Propylene Oxide Profile
INDUSTRIAL CHEMICALS – POSSIBLE CARCINOGEN (IARC 2B)
Propylene Oxide Profile
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. There are numerous other synonyms and product names; see the Hazardous Substances Data Bank (HSDB) for more information.
Propylene oxide has been classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humans. There was insufficient evidence available for the IARC Working Group to assess human carcinogenicity. 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. 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.
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.
Regulations and Guidelines
|Canadian Jurisdictions||OEL (ppm)|
|Canada Labour Code||2 [dsen]|
|BC, MB, NL, NS, PE||2 [dsen]|
|SK, NU, NT||2 [sen]
4 [stel, sen]
|YT||100; 150 [stel]|
|Other Jurisdictions||OEL (ppm)|
|ACGIH 2020 TLV||2 [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 Objectives||1 hour: 480 µg/m3
Annual: 30 µg/m3
|Ontario Ambient Air Quality Criteria||24 hour: 1.5 µg/m3
Annual: 0.3 µg/m 3
|Government of Canada’s Indoor Air Reference Levels||2.7 µg/m3 (critical effect: nasal tumours)||2011|
|Ontario’s Air Pollution – Local Air Quality Regulation||24-hour standard: 1.5 µg/m3; Prohibited discharge into the air if the concentration of propylene oxide exceeds the standard||2020|
|Quebec’s Clean Air Regulation||1 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 375/96||Sets 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:
|Food Additives Permitted for Use||Allowed as a starch-modifying agent||2012|
|Maximum Residue Limits on Food||300 ppm for variety of nuts and spices||
|Cosmetic Ingredient Hotlist||Prohibited for use in cosmetic products||2010|
*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
|Health Canada||DSL – high priority substance with highest potential for exposure||2006|
|CMP Challenge||Batch 1 [Health]||2008|
|Environment Canada’s National Pollutant Release Inventory||NPRI Part (Threshold Category): 1A, Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than: 10 tonnes||2016|
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.
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. 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. However, Health Canada reported in 2008 that no natural health products contained propylene oxide. Propylene oxide is not used in cosmetics in Canada. It is also not currently registered as a pesticide in Canada.
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. 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.
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. According to a joint assessment by Health Canada and Environment Canada, propylene oxide is persistent in air but not in water and in soil. The assessment also found that propylene oxide does not bioaccumulate.
Other air emission sources include automobile exhaust and other combustion exhaust from stationary sources that burn hydrocarbons. Based on propylene oxide usage patterns and limited environmental monitoring information, propylene oxide presence in soil and water is expected to be low.
Exposure to propylene oxide in the general public in Canada via foods is expected to be low. Propylene oxide food additives break down into non-toxic products when combined with water during food production. 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.
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. A search of the US Household Products Database for propylene oxide yielded the following results:
US Household Products Database
|US Household Products 2015|
|Result: 8 products|
|Search Term||Quantity||Product Type|
|‘propylene oxide’||8||Engine 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.
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.
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