IRIS

1,4-Dioxane

CASRN 123-91-1

Noncancer Assessment

Reference Dose for Oral Exposure (RfD) (PDF) (32 pp, 291 K) Last Updated: 08/11/2010

System RfD (mg/kg-day) Basis PoD Composite UF Confidence
Hepatic, Urinary 3 x 10-2 Liver and kidney toxicity NOAEL : 9.6
mg/kg-day
300 Medium

 


Reference Concentration for Inhalation Exposure (RfC) (PDF) (32 pp, 291 K) Last Updated: 09/20/2013

System RfC (mg/m3) Basis PoD Composite UF Confidence
Nervous, Respiratory 3 x 10-2 Atrophy and respiratory metaplasia of the olfactory epithelium LOAEL (HEC): 32.2
mg/m3
1000 Medium

 

Cancer Assessment

Weight of Evidence for Cancer (PDF) (32 pp, 291 K) Last Updated: 09/20/2013

WOE Characterization Framework for WOE Characterization
Likely to be carcinogenic to humans Guidelines for Carcinogen Risk Assessment (U.S. EPA, 2005)
Basis:
  • 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.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (32 pp, 291 K)

Oral Slope Factor: 1 x 10 -1 per mg/kg-day
Drinking Water Unit Risk: 2.9 x 10 -6 per µg/L
Extrapolation Method: Log-logistic model with linear extrapolation from the POD (BMDL50HED) associated with 50% extra cancer risk.
Tumor site(s): Hepatic
Tumor type(s): Hepatocellular adenoma and carcinoma (Kano et al. 2009)



Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure (PDF) (32 pp, 291 K)

Inhalation Unit Risk: 5 x 10 -6 per µg/m3
Extrapolation Method: Multi-tumor dose-response model with linear extrapolation from the POD (BMDL10HED) associated with 10% extra cancer risk.
Tumor site(s): Reproductive, Other, Hepatic, Urinary, Gastrointestinal, Respiratory
Tumor type(s): Multiple (nasal, liver, kidney, peritoneal, mammary gland, and Zymbal gland) (Kasai et al. 2009)


Additional EPA toxicity information may be available by visiting the following sites:

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