Asbestos Exposure

Asbestos Exposure Asbestos is the name given to a group of naturally occurring minerals that occur as bundles of fibers. The fibers can be separated into thin threads that are very durable, resistant to heat, chemicals, and fire, and do not conduct electricity. These properties are very desirable for building materials, and asbestos was used extensively in many industries before the dangers of asbestos exposure were understood.

When materials containing asbestos are disturbed, they can release tiny asbestos fibers which are then inhaled into the lungs. The nearly-indestructible nature of asbestos fibers makes them harmful to the body. They can remain in lung tissue for a very lung time and cause scarring, inflammation, and several malignant and nonmalignant conditions (1).

Clearance of asbestos fibers from the human body is believed to be related to size.
Fibers that are shorter in length than a human macrophage, the type of cell that protectively destroys foreign material in the body, are better removed than those fibers which are longer than the macrophage (generally 14-21 micrometers). Longer fibers may be only partially destroyed, with parts remaining to cause disease reactions (2).

It seems likely that everyone living within industrialized countries is exposed to some degree of asbestos, and most people do not become ill from minor exposure. Health risks from asbestos clearly increase with increased concentrations of exposure and increased length of time of exposure, although some asbestos-related disease can develop in people with only short-term exposure. Some types of asbestos fibers may be more dangerous than others. Also, smoking can greatly increase the risk of lung disease among those people exposed to asbestos (1).

Inhalation of asbestos fibers was first linked to lung disease in 1890. The first deaths attributable to asbestos exposure were reported in 1907. The oldest known asbestos-related disease is asbestosis, which is a fibrotic reaction of the lung parenchyma to the presence of asbestos fibers. It became very frequent in the last quarter of the twentieth century, as did asbestos-related lung cancer. Mesothelioma, which develops after the longest latency period of any of the asbestos related diseases, continues to increase in many countries.

Potential sources of asbestos exposure are widespread. The greatest rates of exposure are generally occupational. People who work with asbestos-containing products in aircraft manufacturing, shipyard workers, auto mechanics who work with brake materials, railroad and refinery workers, asbestos abatement or building demolition workers, asbestos miners and millers, textile workers who weave asbestos into cloth, and asbestos transport workers, among others, are at risk (3). All kinds of construction workers may be exposed to asbestos materials, as well as firefighters and rescue personnel who are exposed to heavily damaged asbestos-containing materials in the course of rescue operations.

Nonoccupational exposure to asbestos is a health risk as well. A significant source of environmental exposure is in public buildings. Asbestos-containing materials that are now banned or regulated are still present in older construction and remain an exposure hazard. During maintenance, repair, demolition or renovation, asbestos fibers may be released, putting building occupants or passers-by at risk.

Of public buildings, schools are a particular concern. Asbestos was used as a spray-on material for school ceilings, mostly from the 1950s through the 1970s, because of its insulating, soundproofing and fireproofing qualities. This material crumbles over time, yielding a dust containing asbestos fibers that are suspended in classroom air. The level of asbestos inside school buildings with asbestos ceiling materials can be 100 times higher than the air outside, though it remains usually three or four orders of magnitude lower than workplace levels associated with well-documented occupational disease (4).  It is hard to quantify the health effects of these elevated asbestos levels, particularly because it can take such a long time for disease to develop following asbestos exposure.

Another type of environmental exposure has been documented in the town of Libby, Montana, where a prominent vermiculite mine operated until 1991. The vermiculite here was heavily contaminated with asbestos. Once considered insignificant in health effects, secondary exposure has been clearly demonstrated to be a risk factor. Long-term mortality studies in Libby demonstrate that activities of family members of asbestos workers, such as doing laundry for a miner or playing in the ball field or mine tailings in town, could result in enough exposure to cause asbestos-related disease (5).

A mortality study in the community found a more than 40-fold increase in standardized mortality rates for asbestosis, as well as elevated rates of asbestos-related malignant neoplasms. Some researchers suspect that there is a connection between asbestos exposure and autoimmune diseases such as lupus, rheumatoid arthritis, and scleroderma (6). Studies of the Libby population may help confirm this link.

Vermiculite mined in Libby, which provided a majority of the world’s supply until 1991, was used primarily for attic insulation. Homeowners and construction workers continue to be at risk of exposure to this asbestos-contaminated product, particularly plumbers, cable installers, telephone repair people, insulators and electricians who may disturb attic insulation.

The US did not begin making laws to limit asbestos exposure until 1971. The United States Environmental Protection Agency (EPA) and Department of Labor, Occupational Safety and Health Administration (OSHA) have heavily regulated the asbestos industries and the occupational handling of asbestos over the past 20-30 years, so exposure for most workers is likely to be much lower than in the past. However, the long lifespan of asbestos building materials means that there are many structures still standing that can present an exposure risk when damaged or demolished. During the World Trade Center disaster, for example, tons of asbestos-containing materials rained down on New York City, and they will have far-reaching health effects.

Internationally, asbestos exposure affects asbestos workers, their families, users of asbestos products, and the general public exposed to building materials in their homes and public buildings. The World Health Organization (WHO) and the International Labor Organization (ILO) are intended to be responsible for occupational health and safety. These organizations have been criticized as responding much too slowly and ineffectively to asbestos issues which can be critical in developing countries desperate for industrial growth (7).

'Asbestos Exposure' Resources:
  1. National Cancer Institute. Asbestos Exposure: Questions and Answers. National Cancer Institute FactSheet. 2007 February.
  2. Sullivan, P. Vermiculite, Respiratory Disease, and Asbestos Exposure in Libby, Montana: Update of a Cohort Mortality Study. Environmental Health Perspectives. 2007 April. Vol.115 (4), pp. 579-585.
  3. O’Reilly, K.M., McLaughlin, A.M., Beckett, W.S., and Sime, P.J.  Asbestos-related Lung Disease.  American Family Physician. 2007 March. Vol. 75 (5), pp. 683-8.
  4. Committee on Environmental Hazards. Asbestos Exposure in Schools. Pediatrics. 1987 February. Vol. 79 (2), pp. 301-305.
  5. Harder, B. More than a Miner Problem. Science News. 2003 July. Vol. 164, issue 2.
  6. Noonan, C., Pfau, J.C., Larson, T.C., and Spence, M.R. Nested Case-Control Study of Autoimmune Disease in an Asbestos-Exposed Population. Environmental Health Perspectives. 2006 August. Vol. 114 (8), pp. 1243-1247.
  7. LaDou, J. The Asbestos Cancer Epidemic. Environmental Health Perspectives. 2004 March. Vol. 112 (3), pp. 285-290.