By Isabelle Robinson, M.Sc.Mar 4 2019
Silica is one of the most commonly found elements on the planet, naturally occurring in most rocks - especially sand and clay. The full name of the compound mineral is silicon dioxide (SiO2).
Silicon dioxide can be found in the form of crystalline elements (such as sand and quartz), as well as non-crystalline or amorphous structures. It is present to varying degrees in most rock, sand, and clays. It is known that sandstone contains a high proportion of silica (approximately 70%), whereas harder rock, like granite, contains around 15-30% of the compound.
Because of its presence in the earth’s crust, silica makes up a large proportion of all building materials. Silica can be found in materials such as asphalt, brick, cement, concrete, drywall, grout, mortar, stone, sand, and tile.
Unlike asbestos, intact crystalline silica in these common construction materials is not hazardous. However, ordinary construction tasks could disturb the mineral. Tasks such as blasting, chipping, drilling, grinding and cutting can create extremely fine particles known as respirable crystalline silica, which can easily enter your lungs. This is particularly hazardous to construction workers or anyone in the area who could potentially breathe in the material. Due to its small size, the silica dust can enter deep within the lungs. In addition to this, it is usually too small to see under normal lighting, making it even more dangerous.
In fact, Silica in building materials is the second biggest risk to construction workers after asbestos exposure. Many medical research papers have found that prolonged or highly concentrated exposure to respirable crystalline silica (RCS) can lead to lung cancer and other serious diseases. Specifically, the American Thoracic Society and the American College of Occupational and Environmental Medicine have confirmed that RCS is linked to lung cancer and other health risks.
In 2005, the Health and Safety Executive (HSE) found that there were over 500 deaths related to the inhalation of RCS while working on construction sites in the UK.
Many illnesses can occur after inhaling crystalline silica, most of which are fatal. These include lung cancer, silicosis, tuberculosis, and chronic obstructive pulmonary disease. In addition to this, RCS has been connected to incidences of renal disease.
Silicosis, in particular, is an extremely unpleasant lung disease which is both disabling and irreversible. In some cases, silicosis has also been fatal. It occurs after a person inhales RCS. Their lungs react to the mineral by developing hard lumps and scars around the particles. When these become too large, they stop the lungs from working effectively, causing difficulties breathing.
In 1996, the World Health Organization (WHO) in association with the International Agency on Cancer Research (IARC) acknowledged the compound to be a “known human carcinogen”, a statement which was reconfirmed 12 years later.
Two reasons why silica dust is so hazardous to health are the smallness of its particles and the low exposure level required in order to be affected. The OSHA regulation 29 CFR 1926.55(a) rules that construction employers monitor silica dust concentrations and keep workers’ exposure to the compound mineral below the permissible exposure level of 50 µg/m3. However, it should be noted that the American Conference of Governmental Industrial Hygienists recommends a threshold limit value of 25 µg/m3. Nevertheless, this lower value is not mandatory under current regulatory guidelines.
- HSE. (2019). Cancer and Construction. Retrieved from hse.gov.uk: http://www.hse.gov.uk/construction/healthrisks/cancer-and-construction/silica-dust.htm
- NY Department of Health. (2019). Silicosis: Silica and Road Construction. Retrieved from New York State: Department of Health: https://www.health.ny.gov/environmental/workplace/lung_disease_registry/silicosis_road.htm
- OSHA. (2019). Work Safely with Silica. Retrieved from Silica-Safe: https://www.silica-safe.org/ask-a-question/faq#question4
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