From the book SAFE FOOD by Michael F. Jacobson, Ph.D, Lisa Lefferts and Anne Garland
"Acesulfame K, sold commercially as Sunette or Sweet One, was approved by the FDA in 1988 as a sugar substitute in packet or tablet form, in chewing gum, dry mixes for beverages, instant coffee and tea, gelatin desserts, puddings and nondairy creamers. The manufacturer has asked the FDA to approve acesulfame K for soft drinks and baked goods.
The public is waiting for an artificial sweetener that is unquestionably safe. But this one isn't it. Even compared to aspartame and saccharin (which are afflicted with their own safety publems - see below), acesulfame K is the worst. The additive is inadequately tested, the FDA based its approval on tests of acesulfame K that fell short of the FDA's own standards. But even those tests indicate that the additive causes cancer in animals, which means it may increase cancer risk in humans. In l987, CSPI urged the FDA not to approve acesulfame K, but was ignored. After the FDA gave the chemical its blessing, CSPI urged that iat be banned. The FDA hasn't yet ruled on that request."
... acetoacetamide, a breakdown product, has been shown to affect the thyroid in rats, rabbits, and dogs. Administration of 1% and 5% acetoacetamide in the diet for three months caused benign thyroid tumors in rats. The rapid appearance of tumors raises serious questions about the chemicalХs carcinogenic potency."