Worker Exposure to Silica During Hydraulic Fracturing

OSHA•NIOSH

Worker Exposure to Silica during Hydraulic Fracturing The National Institute for Occupational Safety and Health (NIOSH) identified exposure to airborne silica as a health hazard to workers conducting some hydraulic fracturing operations during recent field studies.

Introduction Hydraulic fracturing or “fracking” is a process used to “stimulate” well production in the oil and gas industry. It is not a new process, but its use has increased significantly in the last 10 years because

Photo credit: NIOSH of new horizontal drilling and multi-stage fracking (or “completions”) technologies that improve access to natural gas and oil deposits. It involves pumping large volumes of water and sand into a well at high pressure to fracture shale and other tight formations, allowing oil and gas to flow into the well. Silica dust cloud by worker delivering sand from sand mover to transfer belt. NIOSH’s recent field studies show that workers may be exposed to dust with high levels of respirable OSHA and NIOSH have been investigating worker crystalline silica (called “silica” in this Hazard Alert) safety and health hazards in oil and gas extraction, during hydraulic fracturing. including chemical exposures during hydraulic fracturing operations. This Hazard Alert discusses the health hazards OSHA has jurisdiction over the safety and health of associated with hydraulic fracturing and focuses on workers, including workers involved in upstream oil worker exposures to silica in the air. It covers the and gas operations. The General Duty Clause of the health effects of breathing silica, recommends ways Occupational Safety and Health (OSH) Act and OSHA’s to protect workers, and describes how OSHA and General Industry Standards (29 CFR 1910) apply to NIOSH can help. Workers and employers need to be the upstream industry. As part of the enforcement of these regulations, five OSHA regions located in areas of aware of the hazard that silica dust poses. Employers significant upstream activities use national, regional, and must ensure that workers are properly protected from local emphasis programs to inspect oilfield worksites, exposure to silica. This Hazard Alert also provides a including those that may have ongoing hydraulic fracturing brief summary of other health and safety hazards to operations. workers conducting hydraulic fracturing activities. NIOSH made safety and health in the oil and gas extraction industry a priority focus area in 2005 by Crystalline silica is a common mineral found in the creating the National Occupational Research Agenda earth's crust. It occurs primarily as quartz and is a major (NORA) Oil and Gas Extraction Council, which includes component of the sand, clay and stone materials used OSHA and industry leaders in a cooperative effort to to make every day products such as concrete, brick and address occupational safety and health issues. To glass. address an existing lack of information on occupational dust and chemical exposures associated with hydraulic Respirable crystalline silica is the portion of crystalline fracturing, NIOSH established specific industry silica that is small enough to enter the gas-exchange partnerships and initiated the NIOSH Field Effort to regions of the lungs if inhaled; this includes particles Assess Chemical Exposures to Oil and Gas Extraction with aerodynamic diameters less than approximately 10 Workers (http://www.cdc.gov/niosh/docs/2010-130/ micrometers (μm). pdfs/2010-130.pdf). Exposure to silica during hydraulic fracturing has been the focus of the NIOSH study to date.

Why is silica a concern for workers during • Dust released from the transfer belt under the sand hydraulic fracturing? movers. Recent NIOSH field studies identified overexposure • Dust created as sand drops into, or is agitated in, to airborne silica as a health hazard to workers. the blender hopper and on transfer belts. • Dust released from operations of transfer belts Large quantities of silica sand are used during between the sand mover and the blender; and hydraulic fracturing. Sand is delivered via truck • Dust released from the top of the end of the sand and then loaded into sand movers, where it is transfer belt (dragon’s tail) on sand movers. subsequently transferred via conveyer belt and blended with other hydraulic fracturing fluids prior to high pressure injection into the drilling hole. Transporting, moving, and refilling silica sand into and through sand movers, along transfer belts, and into blender hoppers can release dusts containing silica into the air. Workers can be exposed if they breathe the dust into their lungs. NIOSH identified seven primary sources of silica dust

Photo credit: NIOSH exposure during hydraulic fracturing operations: • Dust ejected from thief hatches (access ports) on top of the sand movers during refilling operations while the machines are running (hot loading). • Dust ejected and pulsed through open side fill ports on the sand movers during refilling operations. Silica dust clouds from delivery trucks loading into sand • Dust generated by on-site vehicle traffic. movers.

An Overview of the "Fracking" Process The process known as "fracking" has long been used to extract oil from depleted wells. It is now widely used across the country to tap previously unreachable oil and natural gas locked within deep rock formations.

Graphic: Doug Stevens

Copyright 2012, Los Angeles Times.

Reprinted with permission.

Fracturing fluid is made up of a base fluid, proppant, and chemical additives. Water accounts for about 90 percent of the fracturing mixture and sand accounts for about 9.5 percent. Chemicals account for the remaining one half of one percent of the mixture. The base fluid applies pressure to the formation and delivers the proppant to the fractures. The base fluid is usually water, but can include methanol, liquid carbon dioxide, and liquefied petroleum gas. Proppant consists of particles that hold open the fractures created by hydraulic fracturing, allowing the oil and gas to flow out of the formation and into the well bore. Silica sand is frequently used as a proppant. Other proppants can include sintered bauxite or ceramics, and resin-coated sand. Chemical additives include friction reducers, scale inhibitors, solvents, acids, gelling agents, and biocides that are added to protect equipment, reduce pumping requirements, and maintain the integrity of the oil or gas formation.

NIOSH Findings on Worker The OSHA general industry PEL for quartz, the Exposures to Silica common form of crystalline silica found in sand, is an In cooperation with oil and gas industry partners, NIOSH 8-hour time-weighted average exposure to respirable collected 116 full shift air samples at 11 hydraulic dust calculated using the following formula: fracturing sites in five states (Arkansas, Colorado, North Dakota, Pennsylvania and Texas) to determine the 10 PEL = levels of worker exposure to silica at various jobs at the (% Silica) + 2 worksites. Many air samples showed silica levels for workers in and around the dust generation points above The PEL is approximately equal to 0.1 mg/m3 for pure defined occupational exposure limits.1 quartz silica.

Of the 116 samples collected: The PEL is outlined in 29 CFR 1910.1000 Table Z-3. If other forms of crystalline silica are present, the PEL • 47% showed silica exposures greater than the calculation must be modified as per Table Z-3. calculated OSHA PEL. The NIOSH REL is a fixed value of 0.05 mg/m3. • 79% showed silica exposures greater than the NIOSH REL of 0.05 milligrams per cubic meter (mg/m3). Worker and area samples collected in enclosed but non-filtered cab vehicles (e.g., chemical and blender • 9% of all samples showed silica exposures 10 or trucks) were above the REL, even when spending more times the PEL, with one sample more than most of the day in the cab. Worker and area samples 25 times the PEL. collected in enclosed vehicles with air conditioning • 31% of all samples showed silica exposures 10 or and filtration (e.g., data vans) had silica exposures more times the REL, with one sample more than below the NIOSH REL. 100 times the REL. Health Hazards of Silica Determining worker exposure levels is important Hydraulic fracturing sand contains up to 99% silica. for selecting the right type of control measures, Breathing silica can cause silicosis. Silicosis is a including engineering controls and respiratory lung disease where lung tissue around trapped silica protection. For example, half-face respirators are not protective for silica levels over 10 times the exposure limit. What are the symptoms of silicosis?

NIOSH found that sand Silicosis is classified into three types: chronic/classic, mover and blender accelerated, and acute. operators, and workers Chronic/classic silicosis, the most common type, downwind of these occurs after 10-20 years of moderate to low exposures operations (especially to respirable crystalline silica. Symptoms associated during hot loading), with chronic silicosis may or may not be obvious; had the highest silica therefore, workers need to have a chest X-ray to exposures. Workers determine if there is lung damage. As the disease

Photo credit: NIOSH upwind and not in the progresses, the worker may experience shortness of immediate area of sand breath when exercising and have clinical signs of poor movers (sand delivery oxygen/carbon dioxide exchange. In the later stages, truck spotters) also had the worker may experience fatigue, extreme shortness exposures above the of breath, cough, and, in some cases, respiratory NIOSH REL, possibly failure. Silica dust by worker conducting from the dust created sand transfer operations. Photo Accelerated silicosis can occur after 5-10 years of by traffic at the well site. shows sand mover and transfer high exposures to respirable crystalline silica. It is system. similar to chronic silicosis, but progresses more rapidly. 1 Employers are required to take actions to reduce worker Acute silicosis occurs after only a few months or a few exposures if air samples show levels above OSHA’s calculated years following exposures to extremely high levels of Permissible Exposure Limit (PEL). The OSHA PEL is the respirable crystalline silica. Symptoms of acute silicosis legally enforceable regulatory limit. The NIOSH Recommended Exposure Limit (REL) is a non-mandatory, recommended include rapidly progressive and severe shortness of occupational exposure limit. However, because OSHA recognizes breath, weakness, and weight loss. Though much less that many of its PELs are outdated and inadequate measures of common than other forms of silicosis, acute silicosis worker safety, both OSHA and NIOSH recommend that employers nearly always leads to disability and death. take actions to keep worker exposures below the NIOSH REL.

particles reacts, causing inflammation and scarring Monitor the air to determine worker exposures and reducing the lungs’ ability to take in oxygen.2 to silica Workers who breathe silica day after day are at greater • Collect respirable dust samples to determine risk of developing silicosis. Silica can also cause lung which jobs expose workers to silica above exposure cancer and has been linked to other diseases, such as limits. Employers should consult with a trained tuberculosis, chronic obstructive pulmonary disease, occupational safety and health professional, such and kidney and autoimmune disease.3 as a certified industrial hygienist, or contact OSHA’s free on-site consultation service. What can be done at hydraulic fracturing worksites to protect workers • If air samples show levels above OSHA’s calculated from exposure to silica? PEL, employers are required to take actions to reduce worker exposures. However, both OSHA and NIOSH Under the Occupational Safety and Health Act of 1970, recommend that employers take the actions below employers are responsible for providing safe and to keep worker exposures below the NIOSH REL. healthy working conditions for their workers. Employers must determine which jobs expose workers to silica Control dust exposures by improving existing and take actions to control overexposures and protect engineering controls and safe work practices workers. A combination of engineering controls, work Engineering controls and work practices provide the practice, protective equipment, and product substitution best protection for workers and must be implemented where feasible, along with worker training, is needed first, before respiratory protection is used. Working with to protect workers who are exposed to silica during industry partners, NIOSH has identified the following hydraulic fracturing operations. control options for hydraulic fracturing operations: Short-term work practice and procedural changes Several OSHA standards and directives cover that can be implemented quickly: operations that may expose workers to silica, • Mandate the capping of unused fill ports (e.g., including: cam lock caps) on sand movers. Securing • Air Contaminants (29 CFR 1910.1000) unused fill ports can help reduce the dust released, • Hazard Communication (29 CFR 1910.1200) especially during filling.

• Respiratory Protection (29 CFR 1910.134) • Reduce the drop height between the sand transfer belt and T-belts and blender hoppers. OSHA’s Directive CPL 03-00-007, titled National Limiting the distance that sand falls through the air Emphasis Program – Crystalline Silica, has detailed can help reduce dust. information on silica hazards, guidelines for air sampling, guidance on calculating PELs for dust • Limit the number of workers, and the time containing silica, and other compliance information. workers must spend in areas where dust and silica levels may be elevated, and consider ways to perform dusty operations remotely to completely One way to reduce silica exposure is to use alternative remove employees from these areas. proppants (e.g., sintered bauxite, ceramics, resin- • Apply fresh water to roads and around the well coated sand) where feasible. However, before using site to reduce the dust. other proppants, it is important to evaluate the health hazards associated with them. If safe proppant Practices that involve equipment changes: alternatives are not feasible, then employers should • Enclose points where dust is released. Install monitor worker exposures, take measures to prevent thick plastic stilling or staging curtains around the exposures to silica, and inform workers of hazards, as bottom sides of the sand movers to limit dusts described below. released from belt operation. Enclosures can also be added along and at the ends of the sand transfer 2 NIOSH [1986]. Occupational respiratory diseases. Cincinnati, belt. OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute • Where possible, use enclosed cabs or booths. for Occupational Safety and Health, DHHS (NIOSH) Publication Consider configuring operator cabs and booths with No. 86-102. HEPA filtration and climate controls to further protect 3 NIOSH [2002] Hazard Review, Health Effects of Occupational workers. Exposure to Respirable Crystalline Silica. Cincinnati, OH: U.S. • Use local exhaust ventilation to collect silica- Department of Health and Human Services, Public Health containing dusts and prevent dust escape. Install Service, Centers for Disease Control, National Institute for dust collection systems onto machines or equipment Occupational Safety and Health, DHHS (NIOSH) Publication No. 2002-129. that can release dust.

Provide respiratory protection when it is needed to protect workers

Image credit: Frac Sand Dust Control LLC When engineering and work practice controls are not feasible, while they are being implemented, or when they do not reduce silica levels below OSHA PELs, employers must provide workers with respirators. Whenever respirators are used, the employer must have a respiratory protection program that meets the requirements of OSHA’s Respiratory Protection standard (29 CFR 1910.134). This program must include proper respirator selection, fit testing, medical evaluations, and training. • If respirators are A conceptual example of dust control technologies provided, use at least being used by industry. a NIOSH-approved N95 respirator. If the silica level is more than 10 times the PEL, a half-face respirator is not protective and a respirator that offers a greater level of

Image credit: NOV Appco protection (e.g., a full-facepiece respirator, which will NIOSH-approved N95 filtering protect workers at facepiece (top) and elastomeric silica levels up to 50 (bottom) half-face respirators times the PEL) must can be used only if silica be used. Full-face concentrations are less than 10 A conceptual example of a baghouse assembly on the back of a truck. powered air-purifying times the PEL. respirators (PAPR) provide more protection than half-face air-purifying • Replace transfer belts with screw augers on respirators. In general, workers find PAPRs to be sand movers in new designs or retrofits. Dust more comfortable. can be released from the sand moving belt under the sand movers from the actions of belt movement For more information, see OSHA’s Safety and Health or vibration. Moving sand through an auger system Topics page and eTool on respiratory protection. rather than a belt will help contain the sand and reduce dust release. Provide training and information to workers about the hazards of silica and other chemicals OSHA’s Hazard Communication standard requires that employers provide their workers with training and information about hazardous chemicals used in the workplace. Employers must provide training and information to workers in a manner and language that the worker understands. Employers must: • Prepare and implement a written hazard communication program.

Image credit: NIOSH • Provide training and information on the hazards of silica and other chemicals used in the workplace. • Provide workers access to Safety Data Sheets (SDSs) on silica sand and other hazardous chemicals they are exposed to during hydraulic fracturing operations. A conceptual example of a screw auger retrofit assembly.

• Being struck by high-pressure lines or unexpected OSHA recently revised the Hazard Communication release of pressure (for example, mismatched or standard to conform with the Globally Harmonized worn hammer unions, line failure). System of Classification and Labeling of Chemicals (GHS). "Material Safety Data Sheets" (MSDSs) are now • Fires or explosions from flowback fluids containing referred to as SDSs, and the information on SDSs will ignitable materials (e.g., methane) and other be presented in the standard 16 section format. Refer to flammable materials stored or used at the well site. OSHA's Hazard Communications webpage to get more • Working in confined spaces, such as sand storage information. trailers, frac tanks, and sand movers without taking the required precautions. Consider medical monitoring for workers who See OSHA’s Oil and Gas Well Drilling and Servicing are exposed to silica eTool website (http://www.osha.gov/SLTC/etools/ As part of its National Emphasis Program on Silica, oilandgas/index.html) for more information on safety OSHA recommends that employers medically monitor and health hazards at oil and gas extraction sites. all workers who may be exposed to silica dust levels at or above one-half the PEL. Recommended medical How Can OSHA and NIOSH Help? tests include: OSHA has compliance assistance specialists throughout the nation who can provide information • A