Airpop® EPS vs Styrene

Despite scientific evidence disproving an exposure link to cancer in humans, the 12th edition of the National Toxicology Program (NTP) Report on Carcinogens (RoC) reported styrene—NOT POLYSTYRENE—as a substance “reasonably anticipated to be a human carcinogen.” This is the basis for the State of California Office of Environmental Health Hazard Assessment (OEHHA) to list styrene as one of more than 900 chemicals known to the state of California to cause cancer under Proposition 65.

The term reasonably anticipated is for substances for which there is limited evidence of carcinogenicity from studies in humans, indicating that causal interpretation is credible but that alternative explanations could not adequately be excluded. It is important to recognize that the International Agency for Research on Cancer (IARC), an agency of the World Health Organization, recognize styrene as possibly carcinogenic to humans under Classification Group 2B. This is used for substances “for which there is limited evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals.”

These disparate classifications represent different interpretations of the available data on styrene toxicity when evaluated under laboratory research conditions. There are also important distinctions between the chemical styrene and EPS foam as a finished product.

  • Styrene is a liquid chemical that is used in the manufacture of many plastic products including polystyrene foam, medical applications, consumer electronics, as well as components for automobiles, trucks and boats, among others. Styrene also occurs naturally and is a component of many common foods, such as coffee, strawberries and cinnamon.


  • Styrene should not be confused with EPS. In point, NTP does not report that EPS products pose a risk. This is validated in the National Institute of Environmental Health Sciences (NIEHS) fact sheet on the NTP 12th Report on Carcinogens, clarifying: “The RoC listing of styrene was based on high levels of exposure such as that experienced by workers exposed to styrene in an industrial setting and it was not based on the very small amount of styrene that may possibly leach from [an EPS] cup or plastic containers.”

Linda Birnbaum, a preeminent toxicologist and Director of the NTP & NIEHS, has further clarified, “Let me put your mind at ease right away about [EPS]. Levels of styrene that leach from [EPS] . . . are hundreds if not thousands of times lower than have occurred in the occupational setting where the chemical in vapor form poses a possible risk to workers. In finished products, certainly styrene is not an issue and exposure to it from riding in a boat is infinitesimal.” [“Weighing Cancer Risks, From Cellphones To Coffee”, USA Today, 6/15/2011]


  • The U.S. Department of Health & Human Services (HHS) Agency for Toxic Substances & Disease Registry (ATSDR) has issued a public health statement for styrene, CAS#: 100-42-5 that provides useful information to understand the potential exposure to styrene for workers versus the general public and children. Covering the potential risks associated with styrene beyond cancer, it provides a fact-based, pragmatic understanding of styrene and the potential effects from exposure to it. As a function of its public service, HHS explains how agency regulations and recommendations can differ. They are typically based on ‘not-to-exceed’ levels of a toxic substance in air, water, soil or food that do not exceed a critical value that are derived from levels that affect animals. They are then adjusted to levels that will help protect humans. They further explain that sometimes these not-to-exceed levels differ among federal organizations because they used different exposure time (an 8-hour workday or a 24-hour day), different animal studies or other factors.


  • At the same time OEHHA added styrene to the Proposition 65 List of Chemicals, it also published a “Response to Comments Pertaining to the Notice of Intent to List (NOIL) Styrene as Causing Cancer Under Proposition 65”. Based on industry comments submitted in response to the NOIL issued in 2015, they respond that OEHHA agrees “styrene is not the same as polystyrene”, and points out that polystyrene is not the subject of the proposed listing. OEHHA further notes that, “under Proposition 65 regulations, a warning for styrene would not be required for exposures where there is no significant risk of cancer. OEHHA is listing styrene, not polystyrene. While free or unreacted styrene may be present in such products, only styrene exposures that pose a significant cancer risk would require a warning. Businesses are exempted from the Proposition 65 warning requirement if the exposures they cause are so low as to create no significant risk of cancer.”


The EPS Industry Alliance is a trade association representing expanded polystyrene manufacturers in North America. EPS foam is widely used in building applications to provide energy efficient insulation solutions and as a superior cushioning material in transport packaging to safely deliver products in a variety of applications.


© Copyright 2016 EPS Industry Alliance  │  The information contained herein is subject to change and is provided for informational purposes only. It is provided without warranty, either express or implied. EPS-IA reserves the right to amend this information without notice and assumes no liability or responsibility for any error or omissions in the content of this publication.