title: T25: a simplified carcinogenic potency index: description of the system and study of correlations between carcinogenic potency and species/site specificity and mutagenicity.
abstract: A simplified carcinogenic potency index, the T25, is proposed as a practical method for the inclusion of potency considerations in carcinogen classification systems. The T25 is the chronic daily dose in mg per kg bodyweight which will give 25% of the animals tumours at a specific tissue site, after correction for spontaneous incidence, within the standard life span of that species. Calculated T25 values of a set of 113 US National Cancer Institute/National Toxicology Program (NC/NTP) carcinogens showed excellent correlation (correlation coefficient 0.96, P < 0.0001) with the carcinogenic potency index TD50 of Peto et al. (1984). The mean of T25 values for 51 transspecies, multiple common site NCI/NTP carcinogens were 10-fold lower than those for 62 NCI/NTP single species, single site carcinogens. For these 113 carcinogens, the mean T25 values were approximately 3-fold lower for agents that were also mutagenic in Salmonella compared to the non-mutagenic agents.
authors.affiliation: Department of Environmental Medicine, National Institute of Public Health, Oslo, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Dybing
authors.forename: T
authors.initials: T
authors.lastname: Sanner
authors.forename: H
authors.initials: H
authors.lastname: Roelfzema
authors.forename: D
authors.initials: D
authors.lastname: Kroese
authors.forename: R W
authors.initials: RW
authors.lastname: Tennant
mesh_terms: D000008:Abdominal Neoplasms / Q000139:chemically induced; D002282:Adenocarcinoma, Bronchiolo-Alveolar / Q000139:chemically induced; D000818:Animals; D002070:Butadienes; D015197:Carcinogenicity Tests / Q000379:methods*; D002273:Carcinogens; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced; D002295:Carcinoma, Transitional Cell / Q000139:chemically induced; D002725:Chloroform; D005260:Female; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced; D008175:Lung Neoplasms / Q000139:chemically induced; D008297:Male; D008654:Mesothelioma / Q000139:chemically induced; D051379:Mice; D016296:Mutagenesis; D009374:Neoplasms, Experimental / Q000139:chemically induced; D051381:Rats; D011916:Rats, Inbred F344; D013045:Species Specificity; D014052:Toluidines; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced
chemical_list: D002070:Butadienes; D002273:Carcinogens; D014052:Toluidines; D002725:Chloroform; C023622:2-toluidine; C031763:1,3-butadiene