Bladder tumors in rats fed cyclohexylamine or high doses of a mixture of cyclamate and saccharin.

Papillary transitional cell tumors were found in the urinary bladders in 8 rats out of 80 that received 2600 milligrams per kilogram of body weight per day of a mixture of sodium cyclamate and sodium saccharin (10:1) for up to 105 weeks. From week 79 on, several of these rats received cyclohexylamine hydrochloride (125 milligrams per kilogram per day, the molecular equivalent of the conversion of about 10 percent of the cyclamate dosage to cyclohexylamine) in addition to the sodium cyclamate and sodium saccharin. In another study in which 50 rats were fed daily 15 milligrams of cyclohexylamine sulfate per kilogram of body weight for 2 years, eight males and nine females survived. One of the eight males had a tumor of the urinary bladder. In neither study were bladder tumors found in the control rats or in rats treated with lower doses of the compounds.

Long-term and multigeneration toxicity studies with cyclohexylamine hydrochloride.

Cyclohexylamine (CHA), the metabolite of cyclamate produced in varying degree by gastrointestinal microorganisms, was subjected to a 2-year multi-generation feeding study in rats, at dosages of 15, 50, 100, and 150 mg/kg/d. Observations included growth, feed efficiency, clinical and hematological tests, reproduction, teratology, mortality and gross and microscopic pathology. Rats from the first litters of each generation from F0 through F4 were mated to produce the next succeeding generation. Those from the second litters of F1 through F4 were also mated, half the dams being delivered by hysterotomy for teratological examination, while litters from the other half were raised to maturity. Except for some non-progressive growth retardation in the higher dosage groups, due to lower food consumption, the physical and clinical observations in the test groups fell substantially within normal limits and were not significantly different from the untreated controls. Reproduction rates were normal in all groups but at the higher dosages the size of the litters and their weaning weights were slightly reduced. At the 150 mg/kg level, histopathological examination revealed mucosal thickening of the bladder walls and evidence of renal calcification; however, no bladder tumors were seen, such as occurred in the chronic feeding study in which rats received 2500 mg/kg of a cyclamate: saccharin (10 : 1) mixture. A significantly higher incidence of testicular atrophy, characteristic of aged rats, was observed in the F0 group at the highest dosage level; however, these males continued to be fertile, in two cases up to 6 consecutive matings.

Chronic toxicity study of cyclamate: saccharin (10: 1) in rats.

Chronic rat feeding studies were conducted on a 10: 1 cyclamate/saccharin (C/S) mixture to supplement previous investigations which had established the safety of the individual components. The test mixture was fed at dietary levels designed to furnish 500, 1120, and 2500 mg/kg body weight to groups of 35 male and 45 female rats. The protocol included observations of physical condition, growth response, food efficiency, blood, urine, and postmortem pathology. Reproduction and lactation performance was examined through 2 litters. Teratology was also investigated. Since conversion to cyclohexylamine (CHA) was found to occur in many of the rats, particularly in the higher dosage groups, it was included as an added insult in the diets of about half the animals during the last quarter of the 2-year test period. The only positive finding in these studies which proved to have crucial significance was the occurrence of papillary carcinomas in the bladders of 12 of the 70 rats fed the maximum dietary level of the mixture (equivalent to about 2500 mg/kg body weight) for periods ranging from 78 to 105 weeks (except for one earlier death). This finding was the principal reason for the removal of cyclamates from the "generally recognized as safe" (GRAS) group of non-nutritive sweeteners by the U.S. Department of Health, Education and Welfare. In the opinion of the authors, the sequelae following this precipitate ban on cyclamates, prompted by a verbal report of the preliminary findings, warrant placing the study on record for the information of toxicologists and regulatory agencies throughout the world.

Highlights in the history of saccharin toxicology.

Saccharin has successfully survived a half century of scrutiny of its safety. Experience during almost 60 years of common use in foods, as well as several rat feeding studies including that conducted by the FDA, established its GRAS status under the 1958 Food Additives Amendment. Many chronic one-generation and three (unvalidated) two-generation rat studies subsequently conducted by regulatory and independent agencies in the USA and elsewhere have been interpreted by expert committees, especially those of the National Academy of Sciences/National Research Council, as supportive of saccharin's non-carcinogenicity under possible conditions of use. Not convinced of saccharin's safety, because of the (inconsistent) evidence of bladder tumours in saccharin-treated F1 male rats, the FDA proposed a ban on its use as a food additive. This ban has been temporarily postponed by Congressional moratoria, while better designed and executed studies into the mode of action of this unmetabolized non-genotoxic substance are in progress.

Toxicology then and now.

A review of the history of the evolution of the science of toxicology from the original concepts of Paracelsus through the early development of analytical chemistry and its contributions to the detection of toxic substances in foods and drugs as these have led to modern regulatory rules for public protection is presented. The legal actions taken to protect against adulteration of food prior to the early steps by the U.S. Department of Agriculture that concluded with the passage of the 1906 Food and Drug Act are systematically documented. The history is reviewed of the Food and Drug Administration's role in the use of animal toxicity studies to develop reasonable criteria for safety of foods and drugs for man. Modern concepts of molecular distribution, metabolism, and excretion of substances in the animal body are discussed as these impinge on the so-called "protection index." The legal and often litigious controversies over the claimed carcinogenicity of chemical substances is documented with comments on the Delaney dilemma and the role of in vitro tests in toxicology. The review concludes with a discussion of the hazards of use of stochastic mathematical models to assess carcinogenicity and suggests that the criteria employed in the report of the Scientific Committee of the Food Safety Council are properly structured to give a contemporary evaluation of all the currently available data. References give documentation of events over the past 200 years that explain the present state of toxicology as a discipline.

Caffeine: an update.

While the total annual volume of caffeine has increased over the years, the actual per capita daily intake has not. This is based on the fact that the quantity of caffeine in a soft drink is about the same or, in the case of diet drinks, less than in 1961 when the original GRAS (Generally Recognized as Safe) determinations were made. Since that time, there have been numerous studies on the effect of caffeine on animals and humans. The Select Committee on GRAS Substances (SCOGS) of the Federation of American Societies for Experimental Biology (FASEB) in 1978 reviewed all the data available at that time and concluded that there is "no evidence in the available information on caffeine [that] demonstrates a hazard to the public when it is used in cola-type beverages at levels that are now current and in the manner now practiced...", although they did suggest further study was necessary. The Flavor and Extract Manufacturers' Association (FEMA) Expert Panel has now reviewed not only the same data s the FASEB (SCOGS) Committee, but several more recent studies. On the basis of this review, the Panel reaffirms the GRAS status of caffeine under conditions of its current use as an international ingredient in nonalcoholic beverages.

Acute oral toxicity of selected flavor chemicals.

The acute oral lethal doses are reported in rats or mice for 63 substances which are used in flavorings. For specific groups of compounds which contain several representatives of one structural class, some effects of structure on acute oral toxicity were observed. For pyrazines, the addition and position of methyl groups affected the toxicity while the substitution of ethyl for methyl had little effect. Toxicity increased with the proximity of the methyl group. The thiazoles and thiazolines tested had similar toxicities regardless of the side groups. The furan thioesters tested were about equally toxic, a fact which would be consistent with hydrolysis to the acid plus thiol.