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Asbestos

1332-21-4 

Hazard Summary-Created in April 1992; Revised in January 2000

    Asbestos has been used in building materials, paper products, plastics, and other products.  Exposure mainly occurs in indoor air where it may be released from these materials.  Effects on the lung are a major health concern from asbestos, as chronic (long-term) exposure to asbestos in humans via inhalation can result in a lung disease termed asbestosis.  Asbestosis is characterized by shortness of breath and cough and may lead to severe impairment of respiratory function.  Cancer is also a major concern from asbestos exposure, as inhalation exposure can cause lung cancer and mesothelioma (a rare cancer of the thin membranes lining the abdominal cavity and surrounding internal organs), and possibly gastrointestinal cancers in humans.  EPA has classified asbestos as a Group A, known human carcinogen.


Please Note: The main sources of information for this fact sheet are EPA's Integrated Risk Information System (IRIS), which contains information on the carcinogenic effects of asbestos including the unit cancer risk for inhalation exposure, and the Agency for Toxic Substances and Disease Registry's (ATSDR's) Toxicological Profile for Asbestos.

Uses

  • The main uses of asbestos are in building materials, paper products, asbestos-cement products, friction products, textiles, packings and gaskets, and asbestos-reinforced plastics. (1)
  • Asbestos use in the United States is currently decreasing. (1)

Sources and Potential Exposure

  • Airborne exposure to asbestos may occur through the erosion of natural deposits in asbestos-bearing rocks, from a variety of asbestos-related industries, or from clutches and brakes on cars and trucks.  The concentrations in outdoor air are highly variable. (1)
  • Asbestos has been detected in indoor air, where it is released from a variety of building materials such as insulation and ceiling and floor tiles. It is only released, however, when these building materials are damaged or disintegrate.  Typical concentrations in indoor air range from 1 to 200 nanograms per cubic meter (ng/m3) (0.000001 to 0.002 milligrams per cubic meter (mg/m3)). (1)
  • Asbestos may be released to water from a number of sources, including erosion of natural deposits, corrosion from asbestos-cement pipes, and disintegration of asbestos roofing materials with subsequent transport into sewers. (1)

Assessing Personal Exposure

  • It is possible to test for the presence of asbestos fibers in urine, feces, or mucus.  In addition, a chest X-ray, although it cannot detect the asbestos fibers themselves, can detect early signs of lung disease caused by asbestos. (1)

Health Hazard Information

Acute Effects:
  • No studies were located on the acute (short-term) toxicity of asbestos in animals or humans. (1-4)
Chronic Effects (Noncancer):
  • Chronic inhalation exposure to asbestos in humans can lead to a lung disease called asbestosis, which is a diffuse fibrous scarring of the lungs. Symptoms of asbestosis include shortness of breath, difficulty in breathing, and coughing.  Asbestosis is a progressive disease, i.e., the severity of symptoms tends to increase with time, even after the exposure has stopped.  In severe cases, this disease can lead to death, due to impairment of respiratory function. (1,2)
  • Other effects from asbestos exposure via inhalation in humans include pulmonary hypertension and immunological effects. (1,2)
  • Feeding studies in animals exposed to high doses of asbestos have not detected any evidence of adverse toxic effects. (1,2)
  • EPA has not established a Reference Concentration (RfC) or a Reference Dose (RfD) for asbestos. (5)
Reproductive/Developmental Effects:
  • No studies were located on the developmental or reproductive effects of asbestos in animals or humans via inhalation. (1,2,3)
  • Birth defects were not noted in the offspring of animals exposed to asbestos in the diet during pregnancy. (1)
  • No effects on fertility were observed in animals exposed to asbestos in the diet during breeding, pregnancy, and lactation. (1)
Cancer Risk:
  • A large number of occupational studies have reported that exposure to asbestos via inhalation can cause lung cancer and mesothelioma (a rare cancer of the membranes lining the abdominal cavity and surrounding internal organs). (1,2,3)
  • Individuals who smoke and are also exposed to asbestos have a greater than additive increased risk of developing lung cancer. (1)
  • Several occupational studies have reported an increase in gastrointestinal cancer from inhalation exposure to asbestos and subsequent oral ingestion. (1,2)
  • Long- and intermediate-range asbestos fibers (>5 micrometers (µm)) appear to be more carcinogenic than short fibers (<5 µm). (1)
  • Several epidemiological studies have found an association between asbestos in drinking water and cancer of the esophagus, stomach, and intestines; however confounding factors and the short followup time relative to the long latent period for tumor formation make it difficult to interpret the results. (1,5)
  • A series of large-scale lifetime feeding studies in animals reported that intermediate-range asbestos fibers increased the incidence of a benign tumor of the large intestine in male rats, while short-range asbestos fibers showed no significant increase in tumor incidence. (1,5)
  • EPA considers asbestos to be a human carcinogen (cancer-causing agent) and has ranked it in EPA's Group A. (5)
  • EPA uses mathematical models, based on human and animal studies, to estimate the probability of a person developing cancer from breathing air containing a specified concentration of a chemical. EPA calculated an inhalation unit risk estimate of 2.3 × 10-1 (fibers/cm3)-1. EPA estimates that, if an individual were to continuously breathe air containing asbestos at an average of 0.000004 fibers/cm3 over his or her entire lifetime, that person would theoretically have no more than a one-in-a-million increased chance of developing cancer as a direct result of breathing air containing this chemical. Similarly, EPA estimates that breathing air containing 0.00004 fibers/cm3 would result in not greater than a one-in-a-hundred thousand increased chance of developing cancer, and air containing 0.0004 fibers/cm3 would result in not greater than a one-in-ten-thousand increased chance of developing cancer. (5)

Physical Properties

  • Asbestos is the name applied to a group of six different minerals that occur naturally in the environment. (1)
  • The most common mineral type is white, but others may be blue, gray, or brown. (1)
  • These minerals are made up of long, thin fibers that are somewhat similar to fiberglass. (1)
  • Asbestos is neither volatile nor soluble; however, small fibers may occur in suspension in both air and water. (1)


     

    Health Data from Inhalation Exposure

    Asbestos graph
    ACGIH TLV--American Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.
    NIOSH REL--National Institute of Occupational Safety and Health's recommended exposure limit; NIOSH-recommended exposure limit for an 8- or 10-h time-weighted-average exposure and/or ceiling.
    OSHA PEL--Occupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effect averaged over a  normal 8-h workday or a 40-h workweek.

The health and regulatory values cited in this factsheet were obtained in December 1999.
a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.
b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.  OSHA numbers are regulatory, whereas NIOSH and ACGIH numbers are advisory.

References

  1. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Asbestos (Draft). U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. 1995.
  2. E.J. Calabrese and E.M. Kenyon. Air Toxics and Risk Assessment. Lewis Publishers, Chelsea, MI. 1991.
  3. U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
  4. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.
  5. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Asbestos. National Center for Environmental Assessment, Office of Research and Development, Washington, DC. 1999
  6. National Institute for Occupational Safety and Health (NIOSH). Pocket Guide to Chemical Hazards. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention. Cincinnati, OH. 1997.
  7. Occupational Safety and Health Administration (OSHA). Occupational Safety and Health Standards, Toxic and Hazardous Substances. Code of Federal Regulations. 29 CFR 1910.1001. 1998.
  8. American Conference of Governmental Industrial Hygienists (ACGIH). 1999 TLV's and BEIs. Threshold Limit Values for Chemical Substances and Physical Agents, Biological Exposure Indices. Cincinnati, OH.  1999.
     

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