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Heptachlor epoxide Quickview (CASRN 1024-57-3)

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.

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Status of Data for Heptachlor epoxide

File First On-Line: 09/30/1987; Last Significant Revision: 09/30/1987

Category (section)
Last Revised
Oral RfD Assessment Yes 09/30/1987
Inhalation RfC Assessment No
Carcinogenicity Assessment Yes 09/30/1987
  • 1024-57-3
  • Epoxyheptachlor
  • HCE
  • 1,4,5,6,7,8,8-Heptachloro-2,3-epoxy-2,3,3a,4,7,7a-hexahydro-4,7-methanoindene
  • 1,4,5,6,7,8,8-Heptachloro-2,3-epoxy-3a,4,7,7a-tetrahydro-4,7-methanoindan
  • 2,3,4,5,6,7,7-Heptachloro-1a,1b,5,5a,6,6a-hexahydro-2,5-methano-2h-indeno(1,2- b)oxirene
  • Hiptachlor epoxide
  • 2,5-Methano-2h-oxireno(a)indene, 2,3,4,5,6,7,7-heptachloro-1a,1b,5,5a,6,6a-hexahydro-
  • Velsicol 53-cs-17
  • ENT 25,584
  • Heptachlor epoxide
  • 4,7-Methanoindan, 1,4,5,6,7,8,8-heptachloro-2,3-epoxy-3a,4,7,7a-tetrahydro-
Heptachlor epoxide Source Documents
Chronic Health Hazard Assessments for Noncarcinogenic Effects

Reference Dose for Chronic Oral Exposure (RfD)

Critical Effect
Point of Departure*
Increased liver-to-body weight ratio in both males and females LEL : 1.25 x10-2 mg/kg-day 1000 1.3 x10-5 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)

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:
    • Sufficient evidence exists from rodent studies in which liver carcinomas were induced in two strains of mice of both sexes and in CFN female rats. Several structurally related compounds are liver carcinogens.
    • 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
9.1 per mg/kg-day Linearized multistage procedure, extra risk
Drinking Water Unit Risks
2.6x10-4 per µg/L
Risk Level
E-4 (1 in 10,000) 4x10-1 µg/L
E-5 (1 in 100,000) 4x10-2 µg/L
E-6 (1 in 1,000,000) 4x10-3 µg/L

Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure

Inhalation Unit Risk(s)
Extrapolation Method
2.6 x10-3 per µg/m3 Linearized multistage procedure, extra risk

Inhalation Concentrations at Specified Risk Levels

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

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