Toxicological evaluation of some food additives including anticaking agents, antimicrobials, antioxidants, emulsifiers and thickening agents WHO FOOD ADDITIVES SERIES NO. 5 The evaluations contained in this publication were prepared by the Joint FAO/WHO Expert Committee on Food Additives which met in Geneva, 25 June - 4 July 19731 World Health Organization Geneva 1974 1 Seventeenth Report of the Joint FAO/WHO Expert Committee on Food Additives, Wld Hlth Org. techn. Rep. Ser., 1974, No. 539; FAO Nutrition Meetings Report Series, 1974, No. 53. CALCIUM, POTASSIUM, SODIUM FERROCYANIDE Explanation These compounds were evaluated for acceptable daily intake by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1, Ref. No. 20) in 1969. Since the previous evaluation, additional data have become available and are summarized and discussed in the following monograph. The previously published monograph has been expanded and is reproduced in its entirety below. BIOLOGICAL DATA BIOCHEMICAL ASPECTS Because of the strong chemical bond between iron and the cyanide groups these salts have a low toxicity. Dogs injected i.v. with sodium ferrocyanide (0.5 g/kg bw), excreted the salt without renal damage demonstrated by high urea clearance, absence of gross or microscopic haematuria. Repeated clearance several weeks after injection was found to be entirely normal without chronic haematuria, albuminuria or cylindruria. Sodium ferrocyanide, inulin and creatinine show the same excretory behaviour in respect to plasma clearance. In the dog, ferrocyanide is probably excreted entirely by glomerular filtration (Van Slyke et al., 1935; Berliner et al., 1950; Chinard, 1955). I.v. infusion of ferrocyanide and creatinine (20 mg%) into dogs gave an average clearance ratio of 0.966 ± 0.41. Ferrocyanide clearance ratios showed no relationship to plasma ferrocyanide concentration (Berliner et al., 1950). "Instantaneous" injection into renal artery of dogs of combinations of inulin, creatinine and sodium ferrocyanide showed that there was no displacement of one glomerular substance with respect to another in spite of very rapid changes in serum concentration (Chinard, 1955). Rabbits injected i.v. with either sodium or calcium ferrocyanide (0.25 g/kg bw), showed similar rates of excretion of ferrocyanide in the urine. In another experiment rabbits were injected i.v. with either sodium, calcium or magnesium ferrocyanide and histochemical studies made on the kidneys to determine ferrocyanide distribution. Ferrocyanide appeared to be eliminated via the glomeruli. There was no evidence of tubular excretion. Some storage of ferrocyanide occurred in the proximal convoluted tubule cells after the urine was free of demonstrable ferrocyanide (Gersh & Stieglitz, 1934). Female dogs 10 to 20 kg were injected i.v. with 1000 mg of ferrocyanide. 94 to 98% of the administered ferrocyanide was recovered in the urine in 24 hours. Ferrocyanide could not be detected in red blood cells, gastric juice or faeces (Kleeman et al., 1955). Rats dosed orally with 200 mg/kg potassium ferrocyanide excreted about 47% unchanged in the faeces and 3% in the urine. Faecal and urinary excretion of ferrocyanide and thiocyanate was at a maximum from day 1 to day 3 after dosing, and thereafter declined to a low level (Gage, 1950). TOXICOLOGICAL STUDIES Acute toxicity LD50 Reference Animal Route (mg/kg bw) Rat Oral 1600-3200 Fasset, 1958 Short-term studies Rat Groups of 10 male and 10 female rats were maintained for 13 weeks on diets containing 0, 0.05, 0.5 and 5.0% sodium ferrocyanide. Growth rate and food consumption was normal except at the 5% level, where there was slight depression. Haematocrit and haemoglobin values were depressed at the 5% level. Kidney weight of both males and females at the 5% level and females at the 0.5% level was increased as were male adrenal and female pituitary gland weights in the 5% group. The kidneys of rats at the 0.5% level showed a minimal degree of tubular damage. The effect was more marked at the 5% level, in addition granular and calcified deposits were observed (Oser, 1959). Dog Groups each of eight young beagle dogs (four male, four female) received food containing 0, 10, 100 or 1000 ppm (0%, 0.001%, 0.01% or 0.1%) of sodium ferrocyanide. Diets were offered 1 h/day, 6 days/week. The average intake of sodium ferrocyanide was approximately 0.26, 2.6 and 26 mg/kg bw per day. Body weight and food consumption of control and test animals were similar. Haematologic, biochemical tests, and urine analysis of test and control animals were similar and within normal limits. There were no marked differences in absolute and relative organ weight of test and control animal. Histological studies of organs and tissues indicated chronic inflammation of the liver and kidney of one test animal in the 0.1% group. No effect on kidney histology was noted in any other test animal (Morgareidge, 1970). Long-term studies No data are available. OBSERVATIONS IN MAN Glomerular function was studied in 115 humans, 45 healthy, 70 patients with glomerulonephritis, hypertension and amyloidosis. 10 ml 5% sodium ferrocyanide was nontoxic in adults and 0.0077 g/kg tolerated in infants. 25% was excreted in 80 minutes and the remainder in the next 90 minutes by glomerular filtration. Patients had slower rates of excretion (Forero & Koch, 1942). Following i.v. injections of sodium ferrocyanide in amounts ranging from 0.55 to 6.2 g into humans ferrocyanide and urea clearance rates were found to be essentially similar suggesting that ferrocyanide was excreted like urea with about 40% reabsorption. Subjects receiving excessive doses of ferrocyanide (5X recommended) developed a marked albuminuria accompanied by numerous granular casts, white cells, epithetical cells and rare red blood cells. Symptoms disappeared within two weeks. There was no change in urea clearance during this period (Miller & Winkler, 1936). 0.1% sodium ferrocyanide was administered by i.v. infusion to six infants, nine days to 14 months of age. The comparative rate of glomerular filtration of inulin and sodium ferrocyanide suggested tubular reabsorption of the latter substance in infants. There was no evidence of urinary disturbance in infants given sodium ferrocyanide (Calcagno et al,, 1951). A group of nine human subjects, which included patients with liver and kidney damage were injected (i.v.) with 30 to 50 mg of Fe59-labelled ferrocyanide. In the normal subject an average of 80% (68 to 87%) of the administered radioactivity was recovered in 24 to 48 hours. There was no significant radioactivity detected in pooled faeces, saliva or gastric juice. In normal subjects the half time value (T 1/2) was 135 minutes. The rate of disappearance was slower in patients with renal damage. There was some evidence of in vivo binding of ferrocyanide to plasma albumin. In dogs the T 1/2 of labelled ferrocyanide was 40 to 50 minutes. No significant radioactivity was found in the pooled faeces, saliva or gastric juices of dogs (Kleeman & Epstein, 1956). Comments: Human studies have demonstrated that i.v. injected ferrocyanide is excreted by glomerular filtration. Tubular reabsorption occurs in man but not in dogs. High levels were nephrotoxic in the single short- term study available but no renal function tests were performed. The material is unstable in acid solution. EVALUATION Level causing no toxicological effect Rat: 500 ppm (0.05%) in the diet equivalent to 25 mg/kg bw. Estimate of acceptable daily intake for man 0-0.025 mg/kg bw.* FURTHER WORK OR INFORMATION Required by June 1974. Metabolic studies in man. If these reveal any untoward effects, a long-term study in one species will be required. REFERENCES Berliner, W. R., Kennedy, T. J. & Hilton, J. G. (1950) Amer. J. Physiol., 160, 325-329 Calcagno, P. L., Husson, G. S. & Rubin, M. I. (1951) Proc. Soc. exp. Biol. & Med., 77, 309-311 Chinard, F. P. (1955) Amer. J. Physiol., 180, 617-619 Fassett, D. W. (1958) In: Patty, F. A., Industrial hygiene and toxicology, New York, John Wiley & Sons, Vol. II, p. 2036 Forero, A. & Koch, M. M. (1942) Rev. de med. y alimentacion, 5, 34-46 Gage, J. C. (1950) Unpublished report submitted by I.C.I. Ltd., Industrial Hygiene Research Laboratories Gersh, I. & Stieglitz, E. J. (1934) Anatomical Record, 58, 349-364 Kleeman, C. R. & Epstein, F. H. (1956) Proc. Soc. exp. Biol. & Med., 93, 228-233 Kleeman, C. R. et al. (1955) Amer. J. Physiol., 182, 548-552 Miller, B. F. & Winkler, A. (1936) J. clin. Invest., 15, 489-492 Morgareidge, K. (1970) Unpublished report by Food and Drug Research Lab. Inc., submitted by International Salt Co. Inc. to WHO * Temporary Oser, B. L. (1959) Unpublished report by Food and Drug Research Lab. Inc., submitted by International Salt. Co. Inc. Van Slyke, D. D., Hiller, A. & Miller, B. F. (1935) Amer. J. Physiol., 113, 611-628
See Also: Toxicological Abbreviations