Questions & Answers

 


What is styrene?

SIRC_site_graphics-StyreneIn diagram-what-is-styrene-298x300REVStyrene is a clear, colorless liquid that is an essential component of materials used to make thousands of everyday products. Its molecular formula is C8H8, meaning that it consists entirely of the elements carbon and hydrogen. Styrene is also known by several other names, including vinylbenzene, phenylethylene, cinnamene, Diarex HF 77, styrolene, styrol, and styropol.

Products made from styrene add convenience, value, and quality to daily life. These products range from convenient food containers and protective packaging materials to computer housings; consumer electronics; medical applications; components for automobiles, trucks, trains, boats, aircraft and other means of transport; wind-energy parts; construction and water treatment products; building insulation; military personnel and vehicle armor; ballistic protection; fuel cells; gasoline and other storage tanks; protective sports gear, such as bicycle helmets; and many other important items.

Styrene helps create remarkably strong, flexible, and light-weight products. 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), and styrene-butadiene rubber (SBR). Styrene is also used as a diluent and reactive cross-linker for thermoset polyester resin, which is combined with a reinforcement (such as glass fiber) to form composite materials such as fiberglass. The styrene used in these products comes from factories located all around the U.S. and, indeed, around the world.

Styrene also occurs naturally and is an inherent component of tobacco smoke as well as many commonly-consumed foods and beverages, such as coffee, strawberries, and cinnamon. In fact, it was first extracted from the oriental sweetgum tree (also called levant styrax, after which styrene is named). Learn more at YouKnowStyrene.org.

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Do I come in contact with styrene?

Styrene > Polymerization > Polystyrene GraphicMost people are exposed to styrene every day in tiny amounts that may occur naturally in tobacco smoke and in food or which may be present in the air or consumer products. We also may recognize styrene by its distinctive odor (described by some as floral or sweet at low concentrations) when using certain products such as latexes, paints, auto body patching putties, and polyester resin solutions.

Some people confuse styrene, which is a liquid, with polystyrene, which is a solid plastic made by chemically reacting, or polymerizing, individual styrene molecules into long polymer chains. Styrene and polystyrene are different substances with different chemical and physical properties. Polystyrene is inert and has no smell of styrene. Polystyrene often is used in applications where hygiene is important, such as health care and foodservice products. For more information on polystyrene products, visit the Plastics Foodservice Packaging Group (PFPG) website.

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What about the July 2014 National Research Council review of styrene?

By way of background, in 2012, the U.S. Department of Health and Human Services (HHS) engaged the U.S. National Academy of Sciences (NAS) to conduct an independent review of a 2011 styrene review conducted by the National Toxicology Program for its Report on Carcinogens (for more information, click here). Part of the NAS, the National Research Council (NRC) was assigned to conduct this review. The NRC review, which began in February 2013, was completed in July 2014. The NRC applied the NTP listing criteria, as instructed in the statement of task provided by HHS, and validated NTP’s listing of styrene in the RoC.

SIRC acknowledges the service of the National Research Council committee, and will carefully review the committee’s conclusions and recommendations. We will address questions raised in the report and take any necessary steps to assure the continued safety of consumers, industry workers and plant communities.
Consumers are not at risk from products made from styrene. National Toxicology Program officials confirmed the safety of styrene-based products when styrene was included in its Report on Carcinogens in 2011.

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Is styrene harmful to people who may be exposed to it outside of the workplace?

Styrene is not harmful in the very small amounts we may sometimes encounter in air, consumer products 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 is remedied by exposure to fresh air, and there is no lasting effect. Learn more in the Science section of this website.

Also, styrene is not regulated as a carcinogen by any national governmental authority globally. 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 are expected to provide an assessment of the scientific data on styrene relative to its potential to impact human health or the environment.

A report on a styrene risk assessment by the Harvard Center for Risk Analysis concluded that there are no concerns for the general public, either from environmental or consumer exposures to styrene. However, two non-regulatory bodies, the International Agency for Research on Cancer (IARC) and the U.S. National Toxicology Program (NTP) Report on Carcinogens (RoC) have issued styrene classifications related to carcinogenicity. Following the release of the RoC, Dr. Linda Birnbaum, NTP’s Director stated “Let me put your mind at ease right away about Styrofoam … In finished products, certainly styrene is not an issue” (as quoted on NPR)[1].  Learn more in the Policy section of this website.

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What about the health of workers exposed to styrene?

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 55,000 workers in styrene-related industries in the United States and Europe, with exposures beginning at least 60 years ago. These studies have not shown any link between styrene exposure and any cause of death or serious illness.

A 2011 “Fact Sheet” [2] about styrene prepared by the U.S. National Toxicology Program (NTP) discuses workplace exposures to styrene and recommends “[w]orkers and employers should practice good occupational health behaviors. This may include wearing protective clothing, respirators, and gloves. Work places should be well ventilated.”

Recent industry-sponsored research related to the potential effects of workplace styrene exposure indicated mild and subtle hearing loss in long-term workers (15-26 years’ employment) who experienced styrene exposures averaging 25-33 ppm (parts-per-million) over an 8-hour workday.

Regulatory agencies and business owners and managers work together to protect the health of employees. The U.S. Occupational Safety and Health Administration (OSHA) currently requires employers to limit 8-hour time-weighted average (TWA) workplace inhalation exposures to styrene to 100 ppm (parts-per-million). In 1996 OSHA endorsed a voluntary proposal by SIRC and several other industry groups to adhere to a 50 ppm TWA. Additionally, in 2011, SIRC and styrene industry groups based in Europe and Japan began recommending a world-wide voluntary Occupational Exposure Limit (OEL) of 20 ppm based on an 8-hour TWA. Additional information can be found under “Ototoxicity” in the “Neurotoxicity” section of the Science-Human Health page of this website.

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Does the science support a concern about human cancer risk?

No. Based on the overall results of many scientific studies, the evidence collectively indicates that styrene is not associated with cancer in humans.

SIRC_Site_QA-MoAThis conclusion is supported by several well-respected international groups and regulatory agencies, including the Harvard Center for Risk Analysis, the Texas Commission on Environmental Quality, the European Union, the Danish EPA, and Health and Environment Canada. (*The Canadian review concluded that styrene is “non-toxic,” and as such does not require regulation under the Canadian Environmental Protection Act. It also 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.” As part of its internal evaluation, Health Canada’s classification structure required that styrene be classified as a Class III possible human carcinogen, largely following IARC.)

Since it was formed in 1987, SIRC has carried out a robust research program to further investigate the potential for styrene to cause adverse health effects, and has invested over $20 million in this effort.

  • Human exposure to styrene is highest among workers in some styrene-using industries, and the results of extensive health studies of workers in these industries collectively show that exposure to styrene is not associated with any cause of death or any kind of serious illness, including human cancer. Additional information can be found under “Carcinogenicity” in the Science section of this website.
  • Laboratory animal research includes two-year styrene inhalation studies in rats and mice. The rat study showed no increase in cancer, even at very high exposure levels, while the lung tumors found in the mouse study only developed late in the two-year study and did not affect survival. Additional information can be found in the under “Carcinogenicity” in the Science section of this website.
  • Further research into why mice developed tumors, but rats and people do not, has demonstrated that enzymes present in mouse lung tissues convert styrene to other chemicals (metabolites) that lead to the formation of tumors in mice; these enzymes are not present in rats or people in sufficient quantities to have the same effect. Additional information can be found under “Metabolism and Mode of Action” in the Science section of this website.

Despite what SIRC sees as compelling scientific data that do not indicate a concern about exposure to styrene and cancer, the International Agency for Research on Cancer (IARC) and the U.S. National Toxicology Program’s Report on Carcinogens have published their concerns about the potential for styrene to cause cancer in humans. For more information on these actions, see the Policy section of this website.

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What about the odor of styrene around manufacturing plants?

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 may sometimes  notice an odor. Styrene odor can be detected at levels about 100-fold lower than the recommended worker protection limit. If you have concerns about such odors in your neighborhood, you may wish to contact the plant’s manager or your local health department.

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What happens to styrene released into the environment?

Extensive research shows that styrene does not persist or accumulate in the atmosphere or in soils or surface waters. Studies also have shown that styrene is not likely to occur in drinking water. Additional information can be found in the Science section of this website.

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Are there alternatives to styrene?

Styrene is a key component in: -Green Tech -Carpeting -Insulation -Electronics packaging -Lightweight car parts -Efficient & durable tires -Fresh food packaging -ToysStyrenic materials have excellent performance characteristics, quality, low toxicity, and affordability. Styrene is so widely used because it has been substituted over the years for other materials to create improved products. For example, boats made from styrenic material are more structurally sound. Packaging is more sanitary and less costly. Automobiles feature lighter components, making them more fuel-efficient. And building insulation quality has greatly improved, helping to cut energy use, thereby reducing cost and global warming gas emissions.

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Styrene and styrenic compounds: What’s the difference? (polystyrene, “stryrofoam,” styrene butadiene rubber, etc.)

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.

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What is the Styrene Information & Research Center (SIRC)?

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 evidence-based reviews of the science.

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What is styrene’s impact on the U.S. economy?

5,000 U.S. Manufacturing PlantsIn the United States, the diversified styrene industry as a whole is an approximately $28 billion industry and has an annual industry payroll exceeding $4 billion. Every year the styrene industry contributes nearly $540 million to the United States trade balance and tax revenues of $7 billion annually. Learn more at YouKnowStyrene.org.

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Is synthetic styrene used as a component of fragrances and perfumes?

Not so far as SIRC is aware.
However, it does appear that Styrax (also called Storax) resins and oils – natural products that contain styrene and which are derived from the sap of various trees and shrubs – have been used since antiquity in some fragrances.[3][4][5] In fact, styrene’s common name is derived from Liquidambar orientalis (or Levant styrax), a Turkish sweetgum tree.

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Footnotes    (↵ returns to text)

  1. Dr. Linda Birnbaum, as quoted in “Weighing Cancer Risks, From Cellphones To Coffee,” The Associated Press, National Public Radio, 15 Jun 2011.
  2. NTP 2011, “Styrene,” Fact Sheet, U.S. National Toxicology Program (NTP), June. 2011, accessed 22 Oct 2013; http://www.niehs.nih.gov/health/materials/styrene_508.pdf.
  3. Steffen Arctander, Perfume and Flavor Materials of Natural Origin, 1st ed., pp. 597-602, 1960.
  4. George A. Burdock, Fenaroli’s Handbook of Flavor Ingredients, 6thed., pp. 1853-1855, 2004.
  5. Xavier Fernandez, et al., “Chemical composition of the essential oils from Turkish and Honduras Styrax,” Flavour and Fragrance Journal, v. 20, pp. 70-73, 2005.
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