Propylene Oxide Profile

Propylene Oxide Profile

General Information

Propylene oxide is a flammable, colorless liquid with a sweet, benzene-like odour.[1,2,3] It may also be referred to as epoxy propane or methyloxirane.[3] There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.[3]

Propylene oxide has been classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humans.[1] There was insufficient evidence available for the IARC Working Group to assess human carcinogenicity.[1] One case-control study found non-significant increases in lymphatic and hematopoietic cancers following exposure to propylene oxide. However, no information was given on exposure levels and the study subjects had concurrent exposures to other chemicals.[1] In experimental rats and mice, depending on the method of administration, propylene oxide caused increased incidence of forestomach, nasal, thyroid, adrenal gland, peritoneum, mammary gland, and skin cancers.[2]

Propylene oxide has not been reviewed by IARC since 1994, and more recent exposure and biomarker studies have renewed interest into further investigation of its carcinogenicity.[4]

Regulations and Guidelines

Occupational exposure limits (OEL)[5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]

Canadian JurisdictionsOEL (ppm)
Canada Labour Code2 [dsen]
BC, MB, NL, NS, PE2 [dsen]
NB2 [sen]
QC20 [em]
SK, NU, NT2 [sen]
4 [stel, sen]
YT100; 150 [stel]
Other JurisdictionsOEL (ppm)
ACGIH 2020 TLV2 [dsen]
ppm = parts per million
dsen = dermal sensitizer
sen = potential for sensitization
stel = short term exposure limit (15 min. maximum)
em = exposure must be reduced to the minimum
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value (8 hour maximum)

Canadian environmental guidelines and standards*

Alberta Ambient Air Quality Objectives1 hour: 480 µg/m3
Annual: 30 µg/m3
Ontario Ambient Air Quality Criteria24 hour: 1.5 µg/m3
Annual: 0.3 µg/m 3
Government of Canada’s Indoor Air Reference Levels2.7 µg/m3 (critical effect: nasal tumours)2011[22]
Ontario’s Air Pollution – Local Air Quality Regulation24-hour standard: 1.5 µg/m3; Prohibited discharge into the air if the concentration of propylene oxide exceeds the standard2020[23]
Quebec’s Clean Air Regulation1 hour limit: 3,100 µg/m3
1 year limit: 0.3 µg/m3; Prohibited discharge into the air if the concentration of propylene oxide exceeds the standards
BC’s Contaminated Sites Regulation, BC Reg 375/96Sets soil standards for the protection of human health:
Agricultural and low density residential sites: 30 μg/g
Urban park and high density residential sites: 60 μg/g
Commercial and industrial sites: 150 μg/g


Drinking water: 0.65 µg/L

Sets vapour standards for the protection of human health:
Agricultural, urban park, residential use standard: 2.5 μg/m3
Commercial use standard: 8 μg/m3
Industrial use standard: 25 μg/m3
Parkade use standard: 20 μg/m3
(Vapours derived from soil, sediment, or water)

Food Additives Permitted for UseAllowed as a starch-modifying agent2012[26]
Maximum Residue Limits on Food300 ppm for variety of nuts and spices


Cosmetic Ingredient HotlistProhibited for use in cosmetic products2010[28]
*Standards are legislated and legally enforceable, while guidelines (including Ontario ambient air quality criteria) describe concentrations of contaminants in the environment (e.g. air, water) that are protective against adverse health, environmental, or aesthetic (e.g. odour) effects
µg/m3 = micrograms per cubic metre
µg/g = micrograms per gram
ppm = parts per million

Canadian agencies/organizations

Health CanadaDSL – high priority substance with highest potential for exposure2006[29]
CEPASchedule 12010[30]
CMP ChallengeBatch 1 [Health]2008[31]
Environment Canada’s National Pollutant Release InventoryNPRI Part (Threshold Category): 1A, Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than: 10 tonnes2016[32]
DSL = Domestic Substances List
CEPA = Canadian Environmental Protection Act
CMP = Chemicals Management Plan

Propylene oxide was not included in other Canadian government guidelines, standards, or chemical listings reviewed.

Main Uses

In Canada, propylene oxide is a chemical intermediate used mainly to produce polyether polyols, which are then used to produce polyurethane foams.[2,3,33] Propylene oxide is also used to produce glycol ethers for use in paints and varnishes.[33] Propylene glycols are also manufactured from propylene oxide. Propylene glycols are used in a variety of products including resins, pharmaceuticals, food moisteners, inks, synthetic lubricants, solvents, additives in motor fuels, lubricants, and cleaners. They are also used to produce unsaturated polyester resins used in the textile and construction industries.[2,3,33]

Propylene oxide is approved for use in food as a starch-modifying agent and in natural health products as a preservative in Canada.[33] However, Health Canada reported in 2008 that no natural health products contained propylene oxide.[33] Propylene oxide is not used in cosmetics in Canada.[33] It is also not currently registered as a pesticide in Canada.[34]

In the US, propylene oxide is used to sterilize food products via fumigation.[2,33] In Canada, food items fumigated with propylene oxide are subject to Health Canada’s Maximum Residue Limits.[33] This limit is 0.1 ppm, though this does not apply to almonds, for which there is a higher limit noted in the Canadian Environmental Guidelines table above.[33]

Canadian Production and Trade

Propylene oxide is not manufactured in Canada. Domestic demand is met by imports from the United States.[33]

Production and trade

Import4 t2021[35]
Export1 t2021[35]
t = tonne

Environmental Exposures Overview

Propylene oxide does not occur naturally in the environment. It is released primarily into the air by industrial sites where it is used and stored.[33] According to a joint assessment by Health Canada and Environment Canada, propylene oxide is persistent in air but not in water and in soil.[36] The assessment also found that propylene oxide does not bioaccumulate.[36]

Other air emission sources include automobile exhaust and other combustion exhaust from stationary sources that burn hydrocarbons.[33] Based on propylene oxide usage patterns and limited environmental monitoring information, propylene oxide presence in soil and water is expected to be low.[36]

Exposure may also occur when using consumer products that contain propylene oxide, such as automotive products, spray paints, and paint strippers.[2,36]

Exposure to propylene oxide in the general public in Canada via foods is expected to be low.[33] Propylene oxide food additives break down into non-toxic products when combined with water during food production.[33] Health Canada conducts surveillance of propylene oxide in foods through the Food Safety Action Plan (FSAP). Propylene oxide was not detected in any of the 1,064 samples collected for analysis between 2009-2011.[37]

Propylene oxide releases to the environment are reportable to the National Pollutant Release Inventory (NPRI) in Canada. A total of 0.004 t was recorded for on-site releases in 2015.[38] A search of the US Consumer Product Information Database for propylene oxide yielded the following results:

US Consumer Product Information Database

US Consumer Products 2015[39]
Result: 8 products
Search TermQuantityProduct Type
‘propylene oxide’8Engine sealant (1), grease/lubricants (1), engine cleaner (1), paint cleaner (2), adhesive (1), carpet cleaner (1), mouthwash (1)

Occupational Exposures Overview

Inhalation is the most important route of occupational exposure to propylene oxide.[2]

The main occupations exposed to include workers involved in manufacturing polyurethane polyols and propylene glycol.[1,2] Occupational exposure may also occur in workers who use products containing propylene oxide, such as paint strippers.[2,33]

CAREX Canada has not prioritized Propylene Oxide for exposure estimate development. This is because there is a lack of exposure monitoring data in the Canadian Workplace Exposure Database on which to base an estimate.


1. International Agency for Research on Cancer (IARC). Monograph summary, Volume 60 (1994)
2. National Toxicology Program (NTP). 15th report on carcinogens for Propylene Oxide (2021) (PDF)
3. National Library of Medicine. PubChem (Search term: “propylene oxide”)
4. Ward EM, Schulte PA, Straif K, et al. “Research Recommendations for Selected IARC-Classified Agents.” Environ Health Perspect 2010;119(10):1355-1362.
8. The Canadian Legal Information Institute (CanLII). Manitoba Regulation 217/2006 Workplace Safety and Health Regulation (2022)
10. Government of Newfoundland and Labrador. Regulation 5,12 Occupational Health and Safety Regulations (2018)
11. Government of the Northwest Territories. Occupational Health and Safety Regulations, R-039-2015 (2020) (PDF)
13. The Canadian Legal Information Institute (CanLII). Government of Nunavut’s Occupational Health and Safety Regulations, Nu Reg 003-2016 (2010)
15. Government of Prince Edward Island. Occupational Health and Safety Act Regulations Chapter 0-1 (2013) (PDF)
17. Government of Saskatchewan. The Occupational Health and Safety Regulations, 1996 (2016) (PDF)
18. The Canadian Legal Information Institute (CanLII). Yukon’s Occupational Health Regulations, O.I.C. 1986/164 (2020) (PDF)
19. Occupational Safety and Health Administration (OSHA). Annotated PELs (2020)
20. Alberta Environment and Parks. Ambient Air Quality Objectives (2019)
21. Ontario Ministry of the Environment and Climate Change. Ontario’s Ambient Air Quality Criteria (2019)
22. Government of Canada. Summary of indoor air reference levels (2018)
24. Government of Quebec. Clean Air Regulation, Q-2, r. 4.1 (2020)
25. Government of British Columbia. Contaminated Sites Regulation B.C. Reg. 375/96 (2019)
28. Health Canada. Cosmetic Ingredient Hotlist (2019)
30. Environment and Climate Change Canada. Toxic Substances List – CEPA Schedule 1 (2010)
33. Government of Canada. Methyloxirane (propylene oxide) (2010)
35. International Trade Centre. TradeMap (Free subscription required)
36. Health Canada and Environment Canada. Screening Assessment for Methyloxirane (Propylene oxide) (75-56-9) (2008)
38. Environment and Climate Change Canada. National Pollutant Release Inventory (NPRI) Data Search (Substance name: ‘propylene oxide’)
39. Consumer Product Information Database. What’s in it? (Search term: “Propylene oxide”) (2022)


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