FAO Nutrition Meetings
    Report Series No. 40A,B,C
    WHO/Food Add./67.29


    The content of this document is the result of the deliberations of the
    Joint FAO/WHO Expert Committee on Food Additives which met at Rome,
    13-20 December, 19651 Geneva, 11-18 October, 19662


    1 Ninth Report of the Joint FAO/WHO Expert Committee on Food
    Additives, FAO Nutrition Meetings Report Series, 1966 No. 40; 
    Wld Hlth Org. techn. Rep. Ser., 1966, 339

    2 Tenth Report of the Joint FAO/WHO Expert Committee on Food
    Additives, FAO Nutrition Meetings Report Series, 1967, in press; 

    Food and Agriculture Organization of the United Nations
    World Health Organization


    Synonyms                 Calcium Disodium EDTA; Calcium Disodium

    Chemical names           Calcium disodium ethylenediaminetetraacetate;

                             Calcium disodium

    Empirical formula        C10H12CaN2Na2O8.2H2O

    Structural formula


    Molecular weight         410.31

    Definition               Calcium disodium ethylenediaminetetraacetate,
                             on the anhydrous basis, contains not less
                             than 97 per cent. and not more than the
                             equivalent of 102 per cent.

    Description              Calcium disodium ethylenediaminetetraacetate
                             occurs as white, odourless crystalline
                             granules or as a white to nearly white
                             powder, slightly hygroscopic with a faint
                             saline taste.

    Use                      As a sequestrant.

    Biological Data

    Biochemical aspects of ethylenediaminetetraacetic acid (EDTA) and 
    its salts

    14C-labelled CaNa2EDTA, when fed to rats in doses of 50 mg/kg
    body-weight, was absorbed only to an extent of 2-4 per cent.; 80-90
    per cent. of the dose appeared in the faeces within 24 hours, and
    absorption was still apparent at 48 hours. At the low pH of the
    stomach the calcium chelate is dissociated with subsequent
    precipitation of the free acid, and this is only slowly redissolved in
    the intestines (Foreman et al., 1953).

         Experiments in man also revealed poor absorption; only 2.5 per
    cent. of a 3 g dose given was excreted in the urine (Srbova &
    Teisinger, 1957). These authors also confirmed the dissociation of the
    calcium chelate in the stomach. When 200 mg CaNa2EDTA was introduced
    into the duodenum of rats, the authors found an absorption rate of
    6.5-26 per cent.  A dose of 1.5 mg of 14,C-labelled CaNa2EDTA given
    in a gelatine capsule to normal healthy men was absorbed to an extent
    of 5 per cent. (Foreman & Trujillo, 1954).

         In feeding experiments, in rats receiving disodium EDTA at
    dietary levels of 0.5, 1.0 and 5.0 per cent., the faeces contained
    99.4, 98.2 and 97.5 per cent. of the excreted material (Yang, 1964;
    Fellers et al., 1956)

         Similar experiments conducted also in rats gave essentially the
    same results. Thirty-two hours after a single dose of 95 mg disodium
    EDTA/rat, 93 per cent. was recovered from the colon. After doses of
    47.5, 95.0 and 142.5 mg disodium EDTA the amount of EDTA recovered in
    the urine was directly proportional to the dose given, suggesting that
    EDTA was absorbed from the gastrointestinal tract by passive
    diffusion. The motility of the intestine was not affected by the
    compound (Chan, 1964).

         After parenteral administration to rats, 95-98 per cent. of
    injected 14C-labelled CaNa2EDTA appeared in the urine within 6
    hours. All the material passed through the body unchanged. Peak plasm
    levels were found approximately 50 minutes after administration. Less
    than 0.1 per cent. of the material was oxidized to 14CO2, and no
    organs concentrated the substance. After i.v. injection, CaNa2EDTA
    passed rapidly out of the vascular system to mix with approximately 90
    per cent, of the body water, but did not pass into the red blood cells
    and was cleared through the kidney by tubular excretion as well as by
    glomerular filtration (Foreman et al., 1953), The same was also found
    in man using 14C-labelled CaNa2EDTA. Three thousand milligrams were
    given i.v. to 2 subjects and were almost entirely excreted within
    12-16 hours (Srbova & Teisinger, 1957).

         The maximum radioactivity in the urine after application of
    14C-labelled CaNa2EDTA to the skin was only 10 ppm (Foreman &
    Trujillo, 1954).

         In biological systems, Ca ion will usually be most accessible to
    EDTA. In general, zinc seems to be next most accessible. About 80 per
    cent. of the zinc or liver is freely available to EDTA. The over-all
    availability of the other physiologically important metals is probably
    in the order: Cu>Fe>Mn >Co (Chenoweth, 1961). EDTA removes about
    1.4 per cent. of the total iron from ferritin at pH 7.4 to form an
    iron chelate (Westerfield, 1961). Transfer of Fe from Fe-transferrin
    to EDTA in vitro occurs at a rate of less that 1 per cent. in 24
    hours. in vivo studies in rabbits demonstrated transfer of Iron only
    from FeEDTA to transferrin and not the reverse. It appeared that
    tissue iron beams available to chelating agents including EDTA only

    when an excess of iron was present (Cleton et al., 1963). Equal
    distribution between a mixture of EDTA and siderophilin was obtained
    only at EDTA : siderophilin ratios of 20-25 : 1 (Rubin, 1961). Human
    iron deficiency anaemia was successfully treated with FeEDTA although
    84 per cent. of labelled FeEDTA was excreted in the faeces and none
    appeared in the urine. Red cells, however, contained labelled Fe and
    reticulocytosis occurred. Since FeEDTA administered i.v. was almost
    quantitatively excreted in the urine, it was concluded that FeEDTA was
    degraded prior to absorption, when given orally (Lapinleimu &
    Wegelius, 1959). Rabbits absorbed about 10 per cent. of oral FeEDTA,
    and the rest was excreted in the faeces, while anaemic rats absorbed
    50 per cent. of 6 mg/kg body-weight oral FeEDTA but only 25 per cent.
    FeSO4 (Rubin & Princiotto, 1960). Addition of 1 per cent. Na2 EDTA
    to a diet containing more than optimal amounts of iron and calcium
    lowered the absorption and storage of iron in rats and increased the
    amount present in plasma and urine. The metabolism calcium however,
    was apparently unaffected (Larsen et al., 1960). A diet containing
    0.15 mg of iron, 4.26 of calcium and 1 mg of EDTA per rat (equivalent
    to 100 ppm in the diet) for 83 days had no influence on calcium and
    iron metabolism, e.g. the iron content of liver and plasma (Hawkins,
    et al., 1962).

         CaNa2EDTA increased the excretion of zinc (Perry & Perry, 1959),
    and was active in increasing the availability of zinc in
    soybean-containing diets to poults (Kratzer et al., 1959). CaNa2EDTA
    enhanced the excretion of Co, Hg, Mn, Ni, Pb, Tl and W (Foreman,
    1961). The treatment of heavy metal poisoning with CaEDTA has become
    so well established that its use for more commonly seen metal
    poisonings, e.g. lead, is no longer reported in the literature
    (Foreman, 1961). EDTA could not prevent the accumulation of 90Sr,
    106Ru, 141Ba and 226ra in the skeleton. 91Y, 239Pu and 238U responded
    fairly well to EDTA, the excretion being accelerated (Catsch, 1961).

         EDTA had a lowering effect on serum cholesterol level when given
    orally or intravenously. It may have acted by decreasing the capacity
    of serum to transport cholesterol (Gould, 1961). Disodium EDTA had a
    pyridoxin-like effect on the tryptophan metabolism of patients with
    porphyria or scleroderma, due to a partial correction of imbalance of
    polyvalent cations (Lelievre & Batz, 1961).

         In vitro, 0.0033 M EDTA inhibited the respiration of liver
    homogenates and of isolated mitochondria of liver and kidney (Lelievre
    & Batz, 1961). The acetylation of sulfanilamide by a liver extract was
    also inhibited (Lelievre, 1960). EDTA stimulated glucuronide synthesis
    in rat liver, kidney and intestines but inhibited the process in
    guinea-pig liver (Pogell & Leloir, 1961; Mittinen & Leskinen, 1962).
    Of the heavy metal-containing enzymes, EDTA at a concentration of
    about 10-3M inhibited aldehyde oxidase and homogentisinicase. 
    Succinic dehydrogenase, xanthine oxidase, NADF-cytochrome reductase,
    and ceruloplasmin (oxidation of p-phenylenediamine) were not inhibited
    (Westerfield, 1961). Disodium EDTA was found to be a strong inhibitor
    for delta-aminolevulinic acid dehydrogenase, 5.5 × 10-6 M causing
    50 per cent. inhibition (Gibson et al., 1955). The i.p. injection of

    4.2 mmol/kg body-weight (equivalent to 1722 mg/kg body-weight) CaNa2
    EDTA caused in rats an inhibition of the alkaline phosphatase of
    liver, prostate and serum up to 4 days depending on the dose
    administered; zinc restored the activity (Nigrovic, 1964).

         In vitro, EDTA inhibited blood coagulation by chelating Ca2+.
    The complete coagulation inhibition of human blood required 0.65-1.0
    mg/ml. The i.v. injection of 79-200 mg EDTA/rabbit had no effect on
    blood coagulation (Dyckerhoff et al., 1942).

         I.v. injections of Na2EDTA and CaNa2EDTA had some
    pharmacological effect on the blood pressure of cats; 0-20 mg/kg
    body-wight CaNa2EDTA (as Ca) produce a slight rise; 20-50 mg/kg, a
    biphasic response; and 50 mg/kg, a clear depression (Marquardt &
    Schumacher, 1957).

         One per cent. Na2EDTA enhances the absorption of 14C-labelled
    acidic, neutral and basic compounds (mannitol, inulin, decamethonium
    sulfanilic acid and EDTA itself) from isolated segments of rat
    intestine, probably due to an increased permeability of the intestinal
    wall (Schanker & Johnson, 1961).

    Acute toxicity


    Animal   Route     LD50                 References
                       mg/kg body-weight

    Rat      oral      10 000 ± 740         Oser et al., 1963
    Rabbit   oral       7 000 approx.       Oser et al., 1963
             i.p.         500 approx.       Bauer et al, 1952
    Dog      oral      12 000 approx.       Oser et al., 1964

         The oral LD50 in rats is not affected by the presence of food in
    the stomach or by pre-existing deficiency in Ca, Fe, Cu or Mn (Oser et
    al., 1963).

         Oral doses of over 250 mg/animal cause diarrhoea jr. rats
    (foreman et al, 1953).

         There are many reports in the literature on kidney damage by
    parenteral over-dosage of CaEDTA. A review was given by Lachnit
    (1961). Lesions simulating "versene nephrosis" in man have also been
    produced in rats. Disodium EDTA in doses of 400-500 mg i.p. for 21
    days caused severe hydropic degeneration of the proximal convoluted
    tubules of the kidneys. CaNa2EDTA produced only minimal focal
    hydropic changes in 58 per cent. of animals, disappearing almost 2
    weeks after stopping the injections (Reuber & Schmieller, 1962).

    Short-term studies

         Rat. Groups of 5 male rats received 250 or 500 mg/kg
    body-weight CaNa2EDTA i.p. daily for 3-21 days and some were observed
    for an additional 2 weeks.  Weight gain was satisfactory and histology
    of lung, thymus, kidney, liver, spleen, adrenal, small gut and heart
    was normal for mild to moderate renal hydropic change with focal
    subcapsular swelling and proliferation in glomerular loops at the 500
    mg level. There was very slight involvement with complete recovery at
    the 250 mg level. Lesions were not more severe with simultaneous
    cortisone administration (Reuber & Schmieller, 1962).

         Groups of 3 male and 3 female rats were fed for 4 months or, low
    mineral diet containing one-half the usual portion of salt
    mixture(i.e. 1.25 per cent. instead of 2.50 per cent.) with the
    addition of 0 per cent. and 1.5 per cent. CaNa2EDTA. The test group
    showed a reduced weight gain, but there was no distinct difference in
    general condition of the animals (Yang, 1964).

         In another experiment, 3 groups of 8-13 male and female rats were
    fed a low-mineral diet containing 0 per cent, 0.5 per cent. and 1 per
    cent of CaNa2EDTA for 205 days. No significant differences from the
    controls were shown regarding weight gain, mortality, gross pathology
    of the organs and histopathology of liver, kidney and spleen except a
    very slight dilatation of hepatic sinusoids.  Blood coagulation time,
    total bone ash and blood calcium level were unaffected. No significant
    erosion of molars was noted. Basal metabolism was in the normal range
    (Chan, 1964).

         Dog. Four groups of 1 male and 3 female mongrels were fed diets
    containing 0, 50, 100 and 250 mg/kg body-weight CaNa2EDTA daily for
    12 months. All appeared in good health, without significant change in
    blood cells, haemoglobin and urine (Ph, albumin, sugar sediment).
    Blood sugar, non-protein nitrogen and prothrombin time, remained
    normal. Radiographs of ribs and of long bones showed no adverse
    changes at the 250 mg level. All dogs survived for 1 year. Gross and
    microscopic findings were normal (Oser et al., 1963).

    Long-term studies

         Rat. Four groups of 25 male and 25 female rats ware fed diets
    containing 0, 50, 125 and 250 mg/kg body-weight CaNa2EDTA for 2
    years. Feeding was carried on through 4 successive generations. Rats
    were mated after 12 weeks' feeding and allowed to lactate for 3 weeks
    with 1 week's rest before producing a second litter. Ten male and 10
    female rats of each group (F1 generation) and similar F2 and F3
    generation groups were allowed to produce 2 litters. Of the second
    litters of the F1, F2 and F3 generations only the control and the
    250 mg/kg body-weight groups were kept until the end of 2 years' study
    on the F0 generation. This scheme permitted terminal observation to
    be made on rats receiving test diets for 0, 0.5, 1, 1.5 or 2 years in
    the F3, F2, F1 and F0 generations, respectively. No significant

    abnormalities in appearance and behaviour were noted during the 12
    weeks of the post weaning period in all generations. The feeding
    experiment showed no statistically significant differences in weight
    gain, food efficiency, haemopoiesis, blood sugar, non-protein
    nitrogen, serum calcium, urine, organ weights and histopathology of
    liver, kidney, spleen, heart, adrenals, thyroid and gonads. Fertility,
    lactation and weaning were not adversely affected for each mating.
    Mortality and tumour incidence were unrelated to dosage level. The
    prothrombin time was normal. There was no evidence of any chelate
    effect on calcification of bone and teeth. Liver xanthine oxidase, and
    blood carbonic anhydrase activities were unchanged (Oser et al.,


         CaNa2EDTA is very poorly absorbed from the gut. The compound is
    metabolically inert and no cumulation in the body has been found. A
    vast clinical experience in its use in the treatment of metal
    poisoning has demonstrated its safety in man. Long-term feeding
    studies in rats and the one-year study in dogs gave no evidence of
    interference with mineral metabolism in either species. Adverse
    effects on mineral metabolism and nephrotoxicity were only seen after
    parenteral administration of high doses.


    Level causing no toxicological effect

         Rat. 50 000 ppm in the diet, equivalent to 250 mg/kg

    Estimate of acceptable daily intakes for man

                                      mg/kg bodyweight1

       Unconditional acceptance              0-1.25
       Conditional acceptance                1.25-2.5


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    See Also:
       Toxicological Abbreviations