NATIONAL TOXICOLOGY PROGRAM (NTP)

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The National Toxicology Program’s 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 biennially1.  It 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.

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.  One example of such potential actions would be the U.S. Occupational Safety and Health Administration Hazard Communication Standard, which states that "Chemical manufacturers and importers shall evaluate chemicals produced in their workplaces or imported by them to determine if they are hazardous…and that chemical manufacturers, importers and employers evaluating chemicals shall treat the…RoC as a source establishing that a chemical is a carcinogen or potential carcinogen for hazard communication purposes."  Written hazard communications required of employers for carcinogens include labels and other forms of warning, material safety data sheets, and employee information and training.

Footnotes:

1 The report is supposed to be published biennially, but none has been published since January 2005.

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