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Asbestos Quickview (CASRN 1332-21-4)

Health assessment information on a chemical substance is included in IRIS only after a comprehensive review of toxicity data by U.S. EPA health scientists from several Program Offices, Regional Offices, and the Office of Research and Development.

Disclaimer: This QuickView represents a snapshot of key information. We suggest that you read the IRIS Summary to put this information into complete context.

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Status of Data for Asbestos

File First On-Line: 09/26/1988; Last Significant Revision: 09/26/1988

Category (section)
Last Revised
Oral RfD Assessment No
Inhalation RfC Assessment No
Carcinogenicity Assessment Yes 09/26/1988
  • Asbestos
  • 1332-21-4
  • Calidria-asbestos
Asbestos Source Documents
Revision History
Date Section Description
04/01/1997 III., IV., V. Drinking Water Health Advisories, EPA Regulatory Actions, and supplementary Data were removed from IRIS on or before April 1997. IRIS users were directed to the appropriate EPA Program Offices for this information.
Chronic Health Hazard Assessments for Noncarcinogenic Effects

Reference Dose for Chronic Oral Exposure (RfD)

Not Assessed under the IRIS Program.

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Reference Concentration for Chronic Inhalation Exposure (RfC)

Not Assessed under the IRIS Program.

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Carcinogenicity Assessment for Lifetime Exposure
  • Weight-of-Evidence Characterization
    • A (Human carcinogen)
  • Weight-of-Evidence Narrative:
    • Observation of increased mortality and incidence of lung cancer, mesotheliomas and gastrointestinal cancer in occupationally exposed workers are consistent across investigators and study populations. Animal studies by inhalation in two strains of rats showed similar findings for lung cancer and mesotheliomas. Animal evidence for carcinogenicity via ingestion is limited (male rats fed intermediate-range chrysotile fibers; i.e., >10 um length, developed benign polyps), and epidemiologic data in this regard are inadequate.
    • This may be a synopsis of the full weight-of-evidence narrative. See IRIS Summary.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure

  • Not Assessed under the IRIS Program.

Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure

Inhalation Unit Risk(s)
Extrapolation Method
2.3 x10-1 per f/mL Additive risk of lung cancer and mesothelioma, using relative risk model for lung cancer and absolute risk model for mesothelioma

Inhalation Concentrations at Specified Risk Levels

Risk Level
E-4 (1 in 10,000) 4x10-4 f/mL
E-5 (1 in 100,000) 4x10-5 f/mL
E-6 (1 in 1,000,000) 4x10-6 f/mL

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