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Benzene Quickview (CASRN 71-43-2)

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 Benzene

File First On-Line: 03/01/1988; Last Significant Revision: 04/17/2003

Category (section)
Status
Last Revised
Oral RfD Assessment On-line 04/17/2003
Inhalation RfC Assessment On-line 04/17/2003
Carcinogenicity Assessment On-line 01/09/2000
Synonyms
  • Benzene
  • Coal naphtha
  • Phene
  • Phenyl hydride
  • Polystream
  • 71-43-2
  • Benzol
  • Cyclohexatriene
  • Pyrobenzol
Revision History
Date Section Description
01/19/2000 II., VI. Revised oral carcinogenicity section and references
Chronic Health Hazard Assessments for Noncarcinogenic Effects

Reference Dose for Chronic Oral Exposure (RfD)

Critical Effect
Point of Departure*
UF RfD
Decreased lymphocyte count BMDL : 1.2 mg/kg-day 300 4.0 x10-3 mg/kg-day

* The Point of Departure listed serves as a basis from which the Oral RfD was derived. See Discussion of Conversion Factors and Assumptions for more details.

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Reference Concentration for Chronic Inhalation Exposure (RfC)

Critical Effect
Point of Departure*
UF RfC
Decreased lymphocyte count BMCL : 8.2 mg/m3 300 3x10-2 mg/m3

* The Point of Departure listed serves as a basis from which the Inhalation RfC was derived. See Discussion of Conversion Factors and Assumptions for more details.

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Carcinogenicity Assessment for Lifetime Exposure
  • Weight-of-Evidence Characterization
    • A (Human carcinogen)
    • Known/likely human carcinogen
  • Weight-of-Evidence Narrative:
    • Benzene is classified as a "known" human carcinogen (Category A) under the Risk Assessment Guidelines of 1986. Under the proposed revised Carcinogen Risk Assessment Guidelines (U.S. EPA, 1996), benzene is characterized as a known human carcinogen for all routes of exposure based upon convincing human evidence as well as supporting evidence from animal studies. (U.S. EPA, 1979, 1985, 1998; ATSDR, 1997).
    • 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
1.5 x10-2 per mg/kg-day 1 Linear extrapolation of human occupational data
5.5 x10-2 per mg/kg-day 1 Linear extrapolation of human occupational data

1 This is one endpoint in a range of oral slope factors. See Additional Comments (Carcinogenicity, Oral Exposure).

Drinking Water Unit Risks
4.4x10-7 per µg/L2
1.6x10-6 per µg/L2

2 This is one endpoint in a range of drinking water unit risks. See Additional Comments (Carcinogenicity, Oral Exposure).

Risk Level
Concentration
E-4 (1 in 10,000) 1x102 µg/L1
E-5 (1 in 100,000) 1x101 µg/L1
E-6 (1 in 1,000,000) 1 µg/L1
 
E-4 (1 in 10,000) 1x103 µg/L1
E-5 (1 in 100,000) 1x102 µg/L1
E-6 (1 in 1,000,000) 1x101 µg/L1

1 This is one endpoint in a range of oral slope factors/drinking water unit risks. See Additional Comments (Carcinogenicity, Oral Exposure).


Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure

Inhalation Unit Risk(s)
Extrapolation Method
2.2 x10-6 per µg/m3 3 Low-dose linearity utilizing maximum likelihood estimates
7.8 x10-6 per µg/m3 3 Low-dose linearity utilizing maximum likelihood estimates

3 This is one endpoint in a range of inhalation unit risks. Additional Comments (Carcinogenicity, Inhalation Exposure).

Inhalation Concentrations at Specified Risk Levels

Risk Level
Concentration
E-4 (1 in 10,000) 1.3x101 µg/m31
E-5 (1 in 100,000) 1.3 µg/m31
E-6 (1 in 1,000,000) 1.3x10-1 µg/m31
 
E-4 (1 in 10,000) 4.5x101 µg/m31
E-5 (1 in 100,000) 4.5 µg/m31
E-6 (1 in 1,000,000) 4.5x10-1 µg/m31

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