Respirable dust can penetrate deep into the lungs. The body’s natural defence mechanisms may eliminate much of the respirable dust inhaled. However, in case of prolonged exposure to excessive levels of this dust, it becomes difficult to clear the dust from the lungs and an accumulation can, in the long term, lead to irreversible health effects. Exposure to any type of respirable dust may cause health effects.
For many years, it has been known that prolonged inhalation of fine dust containing a proportion of crystalline silica can cause a specific type of lung damage called silicosis. In fact, silicosis is the world’s oldest known occupational disease. However, the health risks associated with exposure to crystalline silica dust can be controlled and, by using appropriate measures, reduced or eliminated completely. It is just a matter of assessing the risk and taking appropriate action.
A recent hazard assessment of Respirable Crystalline Silica health effects has been commissioned to a team of scientific experts who produced two reports:
- Review and Hazard Assessment of the Health Effects of Respirable Crystalline Silica (RCS) Exposure to inform Classification and Labelling under the Global Harmonised System: Overview Report (Borm P, Brown T, Donaldson K, Rushton L, 2009); and
- Review of the Literature of the Health Effects of Occupational Exposure to Crystalline Silica: Silicosis, Cancer and Autoimmune Diseases (Brown T, Rushton L, 2009)
What is silica?
Silica is one of the most common naturally occurring elements on the planet. Silica, the mineral compound silicon dioxide (SiO2), is found in two forms — crystalline or noncrystalline (also referred to as amorphous). Sand and quartz are common examples of crystalline silica.
When is silica a hazard for construction workers?
Materials that contain crystalline silica are not hazardous unless they are disturbed, generating small-sized particles that can get in your lungs (“respirable crystalline silica”). For example, blasting, cutting, chipping, drilling and grinding materials that contain silica can result in silica dust that is hazardous for construction workers and others to breathe. For a list of construction materials that contain silica go to the “Know the Hazard” section of this website.
What construction materials contain silica?
Many common construction materials contain silica including, for example, asphalt, brick, cement, concrete, drywall, grout, mortar, stone, sand, and tile. A more complete list of building materials that contain silica, as well as information on how to find out if the material you’re working with contains silica, can be found in Step 1 of the Create-A-Plan section of the website.
How much silica dust is too much?
It only takes a very small amount of the very fine respirable silica dust to create a health hazard. Recognizing that very small, respirable silica particles are hazardous, OSHA regulation 29 CFR 1926.55(a) requires construction employers to keep worker exposures at or below a Permissible Exposure Level (PEL) of 0.1 mg/m3. The National Institute for Occupational Safety and Health has a lower Recommended Exposure Level of 0.05 mg/m3. More information about the hazard and links to examples of exposures with and without controls compared to the OSHA PEL, can be found at “Know the Hazard? Why is Silica Hazardous?”.
What illnesses can result from breathing in dust that contains silica?
Inhaling crystalline silica can lead to serious, sometimes fatal illnesses including silicosis, lung cancer, tuberculosis (in those with silicosis), and chronic obstructive pulmonary disease (COPD). In addition, silica exposure has been linked to other illnesses including renal disease and other cancers. In 1996 the World Health Organization – International Agency on Cancer Research (IARC) identified crystalline silica as a “known human carcinogen” (they reaffirmed this position in 2009). The American Thoracic Society and the American College of Occupational and Environmental Medicine have also recognized the adverse health effects of exposure to crystalline silica, including lung cancer.