National Toxicology Program

In response to concerns from people within the United States regarding the relationship between their environment and cancer, the U.S. Congress mandated, as part of the Public Health Service Act (Section 301(b)(4), as amended), that the Secretary, Department of Health and Human Services (DHHS), publish a report which contains a list of all substances (1) which either are known to be human carcinogens or may reasonably be anticipated to be human carcinogens, and (2) to which a significant number of persons residing in the United States are exposed. The Secretary delegated responsibility for preparing these reports to the NTP. The NTP is an interagency program within DHHS headquartered at the National Institute of Environmental Health Sciences (NIEHS) of the National Institutes of Health.

The RoC is an informational scientific and public health document that identifies and discusses agents, substances, mixtures, or exposure circumstances that may pose a hazard to human health by virtue of their carcinogenicity. It serves 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 substances in humans and/or in animals, (2) the potential for human exposure to these substances, and (3) Federal regulations to limit exposures. The RoC does not present quantitative assessments of the risks of cancer associated with these substances. Thus listing of substances in the RoC only indicates a potential hazard and does not establish the exposure conditions that would pose cancer risks to individuals in their daily lives. Such formal risk assessments are the responsibility of the appropriate federal, state, and local health regulatory and research agencies.

Since its inception in 1978, the RoC has strived to improve its scientific review process. In 1996, the scientific review process was expanded to include external peer review that is held in a public forum. At this time, the NTP also revised the criteria to allow for consideration of all relevant information, including mechanism of action, when making decisions about listing nominations in the RoC. In 1999 and 2004, the NTP held public meetings to consider public comments on the review process and conducted its own internal evaluation of the process used for the review of nominations to the 10^th and 11^th RoCs. Following the 2004 meeting, the NTP revised the RoC review process to enhance the scientific development of the report and address guidance in the Office of Management and Budget (OMB) Peer Review Bulletin. On April 16, 2007 the NTP released the final review process applicable for the evaluation of candidate substances (substances that are under consideration for listing in or removing from the RoC) for the 12^th RoC [72 FR 72 18999 16Apr07].

To date, a total of 11 RoCs have been published with the last one, the 11^th RoC, being released on January 31, 2005. The following table contains information on the individual editions of the RoC including the year of release and number of listings in each edition.

RoC Chronology

RoC Edition	Year	Number of Listings
First	1980	26 Chemicals or Industrial Processes *
Second	1981	88 Chemicals or Industrial Processes *
Third	1983	23 "Known"; 98 "Reasonably Anticipated"
Fourth	1985	30 "Known"; 119 "Reasonably Anticipated"
Fifth	1989	23 "Known"; 140 "Reasonably Anticipated", 4 delisted
Sixth	1991	26 "Known"; 148 "Reasonably Anticipated", 2 delisted
Seventh	1994	27 "Known"; 156 "Reasonably Anticipated"
Eighth	1998	29 "Known"; 169 "Reasonably Anticipated"
Ninth	2000	48 "Known"; 170 "Reasonably Anticipated", 2 delisted
Tenth	2002	52 "Known"; 176 "Reasonably Anticipated"
Eleventh	2005	58 "Known"; 188 "Reasonably Anticipated"

* No categories identified for the listings in the First or Second RoC