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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 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.
NIOSH's recent field studies show that workers may be exposed to dust with high levels of respirable crystalline silica (called "silica" in this Hazard Alert) during hydraulic fracturing.
This Hazard Alert discusses the health hazards associated with hydraulic fracturing and focuses on worker exposures to silica in the air. It covers the health effects of breathing silica, recommends ways to protect workers, and describes how OSHA and NIOSH can help. Workers and employers need to be aware of the hazard that silica dust poses. Employers must ensure that workers are properly protected from exposure to silica. This Hazard Alert also provides a brief summary of other health and safety hazards to workers conducting hydraulic fracturing activities.
Why is silica a concern for workers during hydraulic fracturing?
Recent NIOSH field studies identified overexposure to airborne silica as a health hazard to workers.
Large quantities of silica sand are used during hydraulic fracturing. Sand is delivered via truck and then loaded into sand movers, where it is 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 exposure during hydraulic fracturing operations:
An Overview of the "Fracking" Process
NIOSH Findings on Worker Exposures to Silica
In cooperation with oil and gas industry partners, NIOSH collected 116 full shift air samples at 11 hydraulic fracturing sites in five states (Arkansas, Colorado, North Dakota, Pennsylvania, and Texas) to determine the levels of worker exposure to silica at various jobs at the worksites. Many air samples showed silica levels for workers in and around the dust generation points above defined occupational exposure limits.i
Of the 116 samples collected:
Determining worker exposure levels is important for selecting the right type of control measures, including engineering controls and respiratory protection. For example, half-face respirators are not protective for silica levels over 10 times the exposure limit.
NIOSH found that sand mover and blender operators, and workers downwind of these operations (especially during hot loading), had the highest silica exposures. Workers upwind and not in the immediate area of sand movers (sand delivery truck spotters) also had exposures above the NIOSH REL, possibly from the dust created by traffic at the well site. Worker and area samples collected in enclosed but non-filtered cab vehicles (e.g., chemical and blender trucks) were above the REL, even when spending most of the day in the cab. Worker and area samples collected in enclosed vehicles with air conditioning and filtration (e.g., data vans) had silica exposures below the NIOSH REL.
i Employers are required to take actions to reduce worker exposures if air samples show levels above OSHA’s calculated Permissible Exposure Limit (PEL). The OSHA PEL is the legally enforceable regulatory limit. The NIOSH Recommended Exposure Limit (REL) is a non-mandatory, recommended occupational exposure limit. However, because OSHA recognizes that many of its PELs are outdated and inadequate measures of worker safety, both OSHA and NIOSH recommend that employers take actions to keep worker exposures below the NIOSH REL.
Health Hazards of Silica
Hydraulic fracturing sand contains up to 99% silica. Breathing silica can cause silicosis. Silicosis is a lung disease where lung tissue around trapped silica particles reacts, causing inflammation and scarring and reducing the lungs' ability to take in oxygen.ii Workers who breathe silica day after day are at greater risk of developing silicosis. Silica can also cause lung cancer and has been linked to other diseases, such as tuberculosis, chronic obstructive pulmonary disease, and kidney and autoimmune disease.iii
ii NIOSH  Occupational respiratory diseases. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 86-102.
iii NIOSH  Hazard Review, Health Effects of Occupational Exposure to Respirable Crystalline Silica. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2002-129.
What are the symptoms of silicosis?
What can be done at hydraulic fracturing worksites to protect workers from exposure to silica?
Under the Occupational Safety and Health Act of 1970, employers are responsible for providing safe and healthy working conditions for their workers. Employers must determine which jobs expose workers to silica and take actions to control overexposures and protect workers. A combination of engineering controls, work practice, protective equipment, and product substitution where feasible, along with worker training, is needed to protect workers who are exposed to silica during hydraulic fracturing operations.
One way to reduce silica exposures is to use alternative proppants (e.g., sintered bauxite, ceramics, resin-coated sand) where feasible. However, before using other proppants, it is important to evaluate the health hazards associated with them. If safe proppant alternatives are not feasible, then employers should monitor worker exposures, take measures to prevent exposures to silica, and inform workers of hazards, as described below.
Monitor the air to determine worker exposures to silica
Control dust exposures by improving existing engineering controls and safe work practices
Engineering controls and work practices provide the best protection for workers and must be implemented first, before respiratory protection is used. Working with industry partners, NIOSH has identified the following control options for hydraulic fracturing operations:
Short-term work practices and procedural changes that can be implemented quickly:
Practices that involve equipment changes:
Provide respiratory protection when it is needed to protect workers
When engineering and work practices controls are not feasible, while they are being implemented, or when they do not reduce silica exposures 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.
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:
Consider medical monitoring for workers who are exposed to silica
As part of its National Emphasis Program on Silica, OSHA recommends that employers medically monitor all workers who may be exposed to silica dust levels at or above one-half the PEL. Recommended medical tests include:
OSHA recommends that these tests be repeated every three years if the employee has less than 15 years of silica exposure, every two years if the employee has 15 to 20 years of exposure, and every year if the employee has 20 or more years of exposure.
What additional health and safety hazards exist during hydraulic fracturing?
In addition to silica hazards, workers may be exposed to other worksite health hazards that can include exposure to diesel particulate and exhaust gases from equipment, high or low temperature extremes, high noise levels, and overexertion leading to sprains and strains. In addition, fatigue may be a concern due to long working hours.
Hydraulic fracturing sites also have safety hazards similar to those at other oil and gas drilling sites, including:
See OSHA's Oil and Gas Well Drilling and Servicing eTool website for more information on safety and health hazards at oil and gas extraction sites.
How Can OSHA and NIOSH Help?
OSHA has compliance assistance specialists throughout the nation who can provide information to employers and workers about OSHA standards, short educational programs on specific hazards or OSHA rights and responsibilities, and information on additional compliance assistance resources. Contact your local OSHA office for more information.
OSHA's On-Site Consultation Program offers free and confidential advice for small businesses with fewer than 250 employees at a site (and no more than 500 employees nationwide) to help identify and correct hazards at your worksite. On-site consultation services are separate from enforcement and do not result in penalties or citations. To locate the OSHA Consultation Office nearest you, visit OSHA's website or call 1-800-321-OSHA (6742).
OSHA's Cooperative Initiatives: OSHA, NIOSH, and several U.S. onshore exploration and production industry trade associations, companies, and individual experts have formed a Respirable Silica Focus Group to further explore silica exposure during hydraulic fracturing and to develop practical short- and long-term solutions to protect worker safety and health
NIOSH is designing conceptual engineering controls to minimize exposure to silica during hydraulic fracturing. NIOSH is looking for industry partners to help test these engineering controls. If you are interested, please contact NIOSH at firstname.lastname@example.org. NIOSH is also looking for additional partners in drilling and well servicing to help evaluate worker exposures to chemical hazards and develop controls as needed. Please refer to the document NIOSH Field Effort to Assess Chemical Exposure Risks to Gas and Oil Workers [1 MB PDF, 4 pages] for details and contact us if you have questions or wish to participate. In addition, NIOSH has an active program that encourages Prevention through Design considerations so that occupational health and safety aspects (such as dust control) are built into equipment during the design phase.
Employers and workers can always request a NIOSH Health Hazard Evaluation. For more information about this program, please visit the website.
NIOSH recommendations for preventing silicosis, including dust control, sampling and analysis methods, medical monitoring of workers, training, and respiratory protection, can be found at the Silica Topics webpage.
For more information, see Best Practices for Dust Control in Metal/Nonmetal Mining, which discusses dust control in underground mining operations. Research results from this document have direct relevance for minerals handling operations in hydraulic fracturing operations.
Workers have the right to:
For more information, see OSHA's page for workers.
For questions or to get information or advice, to report an emergency, to report a fatality or catastrophe, to order publications, to file a confidential complaint, or to request OSHA’s free on site consultation service, contact your nearest OSHA office, visit www.osha.gov, or call OSHA at 1-800-321-OSHA (6742), TTY 1-877-889-5627.
Many states operate their own occupational safety and health programs approved by OSHA. States enforce similar standards that may have different or additional requirements. A list of state plans is available.
To receive documents or more information about occupational safety and health topics, please contact NIOSH at 1-800-CDC-INFO (1-800-232-4636), TTY 1-888-232-6348, email: email@example.com or visit the NIOSH web site.
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