Estimates of the risk of bladder tumor promotion by saccharin in rats.
Tumor data from an initiation-promotion bioassay in rats are used to illustrate how urinary bladder tumor risk estimates can be modified to reflect tumor promotion by saccharin. Assuming equal carcinogenic potency in humans and rats, the estimated human risk is equal to the probability of tumors in rats due to saccharin promotion following administration of an initiator times the ratio of the proportion of humans that are initiated to the proportion of initiated rats. The proportion of initiated humans may be somewhere between the proportion of deaths due to bladder cancer in the U.S. population, 0.005, and 1.0. The proportion of initiated animals in the bioassay may be somewhere between the proportion of animals with bladder tumors, 0.41, as observed in an initiated group, and 1.0. Hence, the ratio of the proportion of initiated humans to animals may be between 0.005 and 2.4. Then, the risk of bladder tumors is estimated to be between 0.005 and 2.4 times the estimated risk of tumors in rats promoted by saccharin following administration of an initiator. An upper limit on bladder tumor risk is estimated to be between 0.00038 and 0.18 times the percentage of saccharin in the diet. If a threshold dose exists for saccharin bladder tumor promotion which is above the saccharin consumption level of all humans, then the risk is zero.
Gaylor
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National Center for Toxicological Research, Jefferson, Arkansas 72079.
Kadlubar
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FF
West
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D000818:Animals; D051381:Rats; D012307:Risk Factors; D012439:Saccharin / Q000633:toxicity*; D014481:United States; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced* / Q000401:mortality
D012439:Saccharin