The NTP Report on Carcinogens: A valuable resource for public health, a challenge for regulatory science.

The Report on Carcinogens (RoC), from the National Toxicology Program of the USA, is one of the world-leading programs for the identification and acknowledgment of substances that represent a hazard of cancer to humans. RoC covers several essential topics concerning environmental, occupational, and pharmaceutical agents that are known to be, or reasonably anticipated to be carcinogenic to humans. To promote the highest exploitation by its potential users, several RoC aspects and features were put together into one article. For doing so, a comprehensive description is provided regarding RoC history, scope, general features, listing criteria, contents, handbook, and website. Secondary and tertiary aims for this work were (a) to point out some improvement opportunities for the RoC, and (b) to discuss pending issues in regulatory science and cancer hazard assessments. In this regard, for agents classified as probably, likely, reasonably anticipated, possibly or suspected to be a human carcinogen, there is a lack of quantitative knowledge concerning the likelihood of those agents actually being carcinogenic to humans. Elucidating these probabilities is necessary, because the duration of current regulations and the arrival of new acts may depend on it. On the other hand, there is a dramatic imbalance in priorities toward carcinogens, compared with non-carcinogens, in current cancer hazard identification programs. That vision may ignore that the availability on the market of chemicals classified as probably not carcinogenic to humans can also be important for the employment, alimentation, economy, quality of life of consumers, and human health.