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    METIRAM

    First draft prepared by
    M. Caris
    Health Canada, Ottawa, Canada

    EXPLANATION

         Metiram is a non-systemic EBDC fungicide that contains zineb
    and poly (ethylenethiuram disulfide).  It was considered for the
    first time at the present Joint Meeting.

    EVALUATION FOR ACCEPTABLE DAILY INTAKE

    BIOLOGICAL DATA

    Biochemical aspects

    Absorption, distribution and excretion

    Rats

         Male and female Sprague-Dawley rats were administered a single
    oral dose of 14C-labelled metiram at a dose of 5 or 50 mg/kg bw or
    were pretreated with unlabelled test material, 5 mg/kg bw/day for 14
    days followed by a single oral dose of 14C metiram of 5 mg/kg bw. 
    Over 98% of the administered 14C metiram dose was excreted within 7
    days, with the majority of the dose excreted within the first 48
    hours post-dosing.  Mean recovered radioactivity in the faeces
    accounted for 53.9-78.7% of the dose with a smaller percentage
    excreted in the urine, 21.3-46.6%.  Slightly lower proportions of
    radioactivity were excreted in the urine at the high dose when
    compared to the low dose, suggesting that absorption of metiram was
    less at higher doses.  Mean radioactivity excreted in the expired
    air represented 0.4-1.1% of the dose.  The patterns of excretion of
    radioactivity were similar upon single or repeated exposure to
    metiram.  Comparatively, absorption was greater and excretion more
    rapid in rats treated with 0.5 mg of 14C-ETU/kg bw, where 96% of
    the dose was excreted in the urine and only 4.2% in the faeces
    within 3 days post-dosing.  Biliary excretion of 14C-labelled
    metiram accounted for 14.3% and 7.1% of a single 5 mg/kg bw dose in
    males and females, and 4.3% and 3.7% of a single 50 mg/kg bw dose in
    either sex, respectively.  Peak mean plasma concentrations of
    radioactivity occurred after 4 hours in the 5 mg/kg bw dose and
    after 6 hours following administration of a single oral dose of 50
    mg/kg bw, respectively.  After 7 daily oral doses of 14C metiram at
    5 mg/kg bw/day, the highest concentrations of radioactivity were
    found in the thyroid and kidneys with concentrations being slightly
    higher in females than in males.  Whole-body autoradiography of
    these rats confirmed the results of the quantitative tissue
    distributions.  The comparisons between rats sacrificed at 24 hours
    after a single dose or after multiple doses showed evidence of
    accumulation of radioactivity in the body with multiple dosing
    (Hawkins  et al., 1985). 

         Absorption was studied in male CD rats treated dermally on
    their shaved backs with 14C metiram at dose levels of 0.24 or 240
    mg/kg bw equal to 0.004 or 4 mg/cm2, respectively.  Groups of 4
    animals were killed after 1, 2, 4 and 8 hours following application,
    and two groups of 4 animals had the treated skin sites washed after
    8 hours with subsequent sacrifice of the animals, 24 or 96 hours
    post-treatment.  Total radioactivity detected from urinary and

    faecal excretion and tissue residue levels accounted for 0.9% and
    0.2% of the radioactivity at the low and high dose, respectively. 
    The majority of the administered dose was recovered from the treated
    skin of the rats.  Concentrations of radioactivity in plasma and
    tissues were generally below or at the limits of detection (Hawkins
     et al., 1984).

    Biotransformation

    Rats

         Thin layer chromatography (TLC) of the urine of rats treated
    with 14C-metiram as single oral doses of 5 or 50 mg/kg bw, and a
    single oral dose of 100 mg/kg bw of a 15N-metiram and 14C-metiram
    suspension (1:1 ratio), revealed eight principal radioactive
    components.  Incubation with -glucuronidase/sulphatase did not
    significantly alter the proportion of radioactive components.  Polar
    components accounted for the majority of the radioactivity (34-58%)
    and were identified as ethylenediamine, N-acetyl-ethylenediamine and
    possibly ethanolamine and oxalic acid.  Another polar component was
    an acidic compound with similar chromatographic properties to
    glycine.  Major less polar components were identified as
    ethyleneurea (4-11%), ethylenethiourea (10-35%) and ethylene
    bis(isothiocyanate) sulphide (1-3%).  The proportion of radioactive
    components in the bile of rats treated with a single oral dose of
    14C metiram at 10 mg/kg bw as separated by TLC were similar to
    those obtained in the urine.  Metabolite patterns were determined
    for kidney and liver extracts from rats treated with 14C metiram at
    5 mg/kg bw for 7 days.  Radioactive components in the kidney were
    similar to those found in urine; however, of the liver extracts,
    only the -glucuronidase/sulphatase treated sample provided a
    satisfactory pattern which contained mainly polar material and only
    traces of ethyleneurea and ethylenethiourea (Hawkins  et al., 
    1985).

         The proposed metabolic pathway of metiram in animals is
    depicted in Figure 1.

    Toxicological studies

    Acute toxicity studies

         Acute toxicity studies with technical metiram have been
    performed in the rat and mouse, the results of which are summarized
    in Table 1.  WHO has classified metiram as unlikely to present acute
    hazard in normal use (WHO, 1992). Acute studies with the formulated
    trade product, Polyram combi (consisting of 80% metiram complex
    (technical active ingredient) and 20% formulating agents) were
    similarly conducted in several animal species, the results of which
    are given in Table 2.  Both technical and formulated metiram, upon 

    FIGURE 01


        Table 1.  Acute toxicity of technical metiram
                                                                                                                                    
    Species          Sex          Route (vehicle)          LD50              Test material                   Reference
    (strain)                                               (mg/kg bw)
                                                                                                                                    
    Rat              M+F          oral                     > 6810            Technical grade                 Jackh, 1981
    (SD)                          (distilled water)                          (purity unknown)

    Rat              M+F          oral                     M: 9100           Technical grade                 Leuschner, 1979a
    (SD)                          (HPMC)                   F: 8900           (purity unknown) + 2% ETU
                                                           M+F: 9000

    Rat              M+F          oral                     6500              Technical grade                 Hofmann, 1985a
    (SD)                          (tragacanth)                               (purity unknown)

    Rat              M+F          oral                     10 000            Technical grade                 Hofmann, 1975
    (SD)                          (CMC)                                      (purity unknown)

    Rat (SD)         M+F          dermal (water)           > 2000            Technical grade                 Grundler, 1979
                                                                             (77.5% purity) + 2% ETU

    Mouse (NMRI)     M+F          intraperitoneal          M: 208            Technical grade                 Leuschner, 1979b
                                  (HPMC)                   F: 215            (purity unknown) + 2% ETU
                                                           M+F: 212          

    Mouse (NMRI)     M+F          intraperitoneal          80                Technical grade                 Hofmann, 1974a
                                  (tragacanth)                               (purity unknown)

    Rat (SD)         M+F          intraperitoneal          M: 318            Technical grade                 Hofmann & Munk, 1975
                                  (CMC)                    F: 317            (77.5% purity)
                                                           M+F: 318

    Rat (SD)         M+F          inhalation 4 h           > 5.7 (mg/l)      Technical grade                 Klimisch & Zeller, 1980
                                                                             (77.5% purity) + 2% ETU

    Rat (SD)         M+F          inhalation 8 h           (well             Technical grade                 Hofmann, 1985b
                                                           tolerated)        (purity unknown) + 2.2% ETU
                                                                                                                                    

    Table 2.  Acute toxicity of Polyram combi (formulated product)
                                                                                                                                    
    Species          Sex          Route                    LD50              Test                            Reference
    (strain)                      (vehicle)                (mg/kg bw)        material
                                                                                                                                    

    Rat              M+F          oral                     > 10 000          Polyram combi                   Hofmann, 1985c
    (SD)                          (tragacanth)                               (purity unknown)

    Dog              M+F          oral                     *                 Polyram combi                   Chesterman  et al., 1973
    (beagle)                      (water)                                    (purity unknown)

    Mouse (NMRI)     M+F          intraperitoneal          approx 80         Polyram combi                   Hofmann, 1974b
                                  (tragacanth)                               (purity unknown)

    Rat              M+F          dermal                   > 2000            Polyram combi                   Grundler, 1985
    (SD)                                                                     (77.5% purity)

    Rat              M+F          inhalation,              (well             Polyram combi                   Hofmann, 1985d
    (SD)                          8 hr                     tolerated)        (77.5% purity)

    Guinea-pig                    inhalation,              >0.8 (mg/L)       Polyram combi                   Hofmann, 1985e
                                  8 hr                                       (purity unknown)

                                                                                                                                    

    *    Estimation of LD50 precluded due to high incidence of vomiting
    

    oral and dermal administration, were practically non-toxic in the
    rat with LD50 values of > 6500 mg/kg bw and > 2000 mg/kg bw,
    respectively.  Moderate acute toxicity was demonstrated upon
    intraperitoneal administration of technical material in the mouse
    (LD50 = 80-212 mg/kg bw) and rat (LD50 = 318 mg/kg bw).  Technical
    metiram when administered by the inhalation route resulted in an
    LC50 value greater than 5.7 mg/l in the rat.  Eight-hour inhalation
    of the formulated material, Polyram combi was well tolerated in both
    rats and guinea-pigs.  Intentional spiking of the technical material
    with ETU at levels of 2 to 2.2% did not markedly alter the acute
    toxicity profile. 


    Short-term toxicity studies

    Mice

         In a preliminary assessment of the toxicity of metiram (96.8%
    purity, containing 2.2% ETU), groups of 8 CFLP mice per sex were fed
    dietary concentrations of 0, 100, 300, 1000 or 3000 ppm equal to 0,
    16, 40, 120 or 399 mg/kg bw/day for males and 0, 15, 44, 142 or 433
    mg/kg bw/day for females, respectively, for a period of 4 weeks. 
    Body-weight gain of males treated with metiram at 1000 and 3000 ppm
    were significantly lower than that of the corresponding controls
    during the first week of treatment with subsequent recovery of
    weight gain in the ensuing weeks.  Although no consistent effects on
    body weight in treated females were observed on a weekly basis,
    overall weight gain of females at the high dose of 3000 ppm was
    marginally lower than that of the control animals.  Significantly
    increased liver weights were recorded in both sexes treated at
    levels of 1000 and 3000 ppm.  In the absence of routine
    histopathological examination, no microscopic correlation could be
    drawn from the increased liver weights.  There were no effects of
    treatment on survival, clinical signs, food consumption or gross
    pathological changes.  On the basis of the reported findings, a high
    dietary level of 1000 ppm was selected for the long-term study in
    mice (Hunter  et al., 1976b).

         A 3-month study was performed with groups of 10 B6C3F1
    mice/sex treated with metiram (94.8% purity, ETU <0.2%) at
    dietary levels of 0, 300, 1000, 3000 or 7500 ppm, equal to 0, 84,
    302, 853 or 2367 mg/kg bw/day in males and 0, 133, 465, 1448 or 3565
    mg/kg bw/day in females, respectively.  Treatment-related effects
    were observed with respect to serum T3 and T4 concentrations. 
    Serum T4 levels were significantly decreased in both sexes of mice
    treated with metiram at dietary levels of 1000 ppm and higher,
    whereas T3 levels were significantly increased in male mice treated
    at the highest dietary level of 7500 ppm.  Histopathological
    findings attributable to treatment were denoted in the thyroid in
    both sexes treated at dietary levels of 3000 ppm and higher as

    minimal to slight hypertrophy and vacuolation of the follicular
    epithelium.  A slight increase in the severity of fatty degeneration
    of the `X zone' in the adrenals was also observed in female mice
    treated with metiram at 3000 and 7500 ppm.  A dose-related increased
    incidence in the presence of a refractile, granular material
    presumed to be the test material or a metabolite, was noted in the
    superficial layer of the urinary bladder urothelium in all groups of
    treated mice.  Since no morphological changes were observed in the
    urothelium of the bladder to suggest disturbed epithelial function,
    the presence of this granular material was considered to be of
    doubtful toxicological consequence.  Significantly increased organ
    weights were recorded for the adrenals in females at dietary levels
    of 3000 ppm and higher and for the liver in both sexes treated at
    7500 ppm and in males at 3000 ppm.  Statistically significant
    increases in kidney and testicular weights were judged to be of no
    biological consequence.  No histopathological correlation could be
    determined for the increased liver, kidney or testicular weights. 
    Group mean body weights and corresponding weight gains were
    decreased in males treated at the highest dietary level of 7500 ppm. 
    Although significant decreases in body weights were recorded in
    females treated at dietary levels of 1000 ppm and higher, there was
    no dose-response relationship.  There were no adverse treatment-
    related effects on survival, food consumption or on blood
    haematological parameters.  The NOAEL for this study was 300 ppm,
    equal to 84 mg/kg bw/day, based on decreased serum T4 levels in
    both sexes at levels of 1000 ppm and above (Gelbke  et al., 1992a).

    Rats

         Metiram (96.8% purity containing 2.2% ETU) was administered for
    a period of 4 weeks to groups of 20 Sprague-Dawley CD rats/sex at
    dietary levels of 0, 100, 300, 1000 or 3000 ppm, equal to 0, 10, 30,
    100 or 296 mg/kg bw/day in males and 0, 11, 33, 114 or 292 mg/kg
    bw/day in females, respectively.  Following termination of treatment
    with metiram, 10 rats per sex per group were retained for subsequent
    2 and 4 week recovery periods with scheduled sacrifices of 5
    rats/sex/group on each occasion.  Clinical toxicity was manifest as
    signs of hind limb paralysis in rats treated at the highest dietary
    level of 3000 ppm, which due to severity, resulted in early
    sacrifice of 3 females for humane reasons.  Histopathological
    examination confirmed gross morphological alterations in the muscles
    of the hind limbs, characterized by atrophy of the fibres, often
    with associated proliferation of sacrolemmal nuclei, and the
    presence of groups of vacuoles within muscle fibres.  After 4 weeks
    of treatment, the microscopic changes were more marked and extensive
    in females, occurring in all females and in 2 of 9 males treated at
    3000 ppm.  After a withdrawal period of 2 weeks, a varying degree of
    atrophy of muscle fibres was still present in females previously
    treated with 3000 ppm of metiram. Although atrophy was not evident
    in animals after a 4-week recovery period, additional changes, not

    apparent earlier, were the presence of vacuoles and/or areas of fat
    cells within the skeletal fibres.  Target organ effects of treatment
    with metiram were also evident on the thyroid and kidney.  Changes
    in the thyroid were apparent as a dose-related increase in the
    incidence and severity of thyroid hyperplasia in both sexes treated
    at dietary levels of 300 ppm and higher.  Microscopic examination of
    the kidney revealed varying degrees of hydropic vacuolation of the
    proximal tubular epithelial cells in 2 females from each of the 1000
    and 3000 ppm groups in the absence of similar effects at any of the
    other dose levels or corresponding controls.  Examination of bone
    marrow smears revealed a depressed number of myeloid cells in males
    treated at the high dose after 4 weeks of treatment.  Group mean
    body-weight gains were significantly lower in males treated at 1000
    ppm and higher, and in females treated at 300 ppm and higher when
    compared to the controls.  Decreased food intake was recorded in
    both sexes treated at the highest dietary level of 3000 ppm.  There
    were no adverse effects of treatment noted upon ocular examination,
    haematology, blood chemistry, urinalysis and estrus cycle as
    assessed from vaginal smears.  The NOAEL was 100 ppm, equal to 10
    mg/kg bw/day (Hunter  et al., 1976a).

         Groups of 35 Sprague-Dawley CFY strain rats per sex were
    treated with metiram (96.8% purity containing 2.2% ETU) at dietary
    levels of 0, 50, 100, 300 or 900 ppm, equal to 0, 3, 6, 20 or
    61 mg/kg bw/day for males and 0, 4, 8, 24 or 76 mg/kg bw/day for
    females, respectively, for a period of 13 weeks followed by a 6-week
    recovery period.  The principal target organs were the thyroid and
    skeletal muscle.  Treatment-related effects on the thyroid were
    manifest as increased thyroid weights of females treated at 300 and
    900 ppm, decreased percentage uptake of 131I by the thyroid in males
    in all treated groups and in females treated at 100 ppm and higher,
    and decreased T4 levels in both sexes at 300 ppm and higher. 
    Microscopically, an increased incidence of males treated at 900 ppm
    had slight to minimal hyperplasia of the thyroid.  A minimally
    higher incidence at 13 weeks of slight thyroid hyperplasia in
    females at 900 ppm and in males at 100 and 300 ppm when compared to
    the controls was considered to be of equivocal significance.  There
    were no significant changes in the thyroid observed after the 6-week
    recovery period.  Treatment-related morphological changes of the
    skeletal muscle denoted by atrophy of the muscle fibres often
    accompanied by fat cells and associated proliferation of sacrolemmal
    nuclei, were evident in both sexes treated at dietary levels of 300
    ppm and higher.  Varying degrees of muscular atrophy were still
    prevalent after a 6-week recovery period in rats previously treated
    at 300 and 900 ppm.  Other effects of treatment were exhibited at
    the high-dose level of 900 ppm as clinical signs of hind limb
    paralysis, decreased body weights and slight reduction in food
    intake.  There were no treatment-related effects observed with
    respect to survival, water consumption, ophthalmoscopy, haematology,
    urinalysis or examination of bone marrow smears.  Although reduced

    iodine uptake by the thyroid was observed at all dietary levels,
    these changes were shown to be reversible following cessation of
    treatment.  At the lowest dietary levels of 50 and 100 ppm, the
    effects on iodine uptake were not correlated with changes in thyroid
    hormone levels or any overt morphological alterations of the thyroid
    gland, thus rendering the toxicological significance of this finding
    at 50 and 100 ppm as doubtful.  The NOAEL for this study was
    therefore 100 ppm, equal to 6 mg/kg bw/day, based on decreased serum
    T4 levels and increased thyroid weights at dietary levels of 300
    and 900 ppm (Hunter  et al., 1977).

         Metiram (94.8% purity, ETU <0.2%) was administered for a
    period of 3 months to groups of 13 Wistar Chbb:THOM SPF rats per sex
    at dietary levels of 0, 5, 80, 320 or 960 ppm, equal to 0, 0.4, 5.8,
    23.5 or 73.9 mg/kg bw/day in males and 0, 0.4, 6.7, 27.3 or 88.8
    mg/kg bw/day in females, respectively.  Neurofunctional assessment
    revealed general muscle weakness expressed as ataxia and
    significantly reduced forelimb and hindlimb grip strength in females
    treated at the highest dietary level of 960 ppm.  Perfusion fixation
    of tissues from selected rats from the control and treated groups
    failed to reveal any associated neuropathological or morphological
    alterations of the central or peripheral nervous systems.  Thyroid
    hormone levels revealed significantly decreased T4 levels in both
    sexes treated at the high dose of 960 ppm.  Significantly reduced
    RBC values were recorded in both sexes at levels of 320 and 960 ppm. 
    In females, decreases in RBC values were accompanied by decreases in
    mean haemoglobin and haematocrit levels.  Several statistically
    significant changes in blood biochemical parameters of uncertain
    toxicological significance were observed at the highest dietary
    level of 960 ppm.  These changes were recorded as decreased ALAT and
    ALP activity (females), decreased creatinine (both sexes), decreased
    urea (males), and decreases in the electrolytes; potassium (both
    sexes), sodium (females), calcium (both sexes) and magnesium (both
    sexes).  Decreased phosphorus levels were recorded in males at
    dietary levels of 320 ppm and higher.  Other effects of treatment
    expressed in both sexes at the highest dietary level of 960 ppm were
    decreased body weights and corresponding weight gains, as well as
    significantly increased thyroid, liver, kidney and testes (males
    only) weights.  There were no treatment-related gross or
    histopathological changes observed in any of the animals from the
    treated groups.  Treatment with metiram did not result in any
    significant effects on survival, food consumption, ophthalmoscopy or
    urinalysis.  The NOAEL was 80 ppm, equal to 5.8 mg/kg bw/day, based
    on changes in haematological and blood chemical parameters at 320
    ppm (Gelbke  et al., 1992b).

         A 13-week inhalation study was conducted with groups of 28
    Sprague-Dawley CD rats/sex exposed in nose-only chambers to metiram
    (94% purity) 6 hours/day, 5 days/week at concentrations of 0, 2, 20
    or 100 mg/m3.  Concentrations of ETU in the exposure atmospheres

    were calculated to be 0, 0.02, 0.33 or 1.8 mg/m3, respectively. 
    After termination of treatment, one-half of the rats were sacrificed
    while the remaining animals were retained for a 13-week recovery
    period.  The NOAEL was 2 mg/m3.  Pulmonary changes consisting of
    "subacute alveolitis", characterized by accumulations of alveolar
    macrophages within alveolar lumens, accompanied by some polymorpho-
    nuclear leukocytes were observed in rats treated at 20 and 100
    mg/m3.  It was conjectured that the alveolitis observed was not
    treatment-related, but rather, a non-specific dust reaction of the
    polymeric active ingredient artificially ground to particle size
    capable of reaching the alveoli.  Intra-alveolar pigment deposition
    was recorded in a single male and female from the high-dose treated
    group.  There was no evidence of damage to bronchial or bronchiolar
    epithelium in any of the treated groups.  Mean lung/trachea weights
    were increased in both sexes treated at the high dose.  Other
    changes associated with treatment were depositions of golden brown
    granular pigment, similar to that seen in the lungs, within the
    renal cortices in the high dose animals and decreased overall body-
    weight gain in both males and females treated at 20 (11% and 14%)
    and 100 mg/m3 (26% and 33% less than corresponding controls,
    respectively).  After the 13-week recovery, effects of treatment
    persisted in the lungs and kidneys of previously treated animals. 
    No treatment-related findings were noted on survival,
    ophthalmoscopy, haematology or blood chemistry.  Tissue residue
    analysis performed on the urine, plasma, liver, lung and thyroid
    revealed measurable levels of metiram and ETU in the urine and lung
    in rats treated at the mid- and high-dose levels (Ulrich, 1986).

    Rabbits

         A dermal toxicity study was performed with groups of 5 New
    Zeeland white KFM rabbits/sex treated with Polyram DF formulation of
    metiram on the shaved skin of their backs under occlusive conditions
    for 6 hours/day at concentrations of 0 (vehicle control, distilled
    water), 25, 50 or 250 mg/kg bw/day for a minimum of 21 consecutive
    daily applications. Dermal administration of metiram resulted in
    minimal to moderate exfoliation and ulcerative dermatitis in the
    skin of rabbits treated at the high-dose level.  Similar effects
    were not evident at lower dose levels, indicating a NOAEL for local
    irritation to the skin of 50 mg/kg bw/day.  In the absence of
    treatment-related effects on survival, clinical signs, body weights,
    food consumption, ophthalmoscopy, haematology, blood chemistry,
    organ weights or histopathology of the liver and kidneys, the NOAEL
    for systemic toxicity was greater than 250 mg/kg bw/day (Ullmann  et
     al., 1987).

    Dogs

         Groups of 4 beagle dogs/sex were treated with metiram (96.8%
    purity containing 2.2% ETU) for a period of 4 weeks at dietary

    levels of 0, 100, 300, 600 or 900 ppm, equal to 0, 5, 14, 28 or 41
    mg/kg bw/day for males and 0, 5, 15, 27 or 43 mg/kg bw/day for
    females, respectively.  Effects observed were an increased frequency
    of micro-follicles in the thyroids associated with minimal depletion
    of colloid and minimal hyperplasia of the follicular epithelium in
    2/4 males and 2/4 females treated at the high dose of 900 ppm when
    compared to the controls.  Other changes recorded were significantly
    increased liver weights in dogs receiving 600 and 900 ppm, which
    were not associated with any correlative histopathological findings. 
    Significantly increased water consumption was recorded in dogs
    treated at 100, 600 and 900 ppm but not at 300 ppm. The significance
    of increased fluid intake (calculated over 5-day periods) was
    difficult to ascertain since there were no corresponding changes
    noted in urinalysis parameters.  Erythrocyte, haemoglobin and packed
    cell volume values, although significantly decreased in dogs treated
    at 900 ppm when compared to the controls, were found to be within
    normal limits of variability and therefore of doubtful toxicological
    consequence. The NOAEL, based on the aforementioned findings, was
    300 ppm, equal to 14 mg/kg bw/day.  There were no significant
    effects of treatment on survival, clinical signs, body weights, food
    consumption, ophthalmoscopy, blood chemistry or urinalysis
    (Chesterman  et al., 1978).

         Metiram (93.6% purity, ETU < 0.2%) was given to groups of 5
    beagle dogs per sex at dietary concentrations of 0, 30, 80, 1000 or
    3000 ppm, equal to 0, 0.9, 2.5, 29.8 or 76.9 mg/kg bw/day in males
    and 0, 1.1, 2.7, 29.9 or 92.7 mg/kg bw/day in females, respectively,
    for a period of 52 weeks.  The principal effects of treatment were
    manifest on the thyroid.  Microscopic examination revealed thyroid
    follicular hyperplasia in dogs of both sexes treated at 1000 and
    3000 ppm.  This finding was associated with an increased size and
    weight of this organ at 3000 ppm. Gross necropsy revealed thyroid
    thickening in several animals from both the control and treated
    groups. This observation was, however, only correlated with
    histopathological change at dietary levels of 1000 ppm and higher,
    rendering the significance of thyroid thickening at lower levels
    uncertain. Serum T4 levels were decreased in both sexes at 3000 ppm
    and in males at 1000 ppm. A dose-related increased incidence of dogs
    with focal hepatic lipofuscin pigment deposition was noted in both
    sexes at 1000 ppm and higher.  Other effects of treatment with
    metiram were described as an increased incidence of diarrhoea in
    dogs treated at 80 (attributed to single male), 1000 and 3000 ppm;
    slight evidence of anaemia (both sexes at 1000 and 3000 ppm)
    involving an increased number of reticulocytes (both sexes at 3000
    ppm); decreased body-weight gain at 3000 ppm in males and to a
    lesser extent in females; and decreased food intake in both sexes at
    3000 ppm and in females at 1000 ppm.  Significant changes in blood
    chemical parameters at dietary levels of 1000 ppm and higher were
    evident as increased lipid, cholesterol, triglycerides, phospholipid
    levels, ALP activity, and total protein, and decreased albumin and

    A/G ratio as well as disturbances in the protein electrophoretic
    pattern.  There were no effects of treatment on survival,
    neurological parameters, ophthalmoscopy or urinalysis.  The NOAEL
    for this study was 80 ppm, equal to 2.5 mg/kg bw/day (Corney  et
     al., 1991).

    Monkeys

         A preliminary toxicity assessment was performed with groups of
    single male and female rhesus monkeys administered metiram (96.8%
    purity containing 2.2% ETU) orally by gavage as a suspension in 0.5%
    mucilage of tragacanth in water at dose levels of 50, 100 or 500
    mg/kg bw/day for a period of 4 weeks.  Treatment-related toxicity
    was evident as salivation at the time of dosing or immediately
    thereafter and occasional emesis in monkeys treated at 100 and 500
    mg/kg bw/day, body-weight loss in the single female treated at 500
    mg/kg bw/day and changes of the thyroid, representative of early
    follicular hyperplasia in the single high-dose female.  The low dose
    of 50 mg/kg bw/day was well tolerated with no overt signs of
    toxicity (Sortwell  et al., 1977).

         Metiram (96.8% purity containing 2.2% ETU) was administered
    orally by gavage to groups of 4 rhesus monkeys/sex for a period of
    26 weeks at dose levels of 0 (vehicle control, 0.5% tragacanth in
    distilled water), 5, 15 or 75 mg/kg bw/day.  After termination of
    treatment, 1 male and 1 female were retained untreated for a period
    of 15 weeks as recovery animals. In a separate, but concurrently
    conducted study, a further 2 male and 2 female monkeys were treated
    with metiram at doses of 0, 5 or 75 mg/kg bw/day for 26 weeks to
    monitor thyroid function.  The primary effects of treatment with
    metiram were evident in the thyroid and were characterized at dose
    levels of 15 and 75 mg/kg bw/day as minimal thyroid follicular
    hyperplasia, significantly decreased T3 and T4 levels and
    increased thyroid weights.  After a 15-week recovery, morphological
    changes of the thyroid were still apparent in monkeys previously
    treated at the 15 and 75 mg/kg bw/day dose levels.  Assessment of
    thyroid function revealed an initial marked reduction in iodine
    uptake at dose levels of 5 and 75 mg/kg bw/day, followed by a
    significant increase in uptake during the latter part of the study. 
    In the absence of any correlation to thyroid hormone levels or
    morphological alterations, no toxicological significance was
    attributed to fluctuations in iodine uptake by the thyroid at the
    lowest level of 5 mg/kg bw/day.  Other effects resulting from
    treatment were an increased incidence of salivation occurring at the
    time of dosing at the high dose.  Significantly increased liver
    weights at the high-dose level were not associated with any
    histopathological findings.  Treatment with metiram did not
    significantly affect survival, body-weight gains, food or water

    consumption, ophthalmoscopy, haematology, urinalysis or examination
    of bone marrow smears.  The NOAEL was 5 mg/kg bw/day (Sortwell  et
     al., 1979).

    Long-term toxicity/carcinogenicity studies

    Mice

         Dietary administration of metiram (96.8% purity containing 2.2%
    ETU) to groups of 52 CFLP mice/sex at levels of 0, 100, 300 or 1000
    ppm, equal to 0, 8, 24 or 79 mg/kg bw/day for males and 0, 9, 29 or
    95 mg/kg bw/day for females, respectively, for a minimum period of
    88 weeks resulted in a NOAEL for in-life parameters of 300 ppm,
    equal to 24 mg/kg bw/day.  Although there were no statistically
    significant differences in mortality in the treated groups, a
    marginally higher mortality incidence from week 40 onwards was
    recorded in females treated at 1000 ppm, resulting in a minimum 25%
    survival rate being reached in this group before the corresponding
    controls. Group mean body weights were significantly decreased in
    both sexes treated at the 1000 ppm dietary level. Food consumption
    in males treated at 1000 ppm was only marginally (5%) lower than the
    corresponding controls during the first year of treatment.  Clinical
    signs and examination of bone marrow smears were not adversely
    affected by treatment with metiram.  Under the conditions of the
    present study, treatment with metiram at dietary levels up to and
    including 1000 ppm failed to uncover any evidence of carcinogenic
    potential (Hunter  et al., 1979).

    Rats

         Groups of 50 Sprague-Dawley CD rats/sex were administered
    metiram (96.8% purity containing 2.2% ETU) in the diet at levels of
    0, 5, 20, 80 or 320 ppm, equal to 0.2, 0.8, 3.1 or 12.3 mg/kg bw/day
    in males and 0, 0.2, 1.0, 3.8 or 15.5 mg/kg bw/day in females,
    respectively, for 119 weeks for males and 111 weeks for females. 
    Satellite groups of 30 male and 30 female rats per group were used
    for blood sampling and thyroid function tests and were then killed
    after 102 weeks of treatment.  Treatment with metiram resulted in a
    NOAEL of 80 ppm (equal to 3.1 mg/kg bw/day), based on an increased
    incidence of rats treated at the next higher dietary level of 320
    ppm with muscular atrophy.  There were no consistent treatment-
    related effects with respect to survival, clinical signs, body
    weights, food or water consumption, ophthalmoscopy, haematology,
    blood chemistry, thyroid function, urinalysis or organ weights. 
    There was no evidence of metiram-induced carcinogenic potential
    (Hunter  et al., 1981).

    Reproduction studies

    Rats

         A three-generation (two-litter per generation) reproduction
    study was conducted with groups of 12 male and 24 female Crl:COBS
    CD(SD)BR rats fed metiram (96.8% purity containing 2.2% ETU) at
    dietary levels of 0, 5, 40 or 320 ppm, equal to 0, 0.2, 1.8 or 14.2
    mg/kg bw/day in males and 0, 0.3, 2.3 or 19.8 mg/kg bw/day in
    females, respectively.  In the F0 generation, treatment with
    metiram commenced at least 60 days prior to mating.  In the F1 and
    F2 generations, the F1b and F2b derived parental animals,
    respectively were exposed to the test material for a minimum period
    of 90 days.  At day 21 post-partum, 10 F3a pups/sex from each group
    were selected for detailed gross examination, recording of organ
    weights and histopathological assessment.  At the second pairing of
    the F2b generation, all pregnant females from each of the dose
    levels were sacrificed on day 20 of gestation for teratological
    examination.  Appearance of spermatozoa in the vaginal smear or the
    presence of a copulation plug was considered to be day 0 of
    gestation.  Decreases in body-weight gain (4-7%) were noted in both
    the F0 and F1 generation males and females treated at 320 ppm when
    compared to the controls.  Slightly depressed (7-8%) food intake was
    observed in males fed metiram during the F0 and F1 generations. 
    Body weights and food consumption were not adversely affected by
    treatment at lower dietary levels or in any of the treated groups
    from the F2 generation when compared to the controls.  There were
    no treatment-related effects on parental mortality, clinical signs,
    food conversion ratios, reproductive parameters or gross
    pathological alterations.  Statistically significant decreases in
    the mean number of pups born were observed in all treated groups
    during the second mating of both the F1 and F2 generations. 
    Although the differences were statistically significant, there was
    no dose-response relationship and all values in the treated groups
    generally fell within the reported laboratory standard values. 
    Total litter loss was significantly decreased at 320 ppm during the
    second mating of the F1 generation.  In the absence of similar
    effects in the first mating of the F1 or in either of the matings
    in the F0 and F2 generations, the toxicological significance of
    this finding was dubious.  Statistically significant decreases in
    mean litter weights were observed in the treated groups during the
    F1 and F2 generations.  Since the mean pup weights in the treated
    groups were comparable to the controls, the decreased mean litter
    weights may, in part, be attributed to the correspondingly smaller
    litter sizes observed in these groups.  With regard to the
    teratological component, there were no effects on pregnancy rate,
    pre- or post-implantation loss, number of live fetuses, embryo/fetal
    resorptions, fetal sex ratio or fetal/litter weights.  Metiram was
    not teratogenic as determined by gross, skeletal and visceral
    examination of fetuses, following  in utero exposure at dietary

    levels as high as 320 ppm. The NOAEL was 40 ppm, equal to 1.8 mg/kg
    bw/day, based on decreased parental body weight and food consumption
    recorded in the F0 and F1 generations treated at 320 ppm (Cozens
     et al., 1981).

    Special studies on teratogenicity

    Rats

         A preliminary range-finding study was performed with groups of
    6 non-pregnant Crl:Cobs CD(SD)BR female rats administered metiram
    (96.8% purity containing 2.2% ETU) orally by gavage at 0 (vehicle
    control, sodium carboxymethyl cellulose), 150, 300, 600 or 1200
    mg/kg bw/day for 10 consecutive days.  Dose-related clinical effects
    primarily affecting the nervous system were observed at all dose
    levels.  In the absence of microscopic examination,
    histopathological correlation could not be ascertained.  Other
    effects of treatment were related to decreased body-weight gains at
    all dose levels, depressed food intake at 300 mg/kg bw/day and
    higher and decreased water consumption in rats treated at 600 and
    1200 mg/kg bw/day (Palmer & Simmons, 1979a).

         Groups of 20 time-mated female Crl:Cobs CD(SD)BR rats were
    treated with metiram (96.8% purity containing 2.2% ETU) daily by
    gavage during days 6 to 15 of gestation, inclusive, at dose levels
    of 0 (vehicle control, sodium carboxymethyl cellulose), 40, 80 or
    160 mg/kg bw/day.  The day of mating, determined by the presence of
    a vaginal plug or sperm in the vaginal smear, was designated as day
    0 of gestation.  Decreased body-weight gain (4-9%) was noted  in the
    high-dose animals.  There were no significant effects with respect
    to clinical signs, food or water consumption or gross organ/tissue
    changes.  A slight increase in the pre- and post-implantation loss
    was recorded in the 160 mg/kg bw/day group, in conjunction with a
    significant decrease in the mean number of live fetuses and
    decreased litter weight in this group.  It is unlikely that the
    increased pre-implantation loss at the high dose was related to
    treatment, since theoretically, treatment was not initiated until
    after implantation occurred.  Nevertheless, the combined effect of
    pre- and post-implantation loss may have, to a certain degree,
    influenced the decreased litter size and weight noted at the high
    dose level.  There were no effects of treatment on the incidence of
    early or late resorptions, mean fetal weight or sex ratio.  The
    NOAEL for embryo/fetotoxicity was 80 mg/kg bw/day, based on slight
    decreases in litter size and weights.  Treatment with metiram failed
    to uncover any evidence of teratogenic potential.  The NOAEL for
    maternal toxicity was 80 mg/kg bw/day, based on decreased body-
    weight gain (Palmer & Simmons, 1979a).

    Rabbits

         In a range-finding study, groups of 3 pregnant Himalayan
    rabbits were treated orally by gavage with metiram (97.9% purity,
    ETU <0.2%) during days 7 through 19 of gestation at dose levels
    of 0 (vehicle control, distilled water with 0.5% carboxymethyl
    cellulose), 50, 100 or 200 mg/kg bw/day.  Reduced body-weight gains
    and food intake were recorded at the two highest dose levels.  The
    significance of the incidence of single abortion at each of the dose
    levels, upon conduct of the definitive study, was confirmed to be
    treatment-related.  No further relevant details were provided
    (Gelbke  et al., 1988).

         Metiram (97.9% purity, ETU < 0.2%) was administered orally
    by gavage at 0 (vehicle control, distilled water with 0.5%
    carboxymethyl cellulose), 10, 40 or 120 mg/kg bw/day to groups of 15
    artificially inseminated Himalayan rabbits on days 7 through 19 of
    gestation.  The day of artificial insemination was designated as day
    0 of gestation.  Treatment with metiram elicited signs of maternal
    toxicity at 40 and 120 mg/kg bw/day, denoted by abortion, decreased
    body weight and food consumption, the latter associated with
    reduction or absence of defecation.  The high incidence of abortion
    (8/15) recorded at 120 mg/kg bw/day, in conjunction with a single
    death culminated in only 6/15 rabbits treated at this level with
    litters available for examination.  Although 2 of 15 animals aborted
    at 40 mg/kg bw/day, there were, nevertheless, adequate numbers of
    litters secured in the control, 10 and 40 mg/kg bw/day dose groups.
    Since a dose level of 10 mg/kg bw/day was without significant
    effects, this dose was considered the NOAEL for maternal toxicity.
    The NOAEL for developmental toxicity was 40 mg/kg bw/day based on
    the slight decrease in mean fetal weights recorded at 120 mg/kg
    bw/day. A slight decrease in the number of live male fetuses in the
    120 mg/kg bw/day group was considered to be of no toxicological
    consequence, in light of the comparable number of female fetuses and
    the total number of fetuses in the 120 mg/kg bw/day group relative
    to the controls. There were no significant effects of treatment on
    the mean number of live fetuses, early or late resorptions, post-
    implantation loss, or placental weight. There was no evidence
    suggestive of teratogenic potential with metiram at any of the dose
    levels investigated (Gelbke  et al., 1988).

    Special studies on genotoxicity

         Results of mutagenicity assays conducted with metiram are
    presented in Table 3.  The tests conducted to evaluate potential for
    gene mutation in bacteria and induction of chromosomal aberration in
    rat bone marrow were negative.  Unscheduled DNA synthesis in rat
    hepatocytes and a dominant lethal study in mice were also negative. 
    Although metiram demonstrated potential for inducing sister
    chromatid exchange (SCE) in Chinese hamster ovary cells in the

    absence and presence of mouse microsomal activation, there was
    nevertheless, no significant induction of SCE observed with rat
    microsomal activation.  Moreover, an  in vivo SCE assay in bone
    marrow cells of the Chinese hamster was negative.  Metiram exhibited
    a weak promotion activity in mouse embryo fibroblasts in the absence
    of a direct transformation response.  The Meeting concluded that
    metiram was not genotoxic. 

    Special studies on irritation and sensitization

         The eye and skin irritation potential of technical metiram
    (containing 2.2% ETU) were investigated in six Vienna white rabbits.
    There were no signs of irritation when metiram was applied to the
    external ear for 20 hours or to the backs for 1, 5 or 15 minutes.
    When applied to the back for 20 hours, slight reddening occurred 24
    hours after application with subsequent scaling after 8 days.
    Metiram (50 mg) when introduced into the conjunctival sac of the eye
    of these rabbits produced slight redness and edema after 1 hour,
    with no signs of irritation after 8 days (Zeller, 1985a).

         Polyram combi, a formulation of technical metiram, was
    administered to eight Vienna white rabbits to determine skin and eye
    irritation potential.  A 50% aqueous suspension of the test material
    when applied to the backs of the rabbits for a period of 20 hours,
    resulted in slight erythema of the skin, which was reversible within
    8 days.  The instillation of 50 mg of Polyram combi to the
    conjunctival sac of the rabbit eye caused redness and edema which
    were reversible after 8 days.  When 50 l of a 20% aqueous
    suspension was applied, slight reddening of the mucosa occurred,
    whereas 50 l of a 2% aqueous suspension was tolerated without any
    irritation (Zeller, 1985b).

         Metiram technical demonstrated severe sensitizing effects on
    the skin of female Pirbright white, Dunkin Hartley guinea-pigs when
    tested according to the methods of the Magnusson & Kligman
    maximization test (Jackh, 1982).


        Table 3.  Genotoxicity of metiram
                                                                                                                                              
    Test                     Test system                 Concentration         Purity                  Results          Reference
                                                                                                                                              

    Reverse mutation         S. typhimurium              0, 1, 3, 10, 31,      Technical               negative         Oesch, 1977
    (in vitro)               TA 98, 100, 1537            100, 310, 1000,                               1., 2. (rat)
                                                         2000 g/plate 

                             S. typhimurium              0, 1, 10, 50, 100,    Technical + 2.2% ETU    negative         Gelbke & Engelhardt, 
                             TA 98, 100, 1535, 1537      500, 2500 g/plate                            1., 2.           1985
                                                                                                       (rat & mouse)

    Reverse mutation/host    S. typhimurium              500, 1670,            Technical + 2.2% ETU    negative         Jagannath & Myhr, 1985
    mediated (in vivo)       TA 1530                     5000 mg/kg bw 
                             Male CD-1 mice              (single oral doses)
                             (inoculated ip)

    Point mutation           HGPRT locus of Chinese      0, 0.681, 1.0, 4.64,  Technical + 2.2% ETU    negative, 1.     Gelbke & Jackh, 1985
    (in vitro)               hamster ovary (CHO) cell    6.81, 10, 46.4,                               equivocal, 2. 
                             line, K1                    68.1, 100 g/ml                               (rat)

                             HGPRT locus of Chinese      0.5, 1, 5, 10, 50,    Premix 95%              negative         Hoffman & Jackh, 1990
                             hamster ovary (CHO) cell    100, 500 g/ml                                1., 2. (mouse)
                             line, K1

    SCE (in vitro)           Chinese hamster ovary       0, 40, 60, 80, 100,   Technical + 2.2% ETU    positive, 1.     Ivett & Myhr, 1986a
                             CHO, WB1 cells              125, 150, 175, 200                            positive, 2. 
                                                         g/ml                                         (mouse)
                                                                                                       negative, 2. 
                                                                                                       (rat)

    SCE (in vivo)            Chinese hamster, LMP        1000, 3330, 10 000    Premix 95%              negative         Miltenburger et al., 
                             stock (bone marrow)         mg/kg bw                                                       1990

                                                                                                                                              

    Table 3 (contd)
                                                                                                                                              
    Test                     Test system                 Concentration         Purity                  Results          Reference
                                                                                                                                              

    Chromosome aberration    Rat, male Fischer 344       0, 0.24, 1.2, 2.4     Technical + 2.2% ETU    negative         Ivett & Myhr, 1986b
    (in vivo)                (bone marrow)               g/kg bw (acute) 0, 
                                                         0.02, 0.1, 0.2 g/kg 
                                                         bw (5 repeated oral 
                                                         doses)

    Transformation           Mouse embryo fibroblasts    0, 0.1, 0.25, 0.5,    Technical + 2.2% ETU    transformation:  Tu et al., 1985
    promotion (in vitro)     C3H-10T 1/2 (clone 8)       0.75, 1.0 g/ml                               negative
                             cell system                                                               promotion 
                                                                                                       activity: 
                                                                                                       weakly 
                                                                                                       positive

    Unscheduled DNA          Rat (Fischer 344, male)     0.492, 1.23, 2.46,    Technical + 2.2% ETU    negative         Cifone & Myhr, 1984
    synthesis (in vitro)     hepatocytes                 4.92, 12.3, 24.6, 
                                                         49.2, 160 g/ml

    Dominant lethal          Mouse, CD-1 male            0, 600, 1200, 2400    Technical + 2.2% ETU    negative         Palmer & Simons, 1979b
    (in vivo)                                            mg/kg bw/day

                                                                                                                                              

    Results:

    1. = in the presence of metabolic activation derived from the indicated species
    2. = in the absence of metabolic activation
    

    COMMENTS

         Metiram was incompletely absorbed when administered orally to
    rats.  Elimination was primarily via the faeces, with minimal
    biliary excretion.  Comparatively higher urinary excretion at low
    doses suggested that metiram may be more poorly absorbed at higher
    doses.  Highest residual tissue levels were found in the thyroid and
    kidney, with slightly higher concentrations present in females than
    in males.  Comparison of tissue residues after single or multiple
    doses suggested slight accumulation in the body with multiple
    dosing.

         The metabolism of metiram has not been completely elucidated. 
    In the rat, the predominant urinary components were polar and were
    identified as ethylenediamine, N-acetyl-ethylenediamine,
    ethanolamine, oxalic acid and glycine.  Major, less polar components
    were ethyleneurea, ETU and EBIS.

         Metiram was practically non-toxic upon acute oral, dermal and
    inhalation administration to rats.  WHO has classified metiram as
    unlikely to present acute hazard in normal use.

         The principal target organ upon repeated dietary exposure to
    metiram was the thyroid.

         Mice treated with metiram for three months at 0, 300, 1000,
    3000 or 7500 ppm in the diet revealed minimal to slight hypertrophy
    and vacuolation of the thyroid follicular epithelium in both sexes
    at levels of 3000 ppm and higher.  A NOAEL of 300 ppm (equal to 84
    mg/kg bw/day) was based on decreased serum T4 levels in both sexes
    at levels of 1000 ppm and above.

         Thirteen-week dietary administration of metiram to SD CFY rats
    at 0, 50, 100, 300 or 900 ppm revealed a NOAEL of 100 ppm (equal to
    6 mg/kg bw/day) based on decreased serum T4 levels and increased
    thyroid weights at dietary levels of 300 and 900 ppm.  Slight to
    minimal hyperplasia of the thyroid was observed at 900 ppm. 
    Although reduced iodine uptake by the thyroid was observed at all
    dietary levels, these changes were shown to be reversible following
    cessation of treatment.  At the lowest dietary levels of 50 and 100
    ppm, the effects on iodine uptake were not correlated with changes
    in thyroid hormone levels or any overt morphological alterations of
    the thyroid gland, thus rendering the toxicological significance of
    this finding doubtful.

         In a recently conducted three-month study with Wistar rats
    receiving metiram at 0, 5, 80, 320 or 960 ppm in the diet, decreased
    serum T4 levels and increased thyroid weights were observed at 960
    ppm.  Slight evidence of anaemia was observed at 320 ppm, indicating
    a NOAEL of 80 ppm (equal to 5.8 mg/kg bw/day).

         Other effects of treatment in the diet with metiram in the rat
    were manifest as hind limb paralysis with corresponding atrophy of
    muscle fibres. In the 13-week study with SD CFY rats, microscopic
    changes in muscle fibres at levels of 300 ppm (equal to 20 mg/kg
    bw/day) and higher were still prevalent in previously treated rats
    after the 6-week recovery period.  Muscular atrophy was observed in
    a long-term study in SD CD rats treated at the highest level of 320
    ppm (see below).  General muscle weakness/ataxia and reduced grip
    strength of the limbs with no histopathological consequences were
    observed in the 3-month study with Wistar rats fed metiram at the
    highest level of 960 ppm.

         A 52-week study in dogs at dietary levels of 0, 30, 80, 1000 or
    3000 ppm yielded a NOAEL of 80 ppm (equal to 2.5 mg/kg bw/day) based
    on thyroid follicular hyperplasia with increased size, thickening
    and weight of this organ, in conjunction with decreased serum T4
    levels at dietary levels of 1000 ppm and above.  Other effects
    recorded at 1000 ppm and above were a dose-related increased
    incidence of focal hepatic lipofuscin pigment deposition, slight
    evidence of anaemia, diarrhoea and changes in blood biochemical
    parameters.  A preliminary 4-week study in dogs uncovered an
    increased frequency of microfollicles in the thyroid, in association
    with colloid depletion and minimal hyperplasia in both sexes treated
    at the highest level of 900 ppm (equal to 41 mg/kg bw/day).

         Metiram given by gavage to rhesus monkeys at dose levels of 0,
    5, 15 or 75 mg/kg bw/day for a period of 26 weeks indicated a NOAEL
    of 5 mg/kg bw/day based on significantly decreased serum T3 and T4
    levels, increased thyroid weights and minimal thyroid follicular
    hyperplasia at 15 and 75 mg/kg bw/day.  Morphological changes of the
    thyroid were still apparent after a 15-week recovery period.  In the
    absence of any correlation between thyroid hormone levels and
    morphological alterations, no significance was attributed to
    fluctuations in iodine uptake by the thyroid recorded at 5 mg/kg
    bw/day.

         Long-term dietary treatment of mice with metiram at 0, 100, 300
    or 1000 ppm resulted in a NOAEL of 300 ppm (equal to 24 mg/kg
    bw/day) based on decreased body weights recorded at 1000 ppm.

         Chronic dietary administration of metiram to SD CD rats at 0,
    5, 20, 80 or 320 ppm revealed muscular atrophy at 320 ppm (equal to
    12 mg/kg bw/day), with a NOAEL of 80 ppm (equal to 3.1 mg/kg
    bw/day).

         Metiram was not carcinogenic when fed to mice or rats at
    dietary levels of up to 1000 and 320 ppm, respectively.

         A three-generation, two litter per generation reproduction
    study in rats treated at 0, 5, 40 or 320 ppm in the diet failed to

    reveal any adverse effects on reproductive parameters.  The NOAEL
    was 40 ppm (equal to 1.8 mg/kg bw/day), based on decreased parental
    body weight and food consumption recorded in the F0 and F1
    generations treated at 320 ppm.

         Metiram when administered to pregnant rats at 0, 40, 80 or 160
    mg/kg bw/day or rabbits at 0, 10, 40 or 120 mg/kg bw/day during
    critical periods of organogenesis was not teratogenic at any dose. 
    The NOAEL for maternal toxicity in the rat was 80 mg/kg bw/day based
    on decreased body-weight gain and in the rabbit the NOAEL was 10
    mg/kg bw/day based on increased abortions, decreased body weights
    and food consumption.  The NOAELs for embryo/fetotoxicity were 80
    mg/kg bw/day in the rat based on slight decreases in litter size and
    weight and 40 mg/kg bw/day in the rabbit based on decreases in mean
    fetal weights. 

         Metiram has been tested in a series of  in vitro and  in vivo
    genotoxicity assays.  The Meeting concluded that metiram is not
    genotoxic.

         The Meeting allocated an ADI of 0-0.03 mg/kg bw based on a
    NOAEL of 2.5 mg/kg bw/day in the 52-week study in dogs, using a 100-
    fold safety factor.  This ADI is supported by the NOAEL of 3.1 mg/kg
    bw/day observed in the long-term study in rats.  This ADI served as
    the basis for a group ADI that was established for metiram alone or
    in combination with mancozeb, maneb, and zineb.

    TOXICOLOGICAL EVALUATION

    Level causing no toxicological effect

         Mouse:    300 ppm, equal to 24 mg/kg bw/day (88-week study)

         Rat:      80 ppm, equal to 3.1 mg/kg bw/day (111-week study)
                   40 ppm, equal to 1.8 mg/kg bw/day 
                   (reproduction study)

         Rabbit:   10 mg/kg bw/day (teratogenicity study)

         Dog:      80 ppm, equal to 2.5 mg/kg bw/day (52-week study)

         Monkey:   5 mg/kg bw/day (26-week study)

    Estimate of acceptable daily intake for humans

              0-0.03 mg/kg bw (group ADI with mancozeb, maneb, and
              zineb).

    Studies which will provide information valuable in the continued
    evaluation of the compound

         Observations in humans.

    REFERENCES

    Chesterman, H., Heywood, R. & Barker M. (1973) Polyram Combi acute
    oral toxicity study in beagle dogs. Report BASF 73/0047, BASF
    40/73703. Unpublished report dated October 5, 1973 from Huntingdon
    Research Centre, Huntingdon, England. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Chesterman, H., Heywood, R., Ball, S., Street, A. & Prentice, D.
    (1978) Metiram (active ingredient) oral toxicity study in beagle
    dogs (dietary intake for 4 weeks). Report BASF 78/0154, BSF
    201/76422. Unpublished report dated April 26, 1978 from Huntingdon
    Research Centre, Huntingdon, England. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Cifone, M. & Myhr, B. (1984) Report on the evaluation of metiram
    tech. in the rat primary hepatocyte unscheduled DNA synthesis assay.
    Report RZ 84/209. Unpublished report dated July 5, 1984 from Litton
    Bionetics Inc., Maryland, USA. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Corney, S.J., Allen, T.R., Janiak, T. & Springall, C. (1991) 52-week
    oral toxicity (feeding) study with metiram premix 95% in the dog.
    Report No. 91/10786. Unpublished report dated August 22, 1991 from
    RCC, Research & Consulting Company Ltd., Itingen, Switzerland.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Cozens, D., Simons, R., Clark, R., Offer, J. & Gibson, W. (1981)
    Effect of metiram technical on reproductive function of multiple
    generations in the rat. Report RZ 81/132, BSF 200/80692. Unpublished
    report dated March 18, 1981 from Huntingdon Research Centre,
    Huntingdon, England. Submitted to WHO by BASF Aktiengesellschaft,
    FRG.

    Gelbke, H. & Engelhardt, G. (1985) Report on the study of metiram
    (techn.) in the Ames test. Report RZ 85/020. Unpublished report
    dated February 7, 1985 from BASF, Department of Toxicology,
    Ludwigshafen/Rhein, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Gelbke, H. & Jackh, R. (1985) Report on a point mutation test
    carried out on CHO cells (HGPRT locus) with the test substance
    metiram. Report RZ 85/238. Unpublished report dated July 30, 1985
    from BASF, Department of Toxicology, Ludwigshafen/Rhein, FRG.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Gelbke, H., Hellwig, J. & Hildebrand, B. (1988) Report on the study
    of the prenatal toxicity of metiram-premix 95% in rabbits after oral
    administration (gavage). Report BASF 88/0154 and Supplement BASF
    88/0262. Unpublished report dated May 26, 1988 from BASF, Department
    of Toxicology, Ludwigshafen/Rhein, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Gelbke, H., Mellert, W. and Hildebrand, B. (1992a) Study of the oral
    toxicity of metiram premix 95% in B6C3F1 mice. Administration in
    the diet for 3 months. Report No. 92/11223. Unpublished report dated
    October 16, 1992 from BASF, Department of Toxicology,
    Ludwigshafen/Rhein, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Gelbke, H., Mellert, W. & Hildebrand, B. (1992b) Study of the oral
    toxicity of metiram premix 95% in Wistar rats. Administration in the
    diet for 3 months including the examination of neurotoxicology
    (neurofunctional observational battery). Report No. 92/11224.
    Unpublished report dated October 16, 1992 from BASF, Department of
    Toxicology, Ludwigshafen/Rhein, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Grundler, O.J. (1979) Study of the acute dermal toxicity of "Metiram
    tech. with 2% ETU" on the rat (Translation). Report RZ 79/032.
    Unpublished report dated September 25, 1979 from BASF,
    Gewerbehygiene und Toxikologie, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Grundler, O.J. (1985) Report on the study of the acute dermal
    toxicity of Polyram Combi (BAS 222 01 F) in the rat (Translation of
    the original report dated September 25, 1979). Report RZ 85/026.
    Unpublished report dated February 4, 1985 from BASF, Department of
    Toxicology, Ludwigshafen/Rhein, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Hawkins, D., Elsom, L., Girkin, R. & Jackson R. (1984) Report on the
    study of dermal absorption of metiram in rats. Report RZ 85/158, HRC
    BSF 411/84694. Unpublished report dated October 10, 1984 from
    Huntingdon Research Centre, Huntingdon, England. Submitted to WHO by
    BASF Aktiengesellschaft, FRG.

    Hawkins, D., Elsom, L., Midgley, I., Biggs, S. & McCay, C. (1985)
    The biokinetics and metabolism of 14C-metiram in the rat. Report
    BASF 85/0470, HRC BSF 410/85720. Unpublished report dated October
    28, 1985 from Huntingdon Research Centre, Huntingdon, England.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Hofmann H. (1974a) Acute intraperitoneal toxicity of Polyram Combi
    (technical active ingredient) to the mouse. Report RZ 74/011.
    Unpublished report dated March 25, 1974 from BASF, Gewerbehygiene
    und Toxikologie, FRG. Submitted to WHO by BASF Aktiengesellschaft,
    FRG.

    Hofmann, H. (1974b) Acute intraperitoneal toxicity of Polyram Combi
    (technical active ingredient) to the mouse. Report RZ 74/011.
    Unpublished report dated March 25, 1974 from BASF
    Aktiengesellschaft, FRG.

    Hofmann, H. & Munk, R. (1975) Acute intraperitoneal toxicity of the
    technical active ingredient metiram to the rat. Report RZ 75/006.
    Unpublished report dated June 4, 1975 from BASF, Gewerbehygiene und
    Toxikologie, FRG. Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Hofmann, H. (1975) Acute oral toxicity of the technical active
    ingredient metiram to the rat. Report RZ 75/005. Unpublished report
    dated June 4, 1975 from BASF, Gewerbehygiene und Toxikologie, FRG.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Hofmann H. (1985a) Report on the study of the acute oral toxicity of
    Polyram Combi, technical active ingredient, in the rat (Translation
    of original report dated March 25, 1974). Report BASF 85/0485.
    Unpublished report dated February 4, 1985 from BASF, Department of
    Toxicology, Ludwigshafen/Rhein, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Hofmann, H. (1985b) Report on the study of the acute inhalation
    toxicity (inhalation hazard) of Polyram Combi, technical active
    ingredient, in the rat (Translation of original report dated March
    25, 1974). Report RZ 85/028. Unpublished report dated February 4,
    1985 from BASF, Department of Toxicology, Ludwigshafen/Rhein, FRG.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Hofmann, H. (1985c) Report on the study of the acute oral toxicity
    of Polyram Combi (BAS 222 01 F) to rats (Translation of original
    report dated March 25, 1974). Report RZ 85/121. Unpublished report
    dated April 12, 1985 from BASF, Department of Toxicology,
    Ludwigshafen/Rhein, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Hofmann, H. (1985d) Report on the study of the acute inhalation
    toxicity (inhalation hazard) of Polyram Combi (BAS 222 01 F) in rats
    (Translation of original report dated March 25, 1974). Report RZ
    85/124. Unpublished report dated April 12, 1985 from BASF,
    Department of Toxicology, Ludwigshafen/Rhein, FRG. Submitted to WHO
    by BASF Aktiengesellschaft, FRG.

    Hofmann, H. (1985e) Report on the study of the acute inhalation
    toxicity of the spray of a 5% aqueous suspension of Polyram Combi
    (BAS 222 01 F) to guinea-pigs (Translation of original report dated
    March 25, 1974). Report RZ 85/125. Unpublished report dated April
    12, 1985 from BASF, Department of Toxicology, Ludwigshafen/Rhein,
    FRG. Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Hofmann, H. & Jackh, R., 1990. Report on the point mutation test
    carried out on CHO cells (HGPRT locus) with the test substance
    metiram premix 95% with B6C3F1 mice microsomal fraction. Report
    No. 90/0285. Unpublished report dated August 2, 1990 from BASF,
    Department of Toxicology, Ludwigshafen/Rhein, FRG. Submitted to WHO
    by BASF Aktiengesellschaft, FRG.

    Hunter, B., Barnard, A., Heywood, R., Street, A. & Prentice, D.
    (1976a) Preliminary assessment of metiram toxicity to rats in
    dietary administration for four weeks followed by a two and a four
    week withdrawal period. Report RZ 76/024, BSF 172/76245. Unpublished
    report dated October 20, 1976 from Huntingdon Research Centre,
    Huntingdon, England. Submitted to WHO by BASF Aktiengesellschaft,
    FRG.

    Hunter, B., Bridges, J. & Prentice, D. (1976b) Preliminary
    assessment of metiram toxicity to mice in dietary administration for
    4 weeks. Report RZ 76/014, BSF 170/76108. Unpublished report dated
    June 7, 1976 from Huntingdon Research Centre, Huntingdon, England.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Hunter, B., Barnard, A., Heywood, R., Street, A., Prentice, D. &
    Offer, J. (1977) Metiram toxicity to rats in dietary administration
    for 13 weeks followed by a 6 week withdrawal period (final report).
    Report RZ 77/043, BSF/197/77612 and Addendum BASF 87/0205, BSF
    197/8713. Unpublished report dated November 16, 1977 and addendum
    dated May 29, 1987 from Huntingdon Research Centre, Huntingdon,
    England. Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Hunter, B., Barnard, A., Prentice, D. & Gregson, R., 1979. Metiram
    tumorigenicity to mice in long term dietary administration (final
    report). Report RZ 79/033, BSF 198/78265. Unpublished report dated
    June 5, 1979 from Huntingdon Research Centre, Huntingdon, England.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Hunter, B., Barnard, A., Street, A., Heywood, R., Prentice, D.,
    Offer, J. & Gibson, W. (1981) Metiram toxicity and tumorigenicity in
    prolonged dietary administration to the rat. Report RZ 81/280, BSF
    199/80391, WNT No. 77/951 and Addendum BASF 89/0001. Unpublished
    report dated May 7, 1981 and addendum date December 19, 1988 from
    Huntingdon Research Centre, Huntingdon, England. Submitted to WHO by
    BASF Aktiengesellschaft, FRG.

    Ivett, J. & Myhr, B. (1986a) Report on the mutagenicity evaluation
    of metiram in an  in vitro sister chromatid exchange assay in
    Chinese hamster ovary (CHO) cells/amended final report. Report RZ
    86/082. Unpublished report dated March 11, 1986 from Litton
    Bionetics Inc., Maryland, USA. Submitted to WHO by BASF
    Aktiengesellschaft, FRG. 

    Ivett, J. & Myhr, B. (1986b) Report on the mutagenicity evaluation
    of metiram technical K38/33A in the rat bone marrow cytogenetic
    assay. Report RZ 86/265. Unpublished amended report dated August 4,
    1986 from Litton Bionetics, Maryland, USA. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Jackh, R. (1981) Report on the study of the acute oral toxicity of
    metiram technical grade in the rat (Translation). Report BASF
    92/10669. Unpublished report dated July 9, 1981 from BASF,
    Department of Toxicology, Ludwigshafen/Rhein, FRG. Submitted to WHO
    by BASF Aktiengesellschaft, FRG.

    Jackh, R. (1982) Report on the study of the sensitizing effect of
    metiram techn. in the guinea-pig -maximization test (Translation of
    original report dated August 21, 1981). Report RZ 82/068.
    Unpublished report dated February 16, 1982 from BASF, Department of
    Toxicology, Ludwigshafen, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Jagannath, D. & Myhr, B. (1985) Report on the mouse host-mediated
    assay of metiram tech. K38/33A. Report RZ 85/210. Unpublished report
    dated June 28, 1985, from Litton Bionetics Inc., Maryland, USA.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Klimisch, H.J. & Zeller, H. (1980) Report on the determination of
    the acute inhalation toxicity LC50 metiram techn. with 2% ETU as a
    dust aerosol after 4-hour exposure in Sprague-Dawley rats
    (Translation of original report dated September 15, 1980). Report RZ
    83/064. Unpublished report dated September 15, 1980 from
    Gewerbehygiene und Toxikologie, FRG. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Leuschner, F. (1979a) The acute oral toxicity of the preparation
    metiram, techn. agent with 2% ETU in rats. Report BASF 79/0161, WNT-
    Nr. 77/951. Unpublished report dated August 20, 1979 from
    Laboratorium fur Pharmakologie und Toxikologie, Hamburg, FRG.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Leuschner, F. (1979b) The acute intraperitoneal toxicity of the
    preparation metiram, techn. agent with 2% ETU in mice. Report BASF
    79/0162, WNT-Nr. 77/951. Unpublished report dated August 20, 1979
    from Laboratorium fur Pharmakologie und Toxikologie, Hamburg, FRG.
    Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Miltenburger, H., Volkner, W. & Heidemann, A. (1990) Sister
    chromatid exchange assay in bone marrow cells of the Chinese hamster
    with metiram premix 95%. Report No. 90/0569. Unpublished report
    dated September 18, 1990 from CCR, Cytotest Cell Research Gmbh &
    Co., Rossdorf, FRG. Submitted to WHO by BASF Aktiengesellschaft,
    FRG.

    Oesch, F. (1977) Ames test for metiram. Report RZ 77/027.
    Unpublished report dated August 22, 1977 from the Institute of
    Pharmacology, University of Mainz, Germany. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Palmer, A. & Simons, R. (1979a) Effect of metiram technical on
    pregnancy of the rat. Report RZ 79/065, BSF 302/79616. Unpublished
    report dated August 3, 1979 from Huntingdon Research Centre,
    Huntingdon, England. Submitted to WHO by BASF Aktiengesellschaft,
    FRG.

    Palmer, A. & Simons, R. (1979b) Dominant lethal assay of metiram
    technical in the male mouse. Report RZ 79/069, BSF 304/79860.
    Unpublished report dated November, 1979 from Huntingdon Research
    Centre, Huntingdon, England. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Sortwell, R., Heywood, R., Allen, D., Prentice, D. & Cherry, C.
    (1977) Metiram preliminary oral toxicity study in rhesus monkeys.
    Repeated dosage for 4 weeks. Report BASF 77/0149, BSF 265/77264.
    Unpublished report dated April 15, 1977 from Huntingdon Research
    Centre, Huntingdon, England. Submitted to WHO by BASF
    Aktiengesellschaft, FRG.

    Sortwell, R., Allen, D., Heywood, R. & Street, A. (1979) Metiram
    (containing 2.2% ethylenethiourea) oral toxicity study in rhesus
    monkeys (repeated dosage for 26 weeks with recovery period). Final
    report. Report BASF 79/0082, BSF 267/78263. Unpublished report dated
    January 15, 1979 from Huntingdon Research Centre, Huntingdon,
    England. Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Tu, A., Sivak, A., Breen, P. & Hatch, K. (1985) Report on the
    evaluation of metiram in the C3H-10T 1/2 cell system for
    transformation and promotion activities. Report RZ 85/209.
    Unpublished report dated June 18, 1985 from Arthur D. Little, Inc.,
    Maryland, USA. Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Ullmann, L., Sacher, R., Porricello, T., Luetkemeier, H., Vogel, W.,
    Vogel, O., Wilson, J. & Terrier, H. (1987) Report on the subacute
    21-day repeated-dose dermal toxicity study with polyram DF in
    rabbits. Report BASF 87/0260, ZNT No. 86/314. Unpublished report
    dated June 24, 1987 from RCC, Research and Consulting Company AG,
    Switzerland. Submitted to WHO by BASF Aktiengesellschaft, FRG.

    Ulrich, C. (1986) Report on the thirteen week subchronic inhalation
    toxicity study on metiram in rats. Report RZ 86/407 and addendum
    BASF 87/0414. Unpublished report dated December 31, 1986 and
    addendum dated October 7, 1987 from International Research and
    Development Corporation, Mattawan, Michigan, USA. Submitted to WHO
    by BASF Aktiengesellschaft, FRG.

    WHO (1992). The WHO recommended classification of pesticides by
    hazard and guidelines to classification 1992-1993 (WHO/PCS/92.14).
    Available from the International Programme on Chemical Safety, World
    Health Organization, Geneva, Switzerland. 

    Zeller, H. (1985a) Report on the study of the irritation of Polyram
    Combi, technical active ingredient, to the skin and eye of rabbits
    (Translation of original report dated March 25, 1974). Report RZ
    85/027. Unpublished report dated February 4, 1985 from BASF,
    Department of Toxicology, Ludwigshafen, FRG. Submitted to WHO by
    BASF Aktiengesellschaft, FRG.

    Zeller, H. (1985b) Report on the study of the irritation of Polyram
    Combi (BAS 222 01 F) to the skin and eyes of rabbits (Translation of
    original report dated March 25, 1974). Report RZ 85/122. Unpublished
    report dated April 12, 1985 from BASF, Department of Toxicology,
    Ludwigshafen, FRG. Submitted to WHO by BASF Aktiengesellschaft, FRG.


    See Also:
       Toxicological Abbreviations