosene and diesel, is still allowed in the USA. Methane in drinking water is of low toxicological relevance but may indicate inadequate integrity of the gas well. There is a great concern regarding the contamination of ground- and surface water during the production phase. Water that flows to the surface from oil and gas wells, so-called 'produced water', represents a mixture of flow-back, the injected frac fluid returning to the surface, and the reservoir water present in natural oil and gas deposits. Among numerous hazardous compounds, produced water may contain bromide, arsenic, strontium, mercury, barium, radioactive isotopes and organic compounds, particularly benzene, toluene, ethylbenzene and xylenes (BTEX). The sewage outflow, even from specialized treatment plants, may still contain critical concentrations of barium, strontium and arsenic. Evidence suggests that the quality of groundwater and surface water may be compromised by disposal of produced water. Particularly critical is the use of produced water for watering of agricultural areas, where persistent compounds may accumulate. Air contamination can occur as a result of several HF-associated activities. In addition to BTEX, 20 HF-associated air contaminants are group 1A or 1B carcinogens according to the IARC. In the U.S., oil and gas production (including conventional production) represents the second largest source of anthropogenic methane emissions. High-quality epidemiological studies are required, especially in light of recent observations of an association between childhood leukemia and multiple myeloma in the neighborhood of oil and gas production sites. In conclusion, (1) strong evidence supports the conclusion that frac fluids can lead to local environmental contamination; (2) while changes in the chemical composition of soil, water and air are likely to occur, the increased levels are still often below threshold values for safety; (3) point source pollution due to poor maintenance of wells and pipelines can be monitored and remedied; (4) risk assessment should be based on both hazard and exposure evaluation; (5) while the concentrations of frac fluid chemicals are low, some are known carcinogens; therefore, thorough, well-designed studies are needed to assess the risk to human health with high certainty; (6) HF can represent a health risk via long-lasting contamination of soil and water, when strict safety measures are not rigorously applied.

中文翻译：

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对天然气和石油生产中水力压裂造成的人类健康风险进行严格评估。

使用水力压裂（HF）来开采石油和天然气的情况有所增加，同时人们也对与人类健康相关的风险进行了深入的讨论。在评估人类健康风险时，应区分三种技术流程，即（1）钻孔，（2）水力增产，以及（3）天然气或石油生产。在钻探阶段，与后续阶段相比，NOx、作为对流层臭氧形成前体的 NMVOC（非甲烷挥发性有机化合物）和 SOx 等排放量较高。就水力增产而言，压裂液的毒性是相关的。超过 1100 种化合物已被鉴定为成分。趋势是使用更少、危害更小且更可生物降解的物质；然而，美国仍然允许使用煤油和柴油等碳氢化合物。饮用水中的甲烷毒理学相关性较低，但可能表明气井完整性不足。人们非常担心生产阶段地下水和地表水的污染。从油气井流到地表的水，即所谓的“采出水”，是回流水、返回地表的注入压裂液和天然油气沉积物中存在的储层水的混合物。在众多有害化合物中，采出水可能含有溴化物、砷、锶、汞、钡、放射性同位素和有机化合物，特别是苯、甲苯、乙苯和二甲苯 (BTEX)。即使从专门的处理厂流出的污水，仍可能含有临界浓度的钡、锶和砷。有证据表明，地下水和地表水的质量可能会因采出水的处理而受到损害。特别重要的是使用采出水浇灌农业地区，因为持久性化合物可能在农业地区积聚。一些与氢氟酸相关的活动可能会导致空气污染。根据 IARC，除了 BTEX 之外，还有 20 种与 HF 相关的空气污染物属于 1A 或 1B 类致癌物。在美国，石油和天然气生产（包括常规生产）是人为甲烷排放的第二大来源。需要进行高质量的流行病学研究，特别是考虑到最近观察到石油和天然气生产场所附近的儿童白血病与多发性骨髓瘤之间存在关联。综上所述，（1）有力的证据支持压裂液会导致局部环境污染的结论；(2) 当土壤、水和空气的化学成分可能发生变化时，增加的水平通常仍低于安全阈值；（3）由于井、管道维护不善造成的点源污染能够得到监测和治理；(4) 风险评估应基于危害和暴露评估；(5) 虽然压裂液化学物质的浓度较低，但有些化学物质是已知的致癌物质；因此，需要进行彻底、精心设计的研究，以高度确定地评估对人类健康的风险；(6) 如果不严格采取严格的安全措施，HF 可能会通过对土壤和水的长期污染而带来健康风险。