Product Safety Assessment (PSA): Propylene
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Manufacture of Product
Physical Hazard Information
- Propylene is a major industrial chemical intermediate that serves as one of the building blocks for an array of chemical and plastic products. See Product Uses.
- Propylene does not cause adverse health or environmental effects at the low levels typically found in the workplace or in the environment.
- Propylene exposures from both natural and man-made sources are likely only in very low levels. See Exposure Potential.
- Propylene is flammable with a high vapor pressure; use good ventilation and avoid all ignition sources. See Physical Hazard Information.
- Capacity – In 2002, about 22 million metric tons (49 billion pounds) of propylene were produced in Asia, 17 million metric tons (37 billion pounds) in Western Europe, and 21 million metric tons (45 billion pounds) in North America.1 Global capacity for propylene produced for chemical purposes is about 70 million metric tons (154 billion pounds).1 Dow production capacity is about two million metric tons (4 billion pounds) globally at eight production sites in the U.S., Canada, and Europe. Dow capacity in the U.S. exceeds one million metric tons (2.5 billion pounds) at three sites, and ranks in the top 10 U.S. producers of propylene for chemical use.
- Process – Two operations are used to produce propylene: 1) as a by-product of ethylene production and 2) as a by-product of refinery operations. Dow produces propylene as a by-product of ethylene production using a steam cracking process. Steam cracking uses heat to produce a mixture of hydrocarbons from feedstocks such as ethane, propane, natural gas, or liquid petroleum products. Specific products, such as propylene, are then isolated by distillation.
- Natural production – Propylene exists naturally in the environment from sources such as vegetation and combustion, e.g., fires, motor vehicle exhaust, and tobacco smoke.
Commercial propylene is a colorless, low-boiling, flammable, and highly volatile gas. Three grades are available:
- 95-100% polymer grade
- 90-99.8% chemical grade
- 50-70% refinery grade (taken from refinery operations; not produced by Dow)
Essentially all of the propylene produced for chemical purposes is consumed as a chemical intermediate in other chemical manufacturing processes. Commercial propylene is used to produce polypropylene, acrylonitrile, oxo chemicals, propylene oxide, cumene, isopropyl alcohol, acrylic acid and other chemicals which enable the manufacture of many chemicals and plastics.2 Examples include:
- Propylene glycols for paints, household detergents and automotive brake fluids
- Polypropylene fibers for indoor/outdoor carpeting
- Polyurethane systems for rigid foam insulation and flexible foam seat cushions
- ABS resins for telephones and automotive trim parts molded
In addition to its use as a chemical intermediate, propylene is produced and consumed in refinery operations for the production of gasoline components. (See Additional Information for instructions to access a product flow chart). Although propylene can be used as a fuel, this is not an economically attractive use.
Propylene exists naturally in the environment, where it is produced by vegetation and emitted from certain tree species. It is also a combustion product from motor vehicle exhaust, aircraft exhaust and cigarette smoke and is an impurity in some heating gases.3
- Workplace/occupational exposure – The primary exposure to propylene is occupational. The American Conference of Governmental Industrial Hygienists (ACGIH) has adopted a Threshold Limit Value (TLV®) of 500 parts per million (ppm).4 The Netherlands, Denmark and Sweden have established Occupational Exposure Limits (OELs) for propylene at 500 ppm. Both of these are 8-hour time-weighted averages (TWA).5 Exposures can be minimized through sound operating disciplines and procedures. Emissions of propylene in industrial operations should be minimized to avoid the possibility of fire or asphyxiation. Emissions should also be minimized to comply with environmental regulations limiting emissions of volatile organics.
- Consumer exposure – No consumer uses of propylene are known, so exposure to commercially produced propylene is highly unlikely. However, propylene exists naturally in the environment from sources such as vegetation and combustion and could present opportunity for exposure.
- Environmental exposure – Exposure to very low levels of propylene may occur in the environment from the combustion of fossil fuels, space heating, losses from gas plants and refineries, cigarette smoke, and gradual emissions from marine matrices and natural marine environments.6 Propylene concentrations have been observed in the range of 0.1-4.8 parts per billion (ppb) in rural air samples to 4-10.5 ppb in urban air samples, and 7-260 ppb in industrial air samples.7 The observed air concentrations are far below the ACGIH TLV® of 500 ppm.
- Large release – Today’s modern chemical production units are designed to minimize emissions and releases to the environment. However, any propylene which is released into the environment from industrial operations is expected to dissipate primarily to the air, where it is expected to degrade rapidly.8 Propylene releases in production operations are a flammability concern, if the concentration is high enough.9
Propylene is a material intended for industrial applications, not consumer use. Propylene is a gas at normal temperatures and pressures. It is unlikely to be ingested or absorbed through the skin. In addition:
- Propylene is not irritating to the skin or eyes in its gaseous state. However, propylene is typically stored and transported as a liquefied gas under pressure. Although consumer exposure to liquid propylene is extremely unlikely, tissue freezing, severe cold burn and frostbite could result if skin or eye contact should occur with propylene in its liquid state.
- Studies show that propylene has low acute toxicity from inhalation. Inhalation of propylene gas can cause anesthetic effects and at very high concentrations, unconsciousness. However, the asphyxiation limit for humans is about 10 times higher (236,000 ppm) than the lower flammability level for propylene.10
- Propylene is not likely to be mutagenic in humans. Further, propylene is not likely to be a cancer-causing substance, as supported by data from two National Toxicology Program studies on rats and mice.11
- Inhalation exposure studies of pregnant rats showed no maternal, prenatal or developmental toxicity at any tested concentration up to 10,000 ppm. In addition, repeated dose inhalation studies showed no significant effects on male or female reproductive organs.12
Propylene is not expected to persist in the environment. Since propylene is a gas, it is expected to go primarily into the air when released into the environment. Propylene is not expected to bioaccumulate, based on a calculated bioconcentration factor of 13.18 using a log Kow value of 1.77.13
Because of its relatively short half-life in the atmosphere and typically low environmental concentrations, propylene’s contribution to potential global warming is considered minor. Its ozone depletion potential is negligible.
Propylene gas is expected to dissipate primarily to the air rather than to water, so no aquatic toxicity testing has been conducted. According to predictive estimates and calculations, there is a low potential for propylene to increase in concentration over time in aquatic species.
Studies show that propylene can be degraded in the environment. It is not expected to attach to, or be absorbed significantly by, organic matter in soil, sediment or wastewater solids.
In the U.S., propylene is considered a volatile organic compound (VOC) and emissions are regulated at the federal, state, or local level. Propylene is not listed by the U.S. Environmental Protection Agency (EPA) as a hazardous air pollutant (HAP) under the Clean Air Act (CAA). Refer to the Safety Data Sheet, available from the Dow Customer Information Group, for additional regulatory information.
Propylene is a flammable material and should be handled only with adequate ventilation and in areas where ignition sources have been removed (e.g., matches and unprotected light switches). The lower flammability level for propylene is about 20,000 ppm (2.0 volume percent in air). If flammability levels are reached, evacuate the area and call emergency response personnel.
Propylene is a flammable gas. The flash point for propylene is -162ºF (-108ºC).14
Regulations may exist that govern the manufacture, sale, transportation, use and/or disposal of propylene. These regulations may vary by city, state, country or geographic region. Information may be found by consulting the relevant Safety Data Sheet or Contact Us.
- For the Safety Data Sheet, please Contact Us to request this information.
- OECD SIDS Initial Assessment Profile
Search CAS # 115071
- IUCLID Dataset
Search CAS # 115071
Select IUCLID Chemical Data Sheet
- Chemicals Unit of the European Union
- European Chemical Industry Council (CEFIC – http://www.cefic.be/)
- U.S. EPA High Production Volume (HPV) Challenge Program - Propylene Streams Category
- U.S. Environmental Protection Agency
- European Chemical Industry Council (CEFIC) Petrochemistry web site
To access an interactive product flow chart:
Select About petrochemistry
Select From petrochemistry to every day products
- Dow’s Polypropylene web site
- Propylene Oxide web site
Other sources include:
- Chemical Week – Product Focus
- Chemical Market Reporter – Chemical Profile
- International Agency for Research on Cancer IARC review on propylene and a monograph.
- The European Chemicals Bureau (ECB) web site for IUCLIDs
Last Updated: May 2, 2006
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1 Chemical Economics Handbook, SRI Consulting, 2004.
2 List of uses and chart was created from information Chemical Economics Handbook, SRI Consulting, 2004.
3 OECD SIDS Initial Assessment Report for SIAM 16, July 30, 2003, p. 10.
4 Annual Reports for the Year 2005: Committees on Threshold Limit Values (TLVs®) and Biological Exposure Indices (BEIs®), ACGIH, 2006.
5 OECD SIDS Initial Assessment Report for SIAM 16, May 9, 2003 Draft, p. 9-10.
6 OECD SIDS Initial Assessment Report for SIAM 16, May 9, 2003 Draft, p. 10.
7 OECD SIDS Initial Assessment Report for SIAM 16, May 9, 2003 Draft, p. 5.
8 OECD SIDS Initial Assessment Report for SIAM 16, May 9, 2003 Draft, p. 6.
9 OECD SIDS Initial Assessment Report for SIAM 16, May 30, 2003 Draft, p. 6.
10 OECD SIDS Initial Assessment Report for SIAM 16, May 9, 2003 Draft, p. 14.
11 OECD SIDS Initial Assessment Report for SIAM 16, May 9, 2003 Draft, p. 17, 18 and 20.
12 OECD SIDS Initial Assessment Report for SIAM 16, May 9, 2003 Draft, p. 16.
13 OECD SIDS Initial Assessment Report for SIAM 16, May 9, 2003 Draft, p. 8.
14 Fire Protection Guide on Hazardous Materials 2001 Edition, National Fire Protection Association, 2001.
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® TLV is a trademark of the American Conference of Governmental Industrial Hygienists