1,4-Dioxane Quickview (CASRN 123-91-1)

Status of Data for 1,4-Dioxane

File First On-Line: 08/22/1988; Last Significant Revision: 08/11/2010

Category (section)	Status	Last Revised
Oral RfD Assessment	On-line	08/11/2010
Inhalation RfC Assessment	Discussion	08/11/2010
Carcinogenicity Assessment	On-line	08/11/2010

Synonyms

123-91-1 Diethylene oxide 1,4-Dioxane Dioxane, 1,4-

Diethylene dioxide p-Dioxane Dioxane

Chronic Health Hazard Assessments for Noncarcinogenic Effects

Reference Dose for Chronic Oral Exposure (RfD)

Critical Effect	Point of Departure*	UF	RfD
Liver and kidney toxicity	NOAEL : 9.6 mg/kg-day	300	0.03 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.

• Principal and Supporting Studies (Oral RfD)
  • Chronic oral male rat study, Kociba et al. 1974
• Confidence in the Oral RfD
  • Study -- Medium
  • Database -- Medium
  • RfD -- Medium

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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
  • Likely to be carcinogenic to humans
• Weight-of-Evidence Narrative:
  • In accordance with the Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005, 1,4-dioxane is characterized as "likely to be carcinogenic to humans."
  • This may be a synopsis of the full weight-of-evidence narrative. See IRIS Summary.

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Quantitative Estimate of Carcinogenic Risk from Oral Exposure

Oral Slope Factor(s)	Extrapolation Method
1 x10-1 per mg/kg-day	Log-logistic model with linear extrapolation from the POD (BMDL50HED) associated with 50% extra cancer risk.

Drinking Water Unit Risks
2.9x10-6 per µg/L

Risk Level	Concentration
E-4 (1 in 10,000)	35 µg/L
E-5 (1 in 100,000)	3.5 µg/L
E-6 (1 in 1,000,000)	0.35 µg/L

• Dose-Response Data (Carcinogenicity, Oral Exposure)
  • Tumor Type: Hepatocellular adenoma and carcinoma
  • Test Species: Female BDF1 mouse
  • Route: Oral, Drinking water
  • Reference: Kano et al. 2009

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Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure

• Information reviewed but value not estimated. See IRIS Summary.