Occupational Exposures to Respirable Crystalline Silica During Hydraulic Fracturing

Abstract

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.

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“…NGD is an industrial process resulting in potential worker and community exposure to multiple environmental stressors (Esswein et al 2013;King 2012;Witter et al 2013). Diesel-powered heavy equipment is used for worksite development as well as transporting large volumes of water, sand, and chemicals to sites and for waste removal (Witter et al 2013).…”

Modelling the health risks of exposure to respirable crystalline silica from hydraulic fracturing operations in the USA shale plays

“…Occurrence of elevated RCS dust exposure during hydraulic fracturing processes was previously determined [14] . Within the field workers, the T-Belt and Sand Mover Operators have the relative highest exposures to RCS based on the adjusted 8-hr TWA calculated following the OSHA PEL guidelines.…”

“…[14] . workers in pl handled by 4-6 ubsequently co nstant commun nto the wellbo eld workers, an ift for each we Administration th detectable qu e PEL in this st more than the standards, whi and Scala dail et al [14] Figure 4 ased on OSHA [37] ion 1) for expo r both the expo everity values EL data [14] [38] and was used to very times (1) 0-hr work m Esswein The adjusted OSHA PEL exposure and severity value (Adapted from Esswein et al [14] ) The highest median occupational exposures of RCS after the adjustment to the standard 8-hr TWA, were the (L) Sand Mover and (M) T-belt Operators, with median exposures of 27.43 mg/m and 32.62 mg/m respectively, which is consistent with the NIOSH study [14] .…”

“…y passed down ped into the for uids required fo s ≈ 6% in tota ure 2) [13] . [14] There are c 1,000,000 petroleum workers, 90 gas extract responsibil Occupation exposed to approximat December lesser expo…”

Shale gas development in Canada: What are the potential health effects?

“…The fluid used often contains about 15% sand, and excessive exposure of workers to silica has been documented. 5 About 1%-2% of fracking fluid is a mixture of six or more chemicals (Table 1). More than 500 different fracking chemicals are known, some of which are endocrine disrupters.…”