Crystalline silica is a mineral commonly found in sand, soil, stone, granite, concrete, and mortar. Quartz, for example, is one of the most common forms of crystalline silica. Other common forms include cristobalite and tridymite. Crystalline silica is used in the making of numerous products that include glass, pottery, ceramics, bricks and artificial stone.
While crystalline silica is not dangerous in solid form, workers can breathe it in when they chip, cut, drill or grind any materials that contain crystalline silica.
Respirable Crystalline Silica
Tiny particles of crystalline silica, about 100 times smaller than the grains of sand found on beaches, are formed during cutting, drilling and crushing processes. Workers can easily breathe in these particles, also referred to as silica dust, and this, in turn, can lead to serious medical issues.
Any activity which cuts into materials containing crystalline silica can create silica dust, but blasting is of particular concern. It is also used in abrasive sandblasting operations to clean, smooth or shape surfaces. For example, abrasive blasting is often used to remove corrosion and rust from surfaces, and workers can become exposed to the tiny particles used in this process.
According to the U.S. Department of Labor (DOL), over two million workers in the U.S. are exposed to silica dust in the workplace every year. This number includes 100,000 who are at a much higher risk due to their work in abrasive blasting, foundry work, stonecutting, rock drilling, quarry work and tunnelling.
The Risks of Crystalline Silica Exposure
When inhaled, respirable silica dust particles enter the lungs and can cause severe and sometimes fatal diseases of the lungs and kidneys. This risk is exponentially increased by long term exposure to silica dust. The majority of these diseases are irreversible and many can be fatal.
Crystalline silica is a known carcinogen and can put workers at a highly elevated risk for lung cancer, chronic obstructive pulmonary disease (COPD), and kidney disease. Exposure to respirable crystalline silica has also been linked to the development of autoimmune disorders and cardiovascular impairment.
One of the most common health issues associated with crystalline silica is silicosis, which is an irreversible, incurable and sometimes fatal lung disease. It is caused by long term, sustained occupational exposure to respirable crystalline silica. Silicosis occurs when the lungs harden and develop scarring around the inhaled and trapped silica particles. Symptoms may not appear until the accumulated damage is severe, so it can often only be revealed through an x-ray of the lungs.
Silicosis greatly reduces lung function, making sufferers more susceptible to other lung diseases such as tuberculosis. It also puts smokers, whose lungs are already damaged, at a much higher risk.
There are three classifications of silicosis:
- Chronic silicosis occurs after 10 or more years of exposure to low concentrations of crystalline silica.
- Accelerated silicosis results from exposure to high concentrations of crystalline silica and may develop 5 to 10 years after initial exposure.
- Acute silicosis occurs when exposure concentrations are high, and symptoms can appear within a few weeks or for up to 4 or 5 years following initial exposure
OSHA Final Rule
The U.S. Occupational Safety and Health Administration (OSHA) issued a new final rule in 2016 with guidelines for employers on worker exposure to crystalline silica. There are separate rules for construction workers and for general industry and maritime workers. The vast majority of workers exposed to crystalline silica, approximately 1.85 million of the total 2.2 million total workers, are exposed via their work in the construction industry.
The major rule change lies in the major reduction in allowable exposure. The new permissible exposure limit (PEL) set by OSHA is 50 µg/m3, (micrograms of silica per cubic meter of air) averaged over an 8-hour day. Additionally, the rules dictate that employers must assess employee exposure if it might be at or above an action level of 25 µg/m3.
Additional Considerations for Employers
The proposed rules also include provisions for:
- Mandating companies to assign someone to monitor and assess silica exposure
- Limiting workers' access to areas where silica exposures are high
- Enforcing the use of effective methods for reducing exposures
- Providing medical exams, including chest x-rays, to workers with high silica exposures every three years
- Training for workers about silica-related hazards and how to limit exposure
What Employers Can Do
There are a number of actions that employers can take to further protect their workers.
- Replace crystalline silica materials with safer substitutes, whenever possible. For example, substituting a non-silica abrasive material in blasting operations.
- Provide engineering controls or administrative controls, where feasible, such as local exhaust ventilation, and blasting cabinets. Where necessary to reduce exposures below the PEL, use personal protective equipment or other protective measures.
- Use water sprays and other measures to control dust exposures.
- Provide N95 NIOSH certified respirators. Do not allow alterations that alter the respirator and potentially impact the effectiveness of the device.
- Do not allow employees to have beards or moustaches if they must wear a tight-fitting respirator, as these can prevent a proper seal.
- Provide Type CE abrasive-blast supplied-air respirators for abrasive blasting.
- Provide disposable or washable work clothes and on-site shower facilities for employees. Also, consider providing industrial vacuums to allow employees to remove dust from work clothes prior to changing into clean clothes following a shift.
- Ensure workers and supervisors are aware of the operations and jobs that increase crystalline silica exposures in your workplace. Provide ongoing education regarding available protections for your workers and activities which can put them at further risk including smoking.
- Forbid the consumption of food or drinks in areas where crystalline silica dust is present. Provide hand and face washing areas outside of these areas.