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

Major use
We assigned each chemical into one of the following groups based on its major sources and uses: industrial chemicals, chlorinated solvents, products of combustion, pesticides, dyes, radiation and drinking water disinfection, pharmaceuticals, hormones, natural products, and research chemicals.
Industrial chemical
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Found in consumer products
"Likely" indicates that the chemical is contained in consumer products or traces of the chemical are present in products, including food and water, resulting in likely exposure for the general population. For some chemicals marked as "likely," consumer product uses have been discontinued, and this will be indicated in the "Use in Consumer Products" field.
Food additive in US
Chemicals are classified as "Listed" or "Not listed" in the Everything Added to Food in the United States database developed by the US Food and Drug Administration.(22)
California Proposition 65
Chemicals are labeled "Listed" or "Not listed" based on the Proposition 65 list of chemicals updated on May 27, 2005. Listed chemicals are "chemicals known by the State of California to cause cancer or reproductive toxicity"(19).
Air pollutant
Chemicals classified as "Likely" air pollutants are those likely to be found in indoor or outdoor air, including products of combustion and industrial chemicals that may offgas from consumer products, leading to human exposure.
Not likely
Current High Production Volume chemical
Chemicals are classified "Yes" or "No," based on 2002 production volume information submitted to the US EPA: "Yes" for >1 million pounds produced; "No" for < 1 million pounds produced. Some past production volumes are referenced, where appropriate, in the HPV comment column (20). In addition, Scorecard.org is referenced and noted in the HPV comment column when it was inconsistent with current production volume information obtained from US EPA (21).
Production volume information
Production volume information is from the US EPA database on non-confidential production volume information submitted by companies for chemicals under the 1986-2002 Inventory Update Rule (IUR) using the most updated (2002) values (20). The Inventory Update Rule requires the submission of basic production data every four years on chemical substances manufactured (including imported) for commercial purposes in amounts of 25,000 pounds or more at a single site. Out of over 80,000 chemicals on the TSCA Chemical Substances Inventory, reports are required for approximately 9,000 substances. For those substances with annual volumes of 300,000 lbs or more per site, reporters also submit chemical processing and use information.
> 1 billion
General population exposure
This field includes information describing pathways of exposure for the general population obtained from a variety of sources including: IARC Monographs (9), NTP 11th ROC on Carcinogens (4), NTP Study Reports and Abstracts (3), Hazardous Substance Database (10), and other sources located through use of the Google search engine.
General population exposure may occur through ingestion of propylene oxide residues in foods from its use as an indirect food additive. Exposure may also occur by contact with consumer products containing the chemical, especially automotive and paint products which have been found to contain high concentrations of the chemical (11th ROC).
Use in consumer products
Summaries of chemical use in consumer products were developed from information found in US EPA SRD (11), NLM HPD (12), and Scorecard (12). Major uses were taken from IARC Monographs (9), NTP 11th ROC (4), NTP Study Reports (3), HSDB (10), and PAN Pesticides Database (13). If a chemical could not be found in these sources, we searched ToxNet (14), PubChem (15), and The Merck Index (16), and conducted searches by both name and CAS No. using Google.
65 consumer products listed with EPA contain chemical including: auto products, finishes, stains, aerosol paints, paint removers, adhesives, sealants (SRD). Propylene oxide has been detected in 6.2% of 1,159 consumer products that are used indoors; products found to contain the highest concentration of propylene oxide were automotive and paint products (HSDB). Used primarily as a chemical intermediate to produce polyether polyols, propylene glycols and propylene glycol ethers. It is used to a lesser extent in the production of hydroxypropyl starch ethers, as a food additive and as a fumigant for certain dried fruits and nuts (IARC 1994 vol.:60 p.181). Polyurethane polyols are used to make polyurethane foams; whereas, propylene glycols are primarily used to make unsaturated polyester resins for the textile and construction industries. Propylene glycols are also used in drugs, cosmetics, solvents and emollients in food, plasticizers, heat transfer and hydraulic fluids, and antifreezes. In addition, propylene oxide may be used in fumigation chambers for the sterilization of packaged foods and medical equipment and as a pesticide (11th ROC). Currently registered for use as a pesticide (PAN Pesticides Database).
Occupational exposure to women
We extracted the total number of potentially exposed workers and the number of potentially exposed female workers from the National Occupational Exposure Survey (NOES) 1981-1983; we listed specific industry classifications if >5,000 women were potentially exposed in that industry. Note: NOES does not include farm workers.
NOES 1981-1983-Total exposed: 421,140 Females exposed: 317,309 Occupational fields exposed: nurses and other hospital workers, various machine operators.
US EPA cancer classification
The US EPA Weight of Evidence Characterization of the chemicalís carcinogenic potential is listed: Group A: Carcinogenic to humans; Group B: Probably carcinogenic to humans. Group C: Possibly carcinogenic to humans. Group D: Not classifiable as to human carcinogenicity. Group E: Evidence of non-carcinogenicity for humans. NA: Not evaluated by US EPA (17).
B2: Probably Carcinogenic to Humans, inadequate evidence
US EPA Weight of Evidence narrative
US EPA narrative statement of overall weight of evidence for carcinogenicity (animal, human, and other supportive data).
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.
US EPA slope factor basis
Lists target organs used for estimating carcinogenic potency of the chemical (17).
Oral: Forestomach, squamous cell carcinoma-female rat; Inhalation: Nasal cavity hemangioma or hemangiosarcoma-male mouse
NIOSH Pocket Guide - potential carcinogen?
This field indicates whether NIOSH identifies the chemical as a potential carcinogen for workers (yes/no) (24).
NIOSH Pocket Guide - cancer sites
Lists target organs from animal cancer bioassays (24).
Risk assessments not reviewed for this chemical