Workers in dozens of industries face potential exposure to crystalline silica dust, from obvious settings like mining and construction to less expected ones like auto body shops and dental labs. Between 1988 and 2003, federal exposure monitoring identified over 119,000 workers potentially exposed across just 18 selected industries. The real number is far higher, because silica is the second most abundant mineral in the Earth’s crust and turns up in virtually any process that involves cutting, grinding, drilling, or crushing stone, sand, concrete, or mineral-based products.
Construction and Masonry
Construction is the single largest source of silica dust exposure. Concrete, mortar, brick, and natural stone all contain crystalline silica, and nearly every task that disturbs these materials sends fine particles into the air. Cutting concrete with a saw, drilling into brick walls, jackhammering pavement, grinding surfaces smooth, mixing morite or cement, and demolishing old structures all generate respirable dust. Federal data estimated roughly 45,000 exposed workers in masonry stonework, plastering and drywall work, and tile and marble installation alone.
Tuck-pointing, the process of removing and replacing old mortar between bricks, is one of the highest-exposure tasks in all of construction. Workers use power grinders inches from their faces, and the resulting dust cloud can push silica concentrations well above safe limits within minutes. Highway repair crews face similar risks when they saw-cut or mill asphalt and concrete road surfaces.
Mining and Quarrying
Metal mining, coal mining, and nonmetal mineral mining (such as sand and gravel operations) all involve drilling, blasting, and crushing rock that contains quartz. Underground miners face the added problem of enclosed spaces where dust lingers in the air longer. Surface quarry workers encounter it during stone extraction, crushing, and screening. Silicosis was historically so common among miners and quarry workers that it was one of the first recognized occupational lung diseases.
Oil and Gas (Hydraulic Fracturing)
Hydraulic fracturing, or fracking, pumps massive volumes of water and sand into wells at high pressure to crack open rock formations and release oil or gas. That sand is nearly pure crystalline silica. NIOSH field studies found that workers at fracking sites can be exposed to dangerously high airborne silica levels, particularly during sand transfer operations: loading sand from trucks into storage bins, feeding it into blenders, and monitoring it on the wellpad. The exposure is concentrated at specific points in the sand handling chain, making it a relatively modern and sometimes overlooked source of silica risk.
Metal Foundries
Foundries use silica sand to make molds and cores for casting metal parts. Workers are exposed at nearly every stage: mixing sand with binding agents, packing it into mold shapes, pouring molten metal, then shaking out the cooled castings and breaking apart the spent molds. The shakeout and fettling (cleaning and finishing castings) steps are especially dusty. According to the UK’s Health and Safety Executive, sand, fettling residue, and kiln-lining materials all produce respirable crystalline silica when dry.
Engineered Stone Countertop Fabrication
This is one of the fastest-growing sources of silicosis worldwide. Engineered stone (sometimes marketed as quartz countertops) typically contains over 90% crystalline silica, far more than natural granite or marble. Workers who cut, grind, and polish these slabs inhale extremely concentrated dust. Research from California’s Department of Public Health found that 51% of inspected stone fabrication shops had at least one employee exposed above the permissible limit. The industry has drawn urgent regulatory attention because workers are developing severe, accelerated silicosis at younger ages than in traditional stone trades.
Glass, Ceramics, and Pottery
Silica is a primary ingredient in glass, ceramic glazes, and pottery bodies. In a typical pottery plant making products like sinks and toilets, the raw materials include crystalline silica powder, clay, and feldspar. Workers face exposure when bags of silica powder are manually cut open and dumped into blenders, a step that forces visible dust out of the bag. Additional exposure happens in the glaze department, where silica-containing coatings are sprayed onto products before firing.
Even seemingly low-risk areas of a ceramics factory can carry background silica levels. Scrap clay and dust on floors dry out overnight (especially when waste heat from kilns is directed into work areas) and get kicked back into the air as workers move through the space. Production areas including slip houses, mold shops, spray booths, and kiln departments all carry exposure potential.
Automotive Repair and Paint Shops
This is one of the most surprising entries on the list. Auto body repair and paint shops accounted for an estimated 25,027 potentially exposed workers in federal monitoring data, the single highest count among the industries tracked. The exposure comes from sanding body filler, primers, and paint coatings that contain silica-based compounds, as well as from abrasive blasting to strip old finishes. Because these shops are often small businesses with limited ventilation, dust concentrations can build up quickly.
Dental Laboratories
Dental technicians face silica exposure during prosthesis polishing and grinding, tasks they may perform hundreds of times per week. Because the connection between dental lab work and silicosis is less well known, it often goes unrecognized. A published case report describes a 54-year-old dental technician who developed progressive breathing difficulty after 25 years in the trade, with silicosis confirmed through imaging and occupational history. The condition was described as an “overlooked occupational risk” in this profession.
Other At-Risk Industries
Several additional industries carry silica exposure that may not be immediately obvious:
- Testing laboratories: Nearly 18,500 workers were flagged as potentially exposed in lab settings where mineral samples are processed or materials are tested.
- Chemical manufacturing: Plants producing chemical preparations use silica as a filler, abrasive, or raw ingredient.
- Plastics and plumbing fixtures: Some manufacturing processes incorporate silica-containing compounds into plastic products.
- Agriculture: Tilling dry, sandy soil stirs up crystalline silica particles, particularly in arid regions.
- General repair shops: Over 17,000 workers in miscellaneous repair operations were identified as potentially exposed, largely through grinding and cutting tasks.
How Exposure Turns Into Disease
Breathing in fine silica particles causes silicosis, an irreversible scarring of the lungs. It comes in three forms depending on how intense the exposure is. Acute silicosis can develop in just weeks or months after very high exposure, causing the lungs to fill with fluid and often leading to severe illness or death. Accelerated silicosis typically appears after 5 to 10 years of heavy exposure. Chronic silicosis, the most common form, develops after 10 or more years of lower-level exposure. Crystalline silica is also classified as a suspected human carcinogen.
The federal permissible exposure limit is 50 micrograms per cubic meter of air, averaged over an 8-hour workday. The action level, meaning the threshold at which employers must start monitoring and protective measures, is half that: 25 micrograms per cubic meter. Some expert organizations recommend an even lower limit of 25 micrograms as the maximum.
Reducing Exposure on the Job
The two most effective controls are wet methods and local exhaust ventilation. Wet cutting, where water is fed onto a saw blade or grinding wheel, suppresses dust at the source and can dramatically reduce airborne silica levels. Local exhaust ventilation captures dust through hoods or shrouds attached directly to tools. Using both together provides the strongest protection, particularly for masonry cutting with handheld or fixed saws.
For cleanup, vacuuming with a filtered system is far better than dry sweeping, which simply redistributes fine particles back into the air. When engineering controls alone can’t bring exposure below safe limits, respirators are required. For most elevated exposures, a full-facepiece respirator with a high-efficiency particulate filter is standard. At extremely high concentrations, supplied-air systems are necessary.