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Isophorone Quickview (CASRN 78-59-1)

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 Isophorone

File First On-Line: 01/31/1987; Last Significant Revision: 10/01/1992

Category (section)
Last Revised
Oral RfD Assessment Yes 09/01/1989
Inhalation RfC Assessment Message 03/01/1991
Carcinogenicity Assessment Yes 10/01/1992
  • 78-59-1
  • Isoacetophorone
  • Isoforon
  • Isophoron
  • alpha-Isophoron
  • Isophorone
  • alpha-Isophorone
  • 3,5,5-Trimethyl-2-cyclohexenone
Isophorone Source Documents
Chronic Health Hazard Assessments for Noncarcinogenic Effects

Reference Dose for Chronic Oral Exposure (RfD)

Critical Effect
Point of Departure*
Kidney pathology (other effect: Kidney pathology. ) NOEL : 1.50 x102 mg/kg-day 1000 2 x10-1 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)

Information reviewed but value not estimated. See IRIS Summary.

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Carcinogenicity Assessment for Lifetime Exposure
  • Weight-of-Evidence Characterization
    • C (Possible human carcinogen)
  • Weight-of-Evidence Narrative:
    • Based on no data in humans; limited evidence of carcinogenicity of one tumor type in one sex of one animal species as shown by an increase of preputial gland carcinomas in male rats. The apparent renal tubular cell tumor in the male rat is associated with alpha-2u-globulin, considered to be of questionable relevance to humans.
    • 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
9.5 x10-4 per mg/kg-day Linearized multistage procedure, extra risk
Drinking Water Unit Risks
2.7x10-8 per µg/L
Risk Level
E-4 (1 in 10,000) 4x103 µg/L
E-5 (1 in 100,000) 4x102 µg/L
E-6 (1 in 1,000,000) 4x101 µg/L

Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure

  • Not Assessed under the IRIS Program.

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