Information for UOGD Industry Workers

People who work in the unconventional oil and gas development (UOGD, commonly called “fracking”) industry have an annual fatality rate of 27.5 per 100,000, which is more than seven times higher than the rate for all US workers. From 2003-2009, the majority of fatalities were caused by death from motor vehicle accidents, being struck by tools and equipment, explosions, being caught or compressed by moving machinery or tools, and falls. Historically, the primary focus of professionals charged with protecting the health and safety of UOGD workers has been on improving safety and avoiding such accidents. 

Recently, however, the National Institute for Occupational Safety and Health (NIOSH) launched a program to assess the health risks associated with on the job exposures to hazardous substances during UOGD operations. Some of the potentially hazardous exposures identified by NIOSH include: 

  • Silica dust exposures from the transport and movement of “frac sand.”
  • Exposure to chemicals in wastewater from hydraulic fracturing.
  • Exposure to diesel particulates from vehicles and other equipment.
  • Exposure to chemicals including volatile organic compounds (VOCs), hydrogen sulfide, aldehydes, and metals from a variety of sources.
  • Noise exposure from drilling and hydraulic fracturing activities.

Beyond the exposures discussed in this article, it should be noted that natural gas extraction is a 24-hour, all-season industry. As a result, long work shifts, extended work periods, and extreme weather conditions create additional challenges to workers’ health and safety.


Silica, often called quartz, is a common mineral found in soil, sand, concrete, masonry, rock, granite, and other materials. The dust created by cutting, grinding, drilling or otherwise disturbing these materials can contain tiny crystalline silica particles that are potentially harmful when inhaled.

In UOGD operations, exposure to silica dust occurs during the transport and movement of “frac sand,” which is used to prop open rock fractures and increase gas flow. The large amounts of sand required in UOGD are trucked to well sites, loaded into sand movers, transferred to conveyer belts, and blended into the hydraulic fracturing fluid. This process produces large visible clouds of silica dust, which can be inhaled by workers. Breathing in this crystalline silica is known to have the following health risks:

  • Silica exposure can lead to silicosis, a progressive, debilitating, and often-fatal lung disease. Yearly, an average of 160 to 200 US residents and thousands of individuals worldwide are identified as having died from silicosis. Individuals with silicosis are also at increased risk for developing tuberculosis.
  • Silica is a recognized lung carcinogen and can contribute to the development of lung cancer.
  • Silica exposure also contributes to the development of chronic obstructive pulmonary disease, kidney disease, and autoimmune diseases.

In extensive monitoring of worker silica exposure, NIOSH determined that 79% of the samples exceeded the recommended limit, with 31% of samples demonstrating a crystalline silica exposure of greater than ten times the recommended limit (at ten times the recommended limit, a half-face respirator would not provide adequate protection). Based on these findings, the Occupational Safety and Health Administration (OSHA) and NIOSH issued a Hazard Alert that details the results and outlines recommendations to industry to reduce worker exposures. The recommendations include:

  • Air monitoring to determine worker exposure.
  • Controlling dust exposures through NIOSH identified work practices and equipment changes detailed in the alert.
  • Providing appropriate respiratory protection when needed.
  • Providing worker training and information about the hazards of silica.

The alert also suggests consideration of more extensive medical monitoring for workers exposed to silica as recommended in the OSHA National Emphasis Program.

Beyond NIOSH’s findings regarding excessive silica exposure at well sites, concerns have also been raised regarding the silica exposures of both workers and communities as the result of the dramatic increase in sand mining, processing and transport spurred by the growth of UOGD.


The wastewater produced during the UOGD process brings chemicals and other materials to the surface. These “flowback” fluids contain dissolved hydrocarbon gases, water, liquid hydrocarbons, sand, and other chemicals and debris injected into a well during the hydraulic fracturing process. In addition, flowback fluids contain material brought to the surface from the shale formation such as hydrocarbons, metals, salts and naturally occurring radioactive materials.

After arriving at the surface, the contents of flowback fluids are separated out. The fluid containing dilute hydrocarbons and other chemicals are stored onsite in portable tanks. The recovered concentrated oil/condensate is stored in onsite production tanks.

The fluid levels in these large tanks must be periodically checked by industry personnel. Workers access the tanks through hatches on the top of the tanks and manually gauge the distance to the fluid surface. A 2014 study measured exposures to workers performing various tasks related to flowback operations. These results indicated a potential health concern from overall hydrocarbon, and in particular, benzene exposure to the individuals gauging flowback and production tanks. Another study in 2016 reported on the sudden deaths of nine oil and gas extraction workers that occurred while manually gauging or sampling tanks. The suspected cause of the deaths was exposure to hydrocarbon gases and vapors, and oxygen deficient atmospheres.

In response to these risks, NIOSH and OSHA issued a joint Hazard Alert “Health and Safety Risks for Workers Involved in Manual Tank Gauging and Sampling at Oil and Gas Extraction Sites.


There are many sources of diesel exhaust at UOGD well sites, including drilling rigs, air compressors, pump engines, and numerous diesel fueled vehicles. Diesel exhaust can contribute to or exacerbate the development of lung cancer, cardiovascular and pulmonary disease, and other health problems.

Although neither OSHA nor NIOSH currently have diesel particulate exposure limits, California does have a worker exposure limit of 20 µg/m3 time-weighted averages (TWA), which is based on the risk of developing lung cancer. In a 2012 presentation, NIOSH reported results from limited initial assessments of worker exposures to diesel particulates at UOGD sites and determined that 25% of personal breathing zone (PBZ) samples exceeded the California standards, and two samples were more than double the level considered safe. These results suggest that diesel exhaust may represent a health hazard to UOGD workers.


Many other chemicals are used at various stages of the UOGD process, and workers may sometimes be exposed to them. Potentially hazardous chemicals include volatile organic compounds (VOCs), hydrogen sulfide (H2S), and aldehydes.

Volatile organic chemicals (VOCs) are common pollutants associated with UOGD and include benzene, toluene, ethylbenzene, and xylene (commonly called BTEX), and others. Workers are potentially exposed to varying concentrations of VOCs through the handling and storage of flowback and produced water. An additional source of VOC exposure on well sites is unintended fugitive emissions from natural gas production and on-site processing. VOCs can contribute to the development of cancer (benzene is a recognized carcinogen; ethylbenzene and naphthalene are considered possible carcinogens) and can adversely affect most organ systems, with prominent nervous system, respiratory and hematologic (blood) effects.

Hydrogen Sulfide (H2S), also called “sour gas,” exposure is a well-recognized risk in conventional oil and gas extraction, and is also a factor in UOGD. As a result, warning systems and protective measures are in place at UOGD well sites. At low concentrations, H2S is an eye, mucous membrane and respiratory irritant. Brief exposures to high levels of H2S can result in loss of consciousness and death.

Aldehydes such as glutaraldehyde are commonly used as biocides to eliminate bacterial growth that can occur during the UOGD process. Glutaraldehyde is a respiratory, mucous membrane, and eye irritant. Exposure can cause or exacerbate asthma, and skin exposure may result in a rash or other skin eruption from irritant or allergic dermatitis. NIOSH measurements of total aldehydes in and around “frac” tanks where fluids are stored in preparation for being pumped down the well bore were found to exceed recommended limits. These findings suggest that further evaluation of worker personal breathing zone exposure to glutaraldehyde may be appropriate.


“Pipe dope” is a threading compound sometimes used in oilfield work to prevent metal-to-metal damage and seal pipe threads. Pipe dope may contain up to 60% lead, a metal that is known to cause multiple health problems in adults and children. While the extent to which UOGD workers are exposed to lead pipe dope or other hazardous metals is not yet well characterized, one study found the use of lead-containing pipe dope by oil field workers was associated not only with elevated blood lead levels in the workers, but also elevated blood lead levels in their children as a result of take-home lead exposure. Workers should make every effort to shower and change clothes before entering their residence or coming into contact with children. They should also know that alternative lead-free pipe dope formulations are available.


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