In June 2011, the National Toxicology Program (NTP) listed styrene as “reasonably anticipated to be a human carcinogen” in its 12th Report on Carcinogens (RoC).
In 2012, Congress directed the U.S. Department of Health and Human Services (HHS) to engage the National Academy of Sciences (NAS) to conduct an independent review of the validity of the listing and the listing criteria.
By conducting this independent review, the National Academy review panel will be able to determine whether NTP has conveyed to the public the best and most informative scientific conclusions regarding styrene and any potential it may have to cause cancer in humans. The review is underway, as of February 2013.
SIRC has petitioned HHS [read the PDF] to acknowledge the NAS review on the RoC website so that anyone referencing the RoC for information on styrene will be duly informed the styrene listing is in question.
SIRC is also challenging the listing as being unsupported by the science and the result of a seriously flawed process in a lawsuit filed against HHS in the U.S. District Court for District of Columbia on June 10, 2011. The court’s decision is pending. Read more about the legal challenge in the Newsroom.
About the RoC
The Report on Carcinogens (RoC) is an informational scientific and public health document first ordered by Congress in 1978 that identifies and discusses agents, substances, mixtures, or exposure circumstances that may pose a hazard to human health by virtue of their carcinogenicity. The National Toxicology Program (NTP), which is part of the U.S. Department of Health and Human Services’ Centers for Disease Control and Prevention, publishes the RoC. It is intended to serve as a meaningful and useful compilation of data on:
- 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.
- The potential for human exposure to these substances.
- Federal regulations to limit exposures.
The RoC identifies substances, mixtures of chemicals, or exposure circumstances associated with technological processes that cause or might cause cancer and to which a significant number of persons in the United States are exposed. Listed in the RoC are a wide range of substances, including metals, pesticides, drugs, and natural and synthetic chemicals.
The evaluation of substances nominated for listing in the RoC is performed by scientists from the NTP, other federal health research and regulatory agencies, and non-government institutions. Listings in the RoC identify a substance or exposure circumstance as a known or reasonably anticipated human carcinogen. The RoC is a hazard identification document and 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.
Agents, substances, or exposure circumstances are listed as either "known to be a human carcinogen," or "reasonably anticipated to be a human carcinogen." The category "known to be a human carcinogen" is 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," includes substances for which there is limited evidence of carcinogenicity in humans and/or sufficient evidence of carcinogenicity in experimental animals. Conclusions regarding carcinogenicity in humans or animals are based on scientific judgment, with consideration given to all relevant information.
The RoCs are informational (not regulatory) scientific and public health documents that are intended to inform and educate the public and health care professionals about the risk of exposure to carcinogens by providing 1) available cancer data in humans and/or animals for the substance of interest; 2) the potential for exposure to the substances listed; and 3) the regulations promulgated by federal agencies to limit exposures.
It is important to note that these reports do not present quantitative assessments of carcinogenic risk, nor do they address any potential benefits of exposures to listed substances. Listing in the report does not establish that such substances present a risk to persons in their daily lives. Rather, such formal risk assessments are the purview of appropriate federal, state, and local health regulatory and research agencies.The listing of a substance in the RoC is not in itself a regulatory action, but listing may prompt regulatory agencies to consider limiting exposures or uses of a substance.
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