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: (1) Dust ejected from thief hatches (access ports) on top of the sand movers during refilling operations while the machines are running (hot loading). (2) Dust ejected and pulsed through open side fill ports on the sand movers during refilling operations. (3) Dust generated by on-site vehicle traffic. (4) Dust released from the transfer belt under the sand movers. (5) Dust created as sand drops into, or is agitated in, the blender hopper and on transfer belts. (6) Dust released from operations of transfer belts between the sand mover and the blender; and (7) Dust released from the top of the end of the sand transfer belt (dragon's tail) on sand movers. 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. 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 However, because OSHA recognizes that many of its PELs are outdated and inadequate measures of worker safety, both OSHA and NIOSH recommend that employers take actions to keep worker exposures below the NIOSH REL. Of the 116 samples collected: (a) 47% showed silica exposures greater than the calculated OSHA PEL. (b) 79% showed silica exposures greater than the NIOSH REL of 0.05 milligrams per cubic meter (mg/m3). (c) 9% of all samples showed silica exposures 10 or more times the PEL, with one sample more than 25 times the PEL. (d) 31% of all samples showed silica exposures 10 or more times the REL, with one sample more than 100 times the REL. 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. 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. NIOSH [1986] 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. 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. NIOSH [2002] 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? Silicosis is classified into three types: chronic/classic, accelerated, and acute. (1) Chronic/classic silicosis, the most common type, occurs after 10-20 years of moderate to low exposures to respirable crystalline silica. Symptoms associated with chronic silicosis may or may not be obvious; therefore, workers need to have a chest x-ray to determine if there is lung damage. As the disease progresses, the worker may experience shortness of breath when exercising and have clinical signs of poor oxygen/carbon dioxide exchange. In the later stages, the worker may experience fatigue, extreme shortness of breath, cough, and, in some cases, respiratory failure. (2) Accelerated silicosis can occur after 5-10 years of high exposures to respirable crystalline silica. It is similar to chronic silicosis, but progresses more rapidly. (3) Acute silicosis occurs after only a few months or a few years following exposures to extremely high levels of respirable crystalline silica. Symptoms of acute silicosis include rapidly progressive and severe shortness of breath, weakness, and weight loss. Though much less common than other forms of silicosis, acute silicosis nearly always leads to disability and death. See more from topic source: https://www.osha.gov/html/a-z-index.html