Environment and Breast Cancer: Science Review

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1,2-propylene oxide
CAS RN 75-56-9

Cancer studies: Mammary gland tumors
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Originating list
The list(s) or database(s) in which the chemical was identified as showing an increase in mammary gland tumors. CPDB: Carcinogenic Potency Database, IARC: International Agency for Research on Chemicals Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man summaries, NTP TR: National Toxicology Program (NTP) Technical Reports, NTP 11ROC: NTP 11th Report on Carcinogens, CCRIS: Chemical Carcinogenesis Research Information Service.
Carcinogenicity Potency Database, IARC Monographs
Mammary gland tumor summary
A summary of findings related to mammary gland tumors, most often excerpted from IARC Monographs or the NTP 11th ROC, and, in some cases, supplemented by our evaluation of individual studies and reviews, is available for the priority chemicals and 67 others.
Mixed evidence of mammary gland tumors.
Citations to review sources and individual studies reporting mammary gland tumors are listed below.
Source Type
International Agency for Research on Cancer, Monographs on the evaluation of carcinogenic risk of chemicals to man.VOL.: 60 (1994) (p. 181). Propylene oxide.
Reports a study in rats by inhalation that increases mammary tumors: Kuper 1988.
Carcinogenic Potency Database 2005. Gold LS ST, Manley NB, Garfinkel GB, Ames BN. Summary Table by Chemical of Carcinogenicity Results in CPDB on 1485 Chemicals. 2005
Two of four studies report mammary tumors: NTP TR267 and Kuper 1988. Two studies did not report mammary tumors: Lynch 1984 and Dunkelberg 1982.
Kuper CF, Reuzel PG, Feron VJ, Verschuuren H. Chronic inhalation toxicity and carcinogenicity study of propylene oxide in Wistar rats. Food Chem Toxicol 1988;26(2):159-67.
Primary Literature

experimental details
Increased benign mammary tumors significantly, malignant tumors nonsignificantly in female rats. 0, 30, 100, 300 ppm for 6 hr/day, 5 d/wk for 28 months.females: 32/69, 30/71, 39/69, 47/70 fibroadenoma; females: 3/69, 6/71, 5/69, 8/70 adenocarcinoma.
National Toxicology Program Technical Report 267
Primary Literature

experimental details
Nonsignificant increase in malignant mammary tumors in mice. female mice:0, 200, 400 ppm for 6 hrs/d, 5 d/wk for 103 wks. 0/50, 3/50, 3/50 adenocarcinoma. IARC dosen't note mammary tumors from this study.
Dunkelberg H. Carcinogenicity of ethylene oxide and 1,2-propylene oxide upon intragastric administration to rats. Br J Cancer 1982;46(6):924-33.
Primary Literature
A study listed by CPDB 2005 that did not report mammary tumors (rat, oral). Also negative in IARC.
Lynch DW, Lewis TR, Moorman WJ, Burg JR, Groth DH, Khan A, et al. Carcinogenic and toxicologic effects of inhaled ethylene oxide and propylene oxide in F344 rats. Toxicol Appl Pharmacol 1984;76(1):69-84.
Primary Literature
A study listed by CPDB 2005 that did not report mammary tumors. Also negative in IARC.
National Toxicology Program 11th Report on Carcinogens, Table 1. Chemicals nominated to the National Toxicology Program for in-depth toxicological evaluation for carcinogenesis testing in fiscal years 1988-2003.
Not nominated for NTP testing in 1998-2003.