Toxicological evaluation of some food
    additives including anticaking agents,
    antimicrobials, antioxidants, emulsifiers
    and thickening agents


    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


    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.



         These compounds have been evaluated for acceptable daily intake
    by the Joint FAO/WHO Expert Committee (see Annex 1, Refs No. 6 and
    No. 9) in 1961 and 1964.

         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.



         Nitrates are readily absorbed and their excretion is similar to
    that of halogen ions. Practically the whole quantity administered
    orally is excreted unchanged in the urine but a small amount may be
    reduced to nitrite. Normal urine contains 0.1-0.4% nitrate, the excess
    over intake from food probably arising as end-product of metabolism
    (Sollmann, 1957).

         In certain circumstances reduction of nitrate to nitrite can take
    place in the digestive tract by the activity of the intestinal flora.
    If appreciable reduction occurs before the normal rapid elimination of
    the nitrate, poisoning can result. This appears to have occurred in
    cattle (Bradley et al., 1940), and in babies less than six months old,
    especially in dyspeptic infants (Kübler, 1958).

         In experiments with rabbits about one-half of the ingested amount
    of nitrate was excreted in the urine, and only 0.5% was recovered as
    nitrite in the urine (Kübler, 1958).

         Several monovalent anions, including nitrate, when injected into
    animals interfere with the uptake of iodine by the thyroid (Wyngaarden
    & Wright, 1952). Dietary levels of 0.5, 1.0 and 2.5% also reduce the
    rate of iodine uptake by the thyroid. This is significant for animal
    nutrition (Bloomfield et al., 1961). High nitrate content of the diet
    is also responsible for vitamin A deficiency in livestock and for low
    liver stores in other species. Rats given a vitamin A deficient diet
    for two to three weeks to deplete liver stores and then given for six
    days 3% sodium nitrate in their diet as well as vitamin A or carotene
    orally or s.c. on the third and fourth day, had livers assayed on the
    sixth day for vitamin A levels. Animals receiving vitamin A showed no
    reduction but those given carotene had low liver stores. This effect
    was considered due to the toxic action of nitrate on the thyroid since

    conversion of carotene to vitamin A in the body depends on thyroid
    activity (Emerick & Olson, 1962). Calves receiving 54 ppm (0.0054%)
    nitrate in their drinking-water alone or with E. coli or with a
    thyroid depressant showed increased methaemoglobin and interference
    with vitamin A formation without intoxication (McIlwain & Schipper,


    Special studies on reproduction


         Several groups were given drinking-water with 300 (0.03%) to
    3000 ppm (0.3%) nitrate for 100-240 days. Male fertility was
    unimpaired as all groups conceived. Reproductive performance was poor
    at 3000 ppm (0.3%). Food and water consumption and weight gain were
    normal at all levels. No significant gross and microscopic lesions
    were seen in the reproductive organs. No significant alteration was
    seen in serum nitrite, blood urea or serum potassium (Sleight &
    Atallah, 1968).


         Nitrate given in the diet to two-months pregnant cows until they
    calved or aborted at levels inducing 40-50% methaemoglobinaemia ended
    in the majority in normal pregnancies. Two abortions occurred but
    probably not related to nitrate dosing. No gross pathology was seen
    (Winter & Hokanson, 1964).

    Acute toxicity

                   Route     Minimum lethal dose   LD50
    Animal                      (mg/kg bw)         (mg/kg bw)  Reference

    Rat - male     oral      190-2 000             -           Spector,

    Rat - female   oral      460-1 200             -           Spector,

    Rat            oral      -                     3 236       USFDA

    Short-term studies


         Two dogs were fed 2% of sodium nitrate in their diets for 105
    days and for 125 days without any adverse effects (Lehman, 1958).


         Most data have been obtained from livestock fed various forage
    crops with a high nitrate content. Poisoning depends upon the
    conversion of the nitrate to nitrite by the intestinal flora. The
    lowest level that may result in fatal poisoning in cattle has been
    reported to be 1.5% of potassium nitrate in the forage (Bradley et
    al., 1940).

    Long-term studies


         Sodium nitrate was fed to four groups of 20 rats each at dosages
    of 0.1%, 1%, 5% and 10% of the diet for two years. Slight growth
    depression occurred at the 5% level, and additional morphological
    changes due to inanition occurred at the 10% level (Rosenfield &
    Huston, 1950).


         Poisoning in man may result from a total oral daily dose in
    excess of 4 g or from a single dose of more than 1 g. 8 g may be fatal
    and 13-15 g are generally fatal (Sollmann, 1957).

         Numerous cases have been reported of poisoning in small children
    and infants from the use of well water containing nitrates. Among
    these, there were 26 cases in which the nitrate nitrogen content
    of the well water was 21-50 ppm (0.0021-0.005%) (93-221 ppm
    (0.0093-0.0221%) as NO3); 54 cases in which it was 51-100 ppm
    (0.0051-0.01%) (221-443 ppm (0.0221-0.0443%) as NO3, and 52 cases in
    which it was over 100 ppm (0.01%) (443 ppm (0.0443%) as NO3)
    (Rosenfield & Huston, 1950).

         On the other hand 30-60 g/day of sodium nitrate have been taken
    for two months as acidifying diuretic without marked disturbance
    (Sollmann, 1957). A 13-year-old boy took 0.12 g/kg daily for a year
    without injury (Harper, 1949).

         In one instance, a level as low as 50 ppm (0.005%) (as NO3) in
    tap water produced 72% methaemoglobinaemia in a dyspeptic child (Thal
    et al., 1961).

         Healthy babies, however, have tolerated quantities up to
    21 mg/kg bw (as NO3) for one week without any disturbance (Kübler,

         The safe upper limit for nitrate in the drinking-water of babies
    is probably 10-20 ppm (0.001-0.002%). Hypersensitivity to sodium
    nitrate, taking the form of recurrent arthritic attacks has been
    reported in man (Epstein, 1969).


         In the toxicological evaluation of nitrates, it is important to
    take into account the amount of nitrate already present in the food as
    well as in potable water (WHO, 1971).

         Babies less than six months are especially sensitive to nitrate.
    There are no data on which to arrive at an ADI for them. Nitrate
    should on no account be added to baby foods. Water with high nitrate
    content is unsuitable for the preparation of baby foods (WHO, 1971).


    Level causing no toxicological effect

         From consideration of the long-term study in rats, the level
    of sodium nitrate causing no demonstrable effect over a period
    approximating to the life span is assessed at 1% of the diet, or
    500 mg/kg bw daily. In the short-term study with dogs fed 2% sodium
    nitrate in the diet for 105 days, the level producing no demonstrable
    effect likewise corresponds to 500 mg/kg bw per day.

    Estimate of acceptable daily intake for man

         0-5 mg/kg bw.*


    Bloomfield, R. A. et al. (1961) Bibra Bull., 1, 32

    Bradley, W. B., Eppson, H. F. & Beath, O. A. (1940) Wyom. Univ. agr.
         exp. Stat. Bull., 241, 20

    Emerick, R. J. & Olson, O. E. (1962) J. Nutr., 79, 171

    Epstein, S. (1969) Ann. Allergy, 27, 343

    Harper, E. (1949) Virginia Med. Monthly, 76, 32

    Kübler, W. (1958) Z. Kinderheilk., 81, 405

    Lehman, A. J. (1958) Quart. Bull. Ass. Food Drug Off., 22, 136

    McIlwain, P. K. & Schipper, I. A. (1963) J. Amer. Vet. Med. Ass., 142,


    *    Calculated as sodium nitrate.

    Rosenfield, A. B. & Huston, R. (1950) Minn. Med., 33, 787

    Sleight, S. D. & Atallah, O. A. (1968) Toxic. appl. Pharmac., 12, 170

    Sollmann, T. (1957) A manual of pharmacology, Saunders, Philadelphia &

    Spector, W. S. ed. (1956) Handbook of toxicology, Saunders,
         Philadelphia & London, vol. 1

    Thal, W.  Lachhein, L. & Martinek, M. (1961) Arch. Toxikol., 19, 25

    United States Food and Drug Administration (Unpublished data)

    World Health Organization (1971) International standards for drinking
         water, 3rd ed.

    Winter, A. J. & Kokanson, J. F. (1964) Am. J. Vet. Res., 35, 353

    Wyngaarden & Wright (1952) Endocrinol., 50, 537

    See Also:
       Toxicological Abbreviations