Use of the TD50 99 % CI for single dose rodent carcinogenicity studies

The Tumorigenic dose 50 (TD₅₀) is a widely used measure of carcinogenic potency representing the dosage at which 50 % of animals exposed to a compound will develop tumours. The popularity of the TD₅₀ is in part due to the large amount of publicly available data. TD₅₀s were calculated for a large number of compounds in the Carcinogenic Potency Database, which has since been extended in the freely available Lhasa Carcinogenicity database, containing TD₅₀s from over 7500 studies and 1700 compounds. However, due to the age of these studies many are of low quality, often comprising only a single test dosage, therefore raising questions about the applicability of such TD_50 sfor toxicological risk assessment. We investigate whether the lower 99 % confidence interval is sufficient to produce conservative TD₅₀ estimates for these studies.