Plate 03 of 13Health and safety
Silica dust and quarry safety as public bodies state it
Sand, gravel and stone contain crystalline silica, and the fine dust made when rock is broken is a recognised workplace hazard. Here is what the regulators say.
Is the dust from sand, gravel and crushed stone dangerous, and who decides what is safe? This page explains the hazard that health and safety agencies call respirable crystalline silica, where it comes from in aggregate work, which diseases the agencies link to it, and the kinds of control they describe. It also explains that exposure limits are set by regulators, quotes the figures from the agencies that publish them, and points you to the body that governs your own workplace. It is general education, not a compliance guide and not medical advice.
What respirable crystalline silica is
Crystalline silica is a mineral. The US Occupational Safety and Health Administration (OSHA) describes it as a common mineral found in the earth's crust and says that materials such as sand, stone, concrete and mortar contain it. The sands, gravels and stone described in what aggregates are and how they are made therefore often carry some of it, in amounts that depend on the rock.
The word "respirable" matters here. It refers to particles small enough to be breathed deep into the lungs. OSHA says respirable crystalline silica consists of very small particles, at least 100 times smaller than the ordinary sand you might find on beaches and playgrounds. Such particles are made when stone, rock, concrete, brick, block and mortar are cut, sawed, ground, drilled or crushed, so the hazard comes from how a material is worked rather than from the whole grain sitting in a pile.
The silica content of rock varies a great deal. The UK Health and Safety Executive (HSE), Britain's workplace regulator, publishes typical percentages for common materials, shown below. HSE notes in the table that limestone, chalk and marble can contain silica layers even though their typical percentage is low. For how different sands compare, see sand types and what each is used for.
| Material | Percentage of silica |
|---|---|
| Sandstone, gritstone, quartzite | more than 70% |
| Concrete, mortar | 25% to 70% |
| Slate | up to 40% |
| Brick, granite | up to 30% |
| Basalt, dolerite | up to 5% |
| Limestone, chalk, marble | up to 2% (but these can contain silica layers) |
Where the dust comes from in sand, gravel and stone work
The US Mine Safety and Health Administration (MSHA) states that silica dust is generated by mining activities including cutting, sanding, drilling, crushing, grinding, sawing, scraping, jackhammering, excavating and hauling materials that contain silica. Several of those steps, such as drilling, excavating, hauling and crushing, are routine parts of producing sand, gravel and crushed stone.
Processing is where fine dust is most obviously made, because crushing is the step that breaks rock into the sizes explained in aggregate sizes and grading. OSHA also names abrasive blasting with sand, sawing brick or concrete, grinding mortar and manufacturing brick, concrete blocks and stone countertops as sources of exposure. It describes industrial sand used in foundry work and hydraulic fracturing as another source.
The work is not limited to quarries. HSE lists quarrying, slate works, foundries, potteries, stonemasonry and construction work that cuts or breaks stone, concrete or brick among occupations with exposure. Finished products matter too: OSHA lists concrete and mortar among the materials whose cutting, drilling and grinding create respirable dust, and the ingredients of both are covered in concrete and mortar ingredients. OSHA says about 2.3 million people in the United States are exposed to silica at work.
The diseases the agencies link to silica dust
OSHA states that workers who breathe very small crystalline silica particles are at increased risk of serious silica-related diseases, including silicosis (which it calls an incurable lung disease that can lead to disability and death), lung cancer, chronic obstructive pulmonary disease (COPD) and kidney disease. COPD is a group of lung conditions, including emphysema and chronic bronchitis, in which breathing becomes progressively harder.
The US National Institute for Occupational Safety and Health (NIOSH) uses similar wording. It says silica causes inflammation and scarring in the lungs, and that excessive exposure to respirable crystalline silica can lead to silicosis, which it describes as progressive, debilitating and sometimes fatal. NIOSH adds that excessive exposure can also cause lung cancer, COPD, certain autoimmune diseases and chronic renal failure, and that workers exposed to silica, and those who have silicosis, are at increased risk of tuberculosis (TB). It states there is no known cure for silicosis.
The agencies also describe timing. NIOSH says higher exposures mean shorter latency periods, the time between first exposure and the first symptoms. It describes acute silicosis as occurring after a few weeks or months of exposure to very high levels, accelerated silicosis as typically occurring after 5 to 10 years, and chronic silicosis, the most common type, as occurring after 10 or more years of exposure to lower levels. OSHA says silicosis typically occurs after 15 to 20 years of occupational exposure and that symptoms may or may not be obvious, which is why it says workers need a chest x-ray to find out whether there is lung damage.
HSE makes a related point for Britain: the effect of silicosis continues to develop after exposure has stopped and is irreversible. NIOSH says periodic medical monitoring helps detect silicosis at early stages. Anyone worried about their own health or past exposure should speak to a doctor, since this page cannot assess individual cases.
Controls: the layered approach the agencies describe
Safety agencies describe a hierarchy of controls, a ranked list of ways to reduce a hazard. NIOSH names five levels: elimination, substitution, engineering controls, administrative controls and personal protective equipment (PPE). The idea is that removing or reducing the dust at its source is preferred over asking people to protect themselves from it.
For silica, NIOSH's safe work practices page puts weight on engineering controls, meaning equipment or process changes that reduce exposure. It says water spray methods used when cutting stone can prevent dust exposure, because wet methods suppress dust emission. It also describes dry methods such as ventilation controls that use vacuums and high efficiency particulate air (HEPA) filters, and lists other exposure prevention methods: using local exhaust ventilation where work is dusty, using enclosures to isolate work processes, using water and ventilation controls together when possible, replacing water and air filters when needed, and avoiding dry sweeping or compressed air during housekeeping.
Respirators come last. NIOSH says employers should provide workers with respiratory protection when dust controls and safe work practices cannot limit exposures below exposure limits, and OSHA's general industry standard likewise requires respirators when dust controls cannot limit exposures to its permissible limit. In this ordering, PPE is the final layer, used when the layers above it cannot do the job alone. Worker training, written plans and medical examinations also feature in OSHA's requirements.
Specific equipment choices, fit testing and plant design are matters for qualified occupational hygienists and the relevant regulator. Nothing here substitutes for their advice.
Exposure limits are set by regulators
An exposure limit is a legal or regulatory ceiling on the average concentration of a substance in workplace air, usually averaged over a work shift. Limits are set by each country's regulator, and they can change. The figures below are quoted as the agencies publish them, and this page does not interpret anyone's measurements.
United States: OSHA
OSHA has issued two respirable crystalline silica standards, one for construction and one for general industry and maritime. For general industry and maritime, OSHA's page states a permissible exposure limit (PEL) of 50 micrograms of silica per cubic metre of air, averaged over an 8-hour day, and an action level of 25 micrograms per cubic metre. An action level is a lower trigger at which further steps, such as assessing exposures, are required. OSHA states that general industry and maritime employers had to comply with the requirements of the standard by 23 June 2018, with some exceptions for medical surveillance and hydraulic fracturing. NIOSH describes the PEL under OSHA's silica rule as 50 micrograms per cubic metre as an 8-hour time weighted average.
United States: MSHA
Mines are covered by MSHA. According to MSHA, it issued a final rule on 18 April 2024 that lowers the PEL for respirable crystalline silica to 50 micrograms per cubic metre for a full shift, calculated as an 8-hour time weighted average, and establishes an action level of 25. MSHA states the rule took effect on 17 June 2024, with 12 months for coal mine operators and 24 months for metal and nonmetal mine operators to comply.
That timetable has since been affected by litigation. In a Federal Register notice of 6 April 2026, MSHA says industry groups petitioned the US Court of Appeals for the Eighth Circuit, that on 11 April 2025 the court stayed the rule's compliance deadlines, and that the stay was still in effect. MSHA says the existing standards for metal and nonmetal mines continue to apply until the stay ends. NIOSH's page likewise says implementation is delayed pending the outcome of legal challenges. Because this situation can change, MSHA is the place to confirm what applies to a given site.
Great Britain: HSE
HSE states that in Britain respirable crystalline silica has a workplace exposure limit (WEL) of 0.1 milligrams per cubic metre, expressed as an 8-hour time weighted average, and that exposure is also subject to the Control of Substances Hazardous to Health Regulations 2002 (COSHH). HSE says health surveillance must be provided to workers who are regularly exposed to the dust where there is a reasonable likelihood that silicosis may develop. For comparison of units, 0.1 milligrams per cubic metre is 100 micrograms per cubic metre; the two countries state their limits in different units and under different legal frameworks.
Rules differ by country and by site
The agencies above are examples, not a complete list. Many countries have a national workplace-safety regulator and, in some, a separate mine-safety regulator, and each sets its own limits, measurement methods and duties. Even within one country, quarries, construction sites, factories and mines can fall under different rules, as the OSHA and MSHA examples show. An overview of how quarries are overseen in general terms is in how quarries are regulated.
If you work in or near this industry, the right source for what applies to you is your own national workplace-safety regulator, your mine-safety regulator where there is one, or a qualified occupational health and safety professional. Rules and practice differ by country and by site, and your regulator or a qualified professional has the final word.
Where this page stops
The figures and statements above come from workplace regulators and describe workplace exposures. They are not a verdict on sand in everyday life, and we do not extend them to situations the agencies have not addressed. Two common questions have their own pages: what public bodies say about sand for play areas and sandboxes, and how sand is used in pool filters. Both stay with what the sources state.
Frequently asked questions
What does "respirable" mean for dust?
It describes particles small enough to be breathed into the deep parts of the lungs. OSHA describes respirable crystalline silica as particles at least 100 times smaller than ordinary beach or playground sand, and HSE describes the dust as invisibly fine.
Is all sand dangerous because it contains silica?
The agencies quoted here link disease to breathing respirable crystalline silica, mostly in work that cuts, drills, grinds or crushes rock and similar materials. They do not say that whole grains of sand are the hazard. For specific situations, ask the relevant public body or a qualified professional.
Who sets the exposure limit for a quarry?
A regulator does, and it depends on the country. In the United States, MSHA publishes the rule for mines and OSHA publishes standards for construction and general industry. In Great Britain, HSE publishes the workplace exposure limit.
Why are respirators described as the last line of defence?
NIOSH places personal protective equipment at the bottom of its hierarchy of controls and says respiratory protection is for when dust controls and safe work practices cannot limit exposure below the limits. Water, ventilation and enclosure are the engineering controls it lists ahead of that.
The short version
Crystalline silica is a common mineral, and the hazard that agencies describe is breathing the very fine respirable dust made when stone, sand-bearing rock, concrete and similar materials are cut, drilled, ground or crushed. OSHA, NIOSH, MSHA and HSE link that dust to silicosis, lung cancer, COPD and kidney disease, among others, and describe water, ventilation and enclosure ahead of respirators. Limits are set by regulators and differ by country, so the authority that governs your site is the one to consult.