What is Asbestos?
Asbestos is a naturally occurring mineral. It differs from other minerals in its crystal development. The crystal formation of asbestos is in the form of long thin fibers. Asbestos is divided into two mineral groups - Serpentine and Amphibole. The division between the two types of asbestos is based upon the crystalline structure. Serpentines have a sheet or layered structure, whereas amphiboles have a chain-like structure.
As the only member of the serpentine group, Chrysotile is the most common type of asbestos found in buildings. Also known as "white asbestos," Chrysotile makes up approximately 90 to 95 percent of all asbestos contained in buildings in the United States.
In the amphibole group there are five types of asbestos. As an acronym for the Asbestos Mines of South Africa, Amosite is the second most prevalent type of asbestos found in building materials. Amosite is also known as "brown asbestos." Next there is Crocidolite, or "blue asbestos," which is an asbestos found in specialized high temperature applications. The other three types (Anthophylite, Tremolite, and Actinolite) are rare and found mainly in contaminants in other minerals. Asbestos deposits can be found throughout the world and are still mined in Australia, Canada, South Africa, and the former Soviet Union countries.
Over the years asbestos has had many uses. Its primary use is as an insulator or fire retardant, but can also be used as a binder. Due to this versatility, asbestos can be found in many types of building materials. Although the federal government placed a moratorium on the production of many asbestos products in the early 1970's, installation of these products continued through the late 1970's and even into the early 1980's.
Asbestos today is found in numerous building products sold throughout the United States. Under new trade agreements asbestos products are imported from Canada, Mexico, China, Russia and many other nations. Asbestos building products being sold include drywalls, plasters, mortars, grouts, mastics, insulations, ceiling tiles, floor tiles, roofing products, etc. Once installed, most asbestos products are regulated by state and federal regulations. Due to the fact that many of these products are not labeled, one of our challenges here at the University of Minnesota is to make sure asbestos containing materials are not installed in new construction.
Non-building material products that can be purchased in the United States range from crayons to brake pads and may or may not be labeled as asbestos. If you are concerned about a particular product you should contact the company that produces the product for more information.
Asbestos Health Risks
Most health information on asbestos exposure has been derived from studies of workers who have been exposed to asbestos in the course of their occupation. Asbestos fiber concentrations for these workers were many times higher than those encountered by the general public.
Because asbestos fibers are naturally occurring and extremely aerodynamic, virtually everyone is exposed to asbestos. To be a significant health concern, asbestos fibers must be inhaled at high concentrations over an extended period of time. Asbestos fibers then accumulate in the lungs. As exposure increases, the risk of disease also increases. Therefore, measures to minimize exposure and consequently minimize accumulation of fibers will reduce the risk of adverse health effects.
Asbestos is only dangerous if it is inhaled or ingested. As long as asbestos containing materials are not damaged, the asbestos fibers do not become airborne and do not pose a health threat to the building occupants. During an asbestos building survey, inspectors assess the condition of asbestos containing materials. These conditions do deteriorate over time.
If you find that an asbestos-containing item at the University of Minnesota has been damaged, please contact our office for a hazard assessment. Sean Gabor, manager for the Hazardous Materials Program, can be reached at 612-625-7547, or see the emergency response page for more immediate contact numbers.
When asbestos fibers accumulate in the lungs, several types of diseases may occur.
Asbestosis is a scarring of the lung tissue. This scarring impairs the elasticity of the lung and hampers its ability to exchange gases. This leads to inadequate oxygen intake to the blood. Asbestosis restricts breathing leading to decreased lung volume and increased resistance in the airways. It is a slow progressive disease with a latency period of 10 to 40 years.
Mesothelioma is a cancer of the pleural lining. It is considered to be exclusively related to asbestos exposure and can be obtained from limited exposure. By the time it is diagnosed, the victim of Mesothelioma usually has less than two years to live. Similar to Asbestosis, Mesothelioma has a latency period of 10 to 40 years.
Lung cancer is a malignant tumor of the bronchi covering. The tumor grows through surrounding tissue, invading and often obstructing air passages. The time between exposure to asbestos and the occurrence of lung cancer is 20 to 30 years. It should be noted that there is a synergistic effect between smoking and asbestos exposure, which creates an extreme susceptibility to lung cancer.
Digestive System Cancer
Asbestos may cause stomach and other types of digestive system cancer when asbestos fibers ingested through the mouth are swallowed and logged into the stomach and other areas of the digestive track, eventually causing the disease. Like lung cancer, the latency period for digestive system cancers is about 20 to 30 years.
Airborne Fiber Concentrations
Asbestos is known to be hazardous based on studies of high levels of exposure to asbestos workers and laboratory animals. However, the risks associated with low level, non-occupational exposure are not well established. Therefore, the Environmental Protection Agency (EPA) concludes that there is no safe level of exposure to asbestos fibers. On the other hand, the Occupational Safety and Health Administration (OSHA) has set a Permissible Exposure Limit (PEL at 0.1 fibers per cubic centimeter (f/cc)) for an eight-hour time weighted average. Similarly, the Minnesota Department of Health (MDH) has set the Clean Indoor Air Standard for buildings in the state of Minnesota at 0.01 f/cc.