The dangers of engineered stone

Working with engineered or man-made stone can cause exposure to respiratory hazards. OSHA have recently launched a new initiative to protect workers in the engineered stone fabrication and installation industries. The initiative focuses on enhancing enforcement and providing compliance assistance, seeking to reduce exposure to dangerous silica dust.

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Crystalline silica is a mineral found in stone and other construction materials. Materials that contain crystalline silica include:

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Breaking up these materials releases dust. Silica dust is generated during common construction tasks such as cutting, drilling, grinding and polishing stone materials. The dust is made up of small particles that can become airborne and cause a respiratory hazard.

Respirable crystalline silica (RCS) is a term for the fine dust created that gets deep into the lungs when inhaled. This dust is too fine to see with regular lighting and inhaling just a small amount can do a lot of damage.

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Silica dust can cause inflammation when particles enter the lung and, over time, lead to areas of hardened and scarred tissue (fibrosis).

Silicosis is a lung disease caused by inhaling silica dust, usually over a period of many years. Silicosis is incurable. The condition is progressive and can lead to disability and fatality.

Silica dust can also cause lung cancer, kidney disease and autoimmune disease.

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Silica dust exposure is identified as a health hazard for workers involved in manufacturing, finishing and installing natural and manufactured stone.

Engineered stone countertops, also known as “quartz surfacing,” are made from quartz pieces held together with a resin binder. The resulting material looks similar to natural stone and has become increasingly popular for use in home countertops. Engineered stone materials can contain substantially more crystalline silica than natural stone (>90%, compared with <45% in granite). Manufacturing, finishing and installing engineered stone can therefore generate high levels of dangerous silica dust and, without effective control measures in places, put workers at risk of developing silicosis.

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In 2019 the CDC reported an outbreak of silicosis among engineered stone countertop workers in California, Colorado, Washington, and Texas. The CDC identified 18 cases and two fatalities among workers in the stone fabrication industry, many of whom worked primarily with engineered stone materials and were under 50 years of age.

A study published by the American Medical Association in July 2023 included patients in California diagnosed with silicosis associated with engineered stone. Of the 52 male participants, 20 had advanced disease (progressive massive fibrosis), 11 required lung transplants, and 10 patients died due to past silica exposure.

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OSHA launched a new initiative focusing enforcement efforts on industry employers to ensure they are following required safety standards and providing adequate protection for workers. The initiative prioritizes OSHA inspections in workplaces where workers are typically exposed to high levels of silica, to identify hazards and ensure the correct control measures in place.

Industries subject to the prioritized programmed inspections include those engaged in Cut Stone and Stone Product Manufacturing (NAICS 327991) as well as Brick, Stone and Related Construction Material Merchant Wholesalers (NAICS 423320). Outreach efforts will continue to include additional industries that may work with engineered stone.

The focused inspection initiative will support the ongoing National Emphasis Program (NEP) for respirable crystalline silica. Effective since April 2020, the NEP is implemented to identify and reduce or eliminate worker exposures to RCS in general industry, maritime, and construction.

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The federal Occupational Safety and Health Administration (OSHA) has issued two RCS standards to protect workers. The standards for construction (29 CFR 1926.1153) and for general industry and maritime (29 CFR 1910.1053) took effect on June 23, 2016. Similar standards have also been implemented in state OSHA jurisdictions.

Employers must comply with the applicable federal or state OSHA standards to ensure that employee exposures, at a minimum, are not above the permissible exposure limit (PEL). PELs are enforceable regulatory limits on the amount or concentration of a substance in the air.

The PEL for silica dust is 50μg/m3 as an 8-hour time weighted average. OSHA also sets an action level for silica dust at 25μg/m3 as an 8-hour time weighted average.

The standards give requirements for medical surveillance. Under 29 CFR 1926.1153 and 29 CFR 1910.1053 employers must make medical surveillance available at no cost for certain employees exposed to RCS.

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To prevent silicosis in engineered stone fabrication and installation workers, exposure to RCS dust must be minimized through effective engineering controls and work practices.

Using wet methods to cut and work materials, as well as ventilation, is required to reduce the amount of RCS dust in the air. It is important to ensure that the tools used are able to reduce dust effectively. Tools with water directed at the top of the blade only provide cooling, not dust control. The water must be directed at the cutting site to be effective.

Additional tasks such as cleaning up must also be considered. Dry sweeping or dry brushing can contribute to RCS exposure. Using wet sweeping methods or HEPA-filtered vacuums can help to reduce dust levels when cleaning up. Compressed air should not be used to clean clothing or surfaces as this adds to dust levels in the air.

NIOSH-approved respirators should be provided to protect against residual dust levels where required by the standards. Respirators should be used as a last line of defense, after implementing other engineering controls and work practices to reduce RCS dust as much as possible.

NIOSH recommend a respirator with a high-efficiency particulate filter for RCS. The assigned protection factor (APF) required depends on the concentration of dust in the air which is measured through air sampling.

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For more information on respiratory protection for engineered stone contact [email protected].