Crystalline Silica: Medical Monitoring
A physician speaking with a patient and taking notes. Photo by Getty Images
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. Although routine screening and surveillance for other diseases caused by silica is not required in the U.S., it is important to be aware that silica exposure can also cause lung cancer, chronic kidney disease, various autoimmune diseases, and can 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, and exercise intolerance.
In order to make a diagnosis of silicosis, a history of exposure to respirable crystalline silica is needed, along with clinical evidence of the disease through chest x-rays or computerized tomography (CT scans) or a lung biopsy. 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, which 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 and occurs after 10 or more years of exposure to lower levels of silica than those that cause accelerated silicosis.
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 by detection of silicosis and COPD at early stages so they can avoid further exposure. In addition, since silicosis does not occur without causative levels of exposure to respirable crystalline silica, when cases are identified efforts should be made to identify where breakdowns in exposure controls occurred and correct them if still present. In this way, identification of cases helps to improve protections for all those in a workplace.
|Type of silicosis||Exposure level||Latency period||Severity of illness|
|Acute||Very high||Weeks to months||Severe morbidity and mortality are common|
|Accelerated||High||5 to 10 years||Variable, often severe|
|Chronic||Lower than accelerated||More than 10 years||Variable, mild to severe|
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) external icon. 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 and what protections were in place such as engineering controls, use of respirators, 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, in which an HHE 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.
- NIOSH Health Effects of Occupational Exposure to Respirable Crystalline SilicaApril 2002; DHHS (NIOSH) Publication Number 2002-129–This review describes the literature on the health effects of occupational exposure to respirable crystalline silica among workers in the United States and many other countries.
- Occupational Respiratory Disease Surveillance (ORDS): SilicosisNIOSH Topic Page about silicosis disease state-based surveillance.
- Severe Silicosis in Engineered Stone Fabrication Workers — California, Colorado, Texas, and Washington, 2017–2019Morbidity and Mortality Weekly Report: September 27, 2019 / 68(38);813–818.
- Surveillance for Silicosis Deaths Among Persons Aged 15–44 Years — United States, 1999–2015Morbidity and Mortality Weekly Report: July 21, 2017 / 66(28);747–752.
- Summary of Notifiable Noninfectious Conditions and Disease OutbreaksMorbidity and Mortality Weekly Report: October 14, 2016 /63(54);73–78.
- Surveillance for Silicosis — Michigan and New Jersey, 2003–2011Morbidity and Mortality Weekly Report: October 14, 2016 /63(55);73–78.
- Update: Silicosis Mortality – United States, 1999-2013Morbidity and Mortality Weekly Report: June 19, 2015 /23(64);653–654.
- Silicosis Mortality Trends and New Exposures to Respirable Crystalline Silica – United States, 2001-2010Morbidity and Mortality Weekly Report: February 13, 2015 / 15(64);117–120.
- Notes from the Field: Silicosis in a Countertop Fabricator – Texas, 2014Morbidity and Mortality Weekly Report: February 13, 2015 / 64(05);129–130.
- Work-Related Lung Disease (eWoRLD) Surveillance SystemThe National Institute for Occupational Safety and Health (NIOSH) produces this surveillance system, which presents up-to-date summary tables, graphs, and figures of occupationally-related respiratory disease surveillance data on the pneumoconioses, occupational asthma and other airways diseases, and several other respiratory conditions. For many of these diseases, selected data on related exposures are also presented.