Crystalline silica is a common mineral found in the earth’s crust. Sand, stone, concrete and mortar contain crystalline silica. Glass, pottery, ceramics, bricks and artificial stone are also made with crystalline silica. Crushing, drilling or cutting these minerals creates a superfine dust that people breathe into their lungs. Silica dust exposure can lead to severe health problems or death.
The Occupational Safety and Health Administration (OSHA) estimates that 2.3 million workers are exposed to silica as part of their jobs. Learn more about silica dust and ways to test for and prevent exposure.
Job duties that can cause silica dust exposure
Workers in various industries could be exposed to silica dust in their daily duties. These tasks include:
- Abrasive blasting with sand
- Sawing brick or concrete
- Sanding or drilling into concrete walls
- Grinding mortar
- Manufacturing or installing brick, concrete blocks, stone countertops or ceramic products
- Cutting or crushing stone
- Foundry work
- Drilling and hydraulic fracturing (aka fracking)
Health dangers caused by crystalline silica dust
Crystalline silica particles are tiny, at least 100 times smaller than beach sand. They might look like dust in the air, but they’re more insidious than that. Your workers could get disabling silica-related diseases if they breathe in silica dust particles, including:
- Silicosis: A lung disease caused by inhaling silica particles. Over time, the particles cause inflammation and scarring in the lungs, making breathing difficult. Silicosis causes permanent lung damage.
- Lung cancer: A type of cancer that begins in the lungs and can spread to lymph nodes or other parts of the body. It can develop in people with prolonged exposure to harmful substances like silica dust. Even people who have never smoked can develop lung cancer.
- Chronic obstructive pulmonary disease (COPD): COPD is an inflammatory lung disease that obstructs airflow, causing symptoms like breathing difficulty, cough, excessive mucus and wheezing. Long-term exposure to air pollutants, like silica dust, can cause COPD.
- Kidney disease: OSHA reports that workers exposed to respirable crystalline silica have a higher risk of developing kidney disease. Diseased kidneys filter waste from the body less effectively, and kidney disease can sometimes progress to kidney failure.
Ways to reduce silica dust exposure in the workplace
OSHA’s Respirable Crystalline Silica standard protects workers from exposure to dangerous levels of silica dust. The standard establishes a permissible exposure limit (PEL), or the maximum amount of crystalline silica a worker can be exposed to during an eight-hour shift. The PEL must not exceed 50 micrograms per cubic meter.
The standard also requires employers to prevent workers from being exposed to silica dust. Some of the prevention requirements are:
Exposure control plan
You must create a written exposure control plan. Your plan must identify tasks that increase workers’ silica dust exposure, ways to control exposure or restrict access to hazardous areas, and how you will train your employees.
Engineering controls and exposure control methods
You should use engineering controls such as water, ventilation and work methods to minimize worker exposure.
OSHA’s standard includes a handy table that describes respiratory protection and safety control methods for widely used machines and work tasks.
For example, a concrete drill jig vacuums silica dust as it drills into cement. The two primary components are a special drill bit and a dust collection unit. Unlike traditional drill bits, the drill bit on a concrete drill jig has a hollow center. When you drill into concrete, the bit cuts through the concrete, creating silica dust. The vacuum nozzle connects to an opening at the top of the drill bit shaft where the hollow center begins. The vacuum sucks up the silica dust and deposits it into a container. The hollow bit and vacuum combination prevent silica dust from dispersing into the work environment.
Housekeeping
You should implement good housekeeping practices to prevent the accumulation of silica dust. Prevention can include vacuum dust collection and water delivery systems to cut down on dust. Avoid dry brushing, dry sweeping or using compressed air to clean since it pushes crystalline silica dust into the air, causing an inhalation hazard.
Personal protective equipment (PPE)
Use dust masks and respirators if you can’t engineer out the silica dust exposure at your work site. Have each employee trained and fitted when you use respirators.
Employee training
Train your workers on silica dust risks, including proper PPE and ways to limit their exposure. Tell them about the health effects of silica exposure and the purpose of medical surveillance if their job duties require it.
Work site air sampling and analysis
Test your work site if crystalline silica is in the materials you use. According to OSHA, the maximum allowable amount of breathable crystalline silica in the air spread over an eight-hour total weight average (TWA) is 50 micrograms per cubic meter. Breathing in particles above this permissible exposure limit (PEL) can compromise employee safety and health.
You can assess for silica dust using a personal cyclone sampling device. Cyclones are small, lightweight devices worn on clothing. They pull air through at a specified flow rate and separate dust particles based on size. This allows them to measure the amount of silica in the environment.
You can hire a professional silica testing firm to assess the air for silica dust exposures. If you’re not clear on the monitoring techniques for your industry, a professional testing facility might be your best option. Something as simple as an incorrect flow rate can skew results so it’s important to understand the devices and how to calibrate them.
Make sure to follow OSHA’s Appendix A, Methods of Sample Analysis requirements for analyzing air samples for respirable crystalline silica.
Action levels and exposure assessments
OSHA’s action level is when the airborne concentration of silica dust is at 25 micrograms per cubic meter using the eight-hour TWA. Exposures at or above this action level trigger requirements for exposure assessments and medical surveillance.
- If the most recent exposure assessment reveals employee exposures at or above the action level but below the PEL, you must repeat silica exposure monitoring within six months.
- If the most recent exposure assessment reveals employee exposures above the PEL, you must repeat silica exposure monitoring within three months.
Medical surveillance
If dust exposure exceeds OSHA’s action level for 30 or more days each year, you must offer medical exams. The exams must include chest X-rays and lung function tests every three years. Use OSHA’s Appendix B, Medical Surveillance Guidelines to help physicians and licensed health care professionals (PLHCP) understand the medical surveillance provisions of the Respirable Crystalline Silica standard. Appendix B is divided into seven sections:
- Section 1: Silica-related diseases, medical and public health responses
- Section 2: Components of the medical surveillance program
- Section 3: Roles and responsibilities of the PLHCP implementing the program
- Section 4: Confidentiality and other considerations
- Section 5: Additional resources
- Section 6: References used to create the appendix
- Section 7: Sample forms for the written medical report for the employee, the written medical opinion for the employer and the written authorization
Recordkeeping
Keep records of employee training, as well as air sampling, silica exposure and medical exam results. Document your findings and the actions you took to reduce silica dust exposure.
Competent person
OSHA requires construction industry employers to designate a competent person to identify existing and predictable silica hazards. This competent person must have the authority to take prompt corrective measures.
Reassessing exposures
You must reassess for silica exposure whenever a change in production, process, equipment, personnel or work practices could result in new or added exposures.
You can read more about the OSHA standard in these publications:
- Small Entity Compliance Guide for the Respirable Crystalline Silica Standard for Construction (PDF)
- Small Entity Compliance Guide for the Respirable Crystalline Silica Standard for General Industry and Maritime (PDF)
Contact OSHA or an industrial hygienist for help
Remember, the ultimate goal of the guidelines is to prevent exposure and protect workers’ health and safety. If you need help with respirable silica dust, contact OSHA’s On-Site Consultation Program for free, confidential assistance. Or hire an industrial hygienist to perform air quality testing and recommend ways to reduce silica dust.