Frequently Asked Questions - Styrene
What is styrene?
Styrene 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.
Do I come in contact with styrene?
Most 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.
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.
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).
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” 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-permillion) 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.
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.
This 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 “nontoxic,” 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.
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.
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.
Are there alternatives to styrene?
Styrenic 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.
Styrene and styrenic compounds: What’s the difference?
Many different chemical compounds and resins are made with or contain the buildingblock 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 the Styrene Information and 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.
What is styrene’s impact on the U.S. economy?
In 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.
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. In
fact, styrene’s common name is derived from Liquidambar orientalis (or Levant styrax), a
Turkish sweetgum tree.