The U.S. Environmental Protection Agency (EPA) has not developed a formal carcinogen classification of styrene or listed it as a carcinogen on the Integrated Risk Information System (IRIS) database, which is a widely used reference for a chemical’s potential carcinogenicity. The EPA Regulation of Styrene and the EPA Toxics Release Inventory sections of this website below provide additional information.
1. EPA Regulation of Styrene
The U.S. Environmental Protection Agency (EPA) has not classified styrene as a carcinogen under the agency’s Integrated Risk Information System (IRIS), which represents EPA’s official position regarding a chemical substance’s carcinogenicity or toxicity.
EPA’s Integrated Risk Information System (IRIS) is a human health assessment program that evaluates the effects on human health from exposure to environmental contaminants. These assessments support the Agency’s regulatory activities and are widely referenced by other federal agencies and by the states as well. The current IRIS entry for styrene provides an oral and inhalation assessment (IRIS 2013)  and states that EPA’s cancer classification for carcinogenic potential is “now under review.”
SIRC closely monitors EPA’s program offices and activities to ensure the appropriate treatment of styrene. Despite the fact that EPA has not released a carcinogenicity assessment under IRIS, from time-to-time, EPA’s website has contained erroneous references about the possible health effects of styrene, including listing styrene as a suspected carcinogen. SIRC has worked to address and correct these errors, reminding EPA that its own IRIS assessment of styrene’s carcinogenicity has not been completed. SIRC has met and communicated with EPA staff on numerous occasions to provide information about advancements on the science of styrene and has provided comments on rulemakings when relevant. EPA staff has commended SIRC for its willingness to work with the Agency in developing study protocols and in significantly expanding the body of health effects data on styrene to assist the Agency with its formal hazard assessment of styrene.
2. EPA Toxics Release Inventory
The U.S. Environmental Protection Agency (EPA) annually collects information on the release and management (i.e., recycling, energy recovery, and treatment) of chemicals by U.S. manufacturing facilities and makes this Toxics Release Inventory (TRI) information public.
The TRI was established by section 313 of the Emergency Planning and Community Right-to-Know Act (EPCRA) of 1986. The list of chemicals subject to reporting now includes nearly 600 individual chemicals and 30 chemical categories. In general, a chemical is listed if, according to EPA’s listing criteria, it is associated with cancer or other chronic human health effects, significant adverse acute human health effects, or significant adverse environmental effects.
TRI tracks the management of certain chemicals specified by EPA. U.S. facilities in different industry sectors must report annually how much of each chemical is released to the environment or managed through recycling, energy recovery, and treatment. Under the TRI, a “release” of a chemical means that it is emitted to the air or water, or placed in some type of land disposal. TRI reports reflect theses defined “releases,” and not exposures of the public. Furthermore, EPA states “… release estimates alone are not sufficient to determine exposure or to calculate potential risks to human health and the environment.”
Facilities with more than 10 full-time employees that manufacture or process more than 25,000 pounds or use more than 10,000 pounds of any reportable chemical must annually report to EPA the amount of the chemical released to the environment and/or managed through recycling, energy recovery, and treatment.
Release of Reports
TRI data are presented primarily through a publicly accessible database and through EPA publications. Facility-specific information can be retrieved, as can aggregate information for a specific geographic region, industry, or chemical. The names and locations of off-site facilities to which toxic wastes were shipped also are reported, as are the treatment or disposal methods used for wastes, and estimates of their efficiency. Publication of the data is delayed, in part because of the reporting cycle and submission deadlines.
Styrene releases must be reported to the EPA under EPCRA Section 313. The TRI listing of styrene dates back to 1987, and its included in the Senate Committee on Environment and Public Works’ report, Toxic Chemicals Subject to Section 313 of the Emergency Planning and Community Right-To-Know Act of 1986 (Committee Print Number 99-169), which is cross-referenced by statute as the initial list of substances covered by EPCRA Section 313.
Styrene dissipates very rapidly when released into the air or water. Recent TRI reports indicate that styrene releases are declining. These improvements reflect both new control technology put in place and an economic downturn in key styrene-using industries. It is important to note that emissions of styrene do not translate into or signify public health threats.
The U.S. Occupational Safety and Health Administration (OSHA) regulates styrene as a hazardous substance because of short-term reversible central nervous system effects such as drowsiness and delayed reaction time that may be experienced from exposure to styrene in the workplace. The OSHA permissible exposure limit (PEL) for styrene is 100 parts per million (ppm), meaning that a worker should not be exposed to more than an average of 100 ppm styrene during a regular eight-hour workday, without respiratory protection.
After an OSHA rule that would have lowered the styrene PEL to 50 ppm was struck down by a U.S. appeals court in 1992, SIRC and several other associations representing manufacturers of styrene-based products encouraged industry to adopt a 50 ppm exposure guideline. In 1996, OSHA endorsed the styrene industry’s voluntary 50 ppm exposure level guideline. In 2011, based on new industry-sponsored research indicating mild and subtle hearing loss in long-term workers (15-26 years’ employment), SIRC (along with the European Styrene Producers Association and the Japanese Styrene Industry Association) recommended that the guideline be reduced to 20 ppm. This is consistent with the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV®) for styrene. For more information on this research, see “Ototoxicity” in the “Neurotoxicity” section of the Science- Human Health page.
OSHA’s Hazard Communication Standard (HCS)
OSHA’s Hazard Communication Standard (HCS) requires chemical manufacturers and importers to provide hazard information to employees and customers by preparing safety data sheets (SDSs). The OSHA HCS rule was substantially amended in 2012 to harmonize U.S. requirements with global standards. The 2012 HCS does not require any specific labeling or classification for styrene or products made from styrene. Each product’s safety and health characterizations are based on the manufacturer’s evaluation using criteria set by OSHA.
The U.S. Food and Drug Administration (FDA), which regulates food and safety and the safety of food contact packaging, has authorized the use of polystyrene and other styrene-based polymers in food packaging applications for both hot and cold food and drink (Lickly et al. 1995)  and has also designated styrene as “Generally Recognized as Safe.” 
The U.S. Food and Drug Administration (FDA) closely regulates the use of food additives or substances that may migrate into foods from packaging, food preparation, or serving materials. FDA permits materials made from styrene to be used in contact with food products. These materials, such as polystyrene food service and packaging materials, must meet strict guidelines that ensure the consumer’s safety and health.
While the agency has also approved styrene, in very small quantities, for use as a food additive for synthetic flavoring to enhance taste, industry reports it has not been used as a flavoring substance for many years. SIRC filed a petition to the FDA in May 2016 requesting removal of the clearance for styrene due to the abandonment of its use as a synthetic flavoring substance and adjuvant in food.
The concentration of styrene in the diet resulting from all uses of styrene-based food-contact polymers was calculated using measured as well as calculated styrene migration values. This value supports the conclusion, based on the acceptable daily intake and the estimated-daily-intake for styrene, that the use of styrene-based polymers for food-contact surfaces presents no health or safety concerns. The studies underlying this research can be found at the Plastics Foodservice Packaging Group’s website.
The U.S. National Toxicology Program (NTP) is an interagency program headquartered within the U.S. National Institute of Environmental Health Sciences (NIEHS); NIEHS is part of the U.S. Department of Health and Human Services (HHS). NTP publishes the Report on Carcinogens (RoC), which listed styrene as “reasonably anticipated to be a human carcinogen” in its 12th RoC  in June 2011. In 2012, Congress directed the HHS to engage the U.S. National Academy of Sciences (NAS) to conduct an independent review of the validity of this listing and the listing criteria. This website includes more information about the RoC and SIRC’s stance on the listing.
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 this listing.
Under the National Academies structure, the National Research Council (NRC) managed the review of the RoC listing of styrene. The NAS/NRC review 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 submitted several letters to the NRC panel regarding the RoC Styrene Substance Profile and the scientific information about styrene. To learn more, read SIRC’s submission letters, located in the Public Information section of the Newsroom.
SIRC challenged the procedures used by HHS’s NTP to reach its decision to include styrene in the RoC. The lawsuit was filed against HHS in the U.S. District Court for District of Columbia on June 10, 2011. HHS’ procedures were found acceptable in the Court’s 2013 decision; HHS’s treatment of the science (as contrasted with its procedures) was not the subject of the lawsuit. SIRC elected to not appeal the decision in light of the on-going review of HHS’ scientific reasoning by the NRC. Read more about the legal challenge in the Public Information section of this website.
About the RoC
The Report on Carcinogens was created by Congress in 1978 in order to serve as an informational scientific and public health document. The RoC identifies and discusses agents, substances, mixtures, or exposure circumstances that may pose a hazard to human health by virtue of their potential carcinogenicity and to which a significant number of persons in the United States are exposed. The NTP, which publishes the RoC, is an interagency program headquartered within the National Institute of Environmental Health Sciences (NIEHS); NIEHS is part of the U.S. Department of Health and Human Services. The RoC is intended to serve as a meaningful and useful compilation of data on:
1. The carcinogenicity (ability to cause cancer), genotoxicity (ability to damage genes), and biologic mechanisms (modes of action in the body) of the listed substance in humans and/or animals.
2. The potential for human exposure to these substances.
3. Federal regulations to limit exposures.
RoC listings include a wide range of substances, such as metals, pesticides, drugs, and natural and synthetic chemicals.
Listings in the RoC identify a substance or exposure circumstance as “known to be a human carcinogen” or “reasonably anticipated to be a human carcinogen.” The category “known to be a human carcinogen” is intended for those substances for which there is sufficient evidence of carcinogenicity from studies in humans that indicates a causal relationship between exposure to the agent, substance, or mixture and human cancer. The second category, “reasonably anticipated to be a human carcinogen,” is meant to include substances for which there is limited evidence of carcinogenicity in humans and/or sufficient evidence of carcinogenicity in experimental animals. NTP reviews should produce an evidence-based scientific assessment as the foundation for reaching conclusions regarding potential human carcinogenicity.
As a hazard identification document, the RoC does not present quantitative assessments of the risks of cancer associated with exposure to these substances. Thus, a listing in the RoC only indicates a potential hazard and does not estimate cancer risks to individuals associated with exposures in their daily lives. Rather, such formal risk assessments are the purview of appropriate federal, state, and local health regulatory and research agencies.
- U.S. EPA IRIS, Styrene (CASRN 100-42-5), Integrated Risk Information System (IRIS), National Center for Environmental Assessment, Office of Research and Development, United States Environmental Protection Agency, accessed 22 Oct 2013; http://www.epa.gov/iris/subst/0104.htm.↵
- U.S. EPA TRI Website, “What is the Toxics Release Inventory?” Learn about the Toxics Release Inventory, Toxics Release Inventory (TRI) Program, United States Environmental Protection Agency, accessed 22 Oct 2013; http://www2.epa.gov/toxics-release-inventory-tri-program/learn-about-toxics-release-inventory.↵
- U.S. EPA TRI Website, “Are tribes at risk from toxic chemical releases on or near their lands?” TRI for Tribal Communities, Toxics Release Inventory (TRI) Program, United States Environmental Protection Agency, accessed 22 Oct 2013; http://www2.epa.gov/toxics-release-inventory-tri-program/tri-tribal-communities.↵
- U.S.C. § 11023(c), The United States Code, Title 42—The Public Health and Welfare, Section 11023—Toxic chemical release forms, sub-section (c)—Toxic chemicals covered, p. 7090; http://www.gpo.gov/fdsys/pkg/USCODE-2011-title42/html/USCODE-2011-title42-chap116.htm.↵
- Lickly, T.D. et al., “Migration of styrene from polystyrene foam food contact articles,” Food and Chemical Toxicology, v. 33, issue 6, pp.475-481, June 1995, doi:10.1016/0278-6915(95)00009-Q; http://www.sciencedirect.com/science/article/pii/027869159500009Q.↵
- Hall, R.L. and Oser, B.L., “Recent Progress in the Consideration of Flavoring Ingredients Under the Food Additives Amendment 4. GRAS Substances,” Food Technology, v. 24, no. 5, pp. 25-34, 1970.↵
- FDA’s “Generally Recognized as Safe” designation is administered by the U.S. Flavor and Extract Manufacturer’s Association (FEMA). Styrene’s FEMA number is 3233. The reference provided reported uses as a flavoring agent in frozen desserts, such as ice cream, candy, and baked goods.↵
- 12th RoC, US Department of Health and Human Services, Public Health Service, National Toxicology Program, Report on Carcinogens, Twelfth Edition, Substance Profile, Styrene, pp. 383-391, June 2011; https://www.ncbi.nlm.nih.gov/pubmed/21822324.↵