Apr 3, 2018

Improved Tool Decreases Dangerous Airborne Silica Dust

sand mover operator station

During sand transport, a visible cloud of dust containing crystalline silica floats past this top sand-mover operator station. Photo courtesy of Barbara Alexander, NIOSH.

An improved, NIOSH-developed tool, or engineering control, can help reduce the amount of dangerous, airborne crystalline silica dust generated during sand moving for oil and gas extraction, according to research published in the Journal of Occupational and Environmental Hygiene.

During hydraulic fracturing for oil and gas extraction, workers use equipment that pumps millions of pounds of water and sand into rock formations deep underground. The purpose of this pressurized mixture is to create and maintain cracks in the rock to extract the oil and gas trapped within. The problem is that the sand usually contains crystalline silica dust, which, when inhaled, can cause severe illness, including lung cancer and the deadly lung disease silicosis. During certain tasks, such as moving and mixing sand at hydraulic-fracturing sites, airborne crystalline silica dust poses a serious risk to workers' health.

Engineering controls are a critical part of preventing worker exposure to airborne crystalline silica dust. In fact, respirable crystalline silica standard 29 CFR 1910.1053 from the Occupational Safety and Health Administration will require hydraulic-fracturing companies to adopt engineering controls for crystalline silica dust by June 23, 2021.

NIOSH investigators who study and develop these engineering controls showed in previous research that a NIOSH-developed control effectively reduced levels of airborne crystalline silica dust released from inspection hatches on top of sand movers. Known as the NIOSH mini baghouse, it comprises four large bags made of filter material and a baseplate that clamps to the openings on top of sand movers. It is unique in that it has no moving parts, requires no power source, and can retrofit to existing sand movers.

In a study of the third generation of the mini baghouse, investigators tested it at an Arkansas sand mine during May 19–21, 2015. They collected 168 air samples at 12 locations on and near a sand mover, both with the mini baghouse installed and without it, and then measured the levels of respirable crystalline silica dust in the air samples. The measurements showed that air samples taken with the mini baghouse installed contained 98%–99% less respirable crystalline silica dust than those taken without the mini baghouse. In addition, other tests showed that the crystalline silica dust probably contained freshly fractured quartz, which is an especially dangerous type of crystalline silica dust.

Compared to earlier versions, this third-generation mini baghouse performed significantly better due to improvements, such as a larger surface area of a "slipperier" filter fabric. Now, the investigators are studying additional design improvements, including a cover to offer protection from the weather. They also are planning future trials looking at long-term use of the mini baghouse.

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