FREQUENTLY ASKED QUESTIONS
- What is styrene?
- Do I come in contact with styrene?
- Is styrene harmful to my health?
- What about the scent of styrene around manufacturing plants?
- What happens to styrene released into the environment?
- What about the health of workers exposed to styrene?
- Is there a concern about cancer risk?
- Are there alternatives for styrene?
- What is the Styrene Information and Research Center (SIRC)?
- Styrene and Styrenic Compounds: What’s the Difference? (polystyrene, styrofoam, styrene butadiene rubber, etc.)
- Links to more frequently asked questions
Styrene is a clear, colorless liquid that is a component of materials used to make thousands of everyday products for home, school, work and play. Products made from styrene add convenience, value and quality to daily life. They range from packaging such as jewel cases that protect CDs and containers that keep yogurt fresh to toys, recreational equipment, and myriad consumer electronics, construction, transportation, medical, health and safety applications.
Derived from petroleum and natural gas by-products, styrene helps create thousands of remarkably strong, flexible, and light-weight products that represent a vital part of our health, safety and well-being. Probably the most recognizable material is polystyrene, often encountered as expanded polystyrene foam (EPS). Other styrene-based materials include acrylonitrile-butadiene styrene (ABS), styrene-acrylonitrile (SAN), styrene-butadiene rubber (SBR), and unsaturated polyester resin (UPR), which is better known as fiberglass. To learn more about how styrene’s countless benefits bring peace of mind and quality to life, click here: Styrene Uses and Benefits Brochure.
The styrene used in these products is manufactured in petrochemical plants located all around the U.S. and, indeed, around the world. More information can be found under Styrenics and the U.S. Economy. However, styrene also occurs in the environment and is found in many common foods, such as coffee, strawberries and cinnamon. Additional information can be found under Styrene Occurrence in Food. (top)
Most people are exposed to styrene every day in tiny amounts that may be present in the air, or that occur in food. These generally are trace amounts, which were difficult to detect until recent technological advances. We also may recognize styrene by its distinctive odor (described by some as sweet) when using certain products such as latexes, paints and polyester resin solutions.
Some people confuse styrene, which is a liquid, with polystyrene, which is a solid plastic made from polymerized styrene. Styrene and polystyrene are fundamentally different. Polystyrene is inert and has no smell of styrene. Polystyrene often is used in applications where hygiene is important, such as health care and food-service products. For more information on polystyrene products, visit the Plastics Foodservice Packaging Group (PFPG) homepage. (top)
Styrene is not harmful in the very small amounts we sometimes may encounter in air or food. Someone working in an enclosed area with resin solutions containing styrene (patching the surface of a fiberglass boat, for example) may find the odor of styrene causes slight nausea. This goes away with exposure to fresh air, and there is no lasting effect.
In an important decision made in 1994 after an exhaustive assessment of styrene’s possible health and environmental effects, the government agencies Health Canada and Environment Canada concluded that styrene is "non-toxic" for regulatory purposes. Health Canada found that styrene "does not constitute a danger to human life and health" and "does not constitute a danger to the environment on which human life depends."
A report on a styrene risk assessment by the [PDF]Harvard Center for Risk Analysis also concluded that there are no concerns for the general public, either from environmental or consumer exposures to styrene.
Over the last several years, the U.S. Environmental Protection Agency has been conducting a formal review of styrene for its Integrated Risk Information System (IRIS) database. When completed, the findings will provide an assessment of the scientific data on styrene relative to its potential to impact human health or the environment.
Styrene and Human Health has additional information concerning styrene. (top)
Styrene's distinctive odor can be detected even when styrene is present at extremely low levels. People living near facilities that make or use styrene sometimes may notice a slight scent in the air. If you have concerns about such odors in your neighborhood, you may wish to contact the plant's manager or your local health department. The Harvard Center for Risk Analysis (HCRA) also evaluated the public risk from styrene exposure. Findings were reported in HCRA’s May 2002 Risk in Perspective newsletter. (top)
Extensive research shows that styrene exists only briefly in the environment; it is destroyed rapidly in the air and disappears quickly from soils and surface waters. Studies also have shown that styrene is not likely to occur in drinking water. Additional information can be found under Environmental Fate Research and Ecotoxicity Research. (top)
The health of workers in plants making or using styrene has been monitored for many years. Studies looking for long-term health effects related to styrene exposure have examined health records of over 50,000 workers exposed to styrene, going back more than 50 years. These studies have not shown any statistically significant increases in long-term health problems of any kind attributable to styrene exposure in these workers.
In the United States, as in most industrialized countries, strict regulations are in place to protect worker health. In 1989, the U.S. Occupational Safety and Health Administration (OSHA) established a safe exposure standard for styrene of 50 parts per million (ppm) over an eight-hour day. Typically, the actual exposure levels in styrene manufacturing plants are 20 to 50 times below this safety level. In years past, before effective monitoring systems were available, worker exposure to styrene (as well as other materials) often was greater than current exposure levels.
In July 1992, a U.S. appeals court voided the 1989 OSHA rulemaking, and the pre-1989 level of 100 ppm was reinstated as the enforceable limit. However, the Styrene Information and Research Center (SIRC) encouraged its member companies to continue to comply with the 50-ppm exposure limit. Additionally, several states independently adopted and enforce a 50-ppm exposure limit. In February 1996, OSHA endorsed a styrene industry proposal to voluntarily meet a 50 ppm exposure level. Industry’s ongoing voluntary compliance can help OSHA avoid the need for another costly and time-consuming review of styrene.
The Harvard Center for Risk Analysis (HCRA) also evaluated the risk to workers from styrene exposure. HCRA’s Risk in Perspective newsletter addresses this topic. (top)
SIRC has invested many years and some $14 million in funding to develop the most thorough and accurate information about possible cancer effects resulting from styrene exposure. The results of extensive health studies of workers in styrene-related industries collectively show that exposure to styrene does not increase the risk of developing cancer or any other health effect. Results of a two-year styrene inhalation study in rats exposed to high concentrations of styrene, completed in 1996, also showed no increased incidence of cancer. Additional information can be found under Carcinogenicity Research.
From a regulatory viewpoint, in 1989 OSHA and the U.S. Centers for Disease Control and Prevention’s National Institute for Occupational Safety and Health (NIOSH) reviewed the health data on styrene and concluded that styrene does not pose any cancer risk. An international panel of experts from the 12-nation European Community reached the same conclusion in 1988. Canada decided in 1994 that styrene posed no carcinogenic risk. A draft 1996 risk assessment of styrene by the Health & Safety Executive of the United Kingdom also concluded that styrene does not pose a carcinogenic threat.
In 1987, the International Agency for Research on Cancer (IARC) upgraded styrene's classification to a "possible" human carcinogen. Many scientists have disputed this action because it was not based on new cancer data, but resulted from changes in the criteria for IARC classifications. In subsequent reviews in 1994 and 2002, IARC chose to maintain its classification for styrene. SIRC believes that the significant amount of available scientific data indicates this classification is not warranted, and continues to address IARC's decision. It is important to note that IARC's charter stresses that their classifications are for hazard identification only - not to determine the risk of a given substance - and should not be used for regulatory purposes. (top)
No other material can provide the same performance characteristics, quality and cost-effectiveness of styrene. Styrene is so widely used because it has been substituted over the years for other materials to create better products. For example, boats made from styrenic material are more structurally sound, packaging is more sanitary and less costly, automobiles have lighter components making them more fuel-efficient, and building insulation quality has greatly improved, helping to cut energy costs. To learn more about how styrene’s countless benefits bring peace of mind and quality to life, click here: [PDF] Styrene Uses and Benefits Brochure. (top)
SIRC is a non-profit organization established in 1987 by companies involved in the manufacture or use of styrene. SIRC's mission is to evaluate existing data on potential health effects of styrene, to develop additional data where it is needed, and to communicate the results of all these findings when and where appropriate. SIRC has gained worldwide recognition as a source for information on styrene, thus helping to ensure that employee and public health is fully protected, and that regulatory and legislative decisions are based on sound science. (top)
Many different chemical compounds and resins are made with or contain the building-block chemical styrene. All have different chemical and physical properties. Consumers should not make the assumption that because a compound or resin has “styrene” in its name or as part of its name that it is similar to the chemical styrene. Nor should they assume that because a compound or resin does not have “styrene” in its name that it is not made using styrene.
What is Styrene? The basic chemical styrene monomer is a clear, colorless, oily liquid that is a building block used to make thousands of everyday products for home, school, work and play, ranging from food containers and packaging materials to cars, boats, computers, video games and myriad others. While styrene occurs naturally, it is produced in industrial quantities from petroleum and natural gas byproducts. Styrene helps create remarkably strong, flexible, and light-weight products, representing a vital part of the economy and quality of life.
Styrene has an aromatic, almost floral odor at low concentrations, but is quite pungent at high concentrations. The list of alternative names for styrene includes vinyl benzene, phenethylene, cinnamene, Diarex HF 77, styrolene, styrol and styropol. Styrene is named after the styrax trees from whose sap a related resin (benzoin) can be extracted. Styrene also occurs naturally in a variety of foods including fruits, vegetables, nuts, beverages and meats; cinnamon is particularly rich in styrene. Its molecular formula is C8H8, meaning that it consists entirely of the elements carbon and hydrogen. Styrene evaporates quickly.
What is Not Styrene? The following compounds are not styrene and do not have properties similar to the chemical styrene, but all are made from styrene and, in some chases, other compounds.
Polystyrene is a polymer (compound made up of many like molecules) made from styrene monomer; it is one of the most versatile, widely used plastics in the world.
By itself, styrene will react to air (oxygen) over a period of time to form polystyrene, which is a solid. However, commercial polystyrene is made by adding a catalyst to styrene, which causes it to react and form a solid. Polystyrene is produced in two principal forms — (1) solid polystyrene and (2) expanded polystyrene foam. Expanded polystyrene foam, which can be produced in both open-cell and closed-cell forms, is made by dissolving a blowing agent (substance capable of producing a cellular structure in a plastic) into molten polystyrene, which then is formed into a desired shape. Like styrene, polystyrene is made up entirely of the basic elements carbon and hydrogen.
Pure solid polystyrene is colorless and hard, with limited flexibility. It can be transparent or made to take on various colors. It is used, for example, in disposable cutlery, plastic models, CD and DVD cases, laboratory containers and many other objects where a rigid, economical plastic is desired.
Expanded polystyrene foam’s insulating properties make it important as a construction material. Other key products made from foamed (expanded) polystyrene include packing materials (packing peanuts, for example) and foodservice.
Styrofoam® is a trademark for polystyrene thermal insulation manufactured by The Dow Chemical Company. There is not a coffee cup or food container in the world made of Styrofoam, although it is made from polystyrene and the word Styrofoam often is used mistakenly as a generic term for expanded polystyrene foam. In 1941, researchers at a Dow lab “rediscovered” a way to make foamed polystyrene, a method first discovered by Swedish inventor C.G. Munters. Dow acquired the exclusive rights to use Munter’s patents and found ways to make large quantities of extruded polystyrene in a closed-cell form that resisted moisture. Because of its “unsinkability,” it was adopted in 1941 by the U.S. Coast Guard for use in a six-person life raft, and continues to be widely used for flotation, as well as insulation. For more information, visit www.dow.com.
Styrene butadiene rubber (SBR) is a type of rubber, three fourths of which are used in the automotive industry, primarily for tire treads. SBR originally was developed as a substitute for natural rubber, which has a number of supply and technical disadvantages. These drawbacks include being harder to process and less resistant to abrasion than SBR. SBR gives tires better road-hugging ability, especially on wet pavement, for a safer ride, and SBR-based tires also increase vehicle mileage. SBR also is used in shoe heels and soles and gaskets. For more information visit the International Institute of Synthetic Rubber Producers, www.iisrp.com.
Styrene butadiene (SB) latex allows the manufacture of high-gloss, water-resistant coated papers for printing, writing and paperboard packaging. Also, more than 90 percent of all the broadloom carpets produced in the United States are held together by SB latex binder. For more information visit the SB Latex Council, www.regnet.com/sblc/
Acrylonitrile butadiene styrene (ABS) resins are used mostly in automobiles, electrical and electronic applications, consumer goods, and buildings and construction. Everyday items like bicycle helmets, luggage, telephones and housings for computers and kitchen appliances are made from ABS. These resins have superior properties, which makes them cost-effective in comparison with harder-to fabricate alternatives. ABS resins are tough, formable, have substantial heat resistance, and can be produced with gloss finishes.
Styrene acrylonitrile (SAN) resins are used mostly in consumer goods and appliances. SAN resins’ glass-like clarity and the fact that products made from it are dishwasher safe make them the resins of choice for many everyday products. These qualities include impact strength, dimensional stability, heat resistance, and the ability to be washed at high temperature.
Unsaturated polyester resins (UPRs) usually are reinforced with glass fibers to produce composite plastics with improved strength. Reinforced UPRs – commonly called fiberglass – account for about 75 percent of all commercial UPRs. They have a host of uses, including in construction, transportation and fiberglass boat manufacturing. Without it, recreational boats would be made out of wood, aluminum and possibly steel, all of which perform differently and have different cosmetic properties than UPR-based boats, as well as a wide variety of other disadvantages. Un-reinforced UPRs (the remaining 25 percent) are used to make synthetic marble and polymer concrete. For more information, visit the American Composites Manufacturers Association, www.acmanet.org, or its International Cast Polymer Alliance, www.icpa-hq.org, or the National Marine Manufacturers Association, www.nmma.org.
Styrene maleic anhydride (SMA) is a plastic that is made with styrene and maleic anhydride monomers. This small-volume plastic is transparent, has high heat resistance and good dimensional stability, making it suitable for applications including engineered plastics and sizings for paper, binders and coatings.
Styrene oxide is a chemical derived from styrene and a chemical that metabolizes from styrene in biological systems. It is used as a chemical intermediate in the production of styrene glycol and its derivatives, cosmetics, coatings, and agricultural and biological chemicals. Small quantities are used to improve the stability of hydraulic fluids, chlorinated cleaning compositions and other industrial fluids. It is not a large-volume chemical and public exposure is minimal, with the U.S. Department of Health and Human Services’ Library of Medicine Hazardous Substance Data Bank (HSDB) identifying only one U.S. producer. (Editor’s note: Commercial production of this chemical could not be independently confirmed and may have ceased since the HSDB reference was created.)
The links below are to external sites. You will be leaving the SIRC site.
- Plastic bags and recycling. Read this >>
- Plastics, the microwave, toxins. Read this >>
- Recycling plastic. Read this >>
- Polystyrene—Frequently Asked Questions. Read this >>
- Plastic Bag Recycling (more information on where to recycle in your community). Read this >>
- Using Plastics in the microwave FAQ. Read this >>