National Institute for Occupational Safety and Health, Western States Office, Denver, CO, USA.
J Occup Environ Hyg. 2013;10(7):347-56. doi: 10.1080/15459624.2013.788352.
This report describes a previously uncharacterized occupational health hazard: work crew exposures to respirable crystalline silica during hydraulic fracturing. Hydraulic fracturing involves high pressure injection of large volumes of water and sand, and smaller quantities of well treatment chemicals, into a gas or oil well to fracture shale or other rock formations, allowing more efficient recovery of hydrocarbons from a petroleum-bearing reservoir. Crystalline silica ("frac sand") is commonly used as a proppant to hold open cracks and fissures created by hydraulic pressure. Each stage of the process requires hundreds of thousands of pounds of quartz-containing sand; millions of pounds may be needed for all zones of a well. Mechanical handling of frac sand creates respirable crystalline silica dust, a potential exposure hazard for workers. Researchers at the National Institute for Occupational Safety and Health collected 111 personal breathing zone samples at 11 sites in five states to evaluate worker exposures to respirable crystalline silica during hydraulic fracturing. At each of the 11 sites, full-shift samples exceeded occupational health criteria (e.g., the Occupational Safety and Health Administration calculated permissible exposure limit, the NIOSH recommended exposure limit, or the ACGIH threshold limit value), in some cases, by 10 or more times the occupational health criteria. Based on these evaluations, an occupational health hazard was determined to exist for workplace exposures to crystalline silica. Seven points of dust generation were identified, including sand handling machinery and dust generated from the work site itself. Recommendations to control exposures include product substitution (when feasible), engineering controls or modifications to sand handling machinery, administrative controls, and use of personal protective equipment. To our knowledge, this represents the first systematic study of work crew exposures to crystalline silica during hydraulic fracturing. Companies that conduct hydraulic fracturing using silica sand should evaluate their operations to determine the potential for worker exposure to respirable crystalline silica and implement controls as necessary to protect workers.
在水力压裂过程中，工作人员接触可吸入结晶硅尘。水力压裂涉及向天然气或油井中高压注入大量水和沙，以及少量的井处理化学品，以压裂页岩或其他岩层，从而更有效地从含油储层中回收碳氢化合物。结晶硅（“压裂砂”）通常用作支撑剂，以保持水力压裂产生的裂缝和裂隙开放。该过程的每个阶段都需要数十万磅含石英的砂；一个井的所有区域可能需要数百万磅。压裂砂的机械处理会产生可吸入结晶硅尘，这是工人潜在的暴露危害。美国国家职业安全与健康研究所（NIOSH）的研究人员在五个州的 11 个地点收集了 111 个个人呼吸区样本，以评估工人在水力压裂过程中接触可吸入结晶硅尘的情况。在 11 个地点中的每一个，全班样本都超过了职业健康标准（例如，职业安全与健康管理局计算的允许暴露限值、NIOSH 推荐的暴露限值或 ACGIH 阈限值），在某些情况下，超过职业健康标准 10 倍或更多。基于这些评估，确定在工作场所接触结晶硅存在职业健康危害。确定了 7 个粉尘产生点，包括沙处理机械和工作现场本身产生的粉尘。控制暴露的建议包括产品替代（在可行时）、对沙处理机械进行工程控制或修改、行政控制以及使用个人防护设备。据我们所知，这是首次对水力压裂过程中工作人员接触结晶硅的情况进行的系统研究。使用硅砂进行水力压裂的公司应评估其作业，以确定工人接触可吸入结晶硅的潜在风险，并根据需要实施控制措施，以保护工人。
