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. 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.