There’s been a lot of controversy over the past year about silica dust. The Occupational Safety and Health Administration (OSHA) wants to cut the allowable level of airborne silica dust in half; fabricators are doubtful of being able to comply with the reduced levels and fear potential fines. It will take a while for all of this to play out through the regulatory process, but in the meantime, the question is: How can fabrication shop operators best protect their workers without losing their shirts?

Silicosis is an irreversible, but preventable disease, which has long been associated with work in industry occupations using quartz-containing materials. The key to preventing the disease is preventing workers from inhaling the silica dust generated when these materials are cut, drilled, ground or polished. Of concern to health and safety professionals is the fact that in many U.S. fabrication shops, the practice of dry-cutting, grinding and polishing persists. In a 2012 article, an industrial hygiene professor in Oklahoma found that approximately 74% of 47 countertop shops surveyed reported using predominately dry methods in at least one step of their work and only four shops (9%) reported using dust collection or dust suppression systems at all.

Also of concern to state and federal health researchers who track work-related silicosis cases are recent reports of clusters of advanced silicosis in stone countertop fabrication workers in Israel, Spain and Italy. These cases clearly practiced dry-cutting on quartz surfacing materials (high silica content of 70 to 90%); they were not known to regularly wear respiratory protection. Many were in their 30s; some cases underwent lung transplants. In 2014, the first case of this type in North America was identified in a 37-year-old man for whom fabrication of quartz surfacing materials was his only exposure to silica dust.

With all of this said, some factors to consider are what are the tasks, tools and work practices at risk and how can fabrication shop operators take practical and cost-effective steps forward to most effectively reduce exposure for their workers? Earlier this year, OSHA and the National Institute for Occupational Safety and Health (NIOSH) issued some guidance about this in an hazard alert entitled “Worker Exposure to Silica during Countertop Manufacturing, Finishing and Installation.” It contained recommended steps for assessing and controlling worker exposure to silica dust and described the allowable exposure levels. NIOSH is actually getting its engineers into fabrication shops to identify the most straightforward ways to suppress, control and collect the dust. The Marble Institute of America (MIA) with assistance from other members of the Natural Stone Council, contributed much content that assisted both NIOSH and OSHA with the hazard alert – a copy can be found online at

Silica exposure

At least 1.7 million U.S. workers are exposed to respirable crystalline silica, also known as silica dust, in a variety of industries and occupations, including construction, sandblasting and mining. Silicosis is the illness most closely associated with occupational exposure to the material. However, occupational exposures can also lead to the development of silicosis, lung cancer, pulmonary tuberculosis and airway diseases. These exposures may also be related to the development of autoimmune disorders, chronic renal disease and other adverse health effects.

Silica content is generally lower in natural stone products. Engineered stone, quartzite and quartzitic sandstone all have an average of 90% of silica or more in the product. So, how can a fabricator limit the exposure to silica in their shop? First, monitor the air to determine worker exposures to silica. The OSHA Permissible Exposure Limit (PEL) for quartz, the most common form of crystalline silica, is an eight-hour time-weighted average exposure to respirable dust. For pure quartz silica, the PEL is approximately equal to 100 micrograms of respirable crystalline silica per cubic meter of air (µg/m3). NIOSH’s Recommended Exposure Limit (REL) is that employers control exposure to respirable crystalline silica so that no worker is exposed to a time-weighted average concentration of silica greater than 50 µg/m3 of air, as determined by a full-shift sample for up to a 10-hour workday of a 40-hour workweek.

Fabricators can control dust exposures by using engineering controls and safe work practices. NIOSH and OSHA have identified the following control options for countertop manufacturing, finishing and installation operations. They say to use water spraying systems and remote-controlled tools at the impact site where a saw or grinder generates dust. Large bridge or gantry-like saws usually use water sprays and can be remote-controlled for dust control and cooling. Hand-held angle grinders can be modified to deliver water to the point of contact with the stone. Wet-edge milling machines or stone routers can replace dry grinders in shops. They provide a clean edge profile with a diamond wheel. Use hand tools, e.g. drills, masonry saws, grinders, equipped with a shroud and a vacuum with a high efficiency particulate air (HEPA)-filter when wet methods are not practical. Install Local Exhaust Ventilation (LEV) systems at fixed locations to capture dust at its point of origin. Use a combination of both water and ventilation controls, if necessary.

A few work practices are to use wet sweeping or HEPA-filtered vacuuming instead of dry sweeping or compressed air. Replace water and air filters as needed to control dust. Adjust water flow as necessary to control dust, following manufacturers’ recommendations for water flow rates. Pre-wash stone slabs prior to cutting. Implement regular and thorough housekeeping procedures for water slurry and settled dust. In high-exposure areas, such as where cutting or polishing work generates silica dust, provide HEPA-filtered vacuums for cleaning worker clothes and water for hand, face and hair cleaning.

Data from OSHA and NIOSH air monitoring and other published studies provided estimates of countertop industry worker exposure to airborne crystalline silica. In many shops, current practices still involve dry cutting, grinding, polishing and other work that releases silica dust into the air. Phillips et al. (2012) found that approximately 74% of 47 countertop shops in three metropolitan areas of Oklahoma reported using predominantly dry methods in at least one step of their work, and only four shops (9%) reported using dust collection or suppression systems at all.

OSHA reviewed results of exposure samples for sawyers from 10 OSHA Special Emphasis Program (SEP) Inspection reports and one NIOSH report. Among 22 instances in which sawyers used wet methods — often a water-feed to the saw — to reduce dust, full-shift median exposure was 54 µg/m3, with mean exposure of 61 µg/m3 and a range of 15 µg/m3 to 134 µg/m3. A total of 12 results (55%) exceeded 50 µg/m3, and four results (18%) exceeded 100 µg/m3. Where a water-feed to a saw alone is not sufficient, spraying the stone before cutting it or between multiple cuts can further reduce exposures. In one operation where workers used wet sawing, they were still exposed to average silica concentrations of 70 to 110 µg/m3. Using these added controls resulted in exposures below the 50 µg/m3 NIOSH REL. The addition of LEV in the shop further reduced exposures to 15 to 32 µg/m3.

Silica exposure can vary depending on the silica content of the stone used. OSHA collected air samples as part of inspections at several granite and marble shops. In the marble shop, two finishers dry grinding green marble with very low silica content (1.8% quartz) were exposed to airborne silica levels of 39 and 45 µg/m3 (both below the NIOSH REL), even though no engineering controls, such as water sprays or LEV, were used. In the granite shop, which also did not use engineering controls, airborne crystalline silica dust exposures were considerably higher, ranging from 89 to 460 µg/m3. It is reasonable to anticipate that performing similar operations using materials with higher silica content, such as some manufactured stone products, could result in even higher exposures.

On August 23, 2013, OSHA
proposed a new silica rule, matching NIOSH’s REL of 50 μg/m3 of air.

Increased number of cases of silicosis

Back in August 2012, the medical journal CHEST published an article called “Artificial Stone Silicosis: Disease Resurgence Among Artificial Stone Workers.” The report covered a 14-year study period and featured 25 patients with silicosis who were referred for evaluation, including 10 patients who went on to undergo lung transplantation. All the patients were exposed to dry cutting stone products with high crystalline silica content. The patients had moderate-to-severe restrictive lung disease and two of them developed progressive massive fibrosis. Three patients who did not receive lung transplants died during follow-up.

Recently, another study produced by the National Center for Biotechnology Information in March of 2014 identified about 46 cases of silicosis that were reported in Spain in workers cutting and installing engineered stone countertops with silica content of 70 to 90%. The individuals were 29 to 37 years old and had worked in the industry for nine to 17 years.

In May 2014, the Texas Department of State Health Services was notified of a case of silicosis with progressive massive fibrosis in a 37-year-old Hispanic male who worked for an engineered stone countertop company as a polisher, laminator and fabricator. He was exposed to dust for 10 years from working with conglomerate or quartz surfacing materials containing 70 to 90% crystalline silica. This was the first reported case of silicosis associated with exposure to quartz surfacing materials in North America.

In February 2015, NIOSH and OSHA released a Hazard Alert about silica specifically to the stone countertop industry. While stating what the stone industry does, it says manufactured stone countertop production — actually making the engineered or cultured slabs — involves mixing crystalline silica, resins and pigments. Workers in the natural cut stone industry, as well as those involved in finishing and installing both natural and manufactured stone, are at risk of significant silica exposure. In both industries, production operators, inspectors and staff who perform maintenance and housekeeping activities in manufacturing facilities also may be exposed to hazardous levels of airborne silica containing dust.

OSHA’s new proposed silica rule

The current OSHA PEL is approximately equal to 100 µg/m3 of air. On August 23, 2013, OSHA proposed a new silica rule, matching NIOSH’s REL of 50 µg/m3 of air. Why is OSHA proposing a new crystalline silica rule? The current PELs for crystalline silica were adopted in 1971 and have not been updated since that time. According to OSHA, they do not adequately protect workers; they are outdated, inconsistent and hard to understand. OSHA goes on to state that the current PELs are based on research from the 1960s and earlier, and do not reflect more recent scientific evidence. For example, since the current PELs were adopted, the U.S. National Toxicology Program, the International Agency for Research on Cancer and NIOSH have all identified respirable crystalline silica as a human carcinogen. The current PELs are formulas that are difficult for many employers to understand. The PELs for construction and shipyards are based on a method for measuring worker exposures that has not been commonly used for more than 40 years. Lastly, the current PELs for construction and shipyard workers allow them to be exposed to levels that are more than twice as high as workers in the general industry. The proposed rule would provide consistent levels of protection for workers in all sectors covered by the rule.

The proposed rule is expected to prevent thousands of deaths from silicosis, lung cancer, other respiratory diseases and kidney disease. OSHA estimates that the proposed rule will save nearly 700 lives and prevent 1,600 new cases of silicosis per year, once the full effects of the rule are realized.

Who will be affected by the proposed rule? According to OSHA, there are 12,085 workers in the stone cutting industry who are exposed to crystalline silica and 7,441 of them are currently exposed above the proposed PEL. “Many of the stone countertop fabricators may fall into this category and be considered overexposed to crystalline silica,” said Chaolong Qi a NIOSH Research Engineer. “In order to reduce these fabricators’ exposure below the proposed PEL, additional or improved engineering control solutions will be needed, especially when working with engineered quartz stones, which contain high silica content. Research will need to be conducted to identify, optimize or develop practical engineering control solutions and verify their effectiveness in terms of meeting the proposed PEL. It calls for collaborations across the industry, including both fabricators and tool manufacturers, and research institutes to share expertise and tackle this challenge together.”

The proposed rule would require a few different expectations for fabricators. First, it would limit the workers’ exposure to a new PEL of 50 µg/m3, averaged over an eight-hour day. The new PEL would be the same in all industries covered by the rule. Secondly, it would also include provision for measuring how much silica workers are exposed to, limiting workers’ access to areas where silica exposures are high, using effective methods for reducing exposures, providing medical exams to workers with high silica exposures and training for workers about silica-related hazards and how to limit exposure. These provisions are similar to industry consensus standards that many responsible employers have been using for years, and the technology to better protect workers is already widely available.

How can government agencies and the stone fabrication industry work together to reduce the dust?

Stone fabricators have to constantly worry about health and safety in their shop. From noise to slab handling, to silica dust, there are a number of potential hazards. The good news is they are not the only ones working on fixing the problems. NIOSH and different state agencies are trying to find solutions, and they are looking to work together with industry partners.

NIOSH is a U.S. federal agency that conducts research and makes recommendations to prevent worker injury and illness. The mission of the NIOSH research program for the engineering control cross-sector is to eliminate occupational diseases, injuries and fatalities through a focused program of research and prevention. There are four key components for NIOSH to succeed in its mission: high-quality research, practical solutions, partnerships and research to practice®. According to NIOSH, controlling exposures to occupational hazards is the fundamental method of protecting workers. Traditionally, a hierarchy of controls is used as a means of determining how to implement feasible and effective control solutions. The hierarchy is elimination, substitution, engineering controls, administrative controls and personal protective equipment. For engineering control, NIOSH efforts include the following activities: plan and conduct research on engineering control technology to prevent worker exposures to hazards, promote the application of effective engineering control technology for safeguarding worker safety and health, provide expertise in formulating effective and credible workplace standards and provide consultation in the application of effective control solutions and techniques for hazard prevention.

Currently, engineers at NIOSH are conducting research to provide practical recommendations for effective dust controls that will consistently reduce workers’ exposures to crystalline silica below the NIOSH REL and OSHA’s proposed PEL. “There are several areas we will explore to identify, optimize or develop engineering control measures,” said Qi. “The first one is on-tool controls, such as on-tool water-feed and LEV. Many tools nowadays have a water-feed in place to help control the dust. However, little research has been conducted to find out how the control effectiveness would be affected by the amount of water used for different tools. This is also the case for tools with built-in LEV. Through a quantitative evaluation of the data from multiple field trials of workers’ real time exposures to respirable dust when the control parameters such as the water-feed rate and LEV flow rate are adjusted, these on-tool dust controls can be optimized. It is plausible, but not proven yet, that the optimization could help control the dust better with the existing tools.”

NIOSH isn’t stopping there. In addition to the different on-tool controls, control measures such as using a capturing hood and an enclosing hood are being evaluated. “The capturing hood utilizes localized dust extraction nearby the area where dusts are generated,” said Qi. “It is a proven and widely used control method on capturing welding fumes, and it is our hypothesis that this solution could work well for capturing silica dust in stone countertop fabrication shops. It would work the best when positioned close to the generation source of the dust. The enclosing hood can be something like a painting booth inside, which a fabricator does the job with the generated dusts immediately moved away by a ventilation air flow and captured in a dust collector. The operation of the enclosing hood would have minimal interference to the worker’s job so it can work with different fabrication tasks and tools. The nature of the stone countertop fabrication process is rather complicated, as it involves a variety of tasks using different tools, such as cutting, edge profiling, grinding, polishing and so on. Therefore, an engineering control measure like the enclosing hood might provide a simple and universal solution for most of these tasks in fabrication shops. This is a proven control technology to control airborne contaminants such as dusts and volatile organic compounds (VOC) for paint spraying. Our hypothesis is that this control measure could work well in controlling silica dust during the stone countertop fabrication, too. The air flow rate for both the capturing hood and enclosing hood can be optimized through a quantitative evaluation on how varying them affects worker’s real-time exposure to respirable dust.

“The beauty of these engineering control measures is that they could remove dusts from their generation sources so they not only help protect workers, but also reduce some efforts on cleaning up the site,” Qi went on to say. “The site cleaning process, if not done properly, might increase workers’ exposure by re-aerosolizing the settled dusts during the cleaning. We plan to carry out tests over the next several years with one or more of these control measures employed to determine their individual and collective control effectiveness. Based on the test results, an overall control strategy can then be proposed for multiple field trials, validating whether the proposed controls would be able to consistently reduce workers’ exposure to crystalline silica below the NIOSH REL and OSHA’s proposed PEL. If found successful, the control recommendations will be concluded and disseminated to the industry. We hope that our control recommendations could provide guidelines to the industry to start designing and manufacturing engineering control devices specifically for the stone countertop fabrication.”

State Department of Health Occupational Disease surveillance programs

Several state departments of health are funded by NIOSH to track work-related fatalities, diseases and injuries. Some of the early fatalities associated with improper slab handling were identified this way. In many states, cases of silicosis are required to be reported by health care professionals. State health and safety specialists visit workplaces where cases were exposed to help employers improve their prevention measures. To see if your state participates, go to:

State OSHA consultation programs

Most fabrication shop operators are familiar with the enforcement role of OSHA, but fewer realize that OSHA also has a voluntary consultation program geared to helping small employers find effective and economical solutions for workplace hazards. The consultations are confident and do not result in any fines. To learn more, visit:


The MIA has several training documents and videos available online for fabricators to use to educate their staff about silica exposure and “best practices” to limit exposure. To learn more, visit:

Silicosis is an incurable disease that fabricators cannot ignore. By fabricators limiting their workers to the inhalation of dust that contains crystalline silica, they can help prevent silicosis from becoming a greater problem. By continuing safe wet-cutting methods, properly ventilating the area and making sure their employees use the proper respiratory methods, they shouldn’t have to worry about the ever-growing silica problem.            

How OSHA’s Silica Rule Impacts Industry

(Industry Opposition Exists)

Several construction-related trade associations have voiced strong opposition to the proposed silica rule. Additionally, the estimated cost to implement the proposed silica rule is widely debated with the industry indicating that OSHA has understated the real costs. The Construction Industry Safety Coalition (CISC) has just submitted a new report to OSHA on the “Costs to the Construction Industry and Jobs Impacts from OSHA’s Proposed Occupational Exposure Standards for Crystalline Silica.”

In this report, the CISC estimates that OSHA’s proposed silica standard will now cost the industry more than $4.9 billion per year, increasing the original estimate by approximately 20% since the post-hearing economic analysis was submitted. This new analysis shows an additional $1.05 billion per year of indirect costs will be placed on the construction industry in the form of increased prices paid for construction materials and  building products (i.e., block, stone, tile, concrete, paint, countertops, etc.) when manufacturers of those materials pass on some of their costs of complying with the “General Industry” portion of OSHA’s proposed silica standard, while $3.9 billion per year (which was already provided to OSHA) will be direct compliance expenditures by the construction industry for additional equipment, labor, monitoring, medical surveillance, record-keeping, etc.  In addition to the proposed rule being more costly than originally estimated, the report translates the costs into significant job losses for the construction industry and the broader economy. The CISC estimates that the proposed regulation would reduce the number of jobs in the U.S. economy by more than 52,700 yearly. 

*CISC is comprised of 25 trade associations representing virtually every aspect of the construction industry—from home building, to commercial and road construction, to heavy industrial production, to specialty trade contractors and material suppliers. Several members of the Natural Stone Council are CISC members.  

Being Safe in the Shop

Workplace health and safety is one of the most important things a fabricator can worry about in their shop. It’s a topic often brought up in the Stone World/MIA Stone Summits. Two important health and safety issues in the workplace worthy of attention to are heat stress and hearing loss.

Stay cool at work

As the summer months come and work steadily grows, heat and heat stress are something that fabricators don’t always think about. Heat stress happens to workers who are exposed to extreme heat or work in hot environments. According to the National Institute of Occupational Safety and Health (NIOSH), heat stress can result in heat stroke, heat exhaustion, heat cramps or heat rashes.

Heat stress affects a huge variety of workers, including fabricators. Workers at greater risk are those who are 65 years of age or older, are overweight, have heart disease or high blood pressure, or take medications that may be affected by extreme heat, or at a greater risk of heat stress.

Heat stroke is the most serious heat-related disorder, and occurs when the body becomes unable to control its temperature. Its symptoms include hot, dry skin or profuse sweating, hallucinations, chills, throbbing headache, high body temperature, confusion and dizziness and finally slowed speech.

Past heat stroke and heat stress, other health risks to look out for are heat exhaustion, heat syncope, heat cramps and finally heat rash.

For employers, NIOSH suggests that they schedule maintenance and repair jobs in hot areas during cooler months, schedule hot jobs during the cooler part of the day, acclimatize workers by exposing them for progressively longer periods to hot work environments, reduce physical demands and use relief workers or assign extra workers for physically demanding jobs.

Workers should wear light-colored, loose-fitting, breathable clothing such as cotton, gradually build up to heavy work, schedule heavy work during the coolest parts of the day, take more breaks in extreme heat and humidity and drink water frequently, enough water that they never become thirsty, approximately one cup every 15-20 minutes.

Hearing loss

Occupational hearing loss is one of the most common work-related illnesses in the U.S., according to NIOSH. Approximately 22 million U.S. workers are exposed to hazardous noise levels at work, and an additional nine million are exposed to ototoxic chemicals. An estimated $242 million is spent annually on worker’s compensation for hearing loss disability.

A few of the primary noise sources in stone countertop manufacturing shops include stone cutting saws, waterjet cutters, machine polishers, hand-held polishers and compressed air noise, according to NIOSH research. “Most employees working in production areas have full-shift noise exposures above the NIOSH Recommended Exposure Limit and the OSHA Action Level of 85 decibels, A-weighted (dBA),” said Scott Brueck, of NIOSH. “Many employees’ exposure also exceed the OSHA Permissible Exposure Limit of 90 dBA. It is important for fabricators and shop owners to know that hearing loss tends to occur slowly over time and once hearing is lost it cannot be restored.” NIOSH features a Preventing Occupational Hearing Loss – A Practical Guide on their website that goes over how to keep employees safe from any hearing damage.


Stone Average % Silica
Engineered Stone >93
Quartzite 95
Quartzitic sandstone 90
Sandstone 60
Granite 10-45