• Simple chronic silicosis, the most common type of silicosis, results from long-term exposure (usually more than 20 years) to low amounts of silica dust. Simple chronic silicosis may cause people to have difficulty breathing.
• Accelerated silicosis occurs after 5 to 15 years of exposure of higher levels of silica. Swelling of the lungs and other symptoms occur faster in this type of silicosis than in the simple chronic form.
• Acute silicosis results from short-term exposure (weeks or months) of large amounts of silica. The lungs become very inflamed and can fill with fluid, causing severe shortness of breath and low blood oxygen levels. A cough, weight loss, and fatigue may also be present. Acute silicosis progresses rapidly and can be fatal within months.

Crystalline silica is a common mineral found in the earth's crust. Materials like sand, stone, concrete, and mortar contain crystalline silica. It is also used to make products such as glass, pottery, ceramics, bricks, and artificial stone.

Respirable crystalline silica – very small particles at least 100 times smaller than ordinary sand you might find on beaches and playgrounds – is created when cutting, sawing, grinding, drilling, and crushing stone, rock, concrete, brick, block, and mortar. Activities such as abrasive blasting with sand; sawing brick or concrete; sanding or drilling into concrete walls; grinding mortar; manufacturing brick, concrete blocks, stone countertops, or ceramic products; and cutting or crushing stone result in worker exposures to respirable crystalline silica dust. Industrial sand used in certain operations, such as foundry work and hydraulic fracturing (fracking), is also a source of respirable crystalline silica exposure. About 2.3 million people in the U.S. are exposed to silica at work.

Workers who inhale these very small crystalline silica particles are at increased risk of developing serious silica-related diseases, including:

• Silicosis, an incurable lung disease that can lead to disability and death;
• Lung cancer;
• Chronic obstructive pulmonary disease (COPD); and
• Kidney disease.

To protect workers exposed to respirable crystalline silica, OSHA has issued two respirable crystalline silica standards: one for construction, and the other for general industry and maritime.

• Chronic cough
• Shortness of breath with exercise, usually in patients who have progressive massive fibrosis
• Weakness

• Cough
• Fever
• Severe breathing difficulty
• Weight loss
• Night Sweats
• Chest pains

Job Activities Posing Risk

There are various industries where workers can have jobs at risk for exposure to crystalline silica dust. Examples include:

• Construction
• Mining
• Oil and gas extraction
• Stone countertop
• Foundries and other manufacturing settings
• Dentistry

Job activities, such as cutting, quarrying, drilling, and abrasive blasting, can put a worker at risk for exposure if proper engineering controls and respiratory protection are not implemented.

Sources of Exposure

Crystalline silica is found in:

• Soil
• Sand
• Concrete
• Mortar
• Granite and other minerals
• Artificial stone

The most common form of crystalline silica is quartz. However, it can also occur in the form of cristobalite and tridymite. Exposure to cristobalite typically occurs in foundries where intense heat of molten metal causes cristobalite to form in clay molds. Hazardous levels of respirable dust can be released into the air when working with materials that contain crystalline silica.

Medical Monitoring

Medical monitoring or surveillance of workers can help identify health effects related to respirable crystalline silica exposure. An important concern is silicosis, a progressive and irreversible lung disease. Silica exposure can also impair lung function by causing COPD. Routine screening and surveillance for other diseases caused by silica is not required in the U.S. However, it is important to be aware that silica exposure can cause:

• Lung cancer
• Chronic kidney disease
• Various autoimmune diseases

It can also predispose exposed individuals to pulmonary tuberculosis (TB).

As lung tissue turns into scar tissue with silicosis, reduced lung function occurs and gets progressively worse, even after dust exposure has ended. Symptoms typically include:

• Shortness of breath
• Cough
• Wheezing
• Exercise intolerance

In order to make a diagnosis of silicosis, a history of exposure to respirable crystalline silica is needed. Clinical evidence of the disease through chest x-rays or computerized tomography (CT scans) or a lung biopsy is also needed. As appropriate, it is also necessary to exclude alternative diagnoses.

The time from initial exposure to when symptoms first appear (the latency period) with silicosis depends on duration and intensity of exposure. Higher exposures tend to result in shorter latency periods and faster disease development. The table below describes different types of silicosis. The type with the quickest onset is acute silicosis. This can occur after only a few weeks or months exposure to very high levels of respirable crystalline silica. In acute silicosis, affected parts of the lung fill with fluid, typically causing severe illness or death. Accelerated silicosis occurs after high levels of exposure and typically presents after 5 to 10 years. Chronic silicosis is the most common type. It occurs after 10 or more years of exposure to lower levels of silica.

Accelerated and chronic silicosis have the same radiographic appearance and are differentiated based on their different latency periods. Periodic medical monitoring of silica-exposed workers for respiratory symptoms, changes of silicosis on chest imaging, and pulmonary function can help individual workers. Monitoring helps to detect silicosis and COPD at early stages so workers can avoid further exposure.

Silicosis does not occur without causal levels of exposure to respirable crystalline silica. When cases are identified, efforts should be made to identify where failures in exposure controls occurred and correct them. In this way, identifying cases helps to improve protections for all those in a workplace.

There is no cure for silicosis. Employers should always inform workers if they could be exposed to respirable crystalline silica particles during their jobs and provide training on how to prevent exposure at work. Employers should also offer medical examinations to workers with sufficient levels of respirable crystalline silica exposure as required by the Occupational Safety and Health Administration (OSHA) . Under the rule, medical examinations must include:

• A respiratory questionnaire
• A physical examination
• A chest X-ray interpreted by a NIOSH certified B reader (a physician certified by the International Labor Organization (ILO) in interpreting radiological imaging of work-related lung diseases)
• Spirometry testing administered by a technician certified by a NIOSH-approved spirometry training course

Healthcare providers can play an important role in recognizing silica-induced diseases such as silicosis and engaging public health authorities. Providers should consider their patients’ jobs and possible hazardous workplace exposures when diagnosing diseases. If silicosis is a possible diagnosis, it is important to understand exactly what types of tasks were performed. It is also important to identify what protections were in place such as engineering controls, respirator use, and worker training. If deficiencies in current practices are identified, consider reporting or counseling the patient to report the situation to OSHA for general industry or the Mining Safety and Health Administration (MSHA) for mining. The patient can also be counseled about the NIOSH Health Hazard Evaluations (HHE) program. HHEs can be requested by 3 employees, a union representing the workplace, or the employer. Healthcare providers who suspect a patient’s health problems are caused by working with respirable crystalline silica should report the case to their local or state health department.

Health Risks of Exposure

Breathing in dust from silica-containing materials can lead to silicosis. Silica dust particles become trapped in lung tissue causing inflammation and scarring. The particles also reduce the lungs’ ability to take in oxygen. This condition is called silicosis. Silicosis results in permanent lung damage and is a progressive, debilitating, and sometimes fatal disease.

Chronic silicosis typically occurs after 10 or more years of exposure to respirable crystalline silica. However, the disease can occur much more quickly after heavy exposures. Silicosis can develop or progress even after workplace exposures have stopped.

Symptoms of silicosis may include:

• Cough
• Fatigue
• Shortness of breath
• Chest pain

There is no cure for silicosis and some patients may require lung transplantation.

Workers exposed to silica and those who have silicosis are also at increased risk of tuberculosis (TB), a contagious and potentially life-threatening infection.

Exposure to respirable crystalline silica puts workers at risk for developing other serious diseases including the following:

• Lung Cancer – Lung cancer results from cells in the body that grow out of control and develop into tumors. Cancerous cells from the lung can also invade other parts of the body, a process known as metastasis.
• Chronic Obstructive Pulmonary Disease (COPD) – COPD includes chronic bronchitis and emphysema. Symptoms of COPD include shortness of breath, coughing or wheezing, phlegm or sputum production, and trouble breathing.
• Kidney Disease – Studies of workers have shown that increasing levels of silica exposure are associated with increasing risks for chronic kidney disease.
• Autoimmune Disease – Studies of workers have shown that silica exposure is associated with increased risk for a variety of autoimmune diseases. These diseases include rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis (scleroderma).

​​​​​​What is crystalline silica?

An abundant natural material, crystalline silica is found in stone, soil, and sand. It is also found in concrete, brick, mortar, and other construction materials. Crystalline silica comes in several forms, with quartz being the most common. Quartz dust is respirable crystalline silica, which means it can be taken in by breathing.

How are people exposed to crystalline silica?

Exposure to tiny particles of airborne silica, primarily quartz dust, occurs mainly in industrial and occupational settings. For example, workers who use handheld masonry saws to cut materials such as concrete and brick may be exposed to airborne silica. When inhaled, these particles can penetrate deep into the lungs.

The primary route of exposure for the general population is inhaling airborne silica while using commercial products containing quartz. These products include cleansers, cosmetics, art clays and glazes, pet litter, talcum powder, caulk, and paint.

Which cancers are associated with exposure to crystalline silica?

Exposure of workers to respirable crystalline silica is associated with elevated rates of lung cancer. The strongest link between human lung cancer and exposure to respirable crystalline silica has been seen in studies of quarry and granite workers and workers involved in ceramic, pottery, refractory brick, and certain earth industries.

Crystalline silica is a natural component of stone, soil, and sand. It is also found in other materials such as concrete, mortar, granite, and artificial stone. The most common form of crystalline silica is quartz. If you work around these products, you could be exposed. Cutting, drilling, chipping, sanding, or grinding materials that contain crystalline silica can release hazardous levels of respirable dust in the air that workers breathe.

To prevent exposures, control dust by following safe work practices and using engineering controls (strategies used to modify equipment or a process to protect workers from hazards).

Engineering Controls and Safe Work Practices

• Follow dust control methods found in the Occupational Safety and Health Administration (OSHA) compliance guides for the construction industry and general industry and maritime. Dust control methods for mining can be found in the NIOSH Mining Program Report of Investigation: Dust Control Handbook for Industrial Minerals Mining and Processing – Second Edition.
• Use wet methods that apply water at the impact site where dust is generated.
• Remove silica dust using local exhaust ventilation at the point where dust is made.
• Use enclosures when available to isolate the work process.
• Consider using a combination of both water and ventilation controls.
• Ensure that all engineering controls are working properly prior to use and replace water and air filters as necessary to control dust.
• Avoid dry sweeping or using compressed air during regular and thorough housekeeping procedures.
• Use respiratory protection when dust controls and safe work practices cannot limit silica exposures below the Occupational Safety and Health Administration’s permissible exposure limit (PEL).
• Participate in a medical monitoring program when an employer has shown crystalline silica levels are above occupational exposure limits.
• Research methods for engineering controls of various tasks.