Report on Carcinogens Process & Listing Criteria

Preparation Process

NTP prepares the Report on Carcinogens (RoC) on behalf of the Secretary of Health and Human Services and follows an established, multi-step process for the review and evaluation of selected substances. The process has four parts:

  1. Select substances for evaluation.
  2. Prepare draft RoC monographs for selected substances.
  3. Peer review and finalize RoC monographs.
  4. Release the RoC.

A detailed explanation of the process is available for download.

Listing Criteria

NTP applies established criteria to determine whether an agent, substance, mixture, or exposure circumstance should be listed in the Report on Carcinogens:

Known To Be Human Carcinogen

There is sufficient evidence of carcinogenicity from studies in humans , which indicates a causal relationship between exposure to the agent, substance, or mixture, and human cancer.

Reasonably Anticipated To Be Human Carcinogen

There is limited evidence of carcinogenicity from studies in humans , which indicates that causal interpretation is credible, but that alternative explanations, such as chance, bias, or confounding factors, could not adequately be excluded,


there is sufficient evidence of carcinogenicity from studies in experimental animals, which indicates there is an increased incidence of malignant and/or a combination of malignant and benign tumors (1) in multiple species or at multiple tissue sites, or (2) by multiple routes of exposure, or (3) to an unusual degree with regard to incidence, site, or type of tumor, or age at onset,


there is less than sufficient evidence of carcinogenicity in humans or laboratory animals; however, the agent, substance, or mixture belongs to a well-defined, structurally related class of substances whose members are listed in a previous Report on Carcinogens as either known to be a human carcinogen or reasonably anticipated to be a human carcinogen, or there is convincing relevant information that the agent acts through mechanisms indicating it would likely cause cancer in humans.

Conclusions regarding carcinogenicity in humans or experimental animals are based on scientific judgment, with consideration given to all relevant information. Relevant information includes, but is not limited to, dose response, route of exposure, chemical structure, metabolism, pharmacokinetics, sensitive sub-populations, genetic effects, or other data relating to mechanism of action or factors that may be unique to a given substance. For example, there may be substances for which there is evidence of carcinogenicity in laboratory animals, but there are compelling data indicating that the agent acts through mechanisms which do not operate in humans and would therefore not reasonably be anticipated to cause cancer in humans.