“Silicosis: What you need to know”
Each year according to the Occupational Safety and Health Administration (OSHA) more than two million workers in the American workforce are exposed to silica and at least 100,000 of them are at high risk of developing the completely preventable disease, silicosis. According to the National Institute for Occupational Safety and Health (NIOSH) (See Figure 1), silicosis was contributing or underlying cause in 161 deaths in 2005.
Figure 1. Silicosis: Number of deaths, crude and age-adjusted death rates, U.S. residents age 15 and over, 1968–2005.
What is silica dust?
Crystalline silica, or silicon dioxide (SiO2), the agent responsible for silicosis, is formed when oxygen combines with silicon. Crystalline silica is most commonly found in the form of quartz and is a component of sand, common rocks, almost every mineral, and occurs in most soils. Practically all dust to which a brickworker is exposed at brick plants contains some amount of crystalline silica. The clays and shales used in brickmaking all contain variable amounts of crystalline silica and the sands used in coatings similarly contain crystalline silica.
How does silica dust affect the body?
When silica-containing respirable dust exposures exceed safe levels, the number
of silica particles inhaled can exceed the ability of the lung to remove them Extremely tiny particles of silica (too small to see with the naked eye) then build up in the lungs leading to the dust disease silicosis. Crystalline silica has also been classified as a human lung carcinogen.
What is silicosis?
Silicosis is caused by scarring of the lungs due to inhalation of dust containing crystalline silica. Silicosis is a disease where scar tissue forms in the lungs and reduces the ability for oxygen from the air to be exchanged with carbon dioxide in the bloodstream. In severe cases, silicosis can be disabling and even fatal. There is no cure for silicosis and it is not a reversible condition. It can, however, be prevented.
There are three types of silicosis:
- Chronic Silicosis: Usually occurs after many years, often 15 – 20, of excessive exposure to crystalline silica. This is the most common type of silicosis.
- Accelerated Silicosis: Results from exposure to higher levels of crystalline silica and occurs after 5 – 10 years after exposure begins.
- Acute Silicosis: Usually occurs after a few months or as long as 2 years following exposures to extremely high concentrations of respirable crystalline silica. This condition often leads to death.
Symptoms: Symptoms may not appear in the early stages of chronic silicosis. In fact, chronic silicosis may go undetected for 15 to 20 years after exposure. As silicosis progresses, symptoms may include:
- Shortness of Breath
- Severe cough
Because the body’s ability to fight infections may be weakened by silicosis, other illnesses, such as tuberculosis, may result.
Potential Silica Exposures at Brickmaking Operations
| Normal Lung
|| Silicotic Lung
|Guidance: Have member companies develop a list.
||Guidance: Enter range from historic sampling data.
||Guidance: List examples of control
(e.g. local exhaust ventilation; contol booths; water sprays; respirators, etc.)
What can I do to protect myself?
- Be aware of the health effects of breathing air that has silica dust in it.
- Avoid working in dust wherever possible.
- Know what operations in brickmaking are the dustiest.
- Reduce the amount of silica dust by doing the following:
- Use exhaust ventilation where provided.
- Inform appropriate persons if you think exhaust ventilation is not working properly.
- Use work practices that reduce the amount of dust created.
- Avoid dry sweeping of dust. Use HEPA vacuums or wash down using water.
- Avoid use of compressed air to blow off surfaces.
- Clean floors regularly and keep in moistened condition, if possible.
- Where feasible designate foot traffic routes within plants and ensure the routes are routinely cleaned.
- When exhaust ventilation and other controls are not enough to reduce dust levels use your respirator for protection against crystalline silica.
- Remove facial hair (beard, mustache, etc.) that would interfere with your respirator making a proper seal to your face.
- Participate in company dust monitoring and medical screening programs.
Permissible Exposure Limit
OSHA and the Mine Safety and Health Administration (MSHA) have established a Permissible Exposure Limit (PEL) for crystalline silica to which workers may be exposed during an 8-hour shift. The OSHA PEL for brickmaking is dependent on the amount of crystalline silica (quartz) that is present in the dust. The formula for this calculation is given below:
Respirable Dust PEL (Quartz) = 10 mg/m3
% Quartz + 2
This level for crystalline silica as 100% quartz is equivalent to 0.1 mg/m3. The OSHA PEL for general industry can be found at 29 Code of Federal Regulations 1910.1000.
Where can I get additional information?
- OSHA’s Crystalline Silica Safety and Health Topics Page: http://www.osha.gov/SLTC/silicacrystalline/index.html
- OSHA’s Silica Advisor: http://www.osha.gov/SLTC/etools/silica/compare_to_limit/genius/genius.html
- NIOSH Safety and Health Topic: Silica: http://www.cdc.gov/niosh/topics/silica/
- DOL/NIOSH: A Guide to Working Safely with Silica: http://www.msha.gov/S&HINFO/SILICO/SILICAX.pdf
Remember – Silicosis is Preventable. Do Your Part to Protect Yourself.
1NIOSH, Work-Related Lung Disease (WoRLD) Surveillance System, Volume 1: Silicosis: Mortality. NIOSH website, last visited 05-29-2009;
Through the OSHA and Brick Industry Association (BIA) Alliance, BIA developed this fact sheet for informational purposes only. It does not necessarily reflect the official views of OSHA or the U.S. Department of Labor. December/2009