Sponsored jointly by FAO and WHO


    Data and recommendations of the joint meeting
    of the FAO Panel of Experts on Pesticide Residues
    in Food and the Environment and the
    WHO Expert Group on Pesticide Residues
    Geneva, 5 - 14 December 1983

    Food and Agriculture Organization of the United Nations
    Rome 1985



         Benomyl was reviewed by the Joint Meetings of 1973, 1975 and 1978
    (FAO/WHO 1974a,b, 1976a,b, 1979a).1  An acceptable daily intake (ADI)
    was not allocated because of insufficient acute oral, short-term and
    long-term studies. Furthermore, a carcinogenic study, as well as
    observations in humans, were indicated as desirable information. These
    studies have been reviewed and are summarized in the toxicology
    section of the following monograph.

         In the 1978 report it was recommended that residue guideline
    levels for benomyl and carbendazim should be replaced by a single list
    of guideline levels for carbendazim residues that occur as metabolic
    products of benomyl or thiophanate-methyl or from the direct use of
    carbendazim. That procedure is continued in the section on residues of
    this evaluation.

         Extensive information was available on approved uses of benomyl
    in 22 countries, the fate of residues, international maximum residue
    limits (MRLs) and the results of a marked-basket survey in the United
    States. Residue data from supervised trials were available from the
    United States, Africa, the Federal Republic of Germany, the United
    Kingdom, Australia and Japan.




    Absorption, Distribution and Excretion

         Absorption, distribution and elimination in rats following dermal
    application (0.1, 1, 10 and 100 mg) was measured using 14C-labelled
    benomyl. Blood levels, mode of excretion, metabolic products and rate
    of penetration were also examined. A separate group of rats, dosed
    intravenously with 14C-benomyl for comparison of blood level
    concentrations, revealed that absorption into the bloodstream was
    non-linear with respect to dose. Blood values, which were low
    (0.004-0.07 ppm), first appeared 30 min. after treatment, peaked at
    all treatment levels after 4 h and were eliminated in urine after
    30 min. linearly with time. The low blood concentrations resulted from
    limited absorption with rapid metabolism and elimination via the
    urine. The major urinary metabolite identified was 5-HBC and, to a
    lesser extent, MBC. Greater than 95 percent of the radioactivity was
    eliminated in 24 h in the urine following intravenous injection. No
    radioactivity was found in any body tissues sampled 24 h after
    injection (<0.1 percent) (Fisher et al. 1981 ).

         In a similar evaluation, blood levels of benomyl and its
    metabolites were measured in rats following inhalation exposure to
    actual time-weighted averages of 0.32 and 3.3 mg/l. Exposure intervals
    of 0.5, 1, 2 and 6 h were utilized. Urinary residues consisted
    primarily of 5-HBC, with limited amounts of benomyl/MBC detected. The
    methodology did not distinguish between benomyl and MBC. At both
    exposure levels blood concentration of benomyl/MBC was greater than
    that of 5-HBC after 6 h, with levels ranging from 0.39-2.3 and
    0.25-1.2 ppm, respectively. At 18 h post-exposure, 5-HBC was the only
    residue detected in the blood (1.1 ppm) and only at the high dose.

         Rapid elimination of benomyl was also demonstrated in mice and
    hamsters following intragastric intubation. 90 percent of the
    radioactivity was eliminated in the urine and faeces in 72 h. Little
    to no radioactivity was evident in tissues. Conjugates of 5-HBC and
    MBC appeared in the urine and faeces, respectively (Han 1974).

         Lactating and non-lactating goats were given five consecutive
    daily doses of 2-14C benomyl by capsule at rates equivalent to 36 and
    88 ppm in the total daily diet, respectively. Evaluation of
    radioactivity in various tissues, milk (where present), urine and
    faeces, as well as characterization of the bound and unbound residues,
    revealed a similar metabolism and elimination pattern identified for
    rats, dogs, chickens and dairy cows. Most of the radioactivity was
    eliminated in the urine and faeces and identified as 5-HBC and 4-HBC.
    Milk residues, principally of 5-HBC with minor amounts of 4-HBC and
    5-hydroxy-2-aminobenzimidazole (5-HAB), accounted for approximately
    2 percent of the total dose. Approximately 25 percent of the milk
    radioactivity was reincorporated into the natural milk components
    casein and whey protein. There were no detectable residues in muscle
    tissue and fat (<0.01 ppm). However, radioactivity detected in liver
    and kidney amounted to 3.8 and 0.09 ppm, respectively, with 5-HBC
    identified as the principal benomyl metabolite (ca. 6 percent). Much
    of the liver residues were reincorporated into glycogen, protein,
    fatty acids and cholesterol and accounted for approximately 35 percent
    of the liver residues. Further characterization of the bound liver
    tissue residues following enzymatic and trifluoroacetic anhydride
    hydrolysis identified 5-hydroxy-benzimidazole moieties as the
    principal (at least 77 percent) 14C-residue found in goat liver.
    No free benomyl, MBC or 5-hydroxy-MBC were determined in the liver
    (Han 1980; Hardesty 1982).


    1  See Annex 2 for FAO and WHO documentation.

         In a series of metabolic studies, benomyl and/or Benlate were
    administered either by gavage or in the diet to pregnant ChR-CD rats
    to determine the concentration of benomyl, MBC and two MBC metabolites
    (4-OH MBC and 5-OH MBC) in maternal blood and embryonic tissue. The
    design of these studies followed typical teratology schedules wherein
    dosing was administered on days 7 through 16 of gestation and included
    levels of 125 mg/kg/day via gavage or 5 000 - 10 000 ppm ca.
    400-800 mg/kg) in the diet. Blood samples from the dams and tissue
    samples from their embryos were examined at several time points during
    compound administration. Residue analyses revealed that benomyl was
    either much more efficiently metabolized or biologically unavailable
    following dietary administration. The half-life for benomyl/MBC in
    maternal blood, following gavage, was approximately 45 min. and was
    less than 45 min. in embryonic tissue. The metabolite 4-OH MBC was not
    detectable (< 0.03 ppm), while 5-OH MBC demonstrated a half-life for
    maternal blood of 2-3 h and 4-8 h in embryos. Similar analyses
    demonstrated that levels of benomyl/MBC in maternal blood varied
    from 0.23 to 0.61 ppm, regardless of dose, while 5-OH MBC averaged
    0.44-4.4 ppm and 0.33-3.3 ppm in blood and embryo, respectively (Culik
    et al 1981).

    Effects on Enzymes and Other Biochemical Parameters

         A study conducted using acetylcholinesterase from bovine
    erythrocytes showed that benomyl did not inhibit the functioning of
    this enzyme.  The acetylcholinesterase inhibition constant, K1, for
    benomyl was greater than 1  10-3 M (Belasco undated).


    Acute Toxicity

         The acute toxicity of benomyl in several animal species is
    summarized in Table 1.

         Gross and histopathological changes were evaluated and selected
    organs in several species were examined with emphasis on the male
    gonads. Testicular degeneration, necrosis of germinal epithelium and
    aspermatogenesis were observed in male rats following some acute oral
    intubation and acute inhalation exposures. Dogs, exposed via
    inhalation for 4 h at 1.65 mg/l, presented evidence of focal
    aspermatogenesis and reduced spermiogenesis.

        Table 1  Acute Toxicity of Benomyl in Animals

    Chemical                      Species        Sex (Number)        Route          Vehicle             mg/kg b.w.1         Reference

    Benomyl                       Rat            M (1/dose)          Oral           Peanut Oil          ALD > 1 000         Zwicker 1965

                                  Rat            M (1/dose)          Oral           Peanut Oil          ALD > 9 590         Sherman & Krauss

                                  Rat            M/F (10/dose)       Oral           Peanut Oil          LD50 > 10 000       Sherman 1969a

                                  Rabbit         M (1/dose)          Oral           50% Wettable        ALD > 3 400         Fritz 1969

                                  Dog            M (1)               Oral           Evaporated          ALD > 1 000         Sherman 1969b
                                                                                    Milk and
                                                                                    Water (1:1)

                                  Rabbit         M/F (4/dose)        Dermal         50% Wettable        LD50 > 10 000       Busey 1968a

                                  Rat            M (5/dose)          Inhal.         50% Wettable        LC50 > 0.82         Hornberger 1969
                                                                     (4 hr)         Powder              mg/l

                                  Rat            M (6/dose)          Inhal.         50% Wettable        LC50 > 4.01         Busey 1968b
                                                                     (4 hr)         Powder              mg/l (analytical)

                                  Dog            M (10/dose)         Inhal.         50% Wettable        LC50 > 1.65         Littlefield 1969
                                                                     (4 hr)         powder              mg/l (analytical)

    Benlate (53% benomyl)         Rat            M/F (10 dose)       Oral           Aqueous suspension  LD50 > 10 000       Sherman 1969a

    2-Benzimidazole               Rat            M/F (10/dose)       Oral           Corn Oil            LD50 > 10 000       Goodman 1975
    carbamic acid, methyl ester

    Table 1  (con't)

    Chemical                      Species        Sex (Number)        Route          Vehicle             mg/kg b.w.1         Reference
    5-Hydroxy-2-benzimidazole-    Rat            M (1 dose)          Oral           Corn Oil            ALD > 7 500         Snee 1969
    carbamic acid, methyl ester

    2-Aminobenzimidazole          Rat            M (1/dose)          Oral           Peanut Oil          ALD > 3 400         Sherman & Fritz

    1  Based on active ingredient.
    Special Study on Eye and Skin Irritation

         The eye irritation properties of benomyl were examined in albino
    rabbits in several tests using technical grade benomyl, 50 percent
    wettable powder, and a suspension in mineral oil. Mild conjunctival
    irritation and minor transitory corneal opacity were reported in all
    tests (Reinke 1966; Frank 1986, 1972).

         A 50 percent wettable powder applied to the clipped intact and
    abraded abdomen of albino rabbits produced moderate to marked
    erythema, slight oedema and slight desquamation. Exposure was for 24 h
    to occluded skin sites at doses greater than 0.5 g/animal. Albino
    guinea pigs similarly exposed to 10, 25 and 40 percent dilutions of
    technical grade benomyl in dimethyl phthalate presented only mild
    irritation of both intact and abraded skin sites (Busey 1968a; Majkut
    1966; Colburn 1969; Frank 1969).

    Special Study on Sensitization

         Albino guinea pigs exposed to benomyl, either technical material
    or a 50 percent sucrose formulation, produced mild to moderate skin
    sensitization reactions following both intradermal injections or
    repeat applications to abraded skin (Majkut 1966; Colburn 1969; Frank

    Short-term Studies


         Benomyl, intubated into ChR-CD male rats at 200 and 3 400 mg/kg
    in peanut oil five times a week for two weeks produced mortality in
    4/6 animals at the high dose. Animals dosed with 3 400 mg/kg
    demonstrated evidence of degeneration of germinal epithelium,
    multinucleated giant cells and reduction or absence of sperm. Very
    minor changes were observed in the testes of the animals dosed with
    200 mg/kg (Sherman & Krauss 1966). ChR-CD male rats similarly dosed
    with 200 mg/kg of the metabolite 5-hydroxy-2-benzimidazole-carbamic
    acid (methyl ester) presented no toxic symptoms or evidence of effects
    on the testes (Snee 1969).

         Groups of rats (16 of each sex, four-week-old ChR-CD rats/group)
    were fed benomyl (72 percent a.i.) in the diet at dosage levels of 0,
    100, 500 and 2 500 ppm for 90 days. Animals were observed daily for
    behavioral changes and body weights and food consumption were recorded
    at weekly intervals. Haematological examinations were conducted on six
    male and six female rats in each group at 30, 60 and 90 days. Routine
    urinalyses were performed on the same animals as well as plasma
    alkaline phosphatase and glutamic pyruvic transaminase activity. After
    96-103 days of continuous feeding 10 male and 10 female rats in each
    group were killed and selected organs weighed. Additional organs were
    preserved for microscopic examination. The six male and six female

    animals remaining in each group after the terminal sacrifice were
    subjected to a reproduction study.

         There were no gross toxic signs of poisoning and no compound-
    related effects on weight gain, food consumption, food efficiency,
    haematology, biochemistry or urinalysis determinations. Liver-to-body
    weight ratio in females was slightly increased at 2 500 ppm, compared
    with control rats. Cross and microscopic examinations of tissues and
    organs showed no significant effects attributable to the presence of
    benomyl in the diet at levels up to and including 2 500 ppm (Sherman
    et al. 1967).


         Groups of five male and five female New Zealand albino rabbits,
    weighing 2 to 2.4 kg, were exposed to 15 dermal applications of a
    50 percent benomyl formulation (equivalent to 1 000 mg/kg b.w.) on
    both abraded and intact abdominal skin sites. Animals were exposed for
    six hours each day, five days/week for three weeks. After each daily
    application, the abdomen was washed with tap water. Observations were
    made daily for mortality and toxic effects and weekly for body weight
    changes. Gross necropsy and microscopic examinations were performed.
    Slight erythema, oedema and atonia were observed for both abraded and
    intact skin sites. Slight to moderate desquamation was reported
    throughout the study. No apparent compound-related body weight or
    organ-to-body weight changes were reported. Microscopic examination of
    the males demonstrated that administration of 1 000 mg/kg of benomyl
    produced degeneration of the spermatogenic elements of the
    seminiferous tubules of the testes, including vacuolated and
    multinucleated supermatocytes. A slight increase in haematogenic
    activity in the bone marrow, as well as acanthosis and hyperkeratosis
    of the skin, were reported for treated animals (Busey 1968d).

         In a separate repeated-dose dermal study, groups of five male and
    five female New Zealand albino rabbits, weighing 3 kg, were exposed
    to doses of benomyl equivalent to 0, 50, 250, 500, 1 000 and
    5 000 mg/kg b.w. applied to non-occluded abraded dorsal skin sites six
    hours a day, five days a week for three weeks. Test material was
    removed by washing the skin site and drying with a towel. There were
    decreased body weight gains for both males and females at 1 000 mg/kg
    and greater. Mild to moderate skin irritation was reported for all
    groups but was most notable at the higher doses. Functional
    disturbances of the alimentary canal and kidney, including diarrhoea,
    oliguria and haematuria, were observed in males and females at 1 000
    and 5 000 mg/kg. There was a decreased average haemoglobin
    concentration in the 1 000 mg/kg males, although this was not
    significant. Decreased average testicular weights and testes-to-body
    weight ratios were observed at the 1 000 mg/kg dose only. There were
    no histopathological changes reported and the lower testicular weights
    were not considered to be directly related to compound administration
    (Hood 1969).


         Groups of beagle dogs (four males and four females per group)
    were administered benomyl 50 percent wettable powder in the diet at
    dosage levels of 0, 100, 500 and 2 500 ppm (based on active
    ingredient) for three months. Dogs were 7-9 months old. Food
    consumption and body weight data were recorded weekly. Clinical
    laboratory examinations, including haematology, biochemistry and
    urinalysis, were performed pre-test and after 1, 2 and 3 months of
    feeding. At the conclusion of the study all animals were killed,
    selected organs weighed and additional organs subjected to gross and
    microscopic evaluations. There was no mortality or adverse clinical
    observation over the course of the study and growth and food
    consumption were normal. Urinalyses were unaffected by treatment.
    There were no dose-related effects on the haematological values;
    however, alkaline phosphatase and glutamic pyruvic transaminase
    activities were increased in high dose males and females. Furthermore,
    there were significant decreases in the albumin/globulin ratio in both
    males and females fed 2 500 ppm in the diet. Organ-to-body weight
    changes were observed in the high dose males and females for the
    thymus (decreased) and thyroid (increased). One female fed 2 500 ppm
    had an enlarged spleen, which was consistent with the decreased
    erythrocyte count, haemoglobin concentration and haematocrit values.
    Histopathological examination revealed myeloid hyperplasia of the
    spleen and bone marrow with erythroid hyperplasia for this same animal
    at the 3-month examination. Group mean values were not significantly
    different, however. Three out of four males fed 2 500 ppm had reduced
    relative prostate weights when compared with controls. Microscopic
    examination of tissues and organs did not indicate a consistent lesion
    effect in animals fed benomyl for 90 days. A no effect level (NOEL)
    was demonstrated at 500 ppm (Sherman 1968).

    Special Studies on Reproduction

         The effects of exposure to benomyl on male reproductive
    development was evaluated in prepubertal Sprague-Dawley male rats
    (33 days old), which were gavaged daily for 10 days at doses of 0 and
    200 mg/kg/day. Eight animals per group were killed at 3, 17, 31, 45
    and 59 days after the last treatment. Selected tissues, including
    liver, kidneys, testes, seminal vesicles and epididymides, were
    removed, weighed and examined histologically. Samples of seminal fluid
    from the vas deferens were also examined. Observation intervals were
    pre-selected to coincide with stages of spermatogenesis. Data were
    presented on tissue weights, total epididymal sperm counts, vas
    deferens sperm concentrations, or testicular histology. There were no
    effects related to treatment (Carter 1982).

         In a similar experiment, adult male Sprague-Dawley rats (65 days
    old) received 10 daily treatments of 0, 200 or 400 mg benomyl/kg/day
    by gavage. At 14 days after the last treatment, body weight, tissue
    weights, total epididymal sperm counts, sperm concentration in the
    vas deferens and testes histology were performed. Production of
    testosterone by the Leydig cells was artificially stimulated by
    subcutaneous injections of hypothalamic chorionic gonadotrophin (HCG)
    2 h prior to sacrifice. There were no compound-related effects on body
    weight, liver, kidney, adrenal, testes or seminal vesicle weights.
    Caudate epididymal weights were, however, depressed by treatment with
    benomyl. There were also treatment-related reductions in epididymal
    sperm count (caput and caudate) as well as in the vas deferens sperm
    concentration. The study was designed to evaluate alterations in
    spermatozoa undergoing spermiogenesis in the seminiferous tubules
    of the testes during exposure to benomyl. Animals exposed to
    400 mg/kg/day presented histologic evidence of hypospermatocytogenesis
    with generalized disruption of all stages of spermatogenesis, when
    compared with controls (Carter & Laskey 1982).

    Special Studies on Teratogenicity


         Groups of pregnant CD-1 mice (20-25 mice/group) were administered
    benomyl via gavage at dose levels of 0, 50, 100 and 200 mg/kg/day on
    days 7 to 17 of gestation. Animals were killed on day 18, pups
    delivered by Caesarean section, the number of live, dead and resorbed
    foetuses determined, and foetuses examined for gross anomalies. Half
    of the foetuses were examined for visceral abnormalities and the other
    half for skeletal abnormalities. Maternal indices were unaffected by
    treatment. However, foetal mortality increased, foetal weight
    decreased and foetal development was adversely affected by treatment.
    The high dose caused an increased supraoccipital score, decreased
    numbers of caudal and sternal ossifications and increased incidences
    of enlarged lateral ventricles and enlarged renal pelves. The latter,
    while not significant at the lower doses, did demonstrate dose-related
    increases at all other doses. The occurrence of supernumerary ribs and
    subnormal vertebral centrums was significant and increased in a dose-
    related manner at all dose levels. There was an increase in the number
    of abnormal litters and foetuses, which was significantly different
    from the control at 100 and 200 mg/kg/day. Major anomalies included:
    exencephaly, hydrocephaly, cleft palate, hydro-nephrosis, polydactyly,
    oligodactyly, umbilical hernia, fused ribs, fused vertebrae and
    short/kinky tail. Although benomyl demonstrated dose-related
    foetotoxicity at all levels, it was not teratogenic at 50 mg/kg/day in
    mice (Kavlock et al. 1982).


         Groups of rats (ca. 26-28 pregnant ChR-CD rats/group) were
    administered benomyl (53.5 percent a.i.) in the diet at dosages of
    0, 100, 500, 2 500 and 5 000 ppm from day 6 through day 15 of
    gestation. Average doses were equivalent to 0, 8.6, 43.5, 209.5 and
    372.9 mg/kg/day. On day 20 of gestation, all pregnant animals were
    sacrificed and foetuses delivered by Caesarean section.

         Determinations of the number and location of live foetuses, dead
    foetuses and resorption sites were made, as well as of body weights,
    crown-rump length, sex and external gross examination for visible
    abnormalities. Two thirds of the foetuses were prepared for
    examination of skeletal abnormalities, and the rest were examined for
    visceral and soft tissue anomalies.

         There were no mortalities attributable to benomyl, no clinical
    signs of toxicity reported and no adverse effects on body weight of
    dams. Dams in the 5 000 ppm group had a reduced food intake during the
    period benomyl was administered in the diet, but it returned to
    comparable control levels for the remainder of the study. The data
    related to reproduction (implantation sites, resorption sites and
    live/dead foetuses) were not affected by benomyl up to and including
    the highest dose level. There were no external or internal
    abnormalities reported, except for three litters at the highest dose
    with incidences of hydronephrosis and retarded ossification
    (interparietal and occipital bones). There were no teratogenic effects
    noted with the administration of benomyl in the diet to pregnant rats
    during the critical period of organogenesis (Sherman et al. 1970).

         Groups of pregnant Wistar rats (27-28 rats/group) were fed
    benomyl in the diet at dose levels of 0, 1 690, 3380 and 6 760 ppm
    (time-weighted doses of 0, 169, 298 and 505 mg/kg/day, respectively)
    from days 7 to 16 of gestation. Foetuses were delivered by Caesarean
    section on day 21, weighed, examined grossly and fixed for evaluation
    of visceral and skeletal abnormalities. Food consumption decreased at
    3 380 and 6 760 ppm with resultant decreases in body weight gain for
    dams, significantly so in the high dose group. Weight gain was
    significantly reduced in mid- and high-dose group foetuses and a
    significant decrease in the ossification of the supraoccipital bone in
    the latter. Furthermore, the percentage of enlarged renal pelves was
    increased in the two highest dosage groups, compared with the control.
    No dose-related anomalies or major malformations were apparent from
    exposure to benomyl at any of the dose levels utilized (Kavlock et
    al. 1982).

         Benomyl (99.2 percent a.i.) was administered by gavage to groups
    of pregnant rats (ChR-CD) at dose levels of 0, 3, 10, 30, 62.5 and
    125 mg/kg/day from days 7 through 16 of gestation. There were 60 dams
    in the control group (corn oil) and 27 in each of the other test
    groups. Dams were observed daily for signs of toxicity and changes in

         No clinical signs of toxicity or mortality were observed among
    dams in any dose group. Body weight gain was comparable to controls,
    as was the incidence of pregnancy, corpora lutea, implantation sites
    and sex ratio. However, foetal body weight was significantly decreased
    in the 62.5 and 125 mg/kg/day dose groups. There was also an increased
    incidence of embryo-foetal mortality at 125 mg/kg/day.

         Some foetuses exhibited external and visceral malformations,
    which were dose-related and significant at 10 mg/kg/day and greater.
    Malformations observed included microphthalmia, anophthalmia and
    hydrocephaly (distended lateral ventricles). These occurred
    predominantly at the higher doses. Histological examination of eyes
    from all groups revealed pathologic changes, consisting of irregular
    lenses, retro-bulbar glandular adnexa, distorted or compressed retinal
    layers and thickened nerve fibres in the 10, 62.5 and 125 mg/kg/day
    treatment groups. No alterations occurred in control or 30 mg/kg
    groups. Major skeletal malformations observed in the 125 mg/kg dose
    group included fused ribs, fused sternebrae and fused thoracic arches.
    Additional skeletal variations were also increased at 62.5 and
    125 mg/kg/day, including misaligned and unossified sternebrae and
    bipartite vertebral centra.

         Benomyl produced teratogenic responses in ChR-CD rate at doses of
    10 mg/kg/day and greater. Microphthalmia at 10 mg/kg was reported to
    be compound related, on the basis of the severity of the pathologic
    changes and the finding that the increased incidence at 62.5 and
    125 mg/kg/day was not a direct reflection of reduced foetal body
    weight (Staples & Culik 1980).

         Groups of pregnant rats were administered benomyl (99.1 percent
    a.i.) via gavage at dosage levels of 0, 3, 6.25, 10, 20, 30 and
    62.5 mg/kg/day from days 7 through 16 of gestation. Each group
    contained 50 animals, except the high dose group, which contained 20
    female rate. Reproductive status was determined on a per litter basis
    following gross pathological evaluation. The number of implantation
    sites, resorptions, dead and live foetuses, stunted foetuses and mean
    weight of live foetuses per litter were determined. This study was
    performed to determine a no-effect level for microphthalmia and
    hydrocephaly; therefore, only foetal heads were fixed and examined.
    Microphthalmia was determined on the basis of the smallest eye in the
    control group (< 1.8 mm).

         Mean foetal body weight was significantly lower in the high dose
    group. There were only two incidences of malformations, both in the
    62.5 mg/kg/day group. One foetus had internal hydrocephaly and
    another, in a separate litter, had unilateral microphthalmia. These
    were not statistically different from controls. The only type of
    variation reported was subcutaneous haematoma, which was not dose
    related. There was no teratogenic response at 30 mg/kg (Staples 1982).

         The teratogenic potential of benomyl was examined in groups of
    Wistar rats (12 to 30 pregnant rats/group) orally gavaged with dose
    levels of 0, 15.6, 31.2, 62.5 and 125 mg/kg/day administered on days
    7 to 16 of gestation. Pups were delivered by Caesarean section on day
    21 of gestation. Weight gain in high-dose dams was decreased from days
    17 to 20 of gestation. Foetal resorption was increased in this group,
    with six litters completely resorbed. Foetal weight was also adversely
    affected, with significant decreases at 62.5 and 125 mg/kg/day and a
    significant increase in foetal mortality at 125 mg/kg/day. There were
    several skeletal and visceral variants observed among foetuses in the
    62.5 and 125 mg/kg/day group, including: increased supraoccipital
    score, decreased number of sternal and caudal vertebrae, increased
    percentage of enlarged lateral ventricles and enlarged renal pelves.
    Major anomalies observed primarily at 62.5 mg/kg/day and above
    included: encephaloceles, hydrocephaly, microphthalmia, fused
    vertebrae and fused ribs. A dose level of 31.2 mg/kg/day appeared to
    be without adverse effects on the developing rat foetus in this
    evaluation (Kavlock et al. 1982).

         Benomyl was administered via gavage to groups of Wistar rats at
    dose levels of 0, 15.6 and 31.2 mg/kg/day from day 7 of gestation
    through day 15 of lactation (day 22 of gestation was considered day
    0 of lactation). The litters were reduced to 8 pups/litter, equal in
    sex, on day 3 of lactation. The litters were weighed on days 8, 15,
    22, 29 and 100, and locomotor activity was evaluated periodically
    throughout the study. At 100 days of age, several organs were weighed,
    including adrenals, liver, kidney, ovaries, testes and the ventral
    prostate plus seminal vesicles. There were no compound-related effects
    either on litter size at birth or weaning, or on body weights of
    foetuses (by sex). Growth, survival and locomotor activity were
    comparable with controls throughout the study. Organ weights were
    comparable with controls except for decreased testes and ventral
    prostate/seminal vesicle weights, which were significantly reduced at
    31.2 mg/kg/day but not at 15.6 mg/kg (Kavlock et al. 1982).


         Groups of rabbits (15 artificially inseminated albino
    rabbits/group) were administered benomyl (50 percent a.i.) in the diet
    at dosage levels of 0, 100 and 500 ppm from day 8 through day 16 of
    gestation. Mortality, clinical observations and food consumption were
    determined daily and body weights were measured weekly. On day 29 or

    30 of gestation, selected pregnant animals were sacrificed and
    foetuses delivered by Caesarean section; the remaining does were
    allowed to hutch normally on day 35.

         One low level doe and one high level doe aborted on days 3 and 6,
    respectively, and were sacrificed and excluded from the study. There
    were 12 pregnant does in the control group, 13 in the low dose group
    and 9 in the high dose group. Of these, 6, 7 and 5, respectively, were
    sacrificed and foetuses were delivered by Caesarean section; the
    remaining does hutched normally.

         There was no mortality attributable to benomyl. General
    appearance, behaviour, body weight gain and food consumption were
    comparable among all groups. The data related to reproduction
    (implantation sites, resorption sites and live young) were not
    affected by benomyl. There were no external or internal abnormalities
    associated with benomyl treatment of pregnant rabbits. Internal
    development, including somatic and skeletal development, was normal,
    except for a marginal increase in rudimentary ribs at 500 ppm. Numbers
    of pregnant rabbits, of litters and of foetuses examined were less
    than adequate to assess the foetotoxic or teratogenic potential of
    benomyl to pregnant rabbits (Busey 1968c).

    Special Studies on Neurotoxicity


         Studies performed using hens gave no indication of neurotoxic
    potential at single oral doses up to and including 5 000 mg/kg
    (Goldenthal et al. 1978; Jessep & Dean 1979; Jessup 1979).

    Long Term Studies


         Groups of weanling rats (36 male and 36 female Charles River
    albino rats/group) were administered benomyl (50-70 percent a.i.) in
    the diet for 104 weeks at dosage levels of 0, 100, 500 and 2 500 ppm.
    Growth, as observed by body weight changes and food consumption data,
    was recorded weekly for the first year and twice a month thereafter.
    Daily observations were made of behavioural changes and mortality. At
    periodic intervals over the course of the study, haematologic,
    urinalysis and selected clinical chemistry examinations were
    performed. After one year each group was reduced to 30 males and
    30 females by interim sacrifice for gross and microscopic evaluations.
    At the conclusion of the study, all surviving animals were sacrificed
    and gross examinations of tissues and organs were made. Initially,
    microscopic examinations of tissues and organs from the control and
    2 500 ppm groups were conducted, along with liver, kidney and testes

    examinations of animals in the 100 and 500 ppm dose groups. In a
    follow-up pathology evaluation, all of the tissues and organs of the
    control, low-, intermediate- and high-dose groups were examined

         There was no mortality in the study attributable to the presence
    of benomyl in the diet. Survival decreased to approximately 50 percent
    during the second year, but was comparable among all groups. Body
    weight, food consumption and food efficiency were unaffected by
    treatment. The average daily dose for the 2 500 ppm group was
    330 mg/kg b.w./day (initially, M/F), 91-106 mg/kg (at one year) and
    70-85 mg/kg (at two years). There were no compound-related clinical
    manifestations of toxicity. Haematologic, urinalysis and liver
    function examinations were unaffected by treatment. There were no
    observed differences in organ weights or organ-to-body weight changes.
    Histopathological examinations revealed no differences between
    treatment and control groups. The most frequently observed tumors were
    mammary, pituitary and adrenal ones, which were equally distributed
    among all groups. Hepatic toxicity was similar among all groups,
    including controls, with no demonstrated compound-related effects. A
    high incidence of testicular degeneration was observed in control
    males and, therefore, no conclusion could be made with regard to
    compound-related effects on male gonads.

         Benomyl was without adverse effects in this study at levels up to
    and including 2 500 ppm (Sherman et al. 1969; Lee 1977).


         Groups of beagle dogs (four males and females/group) one to two
    years old, were administered benomyl (50 percent a.i.) in the diet at
    dosage levels of 0, 100, 500 and 2 500 ppm for two years. Food
    consumption and body weight data were obtained weekly and animals were
    examined daily for clinical signs of toxicity. Haematological,
    biochemical and urinalysis examinations were performed periodically
    throughout the study. Interim sacrifice after one year was performed
    on one male and one female per group from the control and high-dose
    groups. Organ weights, gross necropsy and histopathological
    evaluations were performed at the conclusion of the study. Only the
    livers and testes were examined histologically in the 100 and 500 ppm
    dose groups.

         There was no mortality related to treatment. Body weight changes
    and food consumption values were similar among all groups, except the
    high dose one, which demonstrated both decreased food intake and body
    weight gain. The average daily dose was 55-58 mg/kg b.w. (initially,
    M&F), 74-79 mg/kg (at one year) and 45-55 mg/kg (at two years). One
    dog in the high-dose group lost its appetite and was replaced. No
    other clinical signs of toxicity were observed. Haematological
    evaluations and urinalyses were similar to the control. Males in the

    2 500 ppm group had increased cholesterol, alkaline phosphatase and
    GPT values (initially), as well as decreased total protein and
    albumin/globulin (A/G) ratio. There were similar, but less marked,
    effects in high dose females. Cholesterol and total protein were
    similar to controls among the females examined.

         The biochemical determinations were indicative of adverse liver
    effects, which were demonstrated as liver cirrhosis among animals in
    the high dose group. There was also slight to marked bile duct
    proliferation in 4/6 dogs at the 2 500 ppm level. Haemosiderosis,
    evident in one dog in the 2 500 ppm group at one year, was not seen in
    other dogs examined at two years after staining specifically for iron.
    Preparation of preserved wet tissue with oil red 0 and sudan black for
    hepatocyte vacuolation confirmed that benomyl was not hepatotoxic at
    100 and 500 ppm in the diet.

         Focal testicular degeneration was present in all treatment
    groups, with marked testicular degeneration (reduced testes weight,
    absence of spermatozoa and spermatic giant cells) in 1/3 dogs at
    2 500 ppm. A complete histological evaluation of the testes and
    secondary sex organs of historical control dogs from the testing
    facility in conjunction with the findings from the present report
    demonstrated that the testicular lesions reported did not appear
    to be attributable to benomyl ingestion. However, an outbreak of
    inflammatory infection causing orchitis in beagle colonies at that
    time may have contributed to the unusually high level in control dogs;
    therefore, no clear evidence exists for the absence of testicular
    effects. Data from the carbendazim two-year dog study provide
    additional confirmatory results for the absence of these effects at
    dietary levels of 100 ppm carbendazim. Furthermore, as indicated, only
    testes and liver were examined microscopically in all dose groups in
    this benomyl two-year dog study. The two-year carbendazim study
    provides added assurance for the absence of adverse effects in organs
    or tissues in other dose groups. Considering the absence of such data
    for benomyl, a NOEL for benomyl of greater than or equal to 100 ppm
    can be assigned (Sherman 1970; Lee 1970, 1971a,b,c, 1977).

    Special Studies for Carcinogenicity


         Male and female CD-1 mice (80 males and 80 females per group)
    were administered benomyl (99 percent a.i.) in the diet at dose levels
    of 0, 500, 1 500 and 5 000 ppm (5 000 ppm was lowered from 7 500 ppm
    after 37 weeks) for two years. Mice were 6-7 weeks old at the start of
    the study. Animals were examined daily for behaviour and clinical
    signs of toxicity, biweekly for palpable masses and regularly weighed
    for body weight changes. Food consumption was similarly determined on
    a routine basis. Mortality was noted and recorded. Peripheral blood
    was collected periodically throughout the study for haematological

    examinations. Urine and faecal samples were collected and evaluated
    prior to terminal sacrifice. Selected organs were weighed, including
    brain, heart, lungs, liver, spleen, kidney, testes and thymus.
    Microscopic examination was performed on tissues and organs.

         Median survival time was unaffected by treatment. Male and female
    mice fed 1 500 and 5 000 ppm benomyl had dose-related body weight
    decreases. Food consumption was variable throughout the study,
    although high dose females appeared to consume less food. The average
    daily intake of benomyl for males was 1 079 mg/kg b.w,/day
    (initially), 878 mg/kg (1 yr.) and 679 mg/kg (2 yr.); for females
    it was 1 442 mg/kg (initially), 1 192 mg/kg (1 yr.) and 959 mg/kg
    (2 yr.). Clinical signs of toxicity were not different between groups.
    Alopecia/dermatitis were observed in all groups with equal severity
    and occurrence. The aetiology of this symptom was unknown. There were
    no apparent differences between treatment and control groups for
    palpable masses, number of mice affected or latency period of
    discovery. Haematology examinations were unremarkable except for
    decreased erythrocyte counts for males at 1 500 and females at
    5 000 ppm. Haemoglobin and haematocrit values were also depressed in
    males of the intermediate dose group.

         Several significant organ weight changes occurred among treated
    groups. In male mice, mean absolute thymus weights were depressed at
    all levels and relative thymus weights decreased at 500 and 1 500 ppm
    (decrease at 5 000 was not significant). Relative thymus weights were
    increased among females at 5 000 and 1 500 ppm (not significant).
    Relative brain weights were increased in males and females at
    5 000 ppm, in males at 500 and in females at 1 500 ppm. The most
    significant compound-related organ weight changes involved absolute
    and relative liver weights for males at 1 500 and 5 000 ppm and for
    females at 5 000 ppm. Male mice also presented decreased absolute
    testes weights at the high dose. The liver and testes weight changes
    were accompanied by histomorphic changes in these tissues.

         The incidence of hepatocellular carcinomas and benign neoplasms
    in female mice was increased and dose dependent. Hepatocellular
    carcinomas were significant in females at 500 and 5 000 ppm, while
    hepatic neoplasms were significant at 1 500 and 5 000 ppm. In male
    mice, hepatocellular carcinomas and neoplasms were significantly
    increased at 500 and 1 500 ppm, but not at the high dose. Lung tumours
    (alveologenic carcinomas) in 500 and 1 500 ppm dose groups were also
    significantly increased in males but not in females. Several non-
    neoplastic organ changes were increased in males (5 000 ppm), but were
    confined to liver (degeneration, pigment, cytomegaly), thymus
    (atrophy) and testes, epididymus, prostate (degeneration of
    seminiferous tubules, atrophy, aspermatogenesis, distended acini).
    Splenic haemosiderosis was significantly increased at 5 000 ppm, as
    was submucosal lymphocytic infiltration of the trachea at 1 500 ppm,
    in female mice.

         The latency period for liver tumour induction (adenomas and
    carcinomas) was determined from palpation, gross necropsy and
    histopathology performed on all animals throughout the study. These
    findings demonstrated that there is no measurable difference in time
    elapsed from mean test day to tumour between control animals and
    treatment groups with regard to liver neoplasms.

         Benomyl, when fed to CD-1 mice at dose levels of 500 and
    5 000 ppm in the diet, is oncogenic in male and female animals. This
    effect was compound-related in males at the low and intermediate dose
    levels. In the liver of female mice, the oncogenic effect was
    compound- and dose-related at all levels. A no-effect level was not
    observed in male or female mice for hepatocellular carcinomas or
    combined hepatocellular neoplasms (Wiechman et al. 1982).

    Human Exposure

         Potential dermal and respiratory exposure to benomyl under actual
    use situations was determined for: mixing procedures for aerial
    application, reentry into treated fields and home use (garden,
    ornamental and greenhouse). Maximum exposure occurred in the loading
    and mixing operation for aerial application, where dermal exposure was
    26 mg benomyl per mixing cycle, primarily to hands and forearms
    (90 percent). Respiratory exposure averaged 0.08 mg of benomyl.
    Reentry data demonstrated dermal and respiratory exposures of 5.9 mg/h
    and less than 0.002 mg/h, respectively. Home use situations produced
    exposures of 1 mg and 0.003 mg per application cycle for dermal and
    respiratory routes, respectively (Everhart & Holt 1982).

         Field use conditions involved in spraying fruit orchards were
    examined for potential dermal and respiratory exposures of humans
    involved in mixing and applying 20 and 100 gallons of Benlate per acre
    (1 acre = 0.4 hectares). The application cycle was approximately
    70 min. and resulted in total dermal and respiratory exposure of 11 or
    15 mg benomyl/cycle. Essentially all exposure was dermal, resulting in
    12.2 mg/cycle dermally, with less than 0.05 mg/cycle via the
    respiratory route (DuPont 1979a, undated).

         Selected blood profiles from 50 factory workers involved in the
    manufacture of Benlate were compared to a control group of 48 workers
    who were not exposed to Benlate. White blood count, red blood count,
    haemoglobin and haematocrit values were comparable among the two
    groups. There were no quantitative estimates of exposure given for the
    factory workers. There were no female employees included in the
    control group (DuPont 1979b).

         An epidemiology survey was performed to determine whether
    potential exposure to Benlate had an adverse effect on the fertility
    of 298 male workers exposed to benomyl between 1970 and 1977. The
    workers ranged from 19 to 64 years of age, with 79 percent between 20
    and 39. Seventy-eight percent of the spouses were similarly aged
    between 20 and 39 years. Exposure duration ranged from less than one
    month to 95 months, with more than 51 percent of the workers
    potentially exposed from 1 to 5 months. The birth rates of exposed
    workers' spouses were compared with those of four comparison
    populations from the same county, state, region and country (USA).
    There was no reduction in fertility as evidenced by the birth rates
    for the study population, which were generally higher than the
    comparison populations. Spermatogenesis among workers was not examined
    (Gooch 1978).

    Special Studies on Mutagenicity

    Results of mutagenicity assays of benomyl are summarized in Table 2.

    Mouse, micronucleus

         Groups of 24 male mice were given two daily doses by gavage of
    250, 500 or 1 000 mg benomyl per kg b.w. on consecutive days. A
    vehicle control (DMSO) group was also included. Eight animals from
    each group were sacrificed 24, 48 or 72 hours after the second dose
    was administered. Bone marrow from the femur of each animal was taken
    for examination. For each animal 500 polychromatic erythrocytes (PCE)
    were examined for micronuclei, and the number of mature erythrocytes
    was counted until 200 PCE were found.

         The statistical procedure used showed that four groups had
    significantly increased numbers of cells with micronuclei. These
    groups included the low- and mid-dose groups at 48 h (15/3.500 and
    16/4 000, respectively as compared with 5/3 000 cells from vehicle
    controls) and in the high-dose group at 24 and 48 h after treatment
    (20/3 500 and 17/3 500, respectively; respective control values were
    5/3 500 and 6/5 000) (Kirkhart 1980).

    Ovary cells in vitro

         Chinese hamster ovary cells in cultures were exposed to varying
    concentrations of benomyl without metabolic activation (0, 0.625,
    1.25, 2.5, 5, or 10 g/ml) and with metabolic activation (0, 9.375,
    18.75, 37.5, 75 or 150 g/ml). EMS and dimethylnitrosamine (DMN) were
    used as positive controls and a vehicle control (0.95 percent ethanol
    in culture medium) was included. Two samples of 25 cells each were 

        Table 2  Results of Mutagenicity Assays of Benomyl/Benlate

    Test Organism                 Test Substance           Results                                      Reference

    Gene Mutation Studies


    Salmonella typhimurium        Benlate or               Positive                                     Kappas et al. 1976
                                  similar formulation

                                                           Negative                                     DuPont 1977

                                                           Series of tests: spot,
                                                           liquid culture and host-mediated
                                                           assays using strains his G46,
                                                           TA1530, TA1535, TA1950 using
                                                           benomyl. No mutagenic activity
                                                           was noted in any of these tests

                                  Benomyl                  Bacterial assays with                        Ercegovich & Rashid 1977;
                                                           Benomyl. Strains TA98,                       Rashid & Ercegovich 1976
                                                           TA100, TA1535, TA1537,
                                                           and TA1538. Doubtful
                                                           mutagenic activity was
                                                           reported for benomyl
                                                           both with and without
                                                           metabolic activation.

                                                           Positive                                     Kappas et al. 1976

                                                           Negative                                     Shirasu et al. 1978

                                                           Negative                                     Ficsor et al. 1978

    Table 2  (con't)

    Test Organism                 Test Substance           Results                                      Reference

                                                           Benomyl was not mutagenic                    Donovan & Krahn 1981
                                                           at doses as high
                                                           as 250 g per plate in
                                                           strains TA1535, 1537,
                                                           98 and 100

                                                           Positive/Negative                            Russel 1978; Donovan & Krahn 1981

    S. typhimurium and                                     Spot tests on plates                         Carere et al. 1978
    Streptomyces coelicolor                                with Salmonella strains
                                                           TA1535, 1536, 1537 and
                                                           1538 and with
                                                           Streptomyces. No
                                                           mutagenic activity was
                                                           reported for benomyl in
                                                           either organism.

    S. typhimurium                Benomyl                  Negative                                     Shirasu et al. 1978
    Escherichia coli              Benlate                  Positive                                     Kappas et al. 1976

                                  Benomyl                  Positive                                     Kappas et al. 1976

                                                           Negative                                     Shirasu et al. 1978

    Table 2  (con't)

    Test Organism                 Test Substance           Results                                      Reference


    Fusarium oxysporum            Benomyl                  Inconclusive                                 Dassenoy & Meyer 1973

    Aspergillus nidulans          Benlate                  Negative                                     Hastie 1970

    A. nidulans                   Benomyl                  Benomyl tested in an excision                Kappas & Bridges 1981
                                                           repair deficient
                                                           strain. A dose-dependent
                                                           effect was reported.

    Saccharomyces                 Benomyl                  Mitotic gene conversion                      De Bertoldi et al.
    cerevisiae and A.                                      study was negative on                        1980
    nidulans                                               testing benomyl with
                                                           metabolic activation.

    A. nidulans                   Benomyl                  Negative for nondisjunction                  De Bertoldi &
                                                           or crossing over.                            Griselli 1980
                                                           Increased frequency of
                                                           segregants due to spindle
                                                           inhibition reported.


    Drosophila melanogaster       Benomyl/Benlate          Genetic toxicity tested                      Lamb & Lilly 1980
                                                           in Drosophila. Noted
                                                           sterility in some broods.
                                                           This was considered to be
                                                           consistent with spindle
                                                           effects of benomyl.

    Table 2  (con't)

    Test Organism                 Test Substance           Results                                      Reference

    Chromosomal Effects
    Cytogenetics - in vitro

    Chinese hamster               Benomyl                  Weakly positive results                      Evans & Mitchell
    ovary cells in vitro                                   for sister chromatid exchange                1980
                                                           were reported, with
                                                           and without metabolic

    Chinese hamster               Benomyl                  Looked for mutations at                      Fitzpatrick & Krahn
    ovary cells in vitro                                   the HGPRT locus. Benomyl                     1980
                                                           was not mutagenic under
                                                           these test conditions.

    Human leukocyte cell          Benlate                  Primary cultures were                        Gupta & Legator
    cultures                                               treated with benomyl.                        1975
                                                           Cells examined in the high
                                                           dose cultures did not show
                                                           a statistically significant
                                                           increase in incidence of
                                                           chromosomal aberrations.

    Table 2  (con't)

    Test Organism                 Test Substance           Results                                      Reference

    Cytogenetics - In Vivo

    Rats                          Benomyl/Fundazol         Bone marrow and cultures of                  Ruzicska et al 1976
                                  50WP                     embryo cells of pregnant
                                                           rats were examined for
                                                           chromosomal aberrations
                                                           after treatment with
                                                           benomyl on days 7 to 14
                                                           of gestation. No increase
                                                           in frequency of cells with
                                                           chromosomal aberrations
                                                           were reported in bone
                                                           marrow cells. Embryonic
                                                           cells had 5 times more
                                                           chromosomal damage at the
                                                           two highest doses (200,
                                                           500 mg/kg) than controls.

    Human                         Benomyl/Fundazol         Peripheral blood cells                       Ruzicska et al 1976
                                  50WP                     from workers at a benomyl
                                                           (Fundazol 50WP) plant were
                                                           examined. No effects attributable
                                                           to benomyl reported.

    Dominant Lethal

    Rat                           Benomyl                  Negative                                     Sherman et al 1975

    Table 2  (con't)

    Test Organism                 Test Substance           Results                                      Reference

    Micronucleus Test

    Mice                          Benomyl                  Dosed by gavage at 250,                      Kirkhart 1980
                                                           500 or 1 000 mg benomyl/kg
                                                           on two consecutive days.
                                                           Reported a statistically
                                                           significant increase in
                                                           number of micronuclei in
                                                           bone marrow from femur
                                                           bones at 48 h in 250 and
                                                           500 mg/kg dose groups and
                                                           1 000 mg group at 24 and
                                                           48 h.

    DNA Damage and Repair

    B6C3F1 Mice and               Benomyl                  Benomyl was tested for DNA                   Tong 1981a,b
    F344 Rats                                              repair using primary
                                                           hepatocyte cultures.
                                                           Benomyl did not induce DNA
                                                           repair in either rat or

    Mitotic Gene Conversion

    S. cerevisiae                 Benlate                  Negative                                     Siebert et al. 1970
                                  Benomyl                  Negative                                     De Bertoldi et al 1980

    A. nidulans                   Benomyl                  Negative                                     De Bertoldi et al 1980

    Table 2  (con't)

    Test Organism                 Test Substance           Results                                      Reference

    Mitotic Crossing-Over

    Differential Toxicity

    Bacillus subtilis             Benomyl                  Negative                                     Shirasu et al. 1978

    Plant Studies

    Allium cepa                   Benomyl                  Negative                                     Dassenay & Meyer 1973

                                                           Positive                                     Richmond & Phillips 1975
    Chromosome Nondisjunction
    Yeast and Fungi

    A. nidulans                   Benlate                  Positive                                     Hastie 1970

                                  Benomyl                  Positive                                     Kappas et al. 1974

                                                           Positive                                     De Bertoldi &
                                                                                                        Griselli 1980

    Microtus oeconomus            Benlate                  Inconclusive                                 Tates 1979
                                  Benomyl                  Inconclusive                                 Tates 1979
        scored for the number of sister chromatid exchanges (SCE) and number
    of chromosomes. A total of 50 cells were scored for each group. The 5
    and 10 g/ml dosage did not allow sufficient numbers of second
    division metaphases to occur for an evaluation.

         The number of SCE in the ethyl methane-sulphonate group was
    triple that of the negative controls, while the three non-activated
    benomyl groups had one-third more SCE than controls. In the
    experiments with activated benomyl, the DMN positive controls had
    approximately twice the number of SCE found in negative controls. The
    benomyl groups had increased numbers of SCE (by approximately 25 to
    100 percent above controls). The number of SCE per cell was increased
    by one sixth to one half above that for negative controls for non-
    activated benomyl. The activated fungicide increased the number of SCE
    by approximately 15 to 100 percent over that seen in controls. Benomyl
    proved weakly positive in this study (Evans & Mitchell 1980).

         A mutagenicity assay with a Chinese hamster ovary cell line,
    which can demonstrate mutations at the gene locus coding for
    hypoxanthine-guanine phosphoribosyl transferase (HGPRT) was conducted
    using benzo(a)pyrene and ethyl methane sulphonate as positive
    controls, as well as a vehicle control (DMSO) Benomyl was added to
    test cultures with or without metabolic activation. Resistance of
    cells to 6-thioguanine was used as the indicator of mutagenic effects.

         A dose-related cytotoxic response was more evident in cultures
    exposed to the chemical without activation. No statistically
    significant differences in mutation frequency were noted in cultures
    treated with activated or nonactivated benomyl at concentrations
    ranging from 17 to 172 M. Positive controls demonstrated that the
    test system was sensitive and cell survival was greater than 10
    percent at most concentrations used. Benomyl was not mutagenic under
    these test conditions (Fitzpatrick & Krahn 1980).

    DNA repair

         DNA repair assays in rat or mouse hepatocyte primary cultures
    (HPC) were evaluated for benomyl along with dimethylnitrosamine,
    dimethylformamide, fluorene and 2-aminofluorene, which were used as
    positive controls. The liver was removed and primary cultures were
    initiated with hepatocytes from B6C3F1 mice or 344 rats. Benomyl and
    tritiated thymidine (10 Ci) were added to the culture medium. After
    18 to 20 h incubation they were fixed and examined microscopically for
    morphological changes and absence of s-phase nuclei indicative of
    cytotoxicity. Autoradiographic techniques are used to determine the
    number of nuclear grains induced by test chemicals. Background counts
    were obtained by evaluating three nuclear-sized areas in the
    cytoplasm; these values were averaged and subtracted from the number
    counted in the nucleus to obtain a net value for each nucleus.

         Benomyl did not induce DNA repair in rat or mouse hepatocytes.
    The dimethylnitrosamine and 2-amine fluorene increased the number of
    nuclear grains from 7 to 15 times the level set as the criterion for a
    positive response (Tong 1981a,b).

    Bacterial tests

         Benomyl and Benlate were tested for mutagenic activity according
    to the plate incorporation procedure, essentially as described by Ames
    et al. (1975). Salmonella typhimurium strains used included
    TA1535, TA1537, TA98 and TA100. DMSO was the solvent used for benomyl
    and water was the solvent for Benlate. One Benlate sample, tested at
    concentrations up to 1 200 g/plate, was not mutagenic under the test
    conditions (DuPont 1977). At concentrations up to 500 g/plate benomyl
    (technical grade) exhibited slight mutagenic activity in TA1537, but
    only in the presence of the activation system. The induced reversion
    frequency was 3.8 times the control value and the average revertants/n
    mole value was 0.06 (Russel 1978). Benomyl was tested with and without
    activation by three different liver microsomal enzyme preparations
    (mouse liver S-9 mixes containing 0.8 or 2.5 mg of protein per plate,
    and rat liver S-9 mix containing 3.5 mg of protein/plate). Only one of
    two trials with strain TA1535 showed a statistically significant dose-
    related trend in the induction of mutations. Dose group differences
    were not significantly greater than controls. Benomyl at dosages as
    high as 250 g/plate was not mutagenic under the test conditions
    (Donovan and Krahn 1981). An analytical grade sample of benomyl was
    not mutagenic at concentrations up to 500 g/plate (Russell 1978).

         A series of spot tests was conducted with paper disks containing
    benomyl. The disks were placed on media, which were streaked with
    S. typhimurium (strains TA1535, TA1536, TA1537, or TA1538)
    or Streptomyces coelicolor. Benomyl was used alone or
    combined with liver microsomal enzymes for activation and
    methylnitrosonitroguanidine was used as a reference mutagen. Disks
    contained 20 g or 500 g benomyl for the S. typhimurium and
    S. coelicolor tests, respectively. No mutagenic activity was noted
    for benomyl in these tests (Carere et al. 1978).

         The mutagenic activity of benomyl, BenlateR and Fundazol 50 WP
    was investigated in a series of spot, liquid culture and host
    mediated assays in strains his G46, TA1530, TA1535 and TA1950 of
    S. typhimurium. Doses of 0.25 to 10 000 g/ml in overlay spot
    test and liquid culture treatments were negative. Nice given
    subcutaneous injections of 500 mg/kg did not produce mutations in
    S. typhimurium strain his G46. No mutagenic activity was
    observed in S. typhimurium TA1950 when rats and mice were orally
    dosed with 4 000 mg/kg benomyl (Ficsor et al. 1978).

         In similar bacterial assays with benomyl in S. typhimurium
    TA98, TA100, TA1535, TA1537 and TA1538, there was doubtful mutagenic
    activity in the base substitution sensitive strains (TA100 or TA1535)
    for benomyl (1 to 325 g/plate) with and without liver microsomal
    activation. Responses were defined in terms of the ratio of the number
    of revertants observed on treated plates to that found on untreated
    control plates and a doubtful response was defined as a ratio of 1.5
    to 2 (Ercegovich & Rashid 1977; Rashid & Ercegovich 1976).

         BenlateR was tested for mutagenic activity in
    S. typhimurium and Escherichia coli, using a simplified
    fluctuation assay. BenlateR was mutagenic in the base pair
    substitution specific strain, TA1535, but not in the frameshift
    specific strain, TA1538. It was also mutagenic for E. coli strain
    WP2 uvrA, which lacks excision repair, but not for E. coli
    strain WP2 (DNA repair proficient) and CM611 (misrepair and excision
    repair deficient). With both S. typhimurium and E. coli, the
    degree of mutagenic activity observed at concentrations between 0.125
    to 1 g/ml was similar when tested at concentrations greater than
    1 mg/ml BenlateR was not mutagenic (Kappas et al. 1976).

         Benomyl was non-mutagenic in S. typhimurium TA1535, TA1537,
    TA1538, TA98 and TA100, and E. coli WP2 hcr. Concentrations
    between 5 and 1 000 g/plate were tested in a plate incorporation
    assay with DMSO as the solvent both in the presence and absence of an
    activation system, which included a 9 000 x g supernatant fraction of
    homogenized livers from Aroclor 1254-treated Sprague Dawley rats
    (Shirasu et al. 1978).

    Tests with yeast and fungi

         Benomyl added to cultures of an Aspergillus nidulans strain,
    which is excision repair deficient, induced back mutations to biotin
    and pyridoxin-requiring strains. Mutagenic activity was observed at
    0.25, 0.3 and 0.4 g/ml but there was a plateau of positive response
    rather than a linear dose-response through zero concentration. Benomyl
    dissolved in ethanol was not mutagenic in either of the repair-
    proficient strains (Kappas & Bridges 1981).

         No mitotic gene conversion was noted in diploid strains of
    Saccharomyces cereviciae or A. nidulans exposed to as much as
    3 200 ppm or 200 ppm benomyl, respectively. Benomyl was activated with
    a mouse liver microsomal fraction; survival at the highest level
    tested was equal to 83 percent and 51 percent for S. cereviciae
    and A. nidulans, respectively (de Bertoldi et al. 1980).

         In another study with A. nidulans exposed to benomyl, no
    non-disjunction or crossing over were reported. An increased frequency
    of segregants occurred, probably due to benomyl's spindle-inhibiting
    effects (de Bertoldi et al. 1980).

    Insect tests

         Gamma radiation was used as the reference mutagen. Treated and
    untreated adult male Drosophila melanogaster were mated with
    virgin females so that at least nine broods of offspring were produced
    from each male. Each male was mated with two untreated females for two
    to three days following treatment. At that time, a subsequent mating
    was conducted. The offspring were classified by sex and phenotype
    (regular or exceptional). Some of the exceptional offspring could have
    resulted from exchanges between the X and Y chromosomes in the parent
    male rather than from whole or partial chromosome loss. Exceptional
    offspring resulting from chromosome loss, breakage or non-disjunction
    could, therefore, not be clearly distinguished from those resulting
    from the sex chromosome exchanges.

         No deaths resulted from the treatments. However, there was an
    increased incidence of sterility in the later broods from treated
    Oregon-R males, but no effect in treated yw+BsY+ males. The
    first and second broods result from germ cells which were post-meiotic
    at the time of treatment, those in the third and fourth broods were
    from meiotic germ cells and those in the last broods were from germ
    cells that were premitotic at the time of treatment. No compound-
    related effects were noted when chromosomes were examined for breakage
    in a second set of experiments and the overall incidence of recessive
    lethal mutation reported was 5/4 807 (0.1 percent). The sterility
    observed in broods from matings involving mitotic spermatogonial cells
    is probably consistent with the suspected spindle effects of the
    chemical (Lamb & Lilly 1980).


         Primary cultures of human leukocytes were treated with BenlateR
    in DMSO at 0, 200, 2 000 or 20 000 ppm. Each test solution (0.1 ml)
    was added to 5 ml cultures, which were examined for cells with
    chromosome breaks, deletions and small fragments after exposure. In
    cultures exposed to 0, 200 or 2 000 ppm benomyl, 1.3, 5.8, and 3.8
    percent of the cells examined had chromosomal aberrations. Cultures
    exposed to the highest dose contained fewer dividing cells, owing to
    toxicity. Those cells examined in high-dosed cultures did not show a
    significantly increased incidence of chromosomal aberrations above
    that in control cultures. The mitotic index was not measured nor were
    replicates performed. Thus, the results are difficult to assess,
    particularly regarding toxicity (Gupta & Legator 1975).

         Bone marrow and cultures of the embryo cells of pregnant rats
    were examined for chromosomal aberrations. The rats were given daily
    doses of 0, 25, 50, 200 or 500 mg Fundazol 50WP per kg b.w. by gavage
    on days 7 through 14 of gestation. No increases in frequency of cells
    with chromosomal aberrations were reported in bone marrow. However,

    embryonic cells from rats given 200 or 500 mg/kg/day had five times
    the frequency of cells with damaged chromosomes. The aberrations were
    described as rings, acentric chromatids and translocations (Ruzicska
    et al. 1976).


         Available information demonstrates that benomyl and carbendazim
    have a similar metabolism. Benomyl is rapidly metabolized to
    carbendazim in mammals and is eliminated preferentially in urine as
    methyl 5-hydroxy-2-benzimidazolecarbamate (5-hydroxycarbendazim,
    5-HBC). In rats following intubation, inhalation and dietary
    exposures, benomyl and carbendazim were present in the blood within
    the first six hours, together with comparable levels of 5-HBC. Within
    18 hours after exposure, only 5-HBC was identified in blood.
    Metabolism proceeds via hydroxylation and ester hydrolysis in the
    liver followed by elimination, primarily in the urine (41-71 percent)
    and to a lesser extent in faeces (21-46 percent). There is no
    retention of 14C activity in muscle tissue or fat; only liver and
    kidney demonstrate bound residues identified as 5-HBC.

         Benomyl is not acutely toxic to mammals. It has an acute oral
    LD50 in rats and an acute dermal LD50 in rabbits above 10 000 mg/kg.
    Gross and histopathological examination of many of these animals
    demonstrated a measurable compound-related effect on the male gonads
    at high doses (testicular degeneration, necrosis of germinal
    epithelium and aspermatogenesis).

         Spermatogenesis in pre-pubertal rats was not affected at dose
    levels affecting adult rats. Previous JMPR evaluations have identified
    variations in teratogenic response dependent on the mode of oral
    administration (diet or gavage). The present Meeting reviewed
    additional data, which confirmed the difference in sensitivity
    according to the route of administration in the rat, the dietary NOEL
    for teratogenicity being 6 760 ppm. This dose did, however, induce
    embryotoxicity. In the mouse, gavage studies resulted in terata
    induction at levels above 50 mg/kg. In the rabbit, a limited study did
    not result in induction of terata at 500 ppm in the diet.

         Short- and long-term dietary studies in rats did not demonstrate
    compound-related effects at doses up to and including 2 500 ppm.
    Ninety-day and two-year dietary studies in dogs demonstrated adverse
    effects on the liver at 2 500 ppm, but not at 500 ppm, evidenced by
    increased cholesterol, alkaline phosphatase and GPT levels, by
    decreased total protein and albumin/globulin ratio, and by bile duct
    proliferation and haemosiderosis (see also carbendazim).

         A carcinogenicity study in CD-1 mice at 500, 1 500 and 5 000 ppm
    in the diet showed oncogenicity at all levels. Neoplastic changes
    included lung carcinomas in males, but not in females, at 500 and
    5 000 ppm. There was an increased incidence of hepatocellular
    carcinomas in males at 500 and 1 500 ppm and in females at 500 and
    5 000 ppm. There was no measurable effect on latency period. It was
    concluded that benomyl was hepatocarcinogenic to mice (see also

         Mutagenicity studies with benomyl gave both positive and negative
    results. Benomyl was positive in the micronucleus, yeast, fungi and
    drosophila tests. Conflicting negative and positive results in other
    tests prevented evaluation of the mutagenic potential. The potential
    impact of these results on human health cannot be adequately assessed
    at this time.

         The monographs on benomyl and carbendazim have stated that the
    metabolism of the two compounds is essentially the same, with benomyl
    being converted rapidly to carbendazim in mammals. Accordingly, the
    available data for benomyl and carbendazim should be considered
    collectively for the evaluation of specific studies such as
    teratology, reproduction, chronic toxicity and oncogenicity, taking
    into account the different molecular weights of the two compounds.

         Previous Meetings in 1970, 1973 and 1976, have discussed the
    etiology and pathogenesis of liver tumours in certain strains of mice,
    with particular emphasis on organochlorine pesticides. It was
    recognized that liver tumours are known to develop spontaneously in
    many strains of mice, at relatively high incidence without intentional
    exposure to chemicals. Evidence of such tumours in several strains of
    mice has been found in many of the oncogenicity studies performed with
    benomyl and carbendazim. Furthermore, one strain of mouse used (HOE
    NMR) is known to have a low background incidence of liver tumours
    (1-2 percent) and did not provide evidence of oncogenicity when
    exposed to carbendazim at doses up to and including 5 000 ppm. Two
    additional studies have been carried out in rats using both benomyl
    and carbendazim. Both studies were negative for oncogenicity at doses
    up to and including 2 500 and 10 000 ppm, respectively. The hepatic
    tumours produced in mice, therefore, appear to be a species-related

         The Meeting expressed concern at the equivocal nature of the
    results of a wide range of mutagenicity studies. The possibility that
    conflicting results were due to variations in the type and amount of
    impurities was considered. However, the Meeting received information
    that current levels of the relevant impurities are very low in
    technical materials.

         In view of established no-observed-effect levels determined in
    several studies, including teratology, reproduction and chronic
    feeding, an ADI for both benomyl and carbendazim could be estimated.
    However, a safety factor of 200 was used to reflect the Meeting's
    concern for the paucity of individual animal data for many studies on
    carbendazim, which reflect the toxicity of benomyl.


    Level causing no toxicological effect

    Rat: 2 500 ppm in the diet, equivalent to 125 mg/kg b.w.

    Dog: (see carbendazim)

    Rat: 30 mg/kg b.w./day (teratology)

    Estimate of acceptable daily intake for man

    0-0.02 mg/kg b.w.



    1.   Data on individual animals in studies on carbendazim that have
         been identified in the monograph.

    2.   Additional data to elucidate the mechanism of degenerative
         testicular effects on mammals.

    3.   Elucidation of the variability of the mutagenicity data.


    Ames, B.N., McCann, J. & Yamasaki, E. Methods for detecting
    1975      carcinogens and mutagens with the Salmonella mammalian-
              microsome mutagenicity test. Mutat. Res., 31: 347-364.

    Belasco, I.J. Study showing the absence of acetylcholinesterase
    (undated) inhibition with a wettable powder formulation (50% benomyl).
              Reported submitted to WHO by DuPont. (Unpublished)

    Busey, W.M. Acute dermal LD50 test and dermal irritation test on
    1968a     rabbits using a wettable powder formulation (50% Benomyl)
              with histological addendum. MRO 581-239. Report dd. 6/21/68
              by Hazleton Laboratories, Inc. submitted to WHO by DuPont.

    Busey, W.M. Acute inhalation exposure test in rats using a wettable
    1968b     powder formulation (50% benomyl). MRO 1126. Report dd.
              10/18/68 by Hazleton Laboratories, Inc. submitted to WHO by
              DuPont. (Unpublished)

    Busey, W.M. Teratology study in rabbits using a wettable powder
    1968c     formulation (50% benomyl) MRO 1079. Report dd. 7/15/68 by
              Hazleton Laboratories, Inc. submitted to WHO by DuPont.

    Busey, W.M. Repeated dermal application test on rabbits using a
    1968d     wettable powder formulation (50% benomyl). HLO No. 298-68.
              Report, dd. 12/13/68 submitted to WHO by DuPont.

    Carere, A., Ortali, V.A., Cardamone, G., Torracca, A.M. & Raschetti,
    1978      R. Microbiological mutagenicity studies of pesticides in
              vitro. Mutat. Res., 57:277-286.

    Carter, S.D. Effect of benomyl on the reproductive development in the
    1982      prepubertal male rat. From Thesis, North Carolina State
              University. Submitted to WHO by DuPont.

    Carter, S.D. & Laskey, J.W. Effect of benomyl on reproduction in the
    1982      male rat. Toxicology Letters II: 87-94.

    Colburn, C.W. Skin irritation and sensitization tests on guinea pigs
    1967      using technical benomyl (> 95% benomyl). HLR No. 84-69.
              Report dd. 4/18/69 submitted to WHO by DuPont. (Unpublished)

    Culik, R. at al. Determination of benomyl/methyl-2-benzimidazole
    1981      carbamate (MBC) concentrations in maternal blood and in the
              concepti of rats exposed to benomyl and Benlate by diet.
              Report submitted to WHO by DuPont. (Unpublished)

    Dessenay, B. & Meyer, J.A. Mutagenic effect of benomyl on Fusarium
    1973      oxysporum. Mutat. Res. 21:119-120.

    De Bertoldi, M. et al. Mutagenicity of pesticides evaluated by means
    1980      of gene-conversion in Saccharomyces cerevisiae and in
              Aspergillus nidulans. Environ. Mutagen., 2: 359-370.

    De Bertoldi, M. & Griselli, M. Different test systems in Aspergillus
    1980      nidulans for the evaluation of mitotic gene conversion,
              crossing-over and nondisfunction. Mutat. Res., 74:303-324.

    Donovan, S.M. & Krahn, D.F. Mutagenicity evaluation in Salmonella
    1981      typhimurium using technical benomyl (> 95% benomyl), HLR
              No. 434-81. Report dd. 8/26/81 submitted to WHO by DuPont.

    DuPont. Mutagenic activity of benomyl in the Salmonella/microsome
    1977      assay (50% benomyl as a wettable powder formulation) HLR No.
              819-77. Report dd. 10/14/77 submitted to WHO by DuPont.

    DuPont. Benlate dust exposure survey - blood profile analysis - 23
    1979a     February 1979, with supplement of 15 March 1979. Report
              submitted to WHO by DuPont. (Unpublished)

    DuPont. Benlate dust exposure survey. Report submitted to WHO by
    1979b     DuPont. (Unpublished)

    DuPont. Applicator exposure during filling and spraying of Benlate
    undated   benomyl fungicide - orchard crops. Report submitted to WHO
              by DuPont (Unpublished)

    Ercegovich, C.D. & Rashid, K.A. Mutagenesis induced in mutant strains
    1977      of Salmonella typhimurium by pesticides, 174th American
              Chemical Society National Meeting. (Text of oral

    Evans, E.L. & Mitchell, A.D. An evaluation of the effect of benomyl on
    1980      sister chromatic exchange frequencies in cultured Chinese
              hamster ovary cells, SRI International, August 1980. Report
              submitted to WHO by DuPont (Unpublished)

    Everhart, L.P. & Holt, R.F. Potential Benlate fungicide exposure
    1982      during mixer/loader operations, crop harvest and home use.
              I. Agric. Food Chem. 30:222-227.

    Ficsor, G., Bordas, S. & Stewart, S.J. Mutagenicity testing of
    1978      benomyl, methyl 2-benzimidazolecarbamate, streptozotocin and
              N-methyl-N1-nitro-N-nitro-soguanidine in Salmonella
              typhimurium in vitro and in rodent host-mediated
              assays. Mutat. res., 51: 151-164.

    Fisher, R.L. et al. Dermal absorption and fate of intravenously
    1981      injected (2-14C)-benomyl in the rat. Report submitted to
              WHO by DuPont. (Unpublished)

    Fitzpatrick, K. & Krahn, D.F. Chinese hamster ovary cell assay for
    1980      mutagenicity using technical benomyl (> 95% benomyl), HLR
              No. 438-80. Report dd. 7/15/83 (revised) submitted to WHO by
              DuPont. (Unpublished)

    Frank K.M. Eye irritation tests in rabbits using technical benomyl
    1968      (95% benomyl) and a wettable powder formulation (50%
              benomyl) HLR No. 255-68. Report dd. 11/14/68 submitted to
              WHO by DuPont. (Unpublished)

    Frank, K.M. Skin irritation and sensitization tests on guinea pigs
    1969      using a wettable powder formulation (50% benomyl) HLR No.
              85-69. Report dd. 4/18/69 submitted to WHO by DuPont.

    Frank, K.M. Eye irritation test in rabbits using a wettable powder
    1972      formulation (50% benomyl) HLR No. 233-72. Report dd. 6/22/72
              submitted to WHO by DuPont. (Unpublished)

    Fritz, S.B. Acute oral ALD test in rabbits using a wettable powder
    1969      formulation (50% benomyl) HLR No. 109-69. Report dd. 5/I/69
              submitted to WHO by DuPont. (Unpublished)

    Goldenthal, E.I. et al. Neurotoxicity study in hens using technical
    1978      benomyl (>95% benomyl), with addendum. Report No. 125-028
              dd. 3/3/78 by International Research and Development
              Corporation submitted to WHO by DuPont. (Unpublished)

    Gooch, J.J. Fertility of workers potentially exposed to benomyl.
    1978      Report dd. October 1978 submitted to WHO by DuPont.

    Goodman, N.C. Intraperitoneal LD50 test in rats using technical
    1975      carbendazim (less than 98%). Report from Haskell
              Laboratories submitted to the WHO by DuPont. (Unpublished)

    Gupta, A.K. & Legator, M.S. Chromosome aberrations in cultured human
    1975      leukocytes after treatment with fungicide Benlate. In
              Proc. Symp. Mutagenicity, Carcinogenicity and Teratogenicity
              of Chemicals, Dept. of Atomic Energy, India, pp. 95-103.

    Han, J. C-Y. Metabolism of 14C-labelled benomyl in the mouse and
    1974      hamster. Report submitted to WHO by DuPont. (Unpublished)

    Han, J. C-Y. Metabolism of 2-14C-benomyl in the lactating nanny goat
    1980      (including supplements I and II). Report submitted to WHO by
              DuPont. (Unpublished)

    Hardesty, P.T. Attempts to characterize liver residues from 14C-
    1982      benomyl dosed goat. Report submitted to WHO by DuPont.

    Hastie, A.C. Benlate-induced instability of Aspergillus Diploids.
    1970      Nature, 226: 771.

    Hood, D.B. Fifteen exposure dermal test on rabbits using a wettable
    1969      powder formulation (50% benomyl) HLR No. 211-69. Report No.
              7/30/69) submitted to WHO by DuPont. (Unpublished)

    Hornberger, C.S. Acute dust inhalation test in rats using a wettable
    1969      powder formulation (50% benomyl) with report on
              spermatogenesis effects HLR No. 95-69. Report dd. 4/24/69
              submitted to WHO by DuPont. (Unpublished)

    Jessep, D.C. & Dean, W. Acute delayed neurotoxicity study in chickens
    1979      using technical benomyl (less than 95% benomyl). Report from
              International Research and Development Corporation submitted
              to WHO by DuPont. (Unpublished)

    Jessup, C.D. Acute delayed neurotoxicity study in chickens using
    1979      technical benomyl (>95% benomyl) HLO 674-79. Report dd.
              12/7/69 by International Research and Development
              Corporation submitted to WHO by DuPont. (Unpublished)

    Kappas, A. et al. On the genetic activity of benzimidazole and
    1974      thiophanate fungicides on diploid Aspergillus nidulans.
              Mutat. Res., 26: 17-27.

    Kappas, A. et al. Benomyl - A novel type of base analogue mutagen?
    1976      Mutat. Res., 40: 379-382.

    Kappas, A. & Bridges, B.A. Induction of point mutations by benomyl in
    1981      DNA-repair-deficient Aspergillus nidulans. Mutat. Res.,
              91: 115-118.

    Kavlock, R.J. et al. Teratogenic effects of benomyl in the Wistar rat
    1982      and CD-1 mouse with emphasis on the route of administration.
              Toxicol. Appl. Pharmacol. 62: 44-54.

    Kirkhart, B. Micronucleus test on benomyl (> 9% benomyl), SRI
    1980      International, 12 Feb. 1980. Report submitted to WHO by
              DuPont. (Unpublished)

    Lamb, M.J. & Lilly, L.J. An investigation of some genetic
    1980      toxicological effects of the fungicide benomyl. Toxicology,
              17: 83-95.

    Lee, K.P. The two-year feeding study in dogs with benomyl. Pathology
    1970      Report No. 129-69 dd. 1/6/70 submitted to WHO by DuPont

    Lee, K.P. The two-year feeding study in dogs with benomyl.
    1971a     Supplementary Pathology Report No. 53-71 dd. 7/28/71
              submitted to WHO by DuPont (Unpublished)

    Lee, K.P. The two year feeding study in dogs with benomyl.
    1971b     Supplementary Pathology Report No. 54-71 dd. 7/27/71
              submitted to WHO by Du Pont. (Unpublished)

    Lee, K.P. Testicular changes in control Beagle Dogs. Pathology Report
    1971c     No. 23-71 dd. 4/7/71 submitted to WHO by Du Pont.

    Lee, K.P. The two year feeding study in rats with benomyl.
    1977      Pathology Report No. 66-77 dd. 11/30/77 submitted to WHO by
              Du Pont. (Unpublished)

    Littlefield N.A. Four-hour acute inhalation exposure test in dogs
    1969      using a wettable powder formulation (50% benomyl) HLR
              192-69. Report dd. 7/14/69 by Hazleton Laboratories, Inc.
              submitted to WHO by DuPont. (Unpublished)

    Majkut, J.C. Skin irritation and sensitization tests on guinea pigs
    1966      using technical benomyl (>95% benomyl) HLR No. 174-66.
              Report dd. 9/28/66 submitted to WHO by DuPont (Unpublished)

    Rashid, K.A. & Ercegovich, C.D. New laboratory tests evaluate
    1976      chemicals for cancer or gene damage. Sci. Agric., 23:7.

    Reinke, R.E. Eye irritation test in rabbits using technical benomyl
    1966      (>95% benomyl) HLR No. 81-66. Report dd. 5/26/66 submitted
              to WHO by DuPont. (Unpublished)

    Richmond, D.V. & Phillips, A. The effect of benomyl and carbendazim on
    1975      mitosis in hyphae of Botrytis cinerea Pers. ex Fr. and
              roots of Allium cepa L. Pestic. Biochem. Physiol. 5:

    Russell J.F. Mutagenic activity of technical benomyl (> 95% benomyl)
    1978      in the Salmonella/microsome assay HLR No. 18-78. Report
              dd. 1/20/78 submitted to WHO by DuPont. (Unpublished)

    Ruzicska, P. et al. Study on the chromosome mutagenicity of fundazol
    1976      50WP (50% benomyl) Egeszsegtudomany (Budapest), 20: 74-83.

    Sherman, H. Three-month feeding study in dogs using a wettable powder
    1968      formulation (50% benomyl) HLR No. 269-68. Report dd.
              11/20/68 submitted to WHO by DuPont. (Unpublished)

    Sherman, H. Acute oral LD50 test in rats using technical benomyl (>95%
    1969a     benomyl) and a wettable powder formulation (50% benomyl) HLR
              No. 17-6. Report dd. 1/22/69 submitted to WHO by DuPont.

    Sherman, H. Acute oral ALD test in a dog using technical benomyl (>95%
    1969b     benomyl) HLR No. 168-69. Report dd. 7/3/69 submitted to WHO
              by DuPont. (Unpublished)

    Sherman, H. Long-term feeding study in dogs with 1-butylcarbamoyl-2
    1970      benzimidazole-carbamic acid, methyl ester (INT-1991). Final
              report HLR No. 48-70 dd. 3/17/70 submitted to WHO by DuPont.

    Sherman, H., Culik, R. & Zapp, J.A. Teratogenic study in rats with 
    1970      1-butylcarbamoyl-2-benzimidazolecarbamic acid, methyl ester
              (INT-1991), Benlate; benomyl). Report submitted to WHO by
              DuPont. (Unpublished)

    Sherman, H. et al. Ninety-day feeding study in rats using a wettable
    1967      powder formulation (70% benomyl) HLR No. 11-67. Report dd.
              1/31/67 submitted to WHO by DuPont. (Unpublished)

    Sherman, H. et al. Long-term feeding study in rats with 
    1969      1-Butyl-carbamoyl-2-benzimidazolecarbamic acid, methyl ester
              (INT-1991). Final Report HLR No. 232-69 dd. 8/15/69 and 
              Addendum submitted to WHO by DuPont. (Unpublished)

    Sherman, H., Culik, R. & Jackson, R.A. Reproduction, teratogenic and
    1975      mutagenic studies with benomyl. Toxicol. Appl.
              Pharmacol. 32: 305-315.

    Sherman, H. & Fritz, S.B. Acute oral ALD test in rats using technical
    1969      2-AB (>95% 2-AB) HLR No. 51-69. Report dd. 3/11/69
              submitted to WHO by DuPont. (Unpublished)

    Sherman, H. & Krauss, W.C. Acute oral ALD test and ten-dose subacute
    1966      oral test in rats using technical benomyl (>95% benomyl)
              HLR No. 100-66. Report dd. 7/15/66 submitted to WHO by
              DuPont. (Unpublished)

    Shirasu, Y. et al. Mutagenicity testing in fungicide 1991 (>95%
    1978      benomyl) in microbial systems. Report by the Institute of
              Environmental Toxicology submitted to WHO by DuPont.

    Siebert, D., Zimmerman, F.K. & Lemperle, E. Genetic effects of
    1970      fungicides, Mutat. Res., 10: 533-543.

    Snee, D.A. Acute oral ALD test in rats and ten-dose subacute oral test
    1969      in rats using technical 5-HBC (> 95% 5-HBC) HLR No. 134-69
              with pathology on the acute oral ALD test described in HLR
              No. 43-69. Report dd. 5/27/69 submitted to WHO by DuPont.

    Staples, R.E. Teratogenicity study in the rat using technical benomyl
    1982      (>95% benomyl) administered by gavage and supplement with
              individual animal data HLR No. 582-82. Report dd. 10/1/82
              submitted to WHO by DuPont. (Unpublished)

    Staples, R.E. & Culik, R. Teratogenicity study in the rat after
    1980      administration by gavage of technical benomyl (>95%
              benomyl), Parts I, II and III. Reports submitted to WHO by
              DuPont. (Unpublished)

    Tates, A.D. Microtus oeconomus (Rodentia), a useful mammal for
              studying the induction of sex-chromosome nondisjunction and
              diploid gametes in male germ cells. Environ. Health
              Perspect,, 31: 151-159.

    Tong, C. Hepatocyte primary culture/DNA repair assay on compound 10,
    1981a     962-02 (>95% benomyl) using mouse hepatoctytes in culture,
              HLO 741-81. Report by the Naylor Dana Institute dd. 10/20/81
              submitted to WHO by DuPont. (Unpublished)

    Tong C.  Hepatocyte primary culture/DNA repair assay on compound
    1981b     10-962-02 (>95% benomyl) using rat hepatocytes in culture,
              HLO 742-81. Report dd. 10/20/81 by the Naylor Dana Institute
              submitted to WHO by DuPont. (Unpublished)

    Wiechman, B.E. et al. Long-term feeding study with methyl
    1982      1-(butylcarbamoyl)-2-benzimidazolecarbamate in mice
              (INT-1991) - HLR No. 20-82 Parts I, II and III (>95%
              benomyl). Report dd. 1/26/82 submitted to WHO by DuPont.

    Zwicker, G.M. Acute oral ALD test in rats using technical benomyl
    1965      (>95% benomyl) HLR No. 174-65. Report dd. 12/15/65
              submitted to WHO by DuPont. (Unpublished)




         Information on approved uses of benomyl was available from the
    United States, Algeria, Austria, Bulgaria, Denmark, France, Kenya, the
    Federal Republic of Germany, the Netherlands, Spain, Switzerland, the
    United Kingdom, Turkey, South Africa, Yugoslavia, Australia, Japan,
    China (Taiwan), the Philippines, Indonesia, Chile and Colombia.
    Because of its large volume, it was not practical to tabulate all
    available information, but current registered uses in the United
    States are presented in Table 1 as typical examples (DuPont 1983a).
    Many other fruits, vegetables and commodities are included among the
    registered uses of other countries where they are grown.


         Data on benomyl residues in crops following seasonal treatments
    with Benlate WP applied according to US good agricultural practice
    (GAP) are summarized in Table 2 (DuPont 1983b).

         The results of supervised trials in the United States on head
    lettuce are summarized in Table 3 (DuPont 1983c).

         Supervised trials of foliar treatments (1 or 2 kg/ha) of wheat at
    15 locations in the United States showed no detectable residues
    (<0.05 mg/kg) in grain or in milled fractions (street grade flour,
    red dog flour, bran, shorts, germ). A maximum of 6.8 mg/kg was found
    in wheat straw. The results of extensive seed treatment trials
    involving wheat, oats and barley showed that residues in either grain
    or straw would not be likely to exceed 0.1 mg/kg (DuPont 1983d).

         Data available from Kenya on residues in dried coffee beans 1 and
    12 days after treatment at 1-1.5 kg/ha showed no measurable residues
    (<0.1 mg/kg) (DuPont 1983e).

         Residues of benomyl in hope treated in the Federal Republic of
    Germany with two applications at 0.05 percent were 0.3 mg/kg in green
    hope and 1.08 mg/kg in dried hope after a 29-day preharvest interval
    and 0.51 mg/kg in green hope and 0.42 mg/kg in dried hope after a
    25-day interval (DuPont 1983f).

         Supervised trials in the Federal Republic of Germany at
    recommended levels gave residues of 0.06-0.25 mg/kg for winter
    wheat, 0.03-0.19 mg/kg for summer wheat, 0.06-0.25 mg/kg for oats,
    0.03-0.13 mg/kg for rye and 0.03-2.53 mg/kg for grapes. (DuPont

         Supervised trials in England on tomatoes and cucumbers treated
    at 50-100 g/100 1 and 38 g/100 1 respectively, resulted in residues
    ranging from <0.02 to 1.17 mg/kg in tomatoes and from <0.02 to
    0.5 mg/kg in cucumbers (DuPont 1983h).

         Some test data from England on residues in the grain and straw of
    winter wheat could not be interpreted owing to some anomalous results
    (DuPont 1983i).

         The results of supervised trials in Australia and Japan on a
    variety of crops are summarized in Tables 4 and 5, respectively
    (DuPont Australia 1983; DuPont 1983j).

        Table 1  Registered Uses of Benomyl in the United States

    Crop                               Application                             Pre-harvest
                                                                               interval                 Remarks
                             Rate (kg a.i./ha or      Number                   (days)
                             specified concentration

    Almonds                  1-1.5                    1-2

    Apples                   0.1-0.5                  at 7-14 day              30                       also post-harvest
                                                      intervals                                         uses

    Avocados                 1-2                      3-4 wk                   30

    Beans                    1.5-2                    2                        14                       28 days for lima

    Blueberries              1                        4                        21

    Cabbage                  2                        1-3                      --                       seed crop only

    Cranberries              0.75                     2-5                      3

    Celery                   0.25-0.5                 7-10 day
                                                      intervals                7

    Citrus                   1.5-3                    1-2                      0                        also post-harvest

    Cucurbits                0.25-0.5                 7-14 day                 --

    Grapes                   0.75-1.5                 14-21 day                7                        east of Rocky Mt.

                             1-1.5                    2-4                      7                        west of Rocky Mt.

    Table 1  (con't)

    Crop                               Application                             Pre-harvest
                                                                               interval                 Remarks
                             Rate (kg a.i./ha or      Number                   (days)
                             specified concentration

    Macadamia nuts           1.75                     7-14 day intervals
                                                      through bloom period

    Mangoes                  1-2                      weekly                   14

    Mushrooms                60 g/100 l               2                        2

    Peanuts                  0.25                     7-14 day                 14

    Pears                    0.2-1.0                  7-14 day                 --                       also post-harvest
                                                      intervals                                         uses

    Pecans                   0.5-1                    3-4 wk                   --                       do not apply after
                                                      intervals                                         shucks split

    Pineapple                240-480 g/100 l          --                       --                       post-harvest

    Rice                     1-2                      2                        21

    Soybeans                 0.5-1                    2 at 14-21               35
                                                      day int.

    Stone fruits             0.75-2.0                 1-2                      none                     east of Rocky Mt.
                             1.5 -2.0                 1-2                      none                     west of Rocky Mt.
                                                                                                        also post-harvest

    Table 1  (con't)

    Crop                               Application                             Pre-harvest
                                                                               interval                 Remarks
                             Rate (kg a.i./ha or      Number                   (days)
                             specified concentration

    Strawberries             1                        7-14 day                 --

    Sugarbeets               0.4-0.5                  14-21 day                21

    Sugarcane                30-60 g/100 l            dip for seed             --                       Hawaii

    Tomatoes                 0.5-1                    7-14 day                 --

    Table 2  Benomyl Residues in Crops Following Seasonal Treatments

                                         Application                      Residue (mg/kg) calculated
                                                                                 as benomyl1                    Control
    Crop                                              Number per                                  
                                  Rate                season              Avg.           Range

      nutmeats                    1.1-2.2 kg/ha       1 to 3              <0.1           -                        0.1
      hulls                       1.1-2.2 kg/ha       1 to 3              0.34           0.2 - 0.74               0.2
    Apples2                       45-120 g/100 l      6 to 12             1.7            0.5 - 4.8                0.1
                                                      Post Dip            0.5            0.12 - 0.88

    Apricots                      30-60 g/100 l       2 to 3              4.5            2.6 - 6.5                0.1
                                                      Post Dip            2.9            0.9 - 5.1

    Avocadoes                     1.1-2.2 kg/ha       3 to 6              0.17           0.11 - 0.18              0.2

    Bananas                       0.2-0.3 kg/ha       6 to 9              <0.12
                                  30-60 g/100 l       Post Dip            0.28           0.15 - 0.43              0.1

    Beans                         1.7-2.2 kg/ha       1 to 2              0.3            0.11 - 0.94              0.1

    Bean vine forage              0.6-2.2 kg/ha       1 to 2              12.66          0.1 - 46                 0.2

    Blueberries                   IR-4 petition - not available.

    Cranberries                   0.6-2.2 kg/ha       2 to 5              2.8            0.75 - 6.0               0.1

    Carrots                       0.1-0.6 kg/ha       6 to 11             0.05           <0.05 - <0.05            0.054

    Celery                        0.2-0.6 kg/ha       4 to 11             0.59           0.01 - 2.6               0.1

    Cherries                      30-60 g/100 l       2 to 3              3.2            0.2 - 12.6               0.1
                                  30 g/100 l          Post Dip            1.3            0.5 - 2.3                0.1

    Table 2  (con't)

                                         Application                      Residue (mg/kg) calculated
                                                                                 as benomyl1                    Control
    Crop                                              Number per                                  
                                  Rate                season              Avg.           Range

    Citrus3                       60-105 g/100 l      1 to 5              0.6            0.2 - 1.3                0.4
                                  500 mg/l            Post Dip            0.73           0.54 - 1.26
                                  1000 mg/l           Post Dip            1.1            0.39 - 2.35
                                  1250 mg/l           Post Dip            1.5            1.3 - 1.8
                                  2500 mg/l           Post Dip            3.3            2.7 - 3.9
                                  5000 mg/l           Post Dip            5.0            4.5 - 5.4

    Cucumber                      0.2-0.6 kg/ha       2 to 6              0.39           0.13 - 0.55              0.1

    Grapes                        1.1-1.7 kg/ha       3 to 5              3.2            0.14 - 10.3              0.1

    Mangoes                       1.1-2.2 kg/ha       5 to 17             0.7            0.15 - 3.0               0.1
    Melons                        0.2-0.8 kg/ha       2 to 7              0.29           0.27 - 0.32              0.1

    Mushrooms                     IR-4 petition not available.

    Nectarines                    0.6 kg/ha           1 to 3              1.8            1.6 - 2.2                0.1

    Macadamia Nuts                2.2-2.8 kg/ha       4 to 10             <0.1           -                        0.1

    Peaches                       11-60 g/100 l       1 to 15             2.4            0.2 - 8.2                0.2
                                  30 g/100 l          Post Dip            4.3            3.9 - 4.7                0.2

    Peanuts                       0.2 - 0.6 kg/ha     2 to 13             0.1            -                        0.1

    Peanut hay & forage           0.4-1.1 1.1 kg/ha   3 to 13             7.7            1.4 - 1.6                0.4
                                  0.4-1.1 kg/ha       3 to 13             7.7            1.4 - 1.6                0.4

    Peanut hulls                  0.2-1.1 kg/ha       1 to 13             0.58           0.16 - 0.98              0.4

    Table 2  (con't)

                                         Application                      Residue (mg/kg) calculated
                                                                                 as benomyl1                    Control
    Crop                                              Number per                                  
                                  Rate                season              Avg.           Range

    Pears3                        60-120 g/100 l      3 to 5              2.3            1.7 - 3.2                0.2
                                                      Post dip            0.38           0.19- 0.55

    Pecans                        1.1-1.4 kg/ha       3 to 6              <0.1                                    0.1

    Pineapple5                    500 mg/l            Post dip            6.8                                     0.1
                                  1250 mg/l           Post dip            8.9                                     0.1
                                  2500 mg/l           Post dip            26.7                                    0.1

    Plums (fresh prunes)          30-60 g/100 l       2 to 4              0.8            0.4 - 1.4                0.2
                                  30 g/100 l          Post dip            1.2            0.5 - 1.9                0.2

    Rice                          0.3-1.1 kg/ha       1 to 2              0.49           0.05 - 2.8               <0.054

    Rice Straw                    0.3-1.1 kg/ha       1 to 2              3.52           <0.05 - 9.0              <0.054

    Soybeans                      O.3-1.1 kg/ha       1 to 2              0.05           0.08- 0.05               <0.054

    Squash                        0.4-0.8 kg/ha       2 to 5              0.3            0.10 - 0.50              0.1

    Strawberries                  30-60 g/100 l       3 to 7              1.1            0.43 - 2.6               0.4

    Sugarbeet roots               0.2-0.6 kg/ha       3 to 6              <0.1           -                        0.1
    Sugarbeet tops                0.4-1.1 kg/ha       1 to 6              1.3            0.15 - 4.7               0.1

    Tomatoes                      15-120 g/100 l      1 to 9              1.1            0.1 - 4.8                0.4

    Table 2  (con't)

                                         Application                      Residue (mg/kg) calculated
                                                                                 as benomyl1                    Control
    Crop                                              Number per                                  
                                  Rate                season              Avg.           Range

    Wheat grain                   0.3-1.4 kg/ha       1 to 2              0.06           <0.05 - 0.23             <0.054

    Wheat straw                   0.3-1.4 kg/ha       1 to 2              1.5            <0.05 - 6.8              <0.054

    Lettuce                       1.1-3.4 kg/ha       1 to 6              2.26           <0.05 - 7.5              <0.054

    1    Residue data is based on fluorometric/colorimetric procedure by Pease and Holt, unless otherwise indicated;

    2    Bananas - 0.1 mg/kg found in pulp from pre- or post-applications or a combination of these;

    3    Pre and postharvest applications;

    4    Residue analysis by liquid chromatographic method of Kirkland;

    5    Postharvest application;

    6    Average of both trimmed and untrimmed lettuce.

    Table 3  Benomyl Residues in Lettuce from Supervised Trials
             in the United States

                                      Application                                      Residue (mg/kg)1
    Location                      Rate (kg/ha)   Number         (days)              Untrimmed      Trimmed

    Scottsdale                    1              5              9, 14, 22           0.67-3.0       <0.05-1.2
                                  2              5              9                   1.1-4.0        <0.05-0.72
                                  1              5              9
                                  2              5              9

    Tacno                         1              5              7                   5.8-7.6        2.7-5.3
                                                 5              14,22               0.98-7.5       0.52-4.7
                                  2              5              14,21               10-19          0.69-7.2

    New York
    Fulton                        2              3              4-22                <0.05-2.7      <0.05-0.17
                                  1.5            3              7                   --             <0.05
                                  3.0            3              15                  --             <0.05-0.06
                                  1.5            4              7                                  0.08
                                  2.0            4              7                                  <0.05
                                  3.0            4              7                                  0.09

    Hannibal                      2              4              7                                  <0.05

    Salinas                       1              2-4            9,22                               <0.05-0.362
                                  2              3              9,22                               <0.05-0.752

    New Jersey
    Bridgeton                     0.5            3              14
                                  1.0            1              14                                 3.72

    Table 3  (con't)


                                      Application                                      Residue (mg/kg)1
    Location                      Rate (kg/ha)   Number         (days)              Untrimmed      Trimmed

    Buena                         1              3              1-13                               0.09-182
                                  2              3              1-13                               0.70-182

    1    Measured as carbendazim by high performance liquid chromatography (HPLC).

    2    As received - number of wrapper leaves undefined.
        Table 4  Residues of Benomyl from Supervised Trials on Crops in

                                                     Residues  Pre-harvest
    Crop            Rate and type      Number        (mg/kg)   interval

    Mangoes         25 g a.i./100 l    6             0.13      0
                                       11            0.17      0
                    25 g+0.5 g/l dip   6             1.13      0
                    25 g+0.5 g/l dip   11            2.1       0
                    0.5 g/l dip        1             2.41      0
                                       1             1.82      0
                                       1             1.53      0

    Rockmelons      525 mg/kg dip      1             1.244
                    940 mg/kg dip      1             1.844
                    210 mg/kg dip      1             0.66
                    405 mg/kg dip      1             0.97
                    615 mg/kg dip      1             1.23
                    790 mg/kg dip      1             1.57
                    985 mg/kg dip      1             1.90
                    397 mg/kg dip      1             1.60

    Strawberries    650-1 300 g/ha     9 at 14-day   2.8-9.8   1-7

    Citrus          0-1 000 mg/l dip   1             n.d.-1.7

    Grapes          0.5-1 kg/ha        4             0.3-1.8   0-5

     grain          250-1 000 g/ha     4             <0.05     0-28
     foliage        250-1 000 g/ha     4             4-31      0-28
     straw          250-1 000 g/ha     4             0.6-5.6   0-28

    1    36 hours after dip.
    2    5 days after dip.
    3    7 days after dip.
    4    <0.1 mg/kg in edible part.

        Table 5   Benomyl Residues from Supervised Trials on Crops in Japan


    Crop                          Application              Interval after
                                                           last application    Residue range
                        Rate & type              Number    (days)              (mg/ha)

    Rice (brown)        200 g/100 l soak         1         146                 <0.03-0.03
                        0.5% seed coat           1         146                 <0.03-0.04

    Rice straw          200 g/100 l soak         1         146-180             0.06-0.07
                        0.5% seed coat           1         146-180             0.06-0.07
                        0.2-1 kg/100 l           3         122-138             <0.04-0.07

    Cabbage             50 g/100 l               6         7-21                <0.05-0.06

    Lettuce             50 g/100 l               2         3-14                0.02-1.10
                        50 g/100 l               4         3-14                0.03-1.58
                        50 g/100 l               6         3-14                0.03-0.77

    Cucumber            50 g/100 l               1-3       1-7                 0.10-0.75
                        200 g/100 l              2-3       14-45               0.07-0.38

    Strawberry          200 g/100 l              1-2       156-268             0.02-0.16

    Tomato              50 g/100 l               3-5       1-14                0.20-0.45
                        50 g/100 l               2-3       14-43               <0.02-0.38

    Watermelon          50 g/100 l               5         1-19                0.03-0.05

    Asparagus           50 g/100 l               5-6       259-315             <0.05

    Onion               50 g/100 l + dip         7         1-7                 <0.04-0.025
                        5 kg/100 l dip           1         112-142             0.02-<0.04

    Sugarbeet           50 g/100 l               2-4       14-21               <0.008-2.02

    Grape               50 g/100 l               1-5       30-122              <0.02-3.67

    Citrus              25-50 g/100 l            1-3       1-14                0.004-1.31

    Citrus juice        25-50 g/100 l            1-3       1                   0.004-0.03

    Peach               50 g/100 l               3-5       1-3                 0.01-1.13

    Pear                50 g/100 l               6         1-7                 0.03-0.15

    Table 5 (continued)


    Crop                          Application              Interval after
                                                           last application    Residue range
                        Rate & type              Number    (days)              (mg/ha)
    Cherry              33 g/100 l               2         14                  0.30-0.58

    Chestnut            50 g/100 l               6         1-7                 0.01-0.25

    Kidney bean         100 g/100 l              2-4       7-21                0.04-0.37

    Tea                 50 g/100 l               1-2       7-28                0.50-35.2

    Wheat               50 g/100 l               1         250-259             <0.02-<0.05

    Potato              0.4% seed coat           1         142-152             <0.02-<0.03

    Sweet potato        200 g/100 l              1         3-6 mo.             0.99-1.69
                        5 kg/100 l dip           1         117-141             <0.02-<0.04
                        0.4% seed coat           1         117-141             <0.02-<0.04

    Taro                5 kg/100 l dip           1         162                 0.06-0.08

    Konnyaku            1-2 kg/100 l             1         150-176             <0.05-0.05

    Shiitake            100 g/100 l              6         27-28               <0.04-0.05

    Enokitake           100-250 mg/l             1         45-55               <0.04-0.28
                        nursery dip

    Namekotake          0.02-0.04%               1         104-131             <0.05-<0.06

    In soil

         Under anaerobic conditions in two soil types, 14C-labelled
    benomyl was degraded only to carbendazim (methyl
    benzimidazolecarbamate, MBC) and a small amount of 
    2-amino-benzimidazole (2-AB). Incorporation of the label into 
    soil humus was shown by fractionation studies (Han 1983a).

         When benomyl was applied to flooded rice fields at recommended
    rates water samples taken at various times showed residues (as
    benomyl) from <0.02 to 0.05 mg/kg. Discharge water samples were in
    the same range. Total residues (benomyl, MBC, and 2-AB) in muds ranged
    as high as 3.8 mg/kg, indicating adsorption on soil particles (DuPont

         The stability of benomyl (14C-labelled) suspensions in water
    was studied as a function of Ph, time and temperature. At pH 7.3 and
    25C, no STB (3-butyl-s-triazino(1,2,a-benzimidazole-2,4(1H,
    3H)dione), BUB 2-(3-butylureido)benzimidazole or 2-AB (<0.1
    percent) was formed during 6 h. After 49 h 0.9 percent STB was
    present. Similar results were obtained at pH 9. At 50C, 4 to 6
    percent conversion to STB was observed in 1 h and 50 percent by
    24-49 h. Less than 1 percent BUB was found after 49 h (Baude 1983a,b).

         Benomyl was shown to inhibit drastically nitrification in soil at
    high levels (1 000 mg/kg) as measured by nitrate production, even
    after incubation for 30 days (Ramakrishna et al. 1979).


         Apples were dipped into a suspension of 14C-benomyl (WP), air
    dried and exposed on a window sill. Aliquots of a dried suspension on
    glass plates were similarly exposed. After 16 days, 34 percent and 17
    percent of the residue on apples and glass, respectively, was parent
    compound and the remainder was MBC (Gardiner 1983). In a similar
    experiment using oranges and glass plates with outdoor exposure, 61
    percent and 19 percent of the parent compound remained on oranges and
    glass, respectively after 15 days. The remainder was again MBC. Juice
    from oranges exposed for 15 days contained only 0.05 mg/kg (Baude
    1983c). Oranges and apples were treated with a wax coating containing
    1 400 mg/kg 14C-Benlate, giving 10 mg/kg benomyl on oranges and
    8 mg/kg on apples. After one week, the surface residue consisted of
    only benomyl or MBC; no STB or BUB was formed (Baude 1983d).

    In animals

         A lactating female goat was given five consecutive daily doses of
    2-14C-benomyl by capsule at a rate equivalent to 36 mg/kg in the
    total daily diet. At sacrifice, 24 h after the last dose, small
    amounts of radioactivity were detected in the liver (3.8 mg/kg),
    bladder (4.5 mg/kg) and kidney (0.09 mg/kg). Activity in muscle and
    fat was equivalent to <0.01 mg/kg. Most of the recovered
    radioactivity (96 percent) was eliminated in the urine and faeces (Han
    1983b). Incubation of liver tissue with either protease or amylase
    failed to release any benomyl metabolites other than methyl 
    5-hydroxy-2-benzimidazolecarbamate. Further attempts to characterize 
    the liver residues were not successful, indicating that the 
    14C-residues were strongly bound or incorporated into the tissue 
    (Hardesty 1983).

    In processing and storage

         In simulated cooking experiments, fresh green beans were
    fortified at the 2 mg/kg level with 2-14C-benomyl and boiled in water
    for 30 min. Control water without beans was also boiled. Slightly more
    than half of the residual was found in the water (as MBC) with the
    remainder in the beans. This residue was identified as MBC
    (99 percent) and a trace of 2-AB (Holt 1983).

         Residue studies were conducted on soybean-based products such as
    infant formulas, vegetable oil, salad dressing, etc. No residue
    (<0.05 mg/kg as benomyl) was detected in any of the samples (DuPont
    1983 1).


         The residue data from supervised trials were mainly based on
    the method of Pease and Holt (1971). A high performance liquid
    chromatographic (HPLC) method has since been developed that can
    distinguish between benomyl, MBC and 2-AB on apple foliage without
    clean-up. This procedure seems promising for further development and
    application (Chiba & Veres 1980).


         A market-basket analysis programme was conducted on fresh, frozen
    and canned foods derived from crops normally treated with benomyl pre-
    or postharvest. Eighteen food items from retail outlets in ten cities
    in the United States were analysed for benomyl plus MBC as MBC using a
    procedure with a limit of determination of 0.05 mg/kg. The foods
    analysed were cucumbers, pickles, apples, applesauce, canned and fresh
    pears, celery, canned grape juice, tomatoes, canned tomato paste,
    puree and sauce, canned peaches, canned and frozen green beans,
    strawberries, frozen orange juice concentrate, dried prunes, dried

    apricots and rice. Of 227 food items analysed, 173 (76 percent) had no
    detectable residues. Of the 54 samples having detectable residues, 26
    had 0.1 mg/kg or less and three had more than 0.5 mg/kg. The highest
    level found was 0.72 mg/kg on one sample of dried apricots (Baude


         The following MRLs were reported to the Meeting (DuPont 1981,


    Country                  Crop                                    MRL (mg/kg)

    Australia                mushrooms, ginger, litchi, citrus       10
                             (postharvest dip)
                             strawberries                            6
                             pome and stone fruits, mangoes          5
                             (postharvest dip)
                             avocados and vegetables                 3
                             grapes, mangoes (pulp) (post-           2
                             harvest dip and rockmelons
                             (postharvest dip)
                             bananas                                 1
                             peanuts and water                       0.2
                             sugarcane (preplanting)                 0.1

    Belgium                  cereals                                 0.5
                             cucurbits and melons                    0.3
                             pepper                                  0.3
                             all other crops except potatoes         2.0
                             and citrus

    Canada                   apples                                  5
                             apricots                                5
                             beans                                   1
                             blackberries                            4
                             boysenberries                           5
                             carrots                                 5
                             cherries                                5
                             citrus fruits                           10
                             cucumbers                               0.5
                             grapes                                  5
                             melons                                  0.5
                             mushrooms                               5
                             peaches                                 10
                             pears                                   5


    Country                  Crop                                    MRL (mg/kg)

    Canada (con't)           pineapples (edible pulp)                1
                             plums                                   5
                             pumpkins                                0.5
                             raspberries                             6
                             strawberries                            5
                             squash                                  0.5
                             tomatoes                                2.5

    Denmark                  citrus                                  10

    Finland                  citrus                                  10

    France                   apples                                  6
                             bananas                                 1
                             citrus                                  1.5
                             pears                                   6

    Federal Republic         bananas                                 0.2
    of Germany               berries                                 1.5
    (expressed as MBC)       citrus                                  7
                             cucumber                                0.5
                             grains                                  0.5
                             grapes                                  3
                             pineapples                              2
                             stone fruit                             2
                             vegetables                              1
                             other crops                             0.1

    Italy                    apricots                                0.5
                             grains                                  0.5
                             grapes                                  1
                             melons                                  1
                             peaches                                 0.5
                             pears                                   1
                             prunes                                  0.5

    Japan                    beans                                   0.5
                             fruits                                  0.7
                             materials for sugar                     0.7
                             rice                                    0.5
                             tea                                     5
                             vegetables                              0.8


    Country                  Crop                                    MRL (mg/kg)

    The Netherlands          apples                                  2
                             beans                                   2
                             celery                                  2
                             cucumbers                               2
                             gherkin                                 2
                             melon                                   2
                             mushroom                                0.5
                             onion                                   2
                             pears                                   2
                             peppers                                 2
                             scorzonera                              2
                             shallots                                2
                             strawberries                            2
                             tomatoes                                2
                             turnip roots                            2
                             wheat                                   0.5

    Norway                   citrus                                  10

    (province of China)      melon                                   3
                             rice                                    1.5
                             citrus                                  3
                             grape                                   3
                             apple                                   3
                             pear                                    3
                             sugarcane (juice)                       1.5
                             banana                                  1.5
                             mushroom                                1.5
                             papaya                                  1.5
                             tobacco                                 3
                             jujube                                  3
                             asparagus                               0.3

    United Kingdom           Does not establish maximum residue limits

    United States            almonds
                              nutmeats                               0.2
                              hulls                                  1
                             apples2                                 7
                             apricots                                15
                             avocadoes                               1


    Country                  Crop                                    MRL (mg/kg)

    United States (con't)    bananas                                 1
                             beans                                   2
                             bean vine forage                        50
                             blueberries                             7
                             cranberries                             7
                             carrots                                 0.2
                             celery                                  3
                             cherries                                15
                             citrus2                                 10
                             cucumber                                1
                             grapes                                  10
                             mangoes                                 3
                             melons                                  1
                             mushrooms                               10
                             nectarines                              15
                             macadamia nuts                          0.2
                             peaches                                 15
                             peanuts                                 0.2
                             peanut hay & forage                     15
                             peanut hulls                            2
                             pears2                                  7
                             pecans                                  0.2
                             pineapple1                              35
                             plums (fresh prunes)                    15
                             rice                                    5
                             rice straw                              15
                             soybeans                                0.2
                             squash                                  1
                             strawberries                            5
                             sugarbeet roots                         0.2
                             sugarbeet tops                          15
                             tomatoes                                5
                             wheat grain                             0.2
                             wheat straw                             15
                             lettuce                                 10

    Yugoslavia               fruits                                  10
                             vegetables                              5

    1    Postharvest application.
    2    Pre and postharvest applications.

         New information was received on approved uses of benomyl in 22
    countries. Data were available on benomyl residues in crops following
    seasonal treatments according to good agricultural practice in the
    United States, Kenya, the Federal Republic of Germany, England,
    Australia and Japan. The residues in commodities for which carbendazim
    guideline levels have been recorded tend to support those levels, with
    exceptions to be noted later, and can be used to propose additional
    limits for asparagus, chestnuts, pineapples, taro and sweet potatoes.

         Information on the fate of benomyl in soil continues to show that
    the primary degradation product is carbendazim together with a small
    amount of 2-AB. Benomyl is strongly bound to soil and does not enter
    the water in flooded rice fields to any significant extent. Water
    stability is temperature-dependent, leading to 50 percent conversion
    to STB in 48 h at 50C. High levels (1 000 mg/kg) of benomyl in soil
    drastically inhibit nitrification. Photodegradation on surfaces (fruit
    or glass) is slow, with the gradual formation of carbendazim over many

         In feeding studies with a lactating goat given 5 daily doses (by
    capsule) of 14C-labelled benomyl, equivalent to 36 mg/kg in the
    total daily diet, most of the fed benomyl (96 percent) was excreted in
    the urine and faeces, with radioactivity equivalent to only about
    3.8 mg/kg found in the liver, 4.5 mg/kg in the bladder and 0.09 mg/kg
    in the kidney. Only methyl 5-hydroxy-2-benzimidazolecarbamate has been
    identified as a liver metabolite.

         Cooking (boiling) green beans fortified at 2 mg/kg with
    radiolabelled benomyl extracted slightly more than half of the residue
    into water (as carbendazim) with the remainder, also as carbendazim,
    in the beans. Because of the degree of extractability into hot water
    thus demonstrated, no maximum residue level for tea could be

         An analytical survey of soybean-based products such as infant
    formulas, vegetable oils, etc. did not show any measurable residues
    (<0.05 mg/kg).

         The improved method of residue analysis of Pease and Holt (1971)
    remains the one of choice for most commodities for regulatory use,
    although newer HPLC-based methods are available, which show promise
    for future development.

         A market-basket type survey of eighteen food items from retail
    sources in ten US cities showed that 76 percent had no detectable
    residues. The highest residue found was 0.73 mg/kg in dried apricots.

         Information on national maximum residue levels was available to
    the Meeting for the United States, Belgium, Denmark, Finland, the
    Federal Republic of Germany, Italy, Japan, The Netherlands, Norway,
    Yugoslavia, Taiwan province of China, Canada and Australia.

         In 1978 the Meeting agreed to replace guideline levels for
    benomyl by those for carbendazim. Those figures are now converted to
    MRLs on the basis of the establishment of an acceptable daily intake
    for both compounds. On that basis, additional recommended maximum
    residue limits for pineapples of 20 mg/kg, asparagus and taro of
    0.1 mg/kg, chestnuts of 0.2 mg/kg and sweet potato of 1 mg/kg can be
    estimated for carbendazim, based on benomyl supervised trials. The
    data also support increasing the MRLs for carbendazim in wheat straw
    from 2 to 5 mg/kg, in melons from 0.5 to 2 mg/kg and in peanut hulls
    from 0.2 to 1 mg/kg.


         See carbendazim. The following maximum residue limits, amending
    or additional to those of 1978, are proposed for carbendazim, based on
    supervised trials with benomyl. The figures were derived by dividing
    residues expressed as benomyl in the trials data by the conversion
    factor of 1.52.


    Commodity           Maximum residue limits           Preharvest interval on
                        (mg/kg)                          which levels are based

    *pineapples         20                               postharvest dip

    wheat straw         5(increased from 2)              -

    melons              2(increased from 0.5)            postharvest dip

    *sweet potatoes     1                                90

    peanut hulls        1(increased from 0.2)            -

    *chestnuts          0.2                              1

    *asparagus          0.1 **                           260

    *taro               0.1 **                           162

    *    New MRLs
    **   At or about the limit of determination

    Baude, F.J. Benlate benomyl fungicide - stability in aqueous
    1983a       suspensions. DuPont research report. (Unpublished)

    Baude, F.J. The stability of Benlate benomyl fungicide at neutral
    1983b       and alkaline pH levels. DuPont research report.

    Baude, F.J. Examination of 14C-residues on glass and oranges
    1983c       treated with methyl 1 (butylcarbamoyl)-2-14C-
                benzimidazolecarbamate. DuPont research report.

    Baude, F.J. Residues on oranges and apples treated with a wax
    1983d       coating containing Benlate benomyl fungicide. DuPont
                research paper. (Unpublished)

    Baude, F.J. Benomyl crop residues - A United States market basket
    1983e       survey. DuPont research report. (Unpublished)

    Chiba, M. & Veres, D.F. High performance liquid chromatographic
    1980        method for simultaneous determination of residual benomyl
                and MBC on apple foliage without cleanup. J. Assoc. Off.
                Anal. Chem., 63: 1291-1295.

    DuPont.     Information table on examples of residue tolerance in
    1981        countries outside of the United States, August 1981.

    DuPont      Table summarizing registered uses of benomyl in the
    1983a       United States. (Unpublished)

    DuPont      Table summarizing benomyl residues in crops from
    1983b       supervised trials in the United States. (Unpublished)

    DuPont      Benomyl residues in lettuce from supervised trials in the
    1983c       United States. (Unpublished)

    DuPont      Residue data on wheat, milled fractions, oats and barley.
    1983d       (Unpublished)

    DuPont      Data on residues in coffee beans from Kenya.
    1983e       (Unpublished)

    DuPont      Data on residues in hops from the Federal Republic of
    1983f       Germany. (Unpublished)

    DuPont      Data on residues in wheat, oats, rye, and grapes from the
    1983g       Federal Republic of Germany. (Unpublished)

    DuPont      Data on residues in tomatoes and cucumbers from England.
    1983h       (Unpublished)

    DuPont      Data on residues in wheat grain and straw from England.
    1983i       (Unpublished)

    DuPont      Data on residues in crops in Australia. (Unpublished)

    DuPont      Data on residues in crops in Japan. (Unpublished)

    DuPont      Monitoring study- benomyl applied to flooded rice fields,
    1983k       February 1978. DuPont research report. (Unpublished)

    DuPont      Letter of 12-9-80 on research results - benomyl residue
    1983 l      data from soy-bean-based products. (Unpublished)

    DuPont      Information table on maximum residue limits for benomyl
    1983m       in Canada from the Food and Drugs Act and Regulations,
                p. 65c, 3/8/79.

    DuPont      Information table on maximum residue limits for
    1983n       benomyl in Australia from the National Health and Medical
                Research Council, 93rd Session, June 1982.

    Gardiner,   Examination of 14C-residues on glass and apples treated
    J.A.        with methyl 1-(butylcarbomoyl)-2-14C-
    1983        benzimidazolecarbamate. DuPont research report.

    Han, J.     Anaerobic soil metabolism of 2-14C-benomyl and methyl 
    C-Y.        2-14C-benzimidazolecarbamate. DuPont research report.
    1983a       (Unpublished)

    Han, J.     Metabolism of 2-14C-benomyl in the lactating nanny goat,
    C-Y.        with supplements I and II. DuPont research reports.
    1983b       (Unpublished)

    Hardesty,   DuPont document No. AMR-71-82. (Unpublished)
    P.T. 1983

    Holt, R.F.  Benomyl cooking studies. DuPont research report.
    1983        (Unpublished)

    Pease, H.L. Improved method for determining benomyl residues. J.
    1971        & Holt, R.F. Assoc. Off. Anal. Chem., 54: 1399-1402.

    Ramakrishna, C., Gowda, N. Effect of benomyl and its hydrolysis
    1979        products, MBC and AB, on nitrification in a flooded soil.
                Bull. T.K.S. & Environ. Contam. Toxicol., 21: 328-333.

    See Also:
       Toxicological Abbreviations
       Benomyl (EHC 148, 1993)
       Benomyl (HSG 81, 1993)
       Benomyl (ICSC)
       Benomyl (WHO Pesticide Residues Series 3)
       Benomyl (WHO Pesticide Residues Series 5)
       Benomyl (JMPR Evaluation 1995 Part II Toxicological and environmental)