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    PESTICIDE RESIDUES IN FOOD - 1983


    Sponsored jointly by FAO and WHO






    EVALUATIONS 1983





    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


    CARBENDAZIM

    Explanation

         Carbendazim (methyl 2-benzimidazole carbamate) was evaluated by
    the Joint Meetings of 1973, 1976, 1977 and 1978 (FAO/WHO 1974, 1977,
    1978, 1979).1  The data available were not considered adequate for
    the estimation of an acceptable daily intake (ADI). Data necessary for
    estimating an ADI were identified in 1976 and 1978 and listed under
    "Further Work or Information". These data have been provided and
    reviewed in this monograph addendum.

         New, additional, or updated information on use patterns,
    environmental chemistry and plant metabolism was also made available
    to the Meeting, along with new or additional data on crop residues
    from supervised trials.

    TOXICOLOGY

    EVALUATION FOR ACCEPTABLE DAILY INTAKE

    BIOCHEMICAL ASPECTS

    Absorption, Distribution and Excretion

         NMRI mice and Wistar rats were given carbendazim, via
    intragastric incubation, as a single dose of 3 mg/kg b.w. and one of
    300 mg/kg b.w. Urine was collected during the first 6 h, after which
    the animals were killed. Analyses revealed no sex differences. Almost
    all metabolites in urine were conjugated as sulphate esters. Cleavage
    of these conjugates by B-glucuronidase/arylsulphatase released 5-HBC
    as the only extractable metabolite from water. Urine of mice contained
    a higher portion of compounds that remained polar after enzyme
    treatment than the corresponding urine of rats. Polarity was caused by
    a functional group (e.g. phenolic hydroxyl group) that was introduced
    into the MBC molecule by a conjugation reaction. These water-soluble
    compounds were not identified. Essentially the same metabolites were
    found in both mouse and rat urine samples with only quantitative
    differences observed between species (Dorn et al. 1983).

    Effects on Enzymes and Other Biochemical Parameters

         Groups of Wistar-SPP male rats and Swiss-SPF male mice were
    administered carbendazim in the diet at dosage levels of 0 to

              

    1  See Annex 2 for FAO and WHO documentation.

    10 000 ppm for 60 days. The induction of liver enzyme activities by
    carbendazim was examined and compared with a positive control, which
    received phenobarbital sodium (administered via drinking water).

         Growth and food consumption were decreased in rats at 10 000 ppm
    but not in mice administered up to 5 000 ppm in the diet. Relative
    liver weights were increased in rats fed 2 000 and 10 000 ppm and in
    mice receiving 1 000 and 5 000 ppm of carbendazim. Phenobarbital
    groups were similarly affected. Protein concentrations in the total
    liver homogenates and in post-mitochondrial fractions of rate were not
    affected by carbendazim, whereas in mice both fractions were increased
    at 5 000 ppm.

         The feeding of carbendazim to rats at dose levels of 2 000 ppm
    and higher resulted in slight to moderate induction of several 
    drug-metabolizing enzymes of phase 1 (7-ethoxy-coumarin-O-deethylase,
    biphenyl-4-hydroxylase, aniline hydroxylase, 
    4-methoxybiphenyl-N-demethylase and cytochrome-o-reductase). Similar 
    increased activities of phase 2 drug metabolizing enzymes (glucuronyl 
    transferase I and II) and glutathione content were moderately to 
    markedly increased at this dose.

         The feeding of carbendazim to mice at dose levels of 1 000 ppm
    and higher resulted in moderate to marked increases in drug
    metabolizing enzymes of phase 1 (including cytochrome P-450 and
    aminopyrine-N-demethylase). Cytochrome-c-reductase activity was
    decreased. Glucuronyl transferase and glutathione-S-transferase
    activities, along with glutathione content, were slightly increased.

         There were no measurable differences noted between rats and mice
    in regard to the metabolism of the test substance, although exhaustion
    of the detoxification mechanism was more evident in the mouse at the
    higher dose levels. The detoxification and elimination of carbendazim
    and its metabolites proceed more rapidly in the rat than in the mouse.
    This is reinforced by the increased glutathione content in rat liver
    and increased activity of phase 2 enzymes (Falke et al. 1982a,b).

    TOXICOLOGICAL STUDIES

    Acute Toxicity

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

         Gross and histopathological changes were observed in the testes
    and epididymides of male rats orally dosed with carbendazim at doses
    of 1 000 mg/kg b.w. and greater. Testes were small, soft and
    discoloured with greater than 70 percent of the tubules showing
    degenerative changes. Sperm was reduced or absent in the epididymides
    examined.

        Table 1   Acute Toxicity of Carbendazim in Animals
                                                                                                                                           

    Chemical            Species        Sex (Number)        Route          Vehicle             ADL/LD501                     Reference
                                                                                              (mg/kg b.w.)
                                                                                                                                           

    Carbendazim         Rat            M/F (10/dose)       Oral           Corn oil            LD50 > 10 000                 Goodman 1975
    (MBC)               Rat            M (1/dose)          Oral           Peanut oil          ALD > 11 000                  Sherman 1965
                        Rat            M/F (10/dose)       Oral           Sesame oil          LD50 > 15 000                 Kramer &
                                                                                                                            Weigand 1971
                        Rat            M (1/dose)          Oral           Peanut oil          ALD > 17 000                  Sherman &
                                                                                                                            Krause 1966
                        Mouse          M (10/dose)         Oral           Propylene           LD50 > 15 000                 Til & Beems
                                                                          glycol                                            1981
                        Dog            M/F (2/dose)        Oral           Sesame oil          ALD50 > 5 000                 Scholz &
                                                                                                                            Weigand 1972
                        G. pig         M (10/dose)         Oral           Corn oil            LD50 > 5 000                  Dashiell 1975a
                        Mouse          M/F (10/dose)       I.P.           Sesame oil          LD50 > 15 000                 Scholz &
                                                                                                                            Weigand 1972
                        Rat            M (10/dose)         I.P.           0.9% saline         LD50 > 2 000                  Scholz &
                                                                          & Tween 80                                        Weigand 1972

                        Rat            M (6/dose)          Inhal.         Dust                ALC>5.9 mg/l                  Server 1975
                                                           (1 h. )                            (time weighted
                                                                                              concentration)
                        Rabbit         M (10/dose)         Dermal         50/50 Aqueous       LD50>10 000                   Edwards 1974a
                                                                          paste
                        Rat            F (5/dose)          Dermal         Sesame oil          ALD > 2 000                   Kramer &
                                                                                                                            Weigand 1971
    75% wettable        Rat            M/F (5/dose)        Oral           Corn oil            LD50 > 5 000                  Hinckle 1981
    powder
    75% Wettable        Rat            M/F (10/dose)       Inhal.         Dust                LC50 > mg/l                   Nash 1982
    Powder                                                 (4 h.)
    75% Wettable        Rabbit         M/F (5/dose)        Dermal         Physiologic         LD50 > 2 000                  Ford 1982
    Powder                                                                saline
                                                                                                                                           

    1  Based on mg/kg a.i.
        Special Studies on Eye and Skin Irritation

         The eye irritation evaluation of technical carbendazim was
    negative in albino rabbits. The 75 percent wettable powder formulation
    when tested in rabbits produced transient corneal opacity in 6/6
    unwashed and 2/3 washed eyes. Biomicroscopic examination confirmed
    this finding as mild to moderate. Conjunctival irritation (redness,
    swelling, discharge) was also transient. All eyes were normal at day
    4 of the observation period. Irritation response was probably related
    to the inert ingredients in the wettable powder formulation (Edwards
    1974b; Henry 1982).

         A 75 percent wettable powder formulation produced transient
    slight irritation when applied to the intact and abraded skin of
    albino rabbits (Ford 1981a). A 55 percent suspension of the 75 percent
    wettable powder formulation in dimethyl phthalate produced mild
    irritation to the shaved intact skin of albino guinea pigs. A 5.5
    percent concentration produced no irritation (Ford 1981b).

    Special Study on Sensitization

         Albino guinea pigs (10 males) exposed to carbendazim, either
    technical material or a 75 percent wettable powder formulation,
    presented no evidence of dermal sensitization following both
    intradermal injections and repeat applications to shaved intact skin
    (Ford 1981b).

    Short-Term Studies

    Rat

         Groups of ChR-CD male rats (6/dose) were intubated with 200,
    3 400 or 5 000 mg carbendazim/kg/day, five times/week for two weeks.
    Mortality occurred in 2/6 rats at the 3 400 mg/kg dose only. Animals
    at all levels demonstrated gross and microscopic evidence of adverse
    effects on testes and reduction or absence of sperm in the
    epididymides. Testes were small and discoloured, with tubular
    degeneration and evidence of aspermatogenesis. Morphological changes
    were also reported at 3 400 mg/kg for the duodenum, bone marrow and
    liver (Sherman 1965; Sherman & Krauss 1966).

         Groups of ChR-CD rats (16 males and 16 females per group) were
    fed carbendazim (72 percent a.i.) in the diet for 90 days at dosage
    levels of 0, 100, 500 and 2 500 ppm. Animals were observed daily for
    behavioural changes and body weight and food consumption were recorded
    at weekly intervals. Haematological examinations were conducted on 10
    male and 10 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 levels. After
    90-98 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
    rats remaining in each group after 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 or
    haematology. There were no control data for biochemistry, urinalysis
    determinations or differential white blood counts. The average daily
    dose for the high dose group animals was 360 mg/kg b.w./day,
    initially, and 123-152 mg/kg b.w./day at sacrifice. Liver to body
    weight ratio in females at 2 500 ppm was slightly increased compared
    with control rats. There were no effects on testicular weights in any
    of the treatment groups. Microscopic examination of selected tissues
    and organs in the control and high dose groups demonstrated no adverse
    effects attributable to the presence of carbendazim in the diet
    (Sherman 1968).

    Rabbit

         New Zealand Albino rabbits (6 males/group) were treated with
    0 and 2 000 mg/kg of carbendazim, applied as a 50 percent aqueous
    paste to the shaved intact dorsal skin. Material was applied
    repeatedly, six hours/day for ten consecutive days. There were no
    untoward effects on body weight, clinical symptoms, organ weights,
    gross or histopathology of selected organs. There was focal necrosis
    of the epidermis and polymorphonuclear cell infiltration of the dermis
    in 5/6 rabbits exposed to carbendazim. No other effects were observed
    (Dashiell 1975b).

    Dog

         Groups of one-year-old beagles (4 males and four females per
    group) were administered carbendazim (53 percent a.i.) in the diet for
    three months at dosage levels of 0, 100, 500 and 2 500 ppm. The
    2 500 ppm level was reduced to 1 500 ppm because of loss of appetite
    and decreased body weight. However, compound administration was
    interrupted when animals were placed on a control diet for a few days
    and then restarted at the 1 500 ppm dietary level. Therefore, the data
    generated from the high dose group are not considered in the
    evaluation of this study.

         Food consumption and body weight data were recorded weekly.
    Clinical laboratory examinations, including haematological,
    biochemistry and urinalysis measurements 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 cageside observations over the
    course of the study and growth and food consumption were normal,
    except as noted at the high dose level (1 500-2 500 ppm). Urinalysis
    measurements were unaffected by treatment. There were no dose-related
    effects on the haematological measurements. Females at the mid-dose
    level showed a trend toward increased cholesterol levels at 1, 2 and
    3 months compared with pre-test and control. High-dose females had
    similarly elevated cholesterol levels. Organ-to-body weight changes
    were observed for the thymus of low- and mid-dose males and for the
    prostate of mid-dose males. All weights for these organs were
    increased compared with control values. However, only liver, kidney
    and testes were examined histologically in low- and mid-dose group
    dogs. Limited histopathology data did not indicate compound-related
    effects (Sherman 1970).

         Groups of beagles (four males and four females per group) were
    administered carbendazim in the diet at dosage levels of 0, 100, 300
    and 1 000 ppm for 13 weeks. The 1 000 ppm level was increased to
    2 000 ppm after six weeks of treatment. Body weights, haematological
    and blood chemistry measurements, urinalysis and liver/kidney function
    tests were examined periodically during the test. Gross and
    microscopic examinations of all animals were performed at the
    conclusion of the study.

         There were no reported compound-related effects on clinical
    behaviour, body weight, food consumption, haematology, kidney function
    (phenol red excretion) or liver function (BSP retention) examinations.
    Blood chemistry measurements were normal, except for a slight decrease
    in albumin in mid- and high-dose males at 12 weeks. These values
    differed from week 0 measurements only in high-dose males. Urinalysis
    was normal except for a high bacteria count in high-dose females at
    week 13. Blood clotting time was slightly reduced in high-dose dogs at
    week 12. There were slight increases in relative liver and thyroid
    weights and a decrease in relative heart weights in the 2 000 ppm
    group compared with control. There were no microscopic changes in
    these organs or any other organs that could be associated with
    treatment. There was an increase in submucosal lymphocytic infiltrates
    in female dogs in all groups, which was significant at the high dose.
    Carbendazim appeared to be without adverse effects on beagles when
    incorporated in the diet for 13 weeks at dietary levels of 300 ppm or
    less (Til et al. 1972). (NOTE: All measurements for males and
    females were combined and averaged. This practice can complicate
    interpretation of the results when there are slight or marginal
    effects in one sex, such as in this study.)

    Special Study on Reproduction

    Rat

         A one-generation reproduction study in rats was performed with 24
    male and 24 female rats that had been removed from a 90-day dietary
    feeding study. Dietary levels of carbendazim administered were 0, 100,
    500 and 2 500 ppm. There were six male and six female rats per group.
    After each female had been exposed to three males from the same dosage
    group they were separated to produce the F1A generation. Litters were
    reduced to 10 pups/litter on the fourth day after birth. The F0
    animals were mated again after approximately one week in order to
    produce the F1B litter. Reproduction indices, litter data at birth
    and on days 4, 12 and 21 were recorded, along with body weights at
    weaning.

         Data presented were extremely limited and submitted as group data
    only. There were no pregnancies at 100 ppm for either F1A or F1B
    matings. There were no apparent effects on the reproduction indices or
    weanling weights. However, the fertility index for all groups, which
    was 33-67 percent, prevents any meaningful interpretation of the data
    (Sherman 1968).

         Groups of ChR-CD rats (three male and 16 female rats/group; high-
    dose group was 20 females) were fed carbendazim in the diet at dosage
    levels of 0, 100, 500, 5 000 and 10 000 ppm and subjected to a
    standard two-litter per generation, three-generation reproduction
    study. Animals were fed from 21 days of age until 100 days of age,
    when they were mated to initiate the study. Number of matings,
    pregnancies and young in each litter at birth, and on days 4, 12 and
    21 were recorded, along with body weights of pups at weaning. Litters
    were culled to 10 pups/litter on day 4. After one week, F0 parents
    were mated again to produce the F1B litters, after the F1A had been
    sacrificed. The F1B litters were maintained on their respective diets
    for 110 days and then mated to produce the F2A and F2B litters. The
    F3A and F3B litters were similarly produced. Gross and
    histopathological examination of selected tissues and organs were
    performed on two males and two females in each of five litters from
    the control, 5 000 and 10 000 ppm dose group pups from the F3B
    litter.

         Reproduction indices, including mating, fecundity, fertility,
    gestation, viability and lactation, were calculated and compared with
    control values. There were no compound-related effects on any of the
    reproduction indices other than reduced average litter weights at
    5 000 and 10 000 ppm in all generations at weaning. Histopathological
    examination of F3B weanlings did not reveal any effects that were
    considered compound related. MBC is considered to be without adverse
    effects on reproduction in the rat when administered in the diet at
    dose levels up to and including 500 ppm (Sherman 1972).

         Carbendazim was administered to groups of Wistar Rats (10 males
    and 20 females/group) at dietary levels of 0, 150, 300 and 2 000 ppm
    for three generations. Two successive litters were reared from each
    female. General condition and behaviour were routinely observed and
    individual body weights were recorded throughout the study. The number
    of pups in each litter were recorded and culled to eight on day 1.
    Total weight of each litter was measured at days 1, 10 and 20. The
    F1A and F2A litters were discarded at weaning and the F1B and
    F2B litters were used to produce succeeding generations. The F3A
    offspring were selected for use in a teratology study, while F3B
    offspring were used in a 4-week short-term toxicity evaluation.

         Health and body weight gain were not affected by carbendazim.
    However, treatment groups weighed significantly more than controls in
    all generations. There were no compound-related effects on fertility
    or survival at birth, day 10 or day 20. Litter size was not affected
    by treatment, except for a marginal decrease in F2A litters in all
    dose groups. There were no differences in the F2B litters at 300 and
    2 000 ppm; however, there was a decrease in litter size and increase
    in mortality at birth at 150 ppm. Birth weight during the lactation
    period was comparable among all groups. There were no gross
    abnormalities related to treatment.

         Autopsy of rats in the four week short-term feeding study
    demonstrated increased relative liver weights and decreased relative
    spleen weights in females fed 2 000 ppm. There were also significant
    decreases in relative ovarian weights for females in all dose groups.
    Histopathology of the livers did not indicate any compound-related
    changes. There was no histopathology of the other organs presented.

         There was no maternal or feto-toxicity evident in the teratology
    portion of the study. There were similarly no differences in visceral
    anomalies at 0 or 2 000 ppm (only groups examined). Thoracic vertebral
    bodies were reduced at 2 000 ppm and a significant reduction of the
    cervical vertebral bodies at 2 000 ppm. However, controls presented
    more significant changes throughout with regard to absent or delayed
    ossification of skeletal structures.

         Although there were no apparent adverse effects on reproduction
    and no teratogenic effects at dietary levels of carbendazim up to and
    including 2 000 ppm, there were no individual animal data presented.
    Histopathology of animals in the four-week study was incomplete and
    did not include evaluations of spleen or ovaries. Such additional data
    are needed to confirm the absence of adverse effects in this three-
    generation reproduction study in rats (Koeter et al. 1976).

    Special Studies on Teratogenicity

    Rat

         Groups of ChR-CD rats (27-28 pregnant rats/group) were
    administered carbendazim (53 percent a.i.) in their diet at dosages of
    0, 100, 500, 2 500, 5 000, 7 500 and 10 000 ppm, from day 6 through
    day 15 of gestation. Average doses were equivalent to 0, 8.9, 45.9,
    218.4, 431.6, 625.5 and 746.9 mg/kg day, respectively. On day 20 of
    gestation all pregnant animals were sacrificed and foetuses delivered
    by Caesarean section.

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

         There was no mortality, no adverse effect on body weight or
    clinical signs of toxicity. Food intake was reduced in the 10 000 ppm
    group during the period the test diet was administered, but returned
    to comparable control levels from days 16 to 20. The data related to
    reproduction (implantation sites, resorption sites and live/dead
    foetuses) were not adversely affected by carbendazim. There were no
    external or internal abnormalities reported that were considered
    compound related. There was no individual litter data presented. It
    was concluded that carbendazim was not teratogenic when administered
    to ChR-CD rats at dietary levels up to and including 10 000 ppm during
    the critical period of organogenesis (Sherman et al. 1970).

         Groups of pregnant Wistar-SPF rats (18-22 females per group) were
    administered carbendazim in the diet at dosage levels of 0, 600, 2 000
    and 6 000 ppm from days 6 through 15 of gestation. On day 21 of
    gestation all pregnant rats were sacrificed and pups delivered by
    Caesarean section.

         Dams were weighed periodically during the test and food
    consumption measured for specific periods. The number of corpora lutes
    were determined, ovaries weighed and foetuses weighed and examined.
    The number of implantation and resorption sites were recorded and the
    empty uterine horns weighed. One third of the foetuses were fixed and
    stained for skeletal examination and the remaining two thirds were
    examined for soft tissue anomalies.

         Although 23 females per group were mated, the pregnancy rate was
    variable, with 18, 22, 20 and 18 pregnant in the 0, 600, 2 000 and
    6 000 ppm groups, respectively. The mean body weight gain and food
    consumption for the high-dose females were significantly decreased in

    comparison with controls. The number of live/dead foetuses,
    implantation sites, embryonal resorptions, foetal resorptions and
    corpora lutea/dam were comparable among all groups. Ovarian weights
    and weight of the empty uterus were not affected by treatment. The
    mean foetal weight/litter and sex ratio were comparable among all
    groups. Pre- and post-implantation losses were not affected by
    treatment.

         No visceral anomalies were reported that were significantly
    different from the control response. Misshapen and fused bones were
    much more frequent occurrences in the high-dose groups then any of the
    other treatment or control groups. Supernumery ribs were also
    significantly increased in high-dose females. Ossification was
    significantly delayed or absent in high-dose group pups, particularly
    for forelimb, hindlimb, sternebrae and skull bones. Ossification was
    significantly delayed or absent in cervical vertebral bodies in all
    treatment groups when compared with control pups.

         There were no individual animal or litter data and variations in
    ossification and other skeletal abnormalities were presented as
    percentages. The teratogenic or fetotoxic potential of carbendazim to
    pregnant Wistar-SPF rats, therefore, cannot be determined from the
    results and data presented (Koeter 1975a).

    Rabbit

         Groups of pregnant New Zealand albino rabbits (3-11 females/
    group) were administered carbendazim in the diet at dosage levels of
    0, 600, 2 000 and 6 000 ppm from day 6 through day 18 of gestation. On
    day 29 of gestation, all pregnant animals were sacrificed and foetuses
    delivered by Caesarean section.

         Does were weighed periodically and food consumption was
    determined for specific periods. The number of corpora lutea were
    determined, ovaries weighed and foetuses weighed and examined. The
    number of implantation sites and resorption sites were recorded and
    the empty uterus weighed. One half of foetuses were stained and
    sectioned for skeletal anomalies and the other half examined for soft
    tissue abnormalities. Only the foetuses in the high-dose and control
    groups were examined for visceral anomalies.

         Although 18 females per group were artificially inseminated the
    pregnancy rate was extremely variable among groups, with 9 in control,
    8 in 600 ppm, 3 in 2 000 ppm, and 11 in the 6 000 ppm group. The mean
    body weight gain was significantly decreased in the high-dose group,
    although food consumption did not vary among groups. The number of
    live/dead foetuses, implantation sites, embryonal resorptions, foetal
    resorptions and corpora lutea/dam were comparable among all groups.
    The ovarian and uterine weights in the high-dose group were depressed
    in comparison with control females. Pre- and post-implantation losses
    were not affected by treatment.

         There were apparent differences between high-dose and control
    groups for visceral anomalies. However, too few litters and foetuses
    were examined to enable making any conclusions.

         There was a significant increase in the number of supernumery
    ribs (bilateral) and skull bones in the high-dose group. Ossification
    was significantly delayed or absent in high-dose group foetuses, most
    notably in the forelimb metacarpals and phalanges. There was also
    incomplete ossification of the sternebrae and skull bones, which was
    significant at 600 ppm and 6 000 ppm. Misshapen sternebrae were also
    present in the 6 000 ppm group.

         There were no individual animal or litter data, variations in
    ossification were presented as percentages and visceral anomalies were
    evaluated in only 2/4 of the groups. The teratogenic potential of
    carbendazim to pregnant New Zealand albino rabbits, therefore, cannot
    be ascertained from the results and data presented (Koeter 1975b).

    Special Study on Neurotoxicity

         A neurotoxicity study performed using chickens gave no indication
    of neurotoxic potential at single oral doses up to and including
    5 000 mg/kg (Goldenthal et al. 1978).

    Long-Term Studies

    Rat

         Groups of weanling rats (36 male and 36 female ChR-CD albino
    rats/group) were administered carbendazim (50-70 percent a.i.) in the
    diet for 104 weeks at dosage levels of 0, 100, 500, 2 500-10 000, and
    5 000 ppm. Growth was observed by body weight changes and food
    consumption data, which were recorded weekly for the first year and
    twice a month thereafter. Daily observations were made with respect to
    behavioural changes and mortality. At periodic intervals throughout
    the study, haematologic, urinalysis and selected clinical chemistry
    examinations were performed. After one year each group was reduced to
    30 male and 30 female rats by interim sacrifice for gross and
    microscopic evaluations. At the conclusion of the study all surviving
    animals were sacrificed and gross pathological examination of tissues
    and organs was made. Microscopic examination of all tissues and organs
    from the control and 2 500 ppm groups were conducted, along with liver
    only from the 100 and 500 ppm groups, and liver, kidney testes and
    bone marrow from the 5 000 ppm group animals.

         The few mortalities observed in the first year were not
    attributable to the presence of carbendazim in the diet. Survival
    decreased during the second year to approximately 50 percent for males
    and 39 percent for females, but was not related to treatment. Body
    weight gain was depressed for males and females in the 2 500-

    10 000 ppm group and for females in the 5 000 ppm group when compared
    to control groups. Food consumption did not differ among groups. The
    average daily dose for the 500 ppm group was 65 mg/kg b.w./day
    (initially, M and F), 18 mg/kg (at one year) and 15 mg/kg (at two
    years). Haematologic examinations demonstrated reduced erythrocyte
    count, haemoglobin and haematocrit values for females at 9-24 months
    in the 2 500 and 5 000 ppm groups; and for males at 24 months in the
    2 500 ppm group. There were no compound-related clinical
    manifestations of toxicity and no effects observed in urinalysis
    examination. Alkaline phosphatase and glutamic pyruvic transaminase
    activities varied throughout the test at 2 500 and 5 000 ppm but did
    not demonstrate a consistent dose response. There were no apparent
    differences in the organ weights or organ-to-body weight measurements,
    except for female livers in the 2 500 and 5 000 ppm group. This
    increase in the liver-to-body weight ratio was reflective of lower
    body weights for both groups and therefore, not compound related.
    Histopathologic evaluation of the livers did not demonstrate any
    compound-related effects. Histopathologic examinations demonstrated an
    increased incidence of pigment deposition in spleen and bone marrow
    for both males and females at the 5 000 ppm level. This is consistent
    with the haematology data for the same group. Males in the 2 500-
    10 000 ppm group presented marginal increases for diffuse testicular
    atrophy and prostatitis. Carbendazim is considered to be without
    adverse effects on ChR-CD rats when incorporated in the diet at levels
    up to and including 500 ppm (Sherman).

         Groups of Wistar rats (60 males and 60 females/group) were
    administered carbendazim (99 percent pure) in the diet at dosage
    levels of 0, 150, 300 and 2 000 ppm for two years. The 2 000 ppm dose
    was increased to 5 000 ppm after one week and then to 10 000 ppm after
    two weeks for the remainder of the study. Clinical signs of toxicity
    and general health were determined daily. Body weight and food
    consumption were measured regularly throughout the study. Haematology
    (peripheral blood), blood chemistry (orbital sinus) and urinalysis
    evaluations were periodically conducted during the study. All animals
    were subjected to complete gross necropsy and selected organs weighed.
    A complete list of tissues and organs was prepared and examined
    microscopically in 20 male and 20 female rats of the control and high-
    dose groups. All tumours and gross abnormalities were also examined
    histologically.

         There were no differences between test groups and control animals
    concerning clinical signs of toxicity or food consumption. Body
    weights were significantly reduced in low-dose males at week 88 to
    term and in high dose females at week 12 to term. Urinalyses and
    kidney function (specific gravity) were comparable among all groups.
    Of the haematological measurements examined, Hgb was depressed in
    high-dose females at week 26, 52 and 103 and PCV was depressed in
    high-dose females at week 103. There were no compound related effects
    in males. SGOT activity was decreased in high-dose males at term, but

    not in females. High-dose females had increased SGPT activity and
    decreased total serum protein at term. There were no compound-related
    effects on organ weights except for increased relative liver weights
    in high-dose females. There were also no compound-related effects on
    mortality, with 50 percent mortality in control males at week 76, and
    at week 92 in treated group males. There was 50 percent mortality in
    control and low-dose females at week 88 and at 92-96 weeks in mid- and
    high-dose females. Survival at termination of the study was comparable
    among all groups.

         There were no measurable histological differences between control
    and treated groups, except for an increased incidence of diffuse
    proliferation of parafollicular cells of the thyroid in the high-dose
    females. The number of tumour-bearing animals and total number of
    primary tumours were comparable among all groups, and there were no
    compound-related oncogenic effects reported. (NOTE: All data presented
    were group mean values with SD. There were no data on individual
    animals.)

         The no observed effect level (NOEL) is 300 ppm, based on body
    weight changes, decreased Hgb and PCV values and increased relative
    liver weight in high-dose females. There was no tumourigenic effect in
    this strain of rat at doses up to and including 10 000 ppm for 104
    weeks (Til et al. 1976).

    Dog

         Groups of beagles (four males and four females/group) were
    administered carbendazim (53 percent a.i.) in the diet at dosage
    levels of 0, 100, 500 and 2 500 ppm for two years. Dogs were one to
    two years of age at the start of the test. Some dogs in the high-dose
    group received only 1500 ppm. 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 from
    the control and 500 ppm groups, as well as one female from the high-
    dose group. One male from the high-dose group was sacrificed in
    extremis after 42 weeks on the test diet. 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 reported for the control or 100 and
    500 ppm dose groups. However, three males in the high-dose group were
    sacrificed after 22 and 42 weeks because of poor nutrition. No females
    in the high-dose group died. Body weight and food consumption were all
    adversely affected in the high-dose group animals, but not at lower
    levels. The average daily intake for the 500 ppm dose group was

    15.0-20 mg/kg (initially, M and F), 14-18 mg/kg (one year) and
    10-16 mg/kg (two years). Dogs in the highest dose group developed
    anorexia, distended abdomens and overall poor nutritional condition.
    Haematological evaluations and urinalyses were not apparently affected
    by treatment. The dogs in the 500 ppm and 1 500-2 500-dose groups had
    increased cholesterol, BUN, total protein, GPT and APase levels and
    presented evidence of a decreased A/G ratio throughout the study. This
    biochemical evidence of liver effect was supported by liver pathology,
    with incidences of hepatic cirrhosis, swollen vacuolated hepatic cells
    and mild chronic hepatitis in dogs fed 500 ppm or more of carbendazim.
    There were no noticeable effects on organ weights and organ-to-body
    weight ratios. Diffuse testicular atrophy (which was marked) and
    aspermatogenesis were observed in 2/4 males at 100 ppm but were not
    present in the other dose group or in control males. Based on the lack
    of supporting data in the other dose group males, these findings are
    not considered as being compound-related.

         The NOEL in this study appears to be 100 ppm. based on the liver
    effects noted at 500 ppm and greater (Sherman 1972).

         Groups of beagles (four males and four females/group) were fed
    carbendazim in the diet at dosage levels of 0, 150, 300 and 2 000 ppm
    for 104 weeks. After 33 weeks the 2 000 ppm dose was increased to
    5 000 ppm. Dogs were 22-27 weeks old at the start of the study. Daily
    examinations were made for clinical signs of poisoning and adverse
    behaviour. Growth, as evidenced by body weight, was recorded regularly
    throughout the study, as were food consumption data. At periodic
    intervals (weeks 13, 26, 52, 78 and 104), haematology, blood chemistry
    and urinalysis were performed. Liver function (BSP retention) and
    kidney function (phenol red excretion) tests were evaluated at weeks
    26, 52 and 104. At the conclusion of 104 weeks of dietary
    administration, each dog was sacrificed and gross and microscopic
    examination of tissues and organs were performed.

         There was no mortality in any group except for one female in the
    high-dose group which was killed in a moribund state after week 36.
    Growth, as measured by body weight, was decreased in mid-dose males
    and high-dose males and females. Food consumption was comparable among
    all groups. Blood clotting times were significantly reduced in high-
    dose males from week 13 to term, with slight decreases noticed in
    high-dose females. Serum alkaline phosphatase activity was increased
    in the high-dose group dogs throughout the study. There were no
    compound-related effects on SGPT or SGOT levels. All other
    haematological and blood chemistry measurements were comparable with
    control groups. There were no differences among groups for BSP
    retention, phenol red excretion or urine analyses.

         Absolute liver and thyroid weights were significantly increased
    in high-dose group dogs. Relative liver, thyroid and pituitary weights
    were also significantly increased at the high dose. There were no

    reported microscopic changes in these organs related to treatment.
    There was an increased incidence of prostatitis (3/4 vs 1/4) in high-
    dose males compared with controls. Also noted in 1/4 high dose males
    was interstitial mononuclear inflammatory cell infiltrates and
    atrophic tubules of the testes.

         (Summary tables only were provided for the number of dogs with
    the indicated pathological response. Severity of response, identity of
    dog involved, gross and histopathology reports of individual animals
    were not provided. Data provided were generally not separated
    according to sex.)

         The feeding of carbendazim in the diet to dogs for two years was
    without apparent adverse effects at levels up to and including 300 ppm
    (Reuzel et al. 1976).

    Special Studies for Carcinogenicity

         Groups of CD-1 mice (80 males and 80 females/group) were
    administered carbendazim (99 percent a.i.) in the diet at dose levels
    of 0, 500, 1 500 and 7 500 ppm for two years. The 7 500 ppm dose was
    reduced to 3 750 ppm after 66 weeks for the males because of increased
    mortality. Females received 7 500 ppm throughout the study period.
    Animals were 6-7 weeks old at the start of the study. Mice 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.
    Selected organs were weighed, including brain, heart, lungs, liver,
    spleen, kidney, testes and thymus. Microscopic examination was
    performed on a complete list of tissues and organs. Urine and faecal
    samples were also analysed.

         Mortality was compound related in male mice. The high-dose group
    males terminated at week 73 because of significant increase in
    mortality. Only nine males in the 1 500 ppm group survived to week
    104, compared with 18 for control males. Females were unaffected by
    treatment in this respect.

         There were no dose related effects on body weight or food
    consumption throughout the study, although terminal body weights for
    low- and mid-dose group males were less than control and high-dose
    group males. Clinical signs of toxicity were similar among all
    treatment and control groups. Haematological determinations in males
    were unaffected by treatment. Females in the 7 500 ppm group had
    reduced erythrocyte counts and marginal decreases in haemoglobin
    concentration.

         Both absolute and relative thymus weights were significantly
    decreased in females in the 500 and 1 500 ppm groups, but not in the
    high-dose group. Absolute liver weight was increased in the 7 500 ppm
    females, with relative liver weight increased in the 1 500 and
    7 500 ppm groups. Organ weights for the males were variable with only
    the kidney and thymus weights apparently decreased by treatment.
    Absolute kidney and thymus weights were depressed in all male
    treatment groups. However, relative kidney and thymus weights were
    significantly decreased in the high-dose males only. The lower
    absolute kidney and thymus weights in the low- and mid-dose group
    males were probably a reflection of reduced terminal body weights.

         Histological examination revealed dose-related changes in the
    thymus (lymphoid depletion) and kidneys (bilateral/unilateral
    accumulation of yellow-brown pigment in the tubules) for mid- and
    high-dose group male mice. Examination of the testes demonstrated a
    marginal increase in the finding of sperm stases (bilateral/unilateral
    combined) in treated males, with a similar finding of increased
    germinal cell atrophy (bilateral only). There was an opposite trend,
    however, for unilateral germinal cell atrophy, where the incidence in
    controls was greater or equal to treated males. These effects are,
    therefore, not considered compound related.

         Examination of livers of male mice revealed a significant
    hepatotoxic effect at 1 500 and 7 500 (3 750) ppm, demonstrated by
    centrilobular hypertrophy, necrosis and swelling. There was no
    increase in the finding of hepatocellular adenoma, which occurred with
    equal frequency in control and treatment groups. A significant
    increase occurred for hepatocellular carcinomas at the 1 500 ppm dose
    only. However, too few high-dose males survived to 17 months
    (510 days) to support the conclusion of no oncogenic effect at that
    dose level.

         Histomorphic evaluation of the female mice revealed an increased
    incidence of lymphoid depletion in the thymus in the mid- and high-
    dose groups. There was a significant accumulation of yellow-brown
    pigment in the macrophages and tubules in the kidneys, as well as an
    increase in cystic tubules for high-dose group females. The occurrence
    of hepatocellular carcinomas was significantly increased in the mid-
    and high-dose females. However, there was no apparent compound-related
    effect on the latency period for this finding. The finding of
    hepatocellular adenomas was marginally increased in the low- and mid-
    dose females, but not in the high-dose group, compared with control.
    Other findings indicative of hepatotoxicity were more prominent in the
    control females than in the treatment groups. Hepatocellular chromatin
    aggregation and necrosis (focal, multifocal, single cell) were
    increased in controls. There was also a significant increase for the
    incidence of macrophages containing yellow-brown pigment. These
    findings appear to indicate different metabolic or detoxification
    mechanisms, which are sex dependent. The carcinogenic response in the

    liver, although significant at 1 500 and 7 500 ppm for females and at
    1 500 ppm for males, is considered a weak response in light of the
    histomorphic changes in the livers in male and female control group
    mice (Wood 1982).

         Carbendazim was administered in the diet to groups of SPF Swiss
    mice (100 males and 100 females/group) at dosage levels of 0, 150, 300
    and 1 000 ppm for 80 weeks. The 1 000 ppm dose was increased to
    2 000 ppm at week 4 and to 5 000 ppm at week 8 for the remainder of
    the study. Animals were observed for behaviour and clinical signs of
    toxicity. Body weight measurements were determined throughout the
    study. Gross necropsies were performed on all animals, liver and
    kidney weights recorded, and a complete list of organs and tissues was
    examined microscopically.

         There were no compound-related effects on general condition,
    mortality or body weight. Survival at term was 70 percent for males
    and 80 percent for females. Relative liver weights in high-dose males
    and females were significantly different from controls. There were no
    changes in kidney weights. Gross and histopathology examinations
    demonstrated a compound-related effect on the livers of both male and
    female mice in the high-dose group. There was a significant increase
    in the number of mice with clear cell foci in high-dose males and
    females and in mixed cell foci for high-dose males. Neoplastic nodules
    were reportedly increased in high-dose females, while the incidence of
    hepatoblastoma was increased in high-dose males. There were no
    differences between control and treatment groups for the finding of
    hepatocellular carcinoma. It was concluded that carbendazim is
    oncogenic to this strain of mouse at dietary doses greater than or
    equal to 5 000 ppm (Beems et al. 1976). (NOTE: All data presented
    were group mean values. There were no data on individual animals.)

         Carbendazim was administered in the diet to groups of HOE NMRKf
    (SPF 71) mice (100-120 males and females/group) for 96 weeks at dosage
    levels of 0, 50, 150, 300 and 1 000 ppm. The 1 000 ppm dose was
    increased to 2 000 ppm at week 4 and to 5 000 ppm at week 8 for the
    remainder of the study. Animals were observed for behaviour and
    general condition, as well as body weight, food/water consumption and
    mortality. Gross necropsies were performed on all animals, liver and
    lung weights were recorded, and a complete list of organ and tissues
    was examined microscopically. An interim sacrifice was made at 18
    months on 20 males and 20 females from the control group and the
    5 000 ppm group.

         There were no compound-related effects on behaviour, body weight
    gain, food/water consumption or mortality. At 22 months there was
    24-31 percent mortality in male mice and 37-52 percent mortality in
    females, for all groups. Mean daily consumption of carbendazim in
    mg/kg was 5.8-7.1 at 50 ppm, 17.1-21.2 at 150 ppm, 34.4-41.9 at
    300 ppm, and 548.4-682.3 at 5 000 ppm.

         Examination of lung and liver weights at 18 and 22 months
    demonstrated an increase in absolute and relative liver weights in
    both male and female mice at 5 000 ppm.

         Macroscopic and microscopic examination of animals at 18 months
    revealed compound-related effects on the liver at 5 000 ppm. There
    were reported increases in centrilobular hypertrophy of liver cells,
    single cell necroses, liver cells in mitosis and pigment in Kupffer
    cells. Controls presented evidence of fatty change of liver cells
    only. Microscopic evaluation of tissues/organs at 22 months
    demonstrated a definite compound-related effect on liver at 5 000 ppm
    in both males and females. There was marked liver cell hypertrophy,
    clear cell foci, liver cells in mitosis, abundant inclusion bodies in
    enlarged cell nuclei, multiple cell necroses and greenish yellow
    pigment in Kupffer cells. Neoplastic nodules (adenomas), carcinomas,
    fibrosarcomas and other tumourigenic responses in the liver were
    equally distributed among all groups. The occurrence of hemangiomas,
    evident in treated groups with none in the control groups, was
    randomly distributed (both by dose and sex), not dose related, not
    significantly different from control and, therefore, not considered
    compound related. The finding of lung neoplasias (such as
    adenomatosis) were equally distributed among all groups. There was no
    effect on incidence or time of onset of tumours by carbendazim and the
    total number of benign and malignant tumours were comparable among
    groups. There was a significant increase in liver toxicity in both
    males and females at 5 000 ppm. However, there was no evidence of a
    carcinogenic effect from carbendazim when administered in the diet to
    mice at doses up to and including 5 000 ppm for 22 months (Kramer &
    Weigand 1982).

    Special Studies on Mutagenicity

         Results of the various mutagenicity assays are summarized in
    Table 2.

    Bacteria

         MBC was examined for mutagenic activity in Salmonella
    typhimurium following the plate incorporation protocol of Ames
    et al. (1975), at concentrations between 1 and 325 /g plate, with
    and without activation. MBC increased the reversion frequency 3-5
    times the control frequency, without activation. Doubtful activity was
    found with activation. Source and purity of test substance were not
    provided and there were no actual data presented (Rashid & Ercegovich
    1976; Ercegovich & Rashid 1977).

         MBC was tested for mutagenic activity on S. typhimurium,
    strains TA1535, TA1537, TA98 and TA100, with and without activation.
    MBC, dissolved in DMSO, was not mutagenic at concentrations between 4
    and 2 500 g/plate (Hoechst 1977).

        Table 2   Mutagenicity Assays
                                                                                                                         

    Test Organism                           Test           Result                                  Reference
                                            Substance
                                                                                                                         

    Gene Mutation Studies

    Bacteria

    Salmonella typhimurium                  MBC            Bacterial assays with MBC.              Ercegovich & Rashid
                                                           Strains TA98, TA100, TA-                1977
                                                           1535, TA1537, and TA1538.
                                                           Doubtful mutagenic activity             Rashid & Ercegovich
                                                           was reported for MBC both               1976
                                                           with and without metabolic
                                                           activation.

                                                           Negative                                Shirasu et al. 1977

                                                           Negative. Results dependent             Russell 1977a,b,
                                                           on sample source and purity.            1978

                                                           Negative.                               Hoechst 1977

                                                           Series of tests: spot and               Ficsor et al. 1978
                                                           liquid culture assays using
                                                           strains his G46 and TA1530,
                                                           TA1535, TA1950. No mutagenic
                                                           activity except one weak
                                                           positive in his G46.
                                                                                                                         

    Table 2 (con't)
                                                                                                                         

    Test Organism                           Test           Result                                  Reference
                                            Substance
                                                                                                                         

                                                           Plates treated with 100 to              Donovan 1981a
                                                           10 000 ug MBC, with activation.
                                                           The number of revertants/
                                                           plate increased from
                                                           4.2 to 8.95 times in the
                                                           trials with positive responses
                                                           in TA98 and from 3.7 to
                                                           6.4 times in TA1537.

                                            MBC            Negative. Same as previous              Donovan 1981b
                                            (Hoechst)      citation, with and without
                                                           activation. Results dependent
                                                           on sample source and purity.

    S. typhimurium
    (host mediated assay)                   MBC            Negative                                Shirasu et al. 1977

    Yeast and Fungi

    Aspergillus nidulans                    MBC            Positive at pH 5.2 and 5.3              Speakman & Nirenberg
                                                                                                   1981
                                                                                                   Nirenberg & Speakman
                                                                                                   1981

                                            MBC            Positive.                               Kappas et al. 1974
                                            MBC            Positive.                               Davidse 1973
                                                                                                                         

    Table 2 (con't)
                                                                                                                         

    Test Organism                           Test           Result                                  Reference
                                            Substance
                                                                                                                         

    Cladosporium
    cucumerinum                             MBC            Positive at pH 6.8                      Speakman & Nirenberg
                                                                                                   1981
                                                                                                   Nirenberg & Speakman
                                                                                                   1981

    Cultured Mammalian Cells

    Chinese hamster ovary                   MBC            Negative                                Waterer & Krahn 1980
    cells in vitro

    Insects

    Drosophila melanogaster                 MBC            Noted sterility in some                 Lamb & Lilly 1980
                                                           broods. This was considered
                                                           to be consistent with
                                                           spindle effects of MBC.

    Mammals

    Mouse, in utero                         MBC            Positive - coat colour                  Fahrig & Seiler 1979
                                                           changes

    Chromosomal effects

    Cytogenetics-in vitro
    Human lymphocytes                       MBC            Grown in culture medium                 Lamb & Lilly 1980
                                                           containing 0.5 mg MBC.
                                                           No compound related chromosome
                                                           aberrations.
                                                                                                                         

    Table 2 (con't)
                                                                                                                         

    Test Organism                           Test           Result                                  Reference
                                            Substance
                                                                                                                         

    Mouse lymphoma L5178Y cells             MBC            Dose-related increase in                Jotz et al. 1980
                                                           mutation frequency with
                                                           metabolic activation at
                                                           TK+/- locus at 100 M.

    Mouse lymphoma L5178Y cells             MBC            MBC was not mutagenic at the            Krahn et al. 1983
                                                           TK+/- locus with or without
                                                           activation at concentrations
                                                           up to and including 200 M.

    Cytogenetics - in vitro

    Rat bone marrow                         MBC            Negative.                               BASF 1975a

    Chinese hamster bone marrow             MBC            Negative.                               Seiler 1976

    Mouse bone marrow                       MBC            Negative.                               Seiler 1976

    Dominant lethal-rodents

    Rat                                     MBC            Negative.                               Benes & Sram 1976
    Mice                                    MBC            Negative.                               BASF 1975b
                                                           Negative.                               Hoechst 1974

    Micronucleus Test

    Mouse bone marrow                       MBC            Positive.                               Seiler 1976
                                                                                                                         

    Table 2 (con't)
                                                                                                                         

    Test Organism                           Test           Result                                  Reference
                                            Substance
                                                                                                                         

    DNA Damage and Repair
    Mice B6C3F1 and F344                    MBC            MBC was tested for DNA                  Tong 1981a,b
                                                           repair using primary hepatocyte
                                                           cultures. MBC did not
                                                           induce DNA repair in either
                                                           rat or mouse.
    Differential Toxicity-
    Bacteria

    Bacillus subtillis                      MBC            Negative.                               Shirasu et al. 1977

    Gene Mutation-Bacteria

    S. typhimurium                          5-hydroxy-MBC  Negative.                               Cannon Laboratories
                                                                                                   1978

                                                           Negative                                Russell 1977b
    Plant Studies

    Allium cepa                             MBC            Positive.                               Richmond & Phillips
                                                                                                   1975
                                                                                                                         
             MBC and some of its commercial preparations were examined for
    mutagenic potential in S. typhimurium following different
    treatment protocols. An overlay spot test was used to test MBC at
    concentrations of 50 and 100 g/spot in strains his G46, TA1530 and
    TA1950. Only one sample of MBC (Seiler) exhibited weak mutagenic
    activity at 100 g/spot. In a plate incorporation assay using strain
    TA100, MBC was not mutagenic at concentrations between 50 and
    200 g/plate. Liquid culture assays with 1 000 g/ml of MBC showed no
    evidence of mutagenicity in his G46 and TA1950 (Ficsor et al.
    1978).

         MBC was non-mutagenic in S. typhimurium strains TA1535,
    TA1537, TA1538, TA98 and TA100, and in Escherichia coli strain 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. 1977).

         MBC and 5-hydroxy-MBC were tested for mutagenic activity in
    S. typhimurium strains TA1535, TA1537, TA1538, TA98 and TA100
    according to the plate incorporation procedure of Ames et al.
    (1975). DMSO was the solvent. Each sample was evaluated in the
    presence and absence of an activation system. Five different samples
    of MBC were tested at concentrations up to 10 mg/plate. A sample of
    technical grade MBC was mutagenic in the presence of rat liver
    homogenate in strains TA1537, TA1538 and TA98. A 99.6 percent pure MBC
    sample, in the presence of rat and mouse activation systems, was
    mutagenic in TA1537, TA98, TA1535 and TA100. Rat and mouse liver
    activation systems gave essentially identical results in TA1537 and
    TA98. A third sample (97.6 percent, Czech-Polish) was mutagenic with
    rat liver activation in strains TA1537, TA98 and TA100. An MBC sample
    from Hoechst (95-100 percent pure) was not mutagenic in any of the
    Salmonella strains. Analytical grade MBC (99.5 percent pure) was
    weakly mutagenic in TA1537 at concentrations up to 15 mg/plate. A
    sample of 5-hydroxy MBC was not mutagenic at concentrations up to
    20 mg/plate (Russell 1977 a, b, 1978; Donovan 1981 a, b).

         In a host mediated assay in male ICR mice given total doses of
    either 1 000 or 4 000 mg MBC/kg the mutation frequencies observed in
    the S. typhimurium strain his G46 from treated animals were
    identical to mutation frequencies in bacteria from control animals
    (Shirasu et al. 1977).

    Yeast and fungi

         MBC was evaluated for mutagenic activity in Aspergillus
    nidulans and Cladosporium cucumerinum. In A. nidulans, MBC
    at a concentration of 2.77 M (0.53 g/ml), caused an increase in the

    frequency of colonies resistant to MBC (2 g/ml) but did not increase
    the frequency of colonies resistant to carboxin (20 g/ml). In C.
    cucumerinum, MBC at 0.58 M (0.11 g/ml) caused an increase in
    carboxin (20 g/ml) resistant colonies, but had no effect on the
    frequency of colonies resistant to MBC (0.8 g/ml). An activation
    system was not used for any of these studies (Speakman & Nirenberg
    1981).

         Experiments were conducted in A. nidulans and C.
    cucumerinum to evaluate the effect of altering the pH of the agar
    medium, using pHs of 5, 5.2-5.3 and 6.8. The pH of the treatment
    medium had a significant effect on the activity of MBC, which was
    mutagenic in A. nidulans only at a pH of 5.2-5.3 (MBC resistance)
    and in C. cucumerinum only at pH 6.8 (carboxin resistance). The
    concentrations of MBC exhibiting mutagenic activities were 0.53 g/ml
    and 0.11 g/ml for A. nidulans and C. cucumerinum,
    respectively. The effect of an activation system was not studied. The
    authors concluded that MBC had weak mutagenic activity (Nirenberg &
    Speakman 1981).

    Cultured mammalian cells

         Chinese hamster ovary cells in culture were exposed to varying
    concentrations of MBC without activation (3 to 654 M) and with
    activation (3 to 628 M), to detect mutations at the gene locus coding
    for hypoxanthine guanine phosphoribosyl transferase (HGPRT). A dose-
    related cytotoxic response was evident in cultures exposed to MBC
    without activation, with a decreased survival at 16 M. No
    statistically significant differences in mutation frequency were noted
    and MBC was not mutagenic under the test conditions used (Waterer &
    Krahn, 1980).

    Insects

         MBC dissolved in DMSO at 0.5 mg/ml did not cause a significant
    increase in the frequency of sex-linked recessive lethals when given
    to Drosophila melanogaster. The only indication that the substance
    may have some potential for damaging germ cells comes from the
    observation that it caused an increased incidence of sterility in the
    later broods from treated Oregon-R males. However, this effect was
    not observed in treated yw+BsZy+ males. 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 mutations reported was 5/4807 (0.1 percent). The sterility
    observed in broods from matings involving mitotic spermatogonial cells
    is consistent with the suspected spindle effects of the chemical (Lamb
    & Lilly 1980).

    Mouse embryo

         Mouse embryos, heterozygous for four different recessive coat
    colour genes, were treated in utero by dosing the mother orally
    with MBC at dose levels of 100 to 300 mg/kg b.w. If mutations are
    induced in pigment precursor cells in a wild type allele of one of the
    genes under study, a spot of an altered colour may appear on the coats
    of the offspring. At 200 mg/kg the number of spots was significantly
    different from controls (Fahrig & Seiler 1979).

    Cytogenetics

         The ability of MBC to cause chromosomal aberrations was evaluated
    in human lymphocytes in culture. MBC, at a concentration of 0.5 mg/ml,
    did not increase the frequency of chromosome aberrations over the DMSO
    control in a system without activation. Cells treated with MBC did
    exhibit grossly contracted chromosomes, an effect induced by spindle
    poisons such as colchicine (Lamb & Lilly, 1980).

         MBC, with and without metabolic activation, was evaluated for its
    ability to induce forward mutations at the thymidine kinase (TK) locus
    in mouse L5178Y lymphoma cells. Metabolic activation was accomplished
    by microsomal enzymes obtained from induced rat liver preparations
    (S-9 mix). Ethylmethane sulphonate (EMS) and 3-methylcholanthrene were
    used as positive controls.

         MBC was mutagenic in this test system with activation, the
    mutation frequency being increased in a dose-related manner. There was
    no mutagenic response without metabolic activation at doses of 50 to
    250 M. The results indicated that metabolic activation enhanced MBC's
    mutagenic activity at 100 M (Jotz et al. 1980).

         The effects of MBC on the mouse lymphoma L5178Y cell line at the
    thymidine kinase (TK+/-) locus were examined both with and without
    metabolic activation. Concentrations tested included 12.5 to 200 M
    of MBC, DMSO as negative control, 2 000 M of ethylmethane
    sulphonate (positive control without activation) and 15 M of
    3-methylcholanthrene (positive control with activation). The positive
    controls gave the expected response. However, MBC, both with and
    without activation tested in replicate trials, was not mutagenic at
    levels up to and including 200 M (Krahn et al. 1983).

         Technical grade MBC was tested for its ability to cause
    chromosome aberrations in rat bone marrow cells in vivo. Male and
    female Sprague-Dawley rats were given a single oral dose of 300 mg/kg.
    Metaphase cells from treated animals, sacrificed at 6, 24, and
    48 hours after treatment, did not exhibit an increased frequency of
    chromosome aberrations (BASF 1975a).

         MBC did not produce chromosome breakage in bone marrow cells from
    Chinese hamsters given oral doses of 1 000 mg/kg. Only one chromatid
    break was observed in a total of 500 metaphases from four animals. The
    mitotic figures were examined in bone marrow cells from ICR mice given
    two oral doses of MBC at 1 000 mg/kg each. Twelve of the 1 000
    nucleated anaphase cells exhibited lagging chromosomes, bridge
    formation, tripolar spindle formation or unequal chromatin
    distribution. MBC does not break chromosomes but probably exerts its
    effect by interfering with spindle function (Seiler 1976).

    Rodent dominant lethal test

         Twenty NMRI mice were given intraperitoneal injections of MBC
    (500 mg/kg) on five successive days. A 0.5 percent solution of the
    vehicle CMC was given to 20 mice and served as controls. Animals
    receiving MBC did not exhibit any clinical signs of toxicity. The body
    weights of control and MBC-treated animal groups were identical after
    the first week of mating. No macroscopically observable pathological
    changes were seen in dissected mice from the MBC-treated group. MBC
    did not exhibit a dominant lethal effect (Hoechst 1974).

         Twenty-two male NMRI mice were given MBC by stomach tube
    (300 mg/kg) on five successive days. The vehicle for delivering MBC
    was not given. The same number of untreated mice served as controls.
    MBC-treated mice did not exhibit clinical symptoms of toxicity, body
    weight changes or macroscopically recognizable pathological changes in
    the internal organs. MBC did not cause a change in the mutagenicity
    index over that of the control (BASF 1975b).

    DNA damage and repair

         DNA repair assays in rat (F344) or mouse (B6C3F1) hepatocyte
    primary cultures (HPC) were evaluated for MBC along with
    dimethylnitrosamine and 2-amino-fluorene, which were used as positive
    controls. MBC and tritiated thymidine (10 Ci) were added to the
    culture medium. After 18 to 20 hours of incubation they were fixed and
    examined microscopically for morphological changes and absence of
    S-phase nuclei indicative of cytotoxicity. Autoradiographic techniques
    were used to determine the number of nuclei grains induced. MBC did
    not induce DNA repair in rat or mouse hepatocytes. The positive
    controls gave the expected response (Tong 1981a,b).

    Differential toxicity to bacterial strains with different repair
    capacities

         MBC (typically 99 percent pure, sources unspecified) was tested
    for toxicity to recombination repair-proficient and repair-deficient
    strains of Bacillus subtilis. MBC was tested at concentrations
    between 20 and 1 000 g/disk. MBC did not cause a zone of killing in
    either strain and, thus, was negative in the assay. The absence of

    toxicity to either strain indicated that MBC was either non-toxic
    under the test conditions or the limited solubility prevented
    diffusion from the disk. An activation system was not used (Shirasu
    et al. 1977 ).

    COMMENTS

         Carbendazim follows a similar metabolic pathway to benomyl in
    rate and mice, being excreted in urine as 5-hydroxy carbendazim
    (5-HBC). Enzyme induction studies demonstrate that the rat is more
    efficient than the mouse in metabolizing and eliminating carbendazim
    and its metabolites.

         Carbendazim is not acutely toxic to mammals as demonstrated by
    acute oral and dermal LD50s of >10 000 mg/kg in rat and rabbit,
    respectively. Gross and histopathological examinations performed in
    many of these acute studies indicated that doses >1 000 mg/kg
    produced adverse effects on the testes (small, soft, discoloured,
    degenerative changes of the tubules) and epididymides (reduced or
    absent sperm).

         A three-generation reproduction study in rats demonstrated a NOEL
    of 500 ppm, with higher doses resulting in reduced average litter
    weights.

         Teratology studies in which the test material was administered in
    the diet of rats indicated in one study the absence of induction of
    terata at 10 000 ppm and in the second study a low incidence of
    misshapen, fused or incompletely ossified bones at 6 000 ppm. A
    limited study in rabbits did not indicate the induction of terata
    following dietary administration at 6 000 ppm (see also benomyl).

         A short-term dietary study in rats indicated increased liver to
    body weight ratios in females at 2 500 ppm, although no compound-
    related histomorphic changes were evident. There were no effects on
    testicular weight and the NOEL was 500 ppm. Two short-term dietary
    studies in dogs demonstrated that 300 and 500 ppm, respectively,
    caused no adverse effects. However, at doses of 1 000 and 2 500 ppm
    animals lost their appetite, lost weight and had increased cholesterol
    levels and relative liver weight increases.

         In two separate long-term feeding studies in rats, carbendazim
    produced relative liver weight increases, deposition of pigment in the
    spleen and bone marrow, and decreased haemoglobin, haematocrit and red
    blood cell counts at the higher doses. It was without adverse effects
    at 300 and 500 ppm, respectively, and there was no oncogenic response
    at doses up to 10 000 ppm.

         Beagles appeared to be more sensitive than rats to dietary
    exposure to carbendazim. Hepatic cirrhosis, vacuolated hepatic cells
    and increased levels of cholesterol, BUN, total protein, GPT and
    alkaline phosphatase, with decreased A/G ratio, were evidence of liver
    toxicity at levels greater than 100 ppm for two years.

         Oncogenicity studies were performed using three strains of mice
    (CD-1, Swiss SPF and HOE-NMR). In CD-1 mice there was a significant
    increase in hepatocellular carcinomas at 1 500 and 7 500 ppm in
    females and 1 500 ppm in males. However, there were also substantial
    histomorphic changes in the livers of male and female control animals.
    There was no oncogenic response at 500 ppm. Swiss mice, exposed for 80
    weeks to 150, 300 and 1 000-5 000 ppm carbendazim, showed an oncogenic
    response at 5 000 ppm, which was evidenced by significant increases in
    the incidence of neoplastic nodules and hepatoblastomas. There were no
    compound-related effects in this study at 300 ppm. HOE-NMR mice
    exposed to 50-5 000 ppm carbendazim for 96 weeks presented no evidence
    of an oncogenic response. It was concluded that carbendazim was
    hepatocarcinogenic to mice at high dose levels.

         Mutagenicity studies with carbendazim gave both positive and
    negative results. Carbendazim 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 data for benomyl and carbendazim have indicated that the
    metabolism of the two compounds is essentially the same, with benomyl
    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 have considered the aetiology and pathogenesis
    of liver tumours in certain strains of mice, with particular emphasis
    on organochlorine pesticides (FAO/WHO 1970, 1973, 1976). It was
    recognized that liver tumours are known to develop spontaneously in
    many strains of mice, at relatively high incidence and 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 for
    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 phenomenon.

         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, but the Meeting was informed that current
    levels of the impurities in question are very low in technical
    material.

         In view of established NOEL 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 concern of the Meeting for the
    paucity of individual animal data for many studies on carbendazim.

    TOXICOLOGICAL EVALUATION

    Level Causing no Toxicological Effect

    Rat:      500 ppm in the diet, equivalent to 25 mg/kg b.w.

    Dog:      100 ppm in the diet, equivalent to 2.5 mg/kg b.w.

    Rat:      Teratology (see benomyl )

    Estimate of Acceptable Daily Intake for Man

    0-0.01 mg/kg b.w.

    FURTHER WORK OR INFORMATION

    Desirable

    1.   Data on individual animals used in studies on carbendazim
         that have been identified in this evaluation addendum.

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

    3.   Elucidation of the variability of the mutagenicity data.

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    Dashiell, O.L. Acute oral LD50 test in guinea pigs using technical MBC
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    Davidse, L.C. Antimitotic activity of methyl benzimidazol-2-yl
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    1974a     (>98% MBC). Report HLR No. 799-74 submitted to WHO by
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    Edwards, D.F. Eye Irritation test in rabbits using technical MBC (>98%
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    Ercegovich, C.D. & Rashid, K.A. Mutagenesis induced in mutant strains
    1977      of Salmonella typhimurium by pesticides. 174th
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    1982a     59-day enzyme induction study in rats. Report from Central
              Institute for Nutrition and Food Research submitted by BASF
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    1982b     60-day enzyme induction study in mice. Report from Central
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    Ficsor, G., Bordas, S. & Stewart, S.J. Mutagenicity testing of
    1978      benomyl, methyl 2-benzimidazolecarbamate, streptozotocin and
              N-methyl-N'-nitro-N-nitro-soguanidine in Salmonella -
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              assays. Mutat. Res. 51: 151-164.

    Ford, L.S. Skin irritation test on rabbits using a wettable powder
    1981a     formulation (75% MBC). Report HLR No. 728-81 submitted to
              WHO by DuPont.(Unpublished)

    Ford, L.S. Primary skin irritation and sensitization of guinea pigs
    1981b     using a wettable powder formulation (75% MBC). Report HLR
              No. 729-81 submitted to WHO by DuPont. (Unpublished)

    Ford, L.S. Acute dermal LD50 test on rabbits using a wettable powder
    1982      formulation (75% MBC). Report HLR No. 822-81 submitted to
              WHO by DuPont. (Unpublished)

    Goldenthal, E.I. et al. Neurotoxicity study in hens using technical
    1978      MBC (>98% MBC). Report HLO-0027-79 by International
              Research & Development Corp. submitted to WHO by DuPont.
              (Unpublished)

    Goodman, N.C. Intraperitoneal LD50 test in rats using technical MBC
    1975      (>98% MBC). Report HLR No. 845-74 submitted to WHO by
              DuPont. (Unpublished)

    Henry, J.E. Eye irritation test in rabbits using a wettable powder
    1982      formulation (>75% MBC). Report HLR No. 66-82 submitted to
              WHO by DuPont. (Unpublished)

    Hinckle, L. Acute oral LD50 test in rats using a wettable powder
    1981      formulation (>75% MBC). Report HLR No. 769-81 submitted to
              WHO by DuPont. (Unpublished)

    Hoechst. Mouse dominant lethal study on MBC. Report submitted to WHO
    1974      by BASF. (Unpublished)

    Hoechst. Salmonella typhimurium mutation study with MBC. Report
    1977      submitted to WHO by BASF. (Unpublished)

    Jotz, M.M. et al. An evaluation of mutagenic potential of MBC (>98%
    1980      MBC) employing the L5178Y TK +/- mouse lymphoma assay.
              Report from SRI International, submitted to WHO by DuPont.
              (Unpublished)

    Kappas, A., Georgopoulos, S.G. & Hastie, A.C. On the genetic activity
    1974      of benzimidazole and thiophanate fungicides on diploid
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              Relat. Subj., 26: 17-27.

    Koeter, H.B.W.M. Effect of HOE 17411F on pregnancy of the rat. Report
    1975a     from Central Institute of Nutrition and Food Research
              submitted by BASF to WHO. (Unpublished)

    Koeter, H.B.W.N. Effect of HOE 17411F on pregnancy of the rat. Report
    1975b     from Central Institute of Nutrition and Food Research
              submitted by BASF to WHO. (Unpublished)

    Koeter, H.B.W.M., Til, H.P. & vander Heijden, C.A. Multigeneration
    1976      study with carbendazim in rats. Report from Central
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    Krahn, D.F. et al. L5178Y mouse lymphoma cell assay for mutagenicity.
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              DuPont. (Unpublished)

    Kramer & Weigand. Toxicological examination. Report submitted by
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    1980      toxicological effects of the fungicide benomyl. Toxicology,
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    Russell, J.F. Mutagenic activity of technical MBC in the
    1977a     Salmonella/microsome assay (>98% MBC). Report HLR No.
              820-77 submitted to WHO by DuPont. (Unpublished)

    Russell, J.F. Mutagenic activity of 5-hydroxy MBC (5-HBC) in the
    1977b     Salmonella/microsome assay. Report HLR No. 821-77
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    Russell, J.F. Mutagenic activity of analytical grade MBC (>99% MBC) in
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    1965      MBC). Report HLR No. 125-65 submitted to WHO by DuPont.
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    1968      formulation (70% MBC). Report HLR No. 95-68 submitted to WHO
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    1972      benzimidazolecarbamic acid, methyl ester (INE-965) (50% and
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    1981      2-yl carbamate (MBC) towards Aspergillus nidulans
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    RESIDUES

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

         Information on the registered uses of carbendazim in the United
    Kingdom, France, Australia, China (Taiwan Province), New Zealand,
    Colombia and Argentina (DuPont 1983a) and from 22 other countries
    (Hoechst 1983) was made available to the Meeting. This is summarized
    in Table 1.

        Table 1  Use Pattern of Carbendazim in Certain Countries
                                                                                               

                                     Application                               Preharvest
    Country                                                                    interval
    and                 Rate                     Number                        (days)
    Crop                (g a.i./ha or as
                        specified)
                                                                                               

    Argentina
    Apple               15-30 g a.i./100 l       2                             7
    Pear                15-30 g a.i./100 l       immerse or spray              postharvest
    Citrus              15-30 g a.i./100 l       immerse or spray              postharvest
    Apple               9-15 g a.i./100 l        4 or more as needed           7
    Pear                9-21 g a.i./100 l        4 or more as needed           7
    Peach               15-17 g a.i./100 l       at 10 to 20-day intervals     7
    Peanut              73 g a.i./100 l          at 15 to 20-day intervals     7
    Beans               21 g a.i./100 l          2-3                           7
    Grape               15-30 g a.i./100 l       3-5                           14
    Tomato              15 g a.i./100 l          at 15-day intervals           7
    Celery              15-22 g a.i./100 l       at 10 to 15-day intervals     7
    Lettuce             same as above            same as above                 7
    Strawberry          same as above            3                             7

    Australia
    Peanuts1            100                      14-day intervals              28
    Pome fruit2         15-30 g/100 l            10 to 14-day intervals        7
    Stone fruit3        15-60 g/100 l            up to 4                       1
    Roses
                                                                                               

    Table 1  (con't)
                                                                                               

                                     Application                               Preharvest
    Country                                                                    interval
    and                 Rate                     Number                        (days)
    Crop                (g a.i./ha or as
                        specified)
                                                                                               

    China (Taiwan Prov.)
    Tobacco             500 g/kg
    Chrysanthemums

    Colombia
    Rice                200-300                  not specified                 10
    Sorghum             200-300                  not specified                 10

    France
    Cereals             270                      1 or more                     apply between stem
                                                                                    erection and first
                                                                                    node stage

    New Zealand
    Stone fruit         20-30 g/100 l            7 to 14-day intervals         1
    Beans               1 125                    2 at specified times          14
    Field tomatoes      150 g/100 l              14-day intervals              3
    Wheat               150-200 g a.i.           1 at specified times

    United Kingdom
    Winter wheat        333                      1                             apply between
                                                                                    leaf
    Winter barley       333                      1                             sheaths erect
                                                                                    and first node
                                                                                    detectable
    Barley              333                      1 to 2                        same as above
    Winter rye          333                      1                             same as above
                                                                                               

    1    South QLD only.
    2    All states.
    3    QLD, NSW, VIC, SA and TAS only.
    
    RESIDUES RESULTING FROM SUPERVISED TRIALS

         Additional information and data were received from the
    manufacturers, which are summarized in Table 2 (DuPont 1983b; BASF
    1983).

        Table 2  Carbendazim Residues in Crops
                                                                                                                          

                                        Application                  Interval                  Carbendazim residues
    Country                                                          after last                                           
    and                      Rate (kg/ha)        Frequency           application         Range                    No. of
    crop                                                             (days)              (mg/kg)                  samples
                                                                                                                          

    Belgium
    Wheat
    grain                    0.28 - 0.48         3X                  0 - 28              <0.05                    30

    Brazil
    Beans
    (carioca)                340 - 680           3X                  31                  <0.05                    2
    beans                    340 - 680           1X                  17                  <0.05                    2

    Onions                   0.16 - 0.32         2X                  1                   0.39 - 1.10              2
                             0.16 - 0.32         3X                  I                   0.24 - 1.30              2
                             0.16 - 0.32         4X                  1                   0.13 - 0.71              2

    Rice

    grain                    0.35                2X                  38                  0.12                     1
    grain                    1.2 kg/ha           4X                  36                  <0.05                    1
    grain                    1.7                 4X                  36                  0.05                     1
    grain                    0.8                 2X                  41                  <0.05                    1
    grain                    1.7                 3X                  36                  0.07                     1
    grain                    0.8                 2X                  41                  <0.05                    1
    grain                    1.7                 2X                  41                  <0.05                    1

    Soybeans

    beans                    0.25 - 0.5          2X                  19 - 35             <0.05                    3
                                                                                                                          

    Table 2  (con't)
                                                                                                                          

                                        Application                  Interval                  Carbendazim residues
    Country                                                          after last                                           
    and                      Rate (kg/ha)        Frequency           application         Range                    No. of
    crop                                                             (days)              (mg/kg)                  samples
                                                                                                                          

    Wheat
    grain                    0.34 - 0.68         2 - 3X              14 - 38             <0.05 - 0.22             1

    Costa Rica
    Bananas

    whole                    0.25 - 0.5          6X                  1                   <0.05 - 0.08             8
    pulp                     0.25 - 0.5          6x                  1                   <0.05                    8
    whole                    0.25                8X                  1                   <0.05                    4
    pulp                     0.25                8X                  1                   <0.05                    4
    whole                    0.25 - 0.5          10X                 1                   <0.05                    2
    pulp                     0.25 - 0.5          10X                 1                   <0.05                    2
    whole                    325 - 650 mg/ha     1X postharvest      1                   0.15 - 2.4               18
    pulp                     325 - 650 mg/ha     1X                  1                   <0.05 - 0.11             18

    Pineapple
    flesh                    0.015- 0.025 g/dip  1 dip               15 - 16             0.25 - 1.10              9
    skin                     same as above       1 dip               15 - 16             8.3 - 60                 9

    Fed. Rep. Germany
    Hops
    dry                      225 - 375 g/ha      2X                  17 - 26             16 - 49                  4
    Potatoes
    unwashed                 30 mg/1 000 kg      1X                  0,28,56,135         0.3 - 1.2                4
    washed                   30 mg/1 000 kg      1X                  0,28,56,135         0.3- 0.8                 4
    peel                     30 mg/1 000 kg      1X                  0,28,56,135         0.3 - 1.6                4
    peeled                   30 mg/1 000 kg      1X                  0,28,56,135         <0.2 - 0.3               4
                                                                                                                          

    Table 2  (con't)
                                                                                                                          

                                        Application                  Interval                  Carbendazim residues
    Country                                                          after last                                           
    and                      Rate (kg/ha)        Frequency           application         Range                    No. of
    crop                                                             (days)              (mg/kg)                  samples
                                                                                                                          

    South Africa
    Pineapple
    fruit                    0.05 - 0.125%       1 dip               26                  4.6 - 6.5                6
    flesh                    0.05 - 0.125%       1 dip               26                  0.2- 0.5                 6

    United Kingdom

    Swedes                   125 g/ha            1X                  52                  <0.06                    1

    United States

    Apples                   0.1 - 0.25          11X                 41                  0.36 - 0.55              2
                             0.1 - 0.25          3x                  81                  <0.05                    2
                             0.1- 0.2                                0 - 17              0.35 - 1.4               6

    Apricots                 1 - 1.5             3 - 4X              0 - 10              <0.05 - 7.1              3

    Beans                    0.75 - 1.5          2x                  8 - 25              1.4 - 42                 12

     beans                   1.3 - 2.6           3X                  10 - 21             0.11 - 0.79              6
     foliage                 1.3 - 2.6           3X                  10 - 21             6.7 - 28                 6
     beams                   0.75 - 2.0          1X                  29 - 41             <0.05                    6

    Blueberries              1 - 2               6X                  14 - 28             0.96 - 5.6               6

    Celery                   0.5                 14X                 7 - 14              0.76 - 1.6               3
                             2.0                 10X                 7 - 10              1.3 - 2.3                2
                                                                                                                          

    Table 2  (con't)
                                                                                                                          

                                        Application                  Interval                  Carbendazim residues
    Country                                                          after last                                           
    and                      Rate (kg/ha)        Frequency           application         Range                    No. of
    crop                                                             (days)              (mg/kg)                  samples
                                                                                                                          

    Cherries                 0.1                 8X                  1 - 7               1.3 - 7.0                3
                             0.2 - 0.4           5X                  1 - 7               0.32 - 0.66              6
                             1.5                 3X                  7                   <0.05                    1
                             1.5                 3X                  14 - 21             <0.05 - 0.46             2
                             0.4 - 0.5           5x                  0 - 7               0.3 - 11.0               5

    Cucumbers                0.5                 10X                 5                   0.33                     1
                             0.5                 6X                  0 - 2               0.08 - 0.26              3

    Eggplant                 0.5 - 1.0           4X                  1 - 14              <0.05 - 0.44             6

    Grapes                   0.5                 9X                  8 - 20              5.0 - 6.5                6
                             1.33                5X                  1 - 7               2.7 - 4.1                4
                             0.75- 1.0           4x                  28 - 138            0.48 - 4.4               2
                             1                   3X                  5 - 7               1.7 - 2.3                2

    Grapefruit               1 kg/ha + dip       4X                  1                   0.88                     1
                             1.5                 4X                  1                   0.80                     1
                             3.0                 4X                  1                   2.1                      1
                             4.0 kg/ha + dip     4X                  I                   3.5                      1

    Oats                     0.5 - 1             4X                  3 - 21              0.18 - 7.6               8

    Oranges                  1 - 2               1X foliar           0 - 7               0.06 - 7.3               4
                             1 lb/100 g          1X dip              0                   1.8                      1
                                                                                                                          

    Table 2  (con't)
                                                                                                                          

                                        Application                  Interval                  Carbendazim residues
    Country                                                          after last                                           
    and                      Rate (kg/ha)        Frequency           application         Range                    No. of
    crop                                                             (days)              (mg/kg)                  samples
                                                                                                                          

    Peaches                  0.5                 2X                  0 - 7               1.5 - 2.6                3
                             1.5                 4X                  3                   1.9                      1
                             1.5                 4X                  0                   1.7                      1
                             0.2 - 0.4           10X                 0 - 14              1.4 - 5.0                6
                             0.75                4X                  1 - 14              0.36 - 3.1               6

    Pears                    1 - 1.5             6X                  125                 <0.05 - 0.08             3

    Peanuts

    nut                      0.5                 7X                  7                   <0.05                    1
    bulb                     0.5                 7X                  7                   0.44                     1
    hay                      0.5                 7x                  7                   3.3                      1
    whole nut                0.25                1X                  30                  <0.05                    1
    meat                     0.25                1X                                      <0.05                    1

    Peppers, bell            0.5 - 1.0           4X                  1 - 14              0.18 - 2.2               6

    Rice
    grain                    1.0                 1X                  49                  <0.05                    1
    straw                    1.0                 1X                  49                  3.0                      1
    head                     1.0                 2X                  26                  1.4                      1
    head                     1.0                 1X                  14                  0.18 - 0.57              2
    forage                   1.0                 1X                  14                  0.08 - 6.6               2
    head                     1.0                 2X                  18                  0.24                     1
    forage                   1.0                 2X                  18                  11                       1
    head                     2 kg/ha             2X                  18                  0.37                     1
    forage                   2 kg/ha             2X                  18                  25                       1
                                                                                                                          

    Table 2  (con't)
                                                                                                                          

                                        Application                  Interval                  Carbendazim residues
    Country                                                          after last                                           
    and                      Rate (kg/ha)        Frequency           application         Range                    No. of
    crop                                                             (days)              (mg/kg)                  samples
                                                                                                                          

    Soybeans
    beans                    0.25 - 1.0          2X                  48 - 51             <0.05 - 0.11             3
    hay                      0.25 - 1.0          2X                  48 - 51             <0.05                    2

    Strawberries             0.5                 4X                  1                   0.54 - 0.75              2
                             0.5 - 1             5X                  0 - 7               1.0 - 3.0                8

    Sugarbeets
    tops                     0.2 - 0.4           2X                  7 - 21              <0.05 - 8.3              15
    root                     0.2 - 0.4           2X                  7 - 21              <0.05 - 8.3              15

    Wheat

    straw                    0.5                 1X                  129 - 134           <0.05                    4
    grain                    0.5                 4X                  129 - 134           <0.05                    4
    straw                    0.1 - 1             2X                  60                  0.42 - 4.4               4
    grain                    0.1 - 1             2X                  60                  <0.05                    4
    straw                    0.1 - 0.25          3X                  45                  <0.05 - 0.07             2
    grain                    0.1 - 0.25          3X                  45                  <0.05                    2
    straw (green)            0.25 - 1            3X                  22                  1.8 - 16                 3
    grain (immature)         0.25 - 1            3X                                      0.71 - 6.8               3

    West Indies
    Bananas
    whole                    0.15                4X                  0 - 3               <0.05 - 0.07             6
    whole                    0.15                1X                  0 - 5               <0.05                    6
                                                                                                                          
        FATE OF RESIDUES

    In Plants

         Alfalfa, soybean, and ryegrass, which were grown in 1 cu ft
    (1 cu ft = 0.0283 cu m) containers in a greenhouse in soil treated
    with 80:20 mixtures of carbendazim (MBC) and 2-aminobenzimidazole
    (2-AB), contained small but detectable residues of both compounds.
    Both 14C-labelled and non-labelled mixtures were applied at the rate
    of 2 kg/ha uniformly incorporated in the 0-10 cm layer of soil. In the
    14C studies, alfalfa contained total 14C residues equivalent to
    0.13 - 0.30 mg/kg of MBC/2-AB. Soybean plants contained 0.32 -
    0.53 mg/kg and ryegrass (20-183 days) had 0.09 - 0.19 mg/kg. Each
    plant contained approximately equal amounts of MBC, 2-AB and a polar
    unknown fraction. Alfalfa from the non-labelled series contained 0.05
    and 0.08 mg/kg, respectively, of MBC and 2-AB at the first cutting and
    <0.05 mg/kg of either compound at the second and third cuttings.
    Soybean plants contained <0.1 mg/kg of 2-AB and 0.59 mg/kg of MBC.
    Ryegrass from six cuttings (20-149 days) contained 0.08 - 0.48 mg/kg
    of MBC and <0.05 mg/kg of 2-AB. All data were on a fresh weight basis
    (Rhodes et al. 1983).

         Bean plants grown to maturity in Delaware (United States)
    contained less than 0.1 mg/kg total 14C-residue in the edible beans
    following two foliar applications of 1 kg a.i./ha of 2-14C-MBC at 25
    percent and 50 percent bloom. Total 14C-residues in the bean foliage
    decreased from about 5 mg/kg one week after the second spray to
    0.2 mg/kg three weeks later. Of the total 14C in the edible beans and
    foliage, 89-95 percent was intact free MBC and 2-8 percent was free
    2-AB. An additional 1-3 percent of the 14C was found as -glycosidic
    conjugates of MBC and 2-AB (Han 1983a).

         Benomyl was sprayed on apple foliage at 1.68 kg/ha leaving
    deposits ranging from 95-120 g/g of leaf. Twelve days after
    application at least 15 percent of the original deposit existed as
    intact benomyl. The MBC concentration in leaves gradually increased,
    remaining above 17 g/g for approx. 80 days as a result of three
    applications (of benomyl). The maximum concentration of 55.8 g/g,
    occurred eight days after the third (and last) application (Chiba &
    Veres 1981).

    In Soil

         In greenhouse studies to determine run-off and leaching of
    2-14C-MBC on soil, a container of Keyport silt loam was treated
    (spray) with labelled MBC, at a rate of 10 kg/ha, by spraying the
    upper one-third (0.093 sq m) of the plot and allowed to stand 24h.
    Artificial rain was then applied at 3.75 cm the first day after
    treatment and 2.5 cm on the third and seventh days. All water that ran
    off or leached through the soil was collected and analysed for total

    14C by counting 2 ml aliquots in a liquid scintillation counter. Soil
    in the plot was divided into increments for analysis, air dried and
    1 g aliquots analysed for total 14C. After each of the three rain
    applications, 0.05 - 0.39 percent of the applied 14C was found in
    run-off water; <0.01 percent was found in the leach water after two
    rains and 0.19 percent after the third one. Soil analyses showed that
    90.6 percent of the applied activity remained in the treated area and
    93.1 percent in the first 10 cm of soil (Rhodes & Long 1983).

         Degradation studies of labelled (2-14C) 2-amino benzimidazole,
    the primary degradation product of carbendazim, in soil showed that
    14C evolution increased exponentially from 1 to 22C, reached a
    maximum at 22, remained almost constant up to 35, then became almost
    nil at 40, when the soil water content was 100 percent of field
    capacity. At 25C evolution increased exponentially from 28 to 94
    percent of field capacity of water; evolution decreased slightly at
    about this temperature. These and other results indicate the presence
    of organisms that are able to decompose 2-AB (Helweg 1979).

         Laboratory studies in two soil types under anaerobic conditions
    using 2-14C-labelled carbendazim showed only a small amount of 2-AB
    (<2 percent) and no other postulated degradation products (<0.05
    percent). Reincorporation of 14C into soil humus was indicated by
    fractionation studies, which showed that the unextracted 14C-residue
    was widely distributed in various organic soil components (Han 1983b).

         Laboratory experiments with flooded soils treated at various
    levels (0-1 000 ppm) with benomyl, MBC and 2-AB showed that benomyl
    exerts a strongly inhibitory effect on nitrofication at 1 000 ppm, as
    measured by nitrate production. No inhibition of nitrification by MBC
    occurred at 10 or 100 ppm but slight retardation was noted at
    1 000 ppm. Substantial inhibition occurred for 2-AB at the 100 and
    1 000 ppm levels. Similar results were obtained in studies involving
    pure cultures of nitrifying bacteria (Ramakrishna et al. 1979).

    METHODS OF RESIDUE ANALYSIS

         The majority of the data presented in Table 2 were obtained using
    the method of Pease and Holt (1971), which is still suitable for
    regulatory purposes.

         Since the last evaluation of carbendazim in 1978, a simple high
    performance liquid chromatographic (HPLC) method has been developed
    to determine individually residues of benomyl and MBC on apple
    leaves without clean-up. In this procedure, sample leaves are
    freeze-dried and tumble-extracted with CHCl3 containing 5 mg/ml
    of n-propyl isocyanate at 1C. The latter converts the MBC into
    1-(n-propylcarbamoyl)-2-benzimidozole carbamate, which is more easily
    extracted and allows its distinction from intact benomyl residues

    during HPLC using a UV detector set at 280 nm. Recoveries of both
    compounds ranged from 78 to 86 percent and a detection level of
    0.2 mg/kg was achieved (Chiba & Veres 1980).

    APPRAISAL

         New information was received on use patterns and registered uses
    for carbendazim in the United Kingdom, France, Australia, China
    (Taiwan province), New Zealand, Colombia, Argentina and 22 other
    countries. Some additional information was available on the fate of
    residues in plants and soil.

         Systemic uptake of labelled carbendazim from treated soil
    (2 kg/ha) was limited, reaching maximum levels of total 14C of
    0.3 mg/kg in alfalfa, 0.53 mg/kg in soybean plants and 0.19 mg/kg in
    ryegrass. Each plant contained approximately equal amounts of
    carbendazim, 2-aminobenzimidazole (2-AB) and a polar unknown fraction.

         Soil mobility of carbendazim is limited, with a maximum of 0.4
    percent of applied 14C being found in run-off water from artificial
    rain and 0.2 percent in leach water. The soil contained 91 percent of
    applied activity in the treated area and 93 percent in the first
    10 cm.

         Degradation of carbendazim in soil under anaerobic conditions
    resulted in only a small amount (<2 percent of the applied dose) of
    2-AB and no other products. The carbendazim was apparently mostly
    incorporated into soil humus. In contrast to benomyl, which is
    strongly inhibitory to soil nitrification at high doses (1 000 ppm),
    carbendazim showed no effects at low levels and only slight inhibition
    at 1 000 ppm. Substantial inhibition was shown by 2-AB at medium
    (100 ppm) to high (1 000 ppm) levels.

         New or additional data on residue levels in various crops
    resulting from supervised trials with carbendazim were received from
    the Federal Republic of Germany and the United States and from trials
    with benomyl from those countries as well as Australia, Japan, Kenya
    and the United Kingdom. The data supported previously recommended
    levels except for bean fodder (formerly bean vines), which should be
    increased from 30 to 50 mg/kg; apricots, grapes and sugarbeet tops
    from 5 to 10 mg/kg; rice straw from 2 to 15 mg/kg; peanut hay from 2
    to 5 mg/kg; and peanut hulls from 0.2 to 1 mg/kg. Additional
    commodities for which recommendations can be made include dry hops
    (50 mg/kg), peppers and blueberries (5 mg/kg), onions (2 mg/kg),
    eggplant and oats (0.5 mg/kg), chestnuts and soybeans (0.2 mg/kg) and
    asparagus, rutabagas and soybean hay (0.1 mg/kg).

         The improved residue analytical method of Pease and Holt is still
    recommended for regulatory use. A simple HPLC method, which
    individually determines residues of benomyl and carbendazim on apple
    leaves without clean-up, has been published that appears to be useful
    for research purposes.

    RECOMMENDATIONS

         The guideline levels listed in 1978 are now converted to maximum
    residue limits on the basis of the establishment of an ADI for
    carbendazim.

         The following maximum residue levels, amending or additional to
    those of 1978, are proposed. Those levels which are based on benomyl
    trials (see benomyl) are indicated with a 1 beside the commodity and
    were derived by dividing benomyl tabular data by the conversion factor
    of 1.52.
                                                                        

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

    Bean fodder         50 (increased from 30)      8
    *Hops, dry          50                          17
    Rice straw          15 (increased from 2)       18
    Apricots            10 (increased from 5)       0
    Grapes              10 (increased from 5)       8
    Sugarbeet tops      10 (increased from 5)       7
    *Pineapple1         20                          Postharvest dip
    Peanut hay          5 (increased from 2)        7
    Wheat straw1        5 (increased from 2)        -
    *Blueberries        5                           14
    *Peppers            5                           7
    Melons1             2 (increased from 0.5)      Postharvest dip
    *Onions             2                           1
    *Sweet potatoes1    1                           90
    Peanut hulls1       1 (increased from 0.2)
    *Eggplant           0.5                         1
    *Oats               0.5                         21
    *Soybeans           0.2                         48
    *Chestnuts1         0.2                         1
    *Soybean hay        0.1**                       48
    *Asparagus1         0.1**                       260
    *Taro1              0.1**                       162
    *Rutabagas          0.1**                       52
                                                                        
    *    New NRLs.
    **   At or about the limit of determination.
    1    Based on benomyl data.

    REFERENCES- RESIDUES

    BASF. Residue data on pineapples, hops and swedes. (Unpublished)
    1983

    Chiba, M. & Veres, D.F. High performance liquid chromatographic method
    1980      for simultaneous determination of residual benomyl and
              methyl 2-benzimidazole carbamate on apple foliage without
              cleanup. J. Assoc. Off. Anal. Chem. 63(6): 1291-1295.

    Chiba, M. & Veres, D.F. Fate of benomyl and its degradation compound
    1981      methyl 2-benzimidazolecarbamate on apple foliage. J. Agric.
              Food Chem., 29: 588-590.

    DuPont. Samples of registered labels for carbendazim in the United
    1983a     Kingdom, France, Australia, Taiwan, New Zealand, Colombia
              and Argentina.

    DuPont. Analytical reports on residue data in various crops.
    1983b     (Unpublished)

    Han, J. C-Y. Characterization of residues in bean plants following
    1983a     foliar spray application with MBC. DuPont Report.
              (Unpublished)

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

    Helweg, A. Influence of temperature, humidity, and inoculation on the
    1979      degradation of 14C-labeled 2-aminobenzimidazole in soil.
              Water, Air, Soil Pollut., 12: 275-281.

    Hoechst. Computer printout of registered or permitted uses of
    1983      carbendazim in 29 countries submitted to the Meeting.

    Pease, H.L. & Holt, R.F. Improved method for determining benomyl
    1971      residues. J. Assoc. Off. Anal. Chem., 54(6): 1399-1402.

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

    Rhodes, R.C. & Long, J.D. Run-off and leaching studies with methyl-2
    1983      14C-benzimidazole-carbamate on soil. DuPont report.
              (Unpublished)

    Rhodes, R.C., Pease, A.L. & Holt, R.F. Greenhouse studies on crop
    1983      uptake of MBC and 2-AB from soil. DuPont report.
              (Unpublished)


    See Also:
       Toxicological Abbreviations
       Carbendazim (EHC 149, 1993)
       Carbendazim (HSG 82, 1993)
       Carbendazim (ICSC)
       Carbendazim (PDS)
       Carbendazim (WHO Pesticide Residues Series 3)
       Carbendazim (Pesticide residues in food: 1976 evaluations)
       Carbendazim (Pesticide residues in food: 1977 evaluations)
       Carbendazim (Pesticide residues in food: 1978 evaluations)
       Carbendazim (Pesticide residues in food: 1985 evaluations Part II Toxicology)
       Carbendazim (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)
       Carbendazim (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)
       Carbendazim (JMPR Evaluations 2005 Part II Toxicological)