The human diet contains an enormous background of natural chemicals, such as plant pesticides and the products of cooking, that have not been a focus of carcinogenicity testing. A broadened perspective that includes these natural chemicals is necessary. A comparison of possible hazards for 80 daily exposures to rodent carcinogens from a variety of sources is presented, using an index (HERP) that relates human exposure to carcinogenic potency in rodents. A similar ordering would be expected with the use of standard risk assessment methodology for the same human exposure values. Results indicate that, when viewed against the large background of naturally occurring carcinogens in typical portions of common foods, the residues of synthetic pesticides or environmental pollutants rank low. A similar result is obtained in a separate comparison of 32 average daily exposures to natural pesticides and synthetic pesticide residues in the diet. Although the findings do not indicate that these natural dietary carcinogens are important in human cancer, they cast doubt on the relative importance for human cancer of low-dose exposures to synthetic chemicals.

No abstract

The Carcinogenic Potency Database (CPDB) is a systematic and unifying resource that standardizes the results of chronic, long-term animal cancer tests which have been conducted since the 1950s. The analyses include sufficient information on each experiment to permit research into many areas of carcinogenesis. Both qualitative and quantitative information is reported on positive and negative experiments that meet a set of inclusion criteria. A measure of carcinogenic potency, TD(50) (daily dose rate in mg/kg body weight/day to induce tumors in half of test animals that would have remained tumor-free at zero dose), is estimated for each tissue-tumor combination reported. This article is the ninth publication of a chronological plot of the CPDB; it presents results on 560 experiments of 188 chemicals in mice, rats, and hamsters from 185 publications in the general literature updated through 1997, and from 15 Reports of the National Toxicology Program in 1997-1998. The test agents cover a wide variety of uses and chemical classes. The CPDB Web Site (http://potency.berkeley.edu/) presents the combined database of all published plots in a variety of formats as well as summary tables by chemical and by target organ, supplemental materials on dosing and survival, a detailed guide to using the plot formats, and documentation of methods and publications. The overall CPDB, including the results in this article, presents easily accessible results of 6153 experiments on 1485 chemicals from 1426 papers and 429 NCI/NTP (National Cancer Institute/National Toxicology program) Technical Reports. A tab-separated format of the full CPDB for reading the data into spreadsheets or database applications is available on the Web Site.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The National Institute of Environmental Health Sciences (NIEHS) and Brogan & Partners are collaborating with JSTOR to digitize, preserve and extend access to Environmental Health Perspectives.A tabulation of carcinogenic potency (TD50) by species for 492 chemicals that induce tumors in rats or mice is presented. With the use of the Carcinogenic Potency Database, experimental results are summarized by indicating in which sex-species groups the chemical was tested and the respective evaluations of carcinogenicity. A comparison of three summary measures of TD50 for chemicals with more than one positive experiment per species shows that the most potent TD50 value is similar to measures that average values or functions of values. This tabulation can be used to investigate associations between rodent potency and other factors such as mutagenicity, teratogenicity, chemical structure, and human exposure. method must be selected to summarize the potency of a carcinogen when there is more than one potency estimate for it. Additional information to summarize the experimental results includes the number of sexspecies groups tested and the evaluations of carcinogenicity in each group.In this paper we present a table summarizing carcinogenic potency in rats and mice for the 492 chemicals that have positive results in the CPDB; we also indicate in which sex-species groups the chemical was tested and the respective evaluations of carcinogenicity. Our intent is that this summary compilation will be a useful reference source for the scientific and regulatory communities, and that it will facilitate the use of our larger published plots of the CPDB. The larger plots provide detailed information on each experiment including the species, sex, strain, route of administration, duration of exposure and of experiment, dose levels, target sites, shape of the dose response, estimates of carcinogenic potency and the confidence limits surrounding it, statistical significance of the carcinogenic dose response, tumor incidences, and bibliographic citation to the published paper or to the

Many important issues in carcinogenesis can be addressed using our Carcinogenic Potency Database, which analyzes and standardizes the literature of chronic carcinogenicity tests in laboratory animals. This review is an update and overview of our analyses during the past 15 years, using the current database that includes results of 5152 experiments on 1298 chemicals. We address the following: 1. More than half the 1298 chemicals tested in long-term experiments have been evaluated as carcinogens. We describe this positivity rate for several subsets of the data (including naturally occurring and synthetic chemicals), and we hypothesize and important role in the interpretation of results for increased cell division due to administration of high doses. 2. Methodological issues in the interpretation of animal cancer tests: constraints on the estimation of carcinogenic potency and validity problems associated with using the limited data from bioassays to estimate human risk, reproducibility of results in carcinogenesis bioassays, comparison of lifetable and summary methods of analysis, and summarizing carcinogenic potency when multiple experiments on a chemical are positive. 3. Positivity is compared in bioassays for two closely related species, rats and mice, tested under similar experimental conditions. We assess what information such a comparison can provide about interspecies extrapolation. 4. Rodent carcinogens induce tumors in 35 different target organs. We describe the frequency of chemicals that induce tumors in rats or mice at each target site, and we compare target sites of mutagenic and nonmutagenic rodent carcinogens. 5. A broad perspective on evaluation of possible cancer hazards from rodent carcinogens is given, by ranking 74 human exposures (natural and synthetic) on the HERP indes.