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.



         Hexamethylenetetramine was evaluated for acceptable daily intake
    by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1,
    Refs No. 6, No. 9 and No. 27) in 1961, 1964 and 1971. 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.



         Under acid conditions, or in the presence of proteins,
    hexamethylenetetramine (HMT) decomposes gradually yielding ammonia
    and formaldehyde (Hutschenreuter, 1956).

         There is a theoretical possibility that bis-chlormethyl ethers
    may be formed in the stomach from the reaction of formaldehyde with
    chloride ions. However, whilst this occurs readily in the gaseous
    phase it is much less likely in liquid phases (Conning, 1973).

         Because of these chemical and biochemical properties it is
    pertinent to consider biochemical information on formaldehyde and its
    metabolite formic acid in relation to the toxicological evaluation of

         Formaldehyde and formic acid occur in fresh unpreserved codfish
    muscle (Amano & Yamada, 1964), also in honey, roasted foods and some
    fruits (Malorny, 1969a).

         Formaldehyde and formic acid are excreted in the urine of dogs
    and cats fed a meal of fish not treated with preservatives, the source
    of the substances being trimethylamine oxide occurring naturally in
    fish muscle (Malorny & Rietbrock, 1962; Malorny et al., 1963;
    Schassan, 1963). The concentration of free formaldehyde in the urine
    of these dogs and cats given unpreserved fish was four to five times
    higher than that found in human subjects who had consumed fish
    preserved with hexamethylenetetramine. Humans fed almost exclusively
    on unpreserved fish did not show an increase in the excretion of
    formaldehyde or formic acid (Malorny & Rietbrock, 1962). Formic acid
    present in the diet is mostly metabolized by man, only 25 mg is
    excreted daily in the urine (Malorny, 1969b).

         Hexamethylenetetramine liberated free formaldehyde in the stomach
    (Malorny & Rietbrock, 1963).

         I.v. infusion in dogs of formaldehyde, 35 mg/kg as a 0.6%
    solution during eight to 10 minutes, was carried out. Two minutes
    after completion of the infusion there was no increase in formaldehyde
    but a high increase in the formic acid level in the blood. The formic
    acid level decreased by 50% in one hour, by 75% after two hours, and
    was back to normal after four hours. In vitro human blood oxidizes
    30% formaldehyde (0.7 mg to 4 ml blood) to formic acid within four
    hours. Addition of methylene blue (0.05% to 0.2%) results in a
    complete oxidation of the formaldehyde (Malorny et al., 1964).

         Similar maximal plasma concentrations of formic acid were found
    after i.v. injection of equimolar solutions of formaldehyde, formic
    acid or sodium formate, and the elimination constants and biological
    half-lives of formic acid in these different cases were also similar
    (Malorny et al., 1965). In another study, it was found that
    elimination of formic acid from the body is much more rapid in rats
    than in dogs, the biological half-lives being about 12 min and 77 min
    respectively, while those of the guinea-pig are 12 min, rabbit 32 min
    and for the cat the value is 67 min. The rate of oxidation of
    formaldehyde to formic acid is comparable in all these species, with a
    half-life of only 1 min (Rietbrock, 1965).

         The kinetics of the absorption of formaldehyde by erythrocytes
    and its conversion to formic acid were studied in rabbits, guinea-
    pigs, rats and cats. The elimination of formic acid was proportional
    to the concentration present but formaldehyde had the same biological
    half-life of 1 min irrespective of species. Using three different i.v.
    infusion rates (8, 2 or 0.5 ml/min) for formaldehyde showed that only
    at 0.5 ml/min there was no free formaldehyde present in the blood but
    only formic acid. Formic acid was eliminated from erythrocytes,
    plasma, liver, kidney, testes, muscle and brain in an exponential
    manner. The half-life varied with species but was always shortest in
    the liver. No relation to catalase activity of the blood was
    established. Pre-treatment of the cat with folic acid reduces the
    half-life for formic acid. Treatment with methotrexate, a folic acid
    inhibitor, prolongs the half-life in the dog from 61 to 480 min
    (Malorny, 1966a).

         Formaldehyde, administered orally to dogs, was rapidly absorbed
    and converted to formic acid. No formaldehyde was detected in the
    plasma and only traces occurred transiently in the erythrocytes. In
    cats the production of formic acid and influx of lactic acid into the
    blood caused a temporary acidosis. When formaldehyde was added to
    human blood in vitro it was rapidly absorbed on to the erythrocytes
    and then oxidized to formate. Both NAD and NADP-independent
    formaldehyde dehydrogenase and catalase appeared to be involved in
    this oxidation, so that both erythrocytes and the liver played an
    important role in the rapid detoxication of orally and parenterally-
    administered formaldehyde (Malorny et al., 1965).

         The elimination of formate is folic acid dependent, since in the
    cat daily injections of folic acid for several days before giving
    formate have been shown to reduce the biological half-life of formate
    considerably, from 67 min without folic acid pre-treatment to 46 min
    after four days' treatment and 17 min after 10 days' treatment
    (Rietbrock, 1965). Interference with liver function prolongs the
    biological half-life of formic acid in rabbits from 35 to 130 min
    (Malorny, 1969a). In vitro experiments with liver homogenate showed
    that after 30 min 31.6%, 3.9% and 8.0% of formaldehyde was found in
    the case of rat, guinea-pig and rat liver respectively (Neugebauer,

         Experiments with 14C-labelled formaldehyde given by stomach tube
    to rats and mice showed that 5 min after application the radioactivity
    was distributed over the total body. After 12 hours, approximately 40%
    had been expired as 14CO2, 10% had been excreted in the urine and 1%
    in the faeces. The homogenized whole animals contained 20% of the
    radioactivity after 24 hours and 10% after 96 hours (Buss et al.,

         When female rats were given 70 mg/kg of 14C-labelled
    formaldehyde i.p., 82% was detected as 14CO2 and the urine
    contained 13 to 14% of the isotope in the form of methionine, serine
    and a formaldehyde-cysteine adduct (Neely, 1964).

         The yellow discolouration observed in rats treated with oral or
    i.m. HMT was shown to be due to a reaction between formaldehyde in the
    urine and kynurenine in the rat hair (Kewitz & Welsch, 1966).


    Special studies on mutagenicity

         Both HMT (Auerbach, 1951) and formaldehyde (Rapoport, 1946) have
    been shown to act as mutagens in Drosophila. Stumm-Tegethoff (1964)
    has demonstrated that formic acid, present as an impurity in
    formaldehyde, is the causative agent in producing the mutagenic effect
    in Drosophila melanogaster. Nafei & Auerbach (1964) have shown that
    mutations only occur in the larval spermatocytes and that the
    conditions necessary for the change only exist for a short time.

    Special studies on reproduction


         In a five-generation study lasting three-and-a-half years, a
    total of 80, 80 and 245 rats were fed 0, 5 and 50 mg/kg daily of HMT
    in the drinking-water. Animals, including pregnant dams, were selected
    from each group at half-yearly intervals, starting at one-and-a-half

    years, for pathological study. No changes attributable to HMT were
    found in test animals or foetuses and placentas at either level.
    Tumours were observed on three of 48 animals at the high dose level
    (Malorny, 1966b).

         Groups of 10 male and 10 female rats were fed 0, 400, 800 and
    1600 mg/kg of hexamethylenetetramine in a normal basic diet for two
    years. The 10 pairs were mated at the age of 20, 28 and 35 weeks. No
    effect was found at all levels on growth, two-year survival,
    reproduction and viability of offspring. Post-sacrifice examination of
    survivors (organs examined and type of examination not stated)
    disclosed no specific pathological changes (Berglund, 1966).

         Twelve female and six male Wistar rats were given 1% HMT in the
    drinking-water starting two weeks before mating. The females were kept
    under treatment during pregnancy and lactation. A similar untreated
    group of 12 females and six males served as control. Twelve treated
    females and 11 controls became pregnant and gave birth to 124 and 118
    babies respectively; no malformations were noted. From these animals,
    24 for each sex were continued on the 1% HMT up to the twentieth week
    of age or were kept untreated. The body weight of treated animals was
    significantly lower than that of the controls, only up to the ninth
    week of age for the males and up to the thirteenth week for the
    females. At the end of the treatment both groups were sacrificed; the
    weight of organs was identical in the treated and control animals;
    there was no gross or histological pathology. In a second experiment,
    rats were given 1% HMT in the drinking-water for three successive
    generations, up to the age of 40 weeks in the F1 and F2 groups and
    of 20 weeks for F3. The three groups were composed of 13 male and
    seven female, 15 male and 11 female, 12 male and 12 female,
    respectively. In addition, a group of 16 male and 16 female
    descendants of 2% HMT-treated parents were given 2% HMT for 59 weeks.
    A group of 48 males and 48 females served as untreated controls. All
    groups were kept under observation for over two years. No evidence of
    carcinogenicity was found in any of the HMT-treated groups (Della
    Porta et al., 1970).

         A five-generation study using eight male and 24 female rats as
    P generation is in progress using eight controls. Test animals
    received 0.2% calcium formate in their drinking-water. No
    abnormalities were detected regarding growth and fertility. No
    disturbances of organ function or retinal or fundal abnormalities were
    noted. Gross and histopathology of 250 rats from three generations
    revealed no abnormal findings related to the administration of calcium
    formate. Tumour incidence was no different from controls. Pregnancy
    and foetuses as well as numbers of pups per litter were similar to
    controls. No malformations or placental changes were detected. Similar
    groups were given 0.4% calcium formate in their drinking-water for two
    generations and will be continued. No abnormalities, including
    histopathology, related to the test substances have been seen.


         A group of two male and four female mongrel dogs was fed from
    1250 to 1875 mg/kg of HMT and a group of four males and four females
    was fed from 125 to 375 mg/kg of formaldehyde for 32 months. The
    control group consisted of two males and one female. Groups formed
    from litters of these animals were also fed test diets; three males
    and two females were fed 1250 mg//kg of HMT, three males and two
    females were fed 375 mg/kg of formaldehyde and two animals of each sex
    served as a control group for 22 months. At the end of the test
    period, the test animals were placed on a normal diet and the controls
    on 1250 mg/kg of HMT for one year. No effect of formaldehyde or HMT
    was found on food consumption, growth, reproduction or litter numbers
    and weights or in monthly observations on blood chemistry and cell
    total and differential counts, and periodic urine examinations.

         However, of 30 litters in the HMT group, 66.7% were noted as
    unusual in that there were stillborn and eaten animals as well as five
    cases of defective animals born; in the formaldehyde group, 60% of 34
    litters were noted as unusual, with 10 cases of defective animals. Of
    16 litters in the control group, 7.7% were noted as unusual, with no
    malformations (Kewitz, 1966).

         According to a preliminary report, groups of eight pregnant
    female beagle dogs received from the fourth to fifty-sixth day after
    mating either 0, 0.0125% and 0.0375% of formalin or 0.06% and 0.125%
    of HMT in their food. Many litters are still in the pre-weaned stage
    at present. So far no adverse effects have been reported with regard
    to rate of pregnancy and duration, behaviour and weight of the mothers
    or litter size, pup weight, incidence of congenital defects or
    survival to weaning of the pups (Tierfarm, 1969).

    Special studies on teratogenicity


         Two groups of 39 male and 44 female CTM mice received five s.c.
    injections on five alternate days of 5 g/kg HMT, a 30% aqueous
    solution, beginning on day 10 of age. They were observed for 100
    weeks. No pathological findings related to treatment were noted nor
    was there any difference from controls regarding tumour incidence
    (Della Porta et al., 1968).


         Twenty rats were given s.c. doses of 1 ml of a 0.4% aqueous
    solution of formaldehyde, in the dorsal region, weekly for 15 months.
    Half the animals died during the experiment without developing
    tumours; of the remaining 10, four showed sarcomas three to five
    months after cessation of treatment. Two of these tumours developed at

    the site of injection and were diagnosed as spindle-cell sarcomas. One
    tumour developed in the liver (male, 21 months) with metastases to the
    colon; the other was in the colon (female, 21 months) (Watanabe et
    al., 1953; Watanabe et al., 1954).

         Twenty rats were injected s.c. on the left dorsal side once or
    twice weekly with 1-2 ml solution of hexamethylene-tetramine, using
    at first a concentration of 9.23% but, after the middle of the
    experiment, a concentration of 35-40%. In addition, shortly before
    each injection of hexamethylene-tetramine, an injection of 0.5 ml 0.1%
    formic acid was given on the right dorsum. Of 14 survivors, eight
    showed tumours at the sites of injection of hexamethylene-tetramine.
    At the sites of formic acid injection small ulcers sometimes formed
    but no s.c. thickening or nodules. Of the eight tumours seven were
    sarcomas and one syringadenoma (Watanabe & Sugimoto, 1955).

         Groups of 15 male and 15 female albino rats were injected s.c.
    with 1 ml of 40% HMT solution and 1 ml of 0.1% formaldehyde solution
    weekly for one-and-a-half years. Control groups of seven males and
    seven females and eight males and eight females were similarly
    injected with doses of sodium chloride or sucrose (equiosmotic with
    40% hexamethylenetetramine) for one-and-a-half years, by which time
    the last animal had died. In the HMT group, one injection-site
    spindle-cell sarcoma, one distal spindle-cell sarcoma, one alveolar
    mammary carcinoma and one fibrosarcoma, in addition to two benign
    tumours were seen. In the formaldehyde group, two malignant tumours
    and three benign fibro-adenomas were seen. In the control group, one
    blastoma in a sodium chloride-injected animal) was found (Kewitz,

         Two groups of 20 male and 20 female rats received five s.c.
    injections of 5 g/kg HMT as 30% aqueous solution on alternate days
    starting at day 10 of age and were observed for 104 weeks. No
    treatment-related abnormalities were seen regarding growth, mortality,
    gross or histopathology or tumour incidence. The test animals had a
    lower tumour incidence than the controls (Della Porta et al., 1968).


         Groups of from nine to 11 mated beagle bitches were fed 0, 3.1 or
    9.4 mg formaldehyde (FA) per kg bw, or 15 or 31 mg hexamethylene-
    tetramine (HMT) kg bw from the fourth to fifty-sixth day after mating.
    These dose levels were based on an average body weight of 12 kg.
    Implantation, maintenance and duration of pregnancy and litter size
    were unaffected by any treatment. At 31 mg HMT kg per day, incidence
    of stillbirths was slightly increased, and post-natal survival to
    weaning was decreased. Birth weight in all treated groups was slightly
    reduced as was post-natal growth. These effects were most noticeable

    at 9.4 mg FA/kg and 31 mg HMT/kg dose levels. No gross abnormalities
    were observed in any offspring either at birth or weaning. Stillborn
    pups were examined for skeletal and tissue malformations but none were
    observed (Hurni & Ohder, 1973).

    Special studies on chick embryo

         Two hundred fertilized chicken eggs were injected with 5 mg HMT
    after 96 hours incubation. The distribution of HMT and formaldehyde
    was determined between the sixth and nineteenth day of incubation in
    the various components of the egg. HMT is continuously metabolized. No
    toxic effect was noted in the chick embryos examined (Pilz, 1967).

         Formaldehyde was injected in another experiment into fertilized
    eggs. There was rapid oxidation to formic acid. After 48 hours some
    90% had been converted to formic acid. The remaining formaldehyde was
    probably bound to the albumin and the shell proteins. Injected sodium
    formate is metabolized at a much slower rate but had disappeared by
    the twelfth day of incubation. Practically no formaldehyde metabolism
    occurs in the extra-embryonal components but embryonic liver and
    erythrocytes rapidly oxidize formaldehyde to formic acid (Lange,

         Sodium formate did not show any toxic or teratogenic effect when
    submitted to the chick embryo test (Malorny, 1969a).

    Acute toxicity

                                  LD50             Reference
    Animal    Route               (mg/kg bw)

    Mouse     Oral
              (formic acid)       1 100            Malorny, 1969a
              (sod. formate)      11 200              "
              (pot. formate)      5 500               "
              (amm. formate)      2 250               "
              (calc. formate)     1 920               "


              (formic acid)       145                 "
              (sod. formate)      807                 "
              (pot. formate)      95                  "
              (amm. formate)      410                 "
              (calc. formate)     154                 "

    Rat       i.v. (HMT)          9 200            Malorny et al., 1965

         One group of 14 six-week-old male and female rats were given a
    single i.v. injection of 10 g HMT/kg bw as an 80% aqueous solution.
    All animals survived without evidence of toxic effect. Two groups of
    five adult rats were given 10 or 20 g HMT/kg bw as an 80% aqueous
    solution by oral intubation. All animals survived (Della Porta, 1968).

    Short-term studies


         Groups of 13 mice were treated daily by cutaneous application 10%
    HMT in chloroform, 1.5% aqueous formaldehyde, and chloroform alone,
    for 300 days. No malignant tumours were found in any group (Kewitz,

         One group of five male and five female rats was given by gavage
    400 mg HMT daily for 90 days. A second group of five male and five
    female rats was given daily intramuscular injections of 200 mg HMT for
    90 days. A third group of 15 male and 15 female rats was given
    repeated oral doses of 400 mg HMT by gavage over 333 days. No adverse
    effects were noted in any group except for a citrus-yellowish
    discolouration of the fur (Brendel, 1964).


         One male and three female cats were fed approximately
    15 000 ppm (1.05%) of formaldehyde (375 mg/kg/day) and two males and
    three females were fed approximately 50 000 ppm (50%) of HMT
    (1250 mg/kg/ day) for two years. The control group consisted of three
    males and three females. One female in the formaldehyde group died in
    the seventh month of pleuritis and a female of the HMT group died in
    the twenty-third month of a pyogenic infection of the nasal cavity and
    paranasal sinuses. No effect of formaldehyde or HMT was found on food
    consumption, weight gain or appearance. Preliminary microscopic
    examination of tissues from test and control animals show no changes
    attributable to formaldehyde or HMT (Kewitz, 1966).

    Long-term studies


         Sixteen groups of 30, 50 or 100 males and an equal number of
    females of CTM, SWR or C3Hf strain mice received in their drinking-
    water either 0, 0.5, 1 or 5% hexamethylenetetramine over 60 weeks. The
    group receiving 5% was treated for 30 weeks only. After the end of
    treatment animals were observed for the remainder of their lifetimes.
    The coats of treated mice showed no discolouration. The group on 5%
    HMT showed slightly reduced growth rate and survival and the SWR group
    on 1% showed also slight growth retardation. Gross and histopathology

    did not show any pathological lesions related to treatment. As regards
    tumour incidence there was no significant difference between treated
    and control groups (Della Porta et al., 1968).

         Groups of 30 male and 30 female NMRI/Ban albino mice were fed 0
    and 1% of HMT and 0.15% formaldehyde for two years. Benign and
    malignant tumours were found in a total of 43 animals: 20 in the HMT
    group, 12 in the formaldehyde group and 11 in the control group.
    Except for one control male and two males receiving HMT all tumours
    occurred in females. Twenty-nine of 36 malignant tumours were s.c.
    carinomas and adenocarcinomas. The author concluded from the data that
    the possibility of an increased tumour incidence effect by HMT could
    not be ruled out. A further study was instituted using groups of 50
    female mice at levels of 0, 0.1, 0.5 and 1% hexamethylenetetramine,
    which, after 31 weeks, showed no difference in tumour incidence
    between the groups (Kewitz, 1966).


         Four groups of 48 male and 48 female rats received for 104 weeks
    either 0 or 1% HMT in their drinking-water while another two groups of
    12 male and 12 female rats received 5% in their drinking-water for
    only two weeks. The coat of treated rats showed a yellowish
    discolouration due to a reaction between formaldehyde present in the
    urine and kynurenine in the rat hair. 50% of the rats given the high
    dose level died within the two weeks of administration, the remainder
    survived for 104 weeks. Growth, mortality experience, gross and
    histopathology of the treated animals showed no specific changes due
    to administration of HMT. Tumour incidence was essentially similar in
    controls and treated animals at 1% level and lower than in controls at
    the 5% level (Della Porta et al., 1968).

         Two groups of 16 male and 16 female rats were given either 0 or
    0.16% HMT in their diet and were observed over 28-30 months. General
    health and behaviour as tested by activity in the revolving drum at 1,
    3, 7 and 14 months showed no significant differences between controls
    and test groups. Body weights of male rats were slightly lower in the
    treated animals. Mortality experience was similar for all groups. The
    addition of HMT had no effect on palatability of the diet. Organ
    weights showed no gross differences and tumour incidence was not
    different between controls and test animals, although not all rats
    were examined by autopsy. Separate mating of the test and control
    groups revealed no differences in fertility as measured by numbers of
    pups produced. The young showed no difference in activity as measured
    by the revolving drum, nor did they show any abnormalities or
    differences in body weight. Organ weights and gross and histopathology
    were unremarkable. Some test rats showed yellowish staining of hair
    (Natvig et al., 1971).


         Twelve human volunteers received orally 1.48-2.96 g sodium
    formate. They excreted on average 13 mg formic acid per 24 hours from
    control diet and only 23% per 24 hours of the additional formic acid.
    Most of the additional load was excreted within six hours and all had
    been eliminated after 12 hours. No cumulation was observed. Excretion
    of formate is accompanied by alkaline urinary pH and mild diuresis.
    The biological half-life of orally administered sodium formate was
    found to be 46 min as determined by plasma levels in three volunteers.
    Four to 7% of the administered dose was excreted in 24 hours. No
    metabolic acidosis was found in man because of rapid metabolism of the
    formate anion but the excess of bicarbonate is excreted as alkaline
    urine. Formic acid is absorbed rapidly from the stomach in
    undissociated form (Malorny, 1969b).


         As the toxicological effects of hexamethylenetetramine appear to
    be due to the liberation of formaldehyde and its oxidation product,
    formic acid, much work has been done on formaldehyde and formates as
    well as on hexamethylenetetramine. The metabolic studies point to
    rapid conversion of formaldehyde to formate and then at a slower rate
    to water and carbon dioxide particularly by the liver and the
    erythrocytes. In man, very little formate is excreted in the urine
    after its oral ingestion. Only one of many long-term studies in
    mice conflicts with other studies in this species as well as in
    the rat. These long-term studies point to a dietary level of 1%
    hexamethylenetetramine as causing no effect in rodents. The
    teratogenicity study in dogs revealed a no effect level of 15 mg/kg.
    Other reproduction studies in rats using dietary levels from 0.1-1%
    hexamethylenetetramine revealed no adverse effects. Although there is
    production of local sarcomata in rats at the site of repeated
    injections, the probability of carcinogenic potential in food additive
    use appears to be excluded as a result of the findings in adequate
    studies using oral administration. In addition, the experiments on
    pregnant and lactating rats indicate the absence of carcinogenic
    effects in the offspring. However, in vitro formation of nitrosamine
    has been reported as a result of the interaction of nitrite with
    hexamethylenetetramine at pH 1-3.


    Level causing no toxicological effect

         Dog: 15 mg/kg bw.

    Estimate of acceptable daily intake for man

         0-0.15 mg/kg bw.


    Amano, K. & Yamada, K. (1964) FAO Symposium on the Significance of
         Fundamental Research in the Utilisation of Fish, Paper WP/II/9

    Auerbach, C. (1951) Cold Spr. Harb. Symp. quant. Biol., 16, 199

    Berglund, F. (1966) Unpublished report

    Brendel, R. (1964) Arzneimittel-Forsch., 14, 51

    Buss, J. et al. (1964) Arch. exp. Path. Pharmak., 247, 380

    Conning, D. (1973) Personal communication

    Della Porta, G., Cabral, J. R. & Parmiani, G. (1970) Tumori, 56, 325

    Della Porta, G., Colnaghi, M. I. & Parmiani, G. (1968) Fd. Cosmet.
         Toxicol., 6, 707

    Hurni, H. & Ohder, H. (1973) Fd. Cosmet. Toxicol., 11, 459

    Hutschenreuter, H. (1956) Z. Lebensmitt.-Untersuch., 104, 161

    Kewitz, H. (1966) Unpublished report

    Kewitz, H. & Welsch, F. (1966) Arch. exp. Path. Pharmak., 254, 101

    Lange, G. (1968) Thesis submitted to Hamburg University

    Malorny, G. (1966a) N.-S. Arch. exp. Path. Pharmak., 255(1), 42

    Malorny, G. (1966b) Unpublished report

    Malorny, G. (1969a) Zeitschr. Ernahrungswiss, 9, 332

    Malorny, G. (1969b) Zeitschr. Ernahrungswiss, 9, 340

    Malorny, G., Netter, K. J. & Seidel, G. (1964) Untersuchungen über die
         Hemmbarkeit enzymatischer Reaktionen durch Formaldehyd und einige
         seiner Homologen, Arch. ext. Path. Pharmak., 247, 381

    Malorny, G. & Rietbrock, N. (1962) Naturwissenschaften, 49, 520

    Malorny, G. & Rietbrock, N. (1963) Vortrag auf der X. Tagung des
         Ernährungswissenschaftlichen Beirats der deutschen
         Fischwirtschaft, Bremen

    Malorny, G., Rietbrock, N. & Schassan, H. H. (1963) Arch. exp. Path.
         Pharmak., 246, 62

    Malorny, G., Rietbrock, N. & Schneider, M. (1965) Arch. exp. Path.
         Pharmak., 250, 419

    Nafei, H. & Auerbach, G. (1964) Z. Vererbunsl., 95, 351

    Natvig, H., Andersen, J. & Wulff Rasmussen, E. (1971) Unpublished
         report submitted to WHO

    Neely, W. B. (1964) Biochem. Pharmacol., 13, 1137

    Neugebauer, G. (1967) Thesis submitted to Hamburg University

    Pilz, R. (1967) Thesis submitted

    Rapoport, I. A. (1946) C. R. Acad. Sci. USSR, 54, 65

    Rietbrock, N. (1965) Arch. exp. Path. Pharmak., 251, 189

    Schassen, H. H. (1963) Inaugural dissertation, Hamburg University

    Stumm-Tegethoff, Bertha (1964) Naturwissenschaften, 51, 646

    Tierfarm, A. G. (1969) Unpublished report

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    Watanabe, F., Matunaga. T. & Yamabe, T. (1953) Trans. Jap. path. Soc.,
         17, 115

    Watanabe, F. & Sugimoto, S. (1955) Gann, 46, 365

    See Also:
       Toxicological Abbreviations
       Hexamethylenetetramine (ICSC)
       Hexamethylenetetramine (FAO Nutrition Meetings Report Series 38a)
       Hexamethylenetetramine (WHO Food Additives Series 1)