Humans' polymorphism would mandate that any finding of carcinogenesis in any strain of animal should signal great concern and caution. Mice Mice have been less well studied than rats. The dosages of saccharin that appear to have elicited an effect in small rodent studies are not much greater than the amounts that some Americans consume. That hardly gives one much confidence that saccharin is safe for human consumption. The question of whether saccharin consumption increases the risk of bladder cancer in humans takes on added importance considering the increasing incidence of that cancer in recent decades.
Bladder cancer is now the fifth most common cancer in the United States.
The National Cancer Institute estimates that 54,500 new cases of bladder cancer would occur in 1997. National Cancer Institute, SEER, Cancer Statistics Review, 1973-1994. The reasons for those increases in men are not known. Several studies, including some of the largest ones, found significant increases in rates of bladder cancer. Women who consumed dietetic beverages for five years or more had a relative risk of 3.7.