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Azobenzene Quickview (CASRN 103-33-3)

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 Azobenzene

File First On-Line: 09/07/1988; Last Significant Revision: 09/07/1988

Category (section)
Last Revised
Oral RfD Assessment No
Inhalation RfC Assessment No
Carcinogenicity Assessment Yes 09/07/1988
  • 103-33-3
  • Azobenzeen
  • Azobenzene
  • Azobenzide
  • Azobenzol
  • Azobisbenzene
  • Azodibenzene
  • Azodibenzeneazofume
  • Azofume
  • Benzeneazobenzene
  • Benzene, azodi
  • more...
Azobenzene Source Documents
Revision History
Date Section Description
04/01/1997 III., IV., V. Drinking Water Health Advisoreis, 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
    • B2 (Probable human carcinogen - based on sufficient evidence of carcinogenicity in animals)
  • Weight-of-Evidence Narrative:
    • Azobenzene induced invasive sarcomas in the spleen and other abdominal organs in male and female F344 rats following dietary administration. It is genotoxic and may be converted to benzidine, a known human carcinogen, under the acidic conditions in the stomach.
    • This may be a synopsis of the full weight-of-evidence narrative. See IRIS Summary.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure

Oral Slope Factor(s)
Extrapolation Method
1.1 x10-1 per mg/kg-day Linearized multistage procedure, extra risk
Drinking Water Unit Risks
3.1x10-6 per µg/L
Risk Level
E-4 (1 in 10,000) 3x101 µg/L
E-5 (1 in 100,000) 3 µg/L
E-6 (1 in 1,000,000) 3x10-1 µg/L

Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure

Inhalation Unit Risk(s)
Extrapolation Method
3.1 x10-5 per µg/m3 Linearized multistage procedure, extra risk

Inhalation Concentrations at Specified Risk Levels

Risk Level
E-4 (1 in 10,000) 3 µg/m3
E-5 (1 in 100,000) 3x10-1 µg/m3
E-6 (1 in 1,000,000) 3x10-2 µg/m3

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