Propylene oxide

CASRN 75-56-9

Health Hazard Assessments for Effects Other than Cancer


Reference Dose for Oral Exposure (RfD) (PDF) (22 pp, 157 K)
Not assessed under the IRIS Program.

Reference Concentration for Inhalation Exposure (RfC) (PDF) (22 pp, 157 K) last updated: 11/01/1990

RfC (mg/m3) System Basis PoD Composite UF Confidence
3 x 10-2 Respiratory Nest-like infolds of the nasal respiratory epithelium LOAEL (HEC): 2.9
mg/m3
100 Medium

Cancer Assessment


Weight of Evidence for Cancer (PDF) (22 pp, 157 K) last updated: 10/01/1990

WOE Characterization Framework for WOE Characterization
B2 (Probable human carcinogen - based on sufficient evidence of carcinogenicity in animals) Guidelines for Carcinogen Risk Assessment (US EPA, 1986)
Basis:
  • Based on inadequate human data and an increased incidence of benign and malignant tumors at the site of exposure in two species of animals, when exposed by subcutaneous injection, by inhalation, and by gavage. There was also evidence of mutagenicity in a variety of test systems. Propylene oxide is structurally similar to other chemicals that demonstrate carcinogenic activity in animals.
  • This may be a synopsis of the full weight-of-evidence narrative.

Quantitative Estimate of Carcinogenic Risk from Oral Exposure (PDF) (22 pp, 157 K)

Oral Slope Factor: 2.4 x10 -1 per mg/kg-day
Drinking Water Unit Risk: 6.8 x10 -6 per µg/L
Extrapolation Method: Linearized multistage procedure, extra risk
Tumor site(s): Gastrointestinal
Tumor type(s): Forestomach, squamous cell carcinoma (Dunkelberg, 1982)


Quantitative Estimate of Carcinogenic Risk from Inhalation Exposure (PDF) (22 pp, 157 K)

Inhalation Unit Risk: 3.7 x10 -6 per µg/m3
Extrapolation Method: Linearized multistage procedure, extra risk
Tumor site(s): Respiratory
Tumor type(s): Nasal cavity hemangioma or hemangiosarcoma (NTP, 1985 Renne et al., 1986)


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