INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
WORLD HEALTH ORGANIZATION
TOXICOLOGICAL EVALUATION OF SOME
FOOD COLOURS, ENZYMES, FLAVOUR
ENHANCERS, THICKENING AGENTS, AND
CERTAIN FOOD ADDITIVES
WHO FOOD ADDITIVES SERIES 6
The evaluations contained in this publication were prepared by the
Joint FAO/WHO Expert Committee on Food Additives which met in Rome,
4-13 June 19741
World Health Organization Geneva 1975
1 Eighteenth Report of the Joint FAO/WHO Expert Committee on
Food Additives, Wld Hlth Org. techn. Rep. Ser., 1974, No. 557.
FAO Nutrition Meetings Report Series, 1974, No. 54.
CALCIUM, POTASSIUM AND SODIUM FERROCYANIDE
Explanation
These compounds have been evaluated for acceptable daily intake
by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1,
Refs Nos 20 and 34) in 1969 and 1973.
Since the previous evaluation additional data have become
available and are summarized and discussed in the following monograph.
The previously published monographs have been expanded and are
reproduced in their 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 gm/kg bw), excreted the salt without renal damage
demonstrated by high urea clearance, absence of gross or microscopic
haematuria. Repeat 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; and Chinard, 1955).
I.v. infusion of ferrocyanide and creatinine (20 mg/litre) only 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 gm/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 (Gersch & Stieglitz, 1934).
Following i.v. injections of sodium ferrocyanide in amounts
ranging from 0.55-6.2 gm 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).
Female dogs 10-20 kg were injected (i.v.) with 1000 mg of
ferrocyanide. 94-98% 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 days 1 to 3 after dosing, and thereafter declined to a low level
(Gage, 1950).
A group of nine human subjects, which included patients with
liver and kidney damage were injected (i.v.) with 30-50 mg of Fe59-
labelled ferrocyanide. In the normal subject an average of 80%
(68-87%) of the administered radioactivity was recovered in 24-48
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 40-50 minutes. No significant radioactivity
was found in the pooled faeces, saliva or gastric juices of dogs
(Kleeman & Epstein, 1956).
Glomerular function was studied in 115 humans, 45 healthy, 70
patients with glomerulonephritis, hypertension and amyloidoris. 10 ml
5% sodium ferrocyanide was non-toxic in adults and 0.0077 g/kg
tolerated in infants. Twenty-five per cent. 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).
TOXICOLOGICAL STUDIES
Acute toxicity
LD50
Animal Route (mg/kg bw) Reference
Rat Oral 1 600-3 200 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 were 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
Four groups of four male and four female beagles received in
their diet 0, 10, 100 and 1000 ppm of sodium ferrocyanide for 13
weeks. No abnormalities were noted regarding appearance, behaviour,
body weight change, physical condition, haematology, biochemical
parameters, urinary pathology, gross and histopathology. No compound-
related effects were seen (Morgaridge, 1970).
Long-term studies
No data are available.
Comments:
Human studies have demonstrated that i.v. injected ferrocyanide
is excreted by glomerular filtration. Some tubular reabsorption
occurs in man but not in dogs. High levels were nephrotoxic in the
short-term study in rats, but studies in dogs and man showed no
adverse effects. No long-term studies are available. Evaluation can be
based on the animal studies and human observations.
EVALUATION
Level causing no toxicological effect
Rat: 0.05% (= 500 ppm) in the diet equivalent to 25 mg/kg bw
Estimate of acceptable daily intake for man
0-0.025* mg/kg bw
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. (1955) In: Patty F. A. Industrial Hygiene and
Toxicology, New York, John Wiley & Sons, Vol. II, p. 2036
Forero, A. & Koch, M. y 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. et al. (1955) Amer. J. Physiol., 182, 548-552
Kleeman, C. R. & Epstein, F. H. (1956) Proc. Soc. exp. Biol. & Med.,
93, 228-233
Miller, B. F. & Winkler, A. (1936) J. clin. Invest., 15, 489-492
Morgaridge, K. (1970) FDRL Report No. 91015 dated 10.9.1970 submitted
by International Salt Co. Inc.
Oser, B. L. (1959) Unpublished report by Food & Drugs Research Lab.
Inc., submitted by International Salt Co. Inc.
Van Slyke, D. D., Hiller, A. & Miller, B. F. (1935) Amer. J. Physiol.,
113, 61].-628
* Calculated as sodium ferrocyanide.