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    BITERTANOL        JMPR 1998

    First draft prepared by
    R. Solecki
    Pesticide and Biocide Division, Federal Insitute 
    for Health Protection of Consumers 
    and Veterinary Medicine, Berlin, Germany

         Explanation
         Evaluation for acceptable daily intake 
              Biochemical aspects 
                   Absorption, distribution, and excretion
                   Biotransformation 
              Toxicological studies 
                   Acute toxicity
                   Short-term studies of toxicity
                   Long-term studies of toxicity and carcinogenicity
                   Genotoxicity 
                   Reproductive toxicity
                        Multigeneration reproductive toxicity
                        Developmental toxicity 
                   Special studies 
                        Effects on the central nervous system 
                        Toxicity in combinations 
                        Effect on the liver 
                   Studies on metabolites 
                        1-(Triazol-1-yl)-1-(4'-phenylphenoxy)-
                             3,3-dimethylbutan-2-one (plants, soil) 
                        Bitertanol benzoic acid (soil)
                        1,2,4-triazole (photodegradation, soil)
              Observations in humans 
         Comments 
         Toxicological evaluation 
         References 


    Explanation

         Bitertanol was previously evaluated toxicologically by the Joint
    Meeting in 1983, 1987, and 1988 (Annex 1, references 40, 50, and 53).
    The 1983 JMPR allocated a temporary ADI of 0-0.005 mg/kg bw and
    requested studies on metabolism in order to clarify the metabolic
    pathway of bitertanol, a study of toxicity in dogs treated orally for
    a minimum of one year, and a long-term study of toxicity and
    carcinogenicity in rats at appropriate doses. Relevant data were
    submitted for evaluation by the 1987 JMPR, when an ADI of 0-0.003
    mg/kg bw was established on the basis of a NOAEL of 10 ppm in a
    one-year study in dogs. In 1988, the Meeting concluded that, upon
    further consideration of the data from two-year and one-year studies
    of toxicity in dogs, the NOAEL was 25 ppm (equal to 1 mg/kg bw per
    day). Therefore, an ADI of 0-0.01 mg/kg bw was allocated using a
    safety factor of 100. The compound was reviewed at the present Meeting
    within the CCPR periodic review programme. This monograph summarizes

    new data on bitertanol and data that were not previously reviewed and
    includes relevant data from the previous monographs (Annex 1,
    references 41 and 52).

    Evaluation for acceptable daily intake

    1.  Biochemical aspects 

     (a)  Absorption, distribution, and excretion

         Groups of five male and five female Wistar rats received
    [14C-phenyl]-bitertanol as a solution in ethylene glycol as a single
    oral dose of 100 or 1000 mg/kg bw or a single intravenous dose of
    100 mg/kg bw as well as 14 daily oral doses of unlabelled chemical at
    100 mg/kg bw, followed by a single oral dose of 14C-bitertanol at
    100 mg/kg bw. Urine and faeces were collected 6 and 24 h after dosing
    and then at subsequent 24-h intervals until sacrifice seven days
    later. Serial blood samples were collected during this period. 

         Total absorption of radiolabel was found to depend on the dose
    over the range studied. Faecal excretion of radiolabel after
    intravenous administration showed that biliary excretion was
    predominant. Urinary excretion represented 4-11% of the administered
    dose, while no radiolabel was detected in expired air. The total
    recovery of radiolabel was > 92%. Pharmaco-kinetic analysis indicated
    that absorption of bitertanol after oral administration follows a
    first-order pattern for single and repeated doses of 100 mg/kg bw but
    not at the higher dose (1000 mg/kg), suggesting saturation of
    absorption, distribution, or elimination. The highest concentrations
    detected in tissues were in the liver (17.9 ppm, females) and kidney
    (5.9 ppm, males) of animals at the high dose. Seven days after dosing,
    0.2-0.4% of the administered radiolabel remained in the body (Puhl &
    Hurley, 1983).

         The biokinetic behaviour of bitertanol in rats was investigated
    in studies requested by the Japanese registration authority, which
    were conducted in compliance with standards of good laboratory
    practice. The compound was uniformly labelled with 14C in the phenyl
    moiety, as shown in Figure 1 and was administered orally to male and
    female rats at a dose of 10 mg/kg bw. Radiolabel was determined over
    time in the excreta and plasma, and the body and individual organs and
    tissues were assayed for total radiolabel at sacrifice. Male rats were
    also given the same dose intraduodenally after bile fistulation, and
    total radiolabel was assayed in excreta, including the bile, and in
    the body at sacrifice. Total radiolabel was also determined over time
    in various organs of male rats after oral administration of a single
    dose of 10 mg/kg bw. 

    FIGURE 1

         About 84% of the dose was absorbed after oral administration.
    Absorption commenced immediately, and the plasma concentration
    increased from 25 to 75% of the peak value within 1-2 h. The
    radiolabel was eliminated rapidly and almost completely from the body
    within the 72-h test period. More than 90% of the recovered radiolabel
    was excreted with the faeces, and about 7% with the urine. On average,
    the residual radiolabel in the body (excluding the gastrointestinal
    tract) after 72 h represented 0.5% of the administered dose. The
    results obtained after bile fistulation indicate that the largest
    fraction of faecally eliminated radioactivity was first absorbed and
    then eliminated into the gut lumen with the bile (about 77%). Most of
    the radiolabel eliminated in the bile underwent enterohepatic
    circulation. The radiolabel was rapidly distributed from the
    intravascular space to the peripheral tissues. The maximum
    concentration in plasma was reached after 3-8 h. The terminal phase of
    elimination of radiolabel from the plasma was described by linear
    regression analysis, which yielded a half-life of about 26 h. The
    distribution of total radiolabel in individual organs of male rats at
    various times after administration of a single oral dose of 10 mg/kg
    was generally similar to that observed 72 h after administration. The
    highest concentrations were found in the liver and kidney (Klein,
    1988a,b, 1989).

         After a 50% formulation of 14C-labelled bitertanol was applied
    to the skin of adult male and female albino rabbits, the mean level of
    dermal penetration was around 10%. There were no marked sex-specific
    differences. Since this experiment was designed to simulate
    'worst-case' conditions, lower absorption rates might expected in
    practice (Hixson, 1984).

     (b)  Biotransformation

         In the first study described above, bitertanol was extensively
    metabolized, and the metabolite profile was similar in the groups
    receiving 100 or 1000 mg/kg bw. The relative amounts of metabolites
    were also similar, except that the animals receiving the highest oral
    dose eliminated much more unchanged parent compound than the others.
    Fourteen metabolites (plus bitertanol), representing 38-76% of the

    recovered radiolabel, were identified or characterized. Hydroxylation
    of the  para position of the biphenyl and methyl groups of the
     tert-butyl moieties gave rise to phenolic and diol metabolites.
    Although one diastereomer of the latter was detected, it underwent
    oxidation to the corresponding butanoic acid and subsequent ring
    hydroxylation. The parahydroxylated diol was also detected, as was
    4,4-dihydroxy-biophenyl, and other hydroxylated metabolites were also
    tentatively identified. The metabolic reactions thus included ring
    monohydroxylation, ring dihydroxylation, aryl  O-methylation,
    aliphatic hydroxylation, aliphatic oxidation to carboxylic acids, and
    ether cleavage. In addition to the metabolites shown in Figure 2,
    glucuronide and sulfate conjugates of some metabolites, including
     para-hydroxybitertanol, were also detected in faeces and urine (Puhl
    & Hurley, 1983).

         In the second set of studies described above, the structures and
    amounts of metabolites were determined in faeces, urine, and bile and
    in the liver, kidneys, and perirenal fat at various times after
    treatment. The metabolism of bitertanol began immediately after
    absorption from the gastrointestinal tract lumen. The parent compound
    was not detected in urine or bile, and the only metabolite identified
    in the bile was  para-hydroxybitertanol. Excretion of the unchanged
    parent compound in the urine was unlikely because of its lipophilic
    character. Metabolic degradation of bitertanol in the organs was
    rapid: within 8 h, the concentration in the liver fell from around 15%
    to about 2% of the total radiolabel in the organs. The main metabolite
    in the liver was also  para-hydroxybitertanol; smaller amounts of
     para-hydroxy-bitertanol acid,  para-hydroxybitertanol alcohol, and
    bitertanol acid were also identified. The distribution of metabolites
    in the kidneys was similar: total organ radiolabel fell from around
    14% to about 2.5% within 8 h; the main metabolite was again
     para-hydroxybitertanol, which represented 30-50% of the organ
    radiolabel. Furthermore, the amounts of metabolites in the liver and
    kidneys were similar. The total amount of radiolabel in fat samples
    was too low to permit reliable quantification or identification of
    possible metabolites, due mainly to the small amount of fat available
    in the young animals. A proposed metabolic pathway for bitertanol in
    rats is given in Figure 3. The parent compound found in the faeces of
    orally treated rats was probably due to the unabsorbed fraction of
    administered radiolabel, representing about 15% of the original dose.
    The main metabolite in the liver and kidneys,
     para-hydroxy-bitertanol, was also identified in the faeces. The
    amounts of the other biotransformation products in the organs were
    probably too low for detection in the excreta (Klein, 1988b, 1989).

    2.  Toxicological studies

     (a)  Acute toxicity 

         The methods used in the studies summarized below complied to a
    certain extent with OECD guidelines. At the time that most of the
    studies were performed, compliance with good laboratory practice (GLP)
    was not compulsory. The results of studies on the acute toxicity of

    FIGURE 2

    FIGURE 3

    bitertanol are summarized in Table 1. Bitertanol had very low acute
    toxicity in rats, mice, and dogs treated orally. No significant sex
    difference was observed. The LD50 values are 4000-5000 mg/kg bw or
    higher. The toxicological properties of the A and B isomers are
    similar. The symptoms included nonspecific signs, such as deteriorated
    general condition, isolation from the group, and piloerection;
    however, central nervous system effects were also seen, including
    sedation, spasms, and respiratory disturbances. Lobulation of the
    liver and irritation of the glandular stomach mucosa were observed at
    necropsy of orally treated rats. Further signs in dogs were vomiting
    and diarrhoea. Sheep were more susceptible, with an oral LD50 of
    about 1000 mg/kg bw. Bitertanol was moderately toxic to rats and mice
    after intraperitoneal injection. 

         Dermal exposure to a dose of 5000 mg/kg bw was tolerated by rats
    with no observed signs. It was not toxic to rats after inhalation in
    an aerosol, even at the highest test concentration. An initial test
    showed no primary irritation of the intact or abraded skin of rabbits
    inspected 24 and 72 h after the beginning of exposure (Thyssen &
    Kimmerle, 1977a). In a study in rabbits, the active ingredient was
    found to be slightly irritating to intact and abraded skin (Iyatomy,
    1981).

         A five-minute treatment of the eye of rabbits did not cause
    primary irritation of the mucous membranes. Slight to moderate
    reddening of the conjunctivae, which persisted for about 48 h, was
    observed after a 24-h exposure (Thyssen & Kimmerle, 1977a). A reaction
    that was reversible within four days was seen in rabbit conjunctivae;
    the cornea and iris were unaffected (Iyatomy, 1981).

         After an initial administration of 0.05 mg bitertanol per animal
    to female Pirbright guinea-pigs, nine repeated intracutaneous
    injections of emulsified bitertanol (0.1 mg) over three consecutive
    weeks had no sensitizing effect. Intracutaneous injection of an
    additional 0.05 mg after a further two weeks also failed to produce
    signs of dermal sensitization (Thyssen, 1977).

         Magnusson and Kligman tests in 20 male and 20 female Pirbright
    guinea-pigs with Freund's adjuvant provided no evidence of sensitizing
    effects of bitertanol at a concentration of 1% for intradermal
    induction, 25% for topical induction, and 25% for challenge (Flucke,
    1981). 

     (b)  Short-term studies of toxicity

     Rats

         Groups of 20 male and 20 female Wistar rats were given bitertanol
    (purity, 96.5%) by gavage at doses of 0, 30, 100, or 300 mg/kg bw per
    day for 28 days. Half of the animals were then sacrificed, and the
    other half were observed for a further 28 days. The method used in

        Table 1. Acute toxicity of bitertanol

                                                                                                                        
    Species     Strain           Sex      Route                LD50 or LC50      Purity     Reference
                                                               (mg/kg bw or      (%)
                                                               mg/m3 air)
                                                                                                                        

    Rat         NR               M        Oral                 > 5000            99.1 A     Mihail (1978a)
    Rat         NR               M        Oral                 > 5000            97.1 B     Mihail (1978b)
    Rat         Wistar           M/F      Oral (fasted)        > 5000            96.5       Thyssen & Kimmerle (1977a)
    Rat         NR               M        Oral                 > 5000            97.3       Flucke (1978)
    Rat         NR               M        Oral                 4000              95.0       Flucke (1979)
    Rat         NR               M        Oral                 3700              95.0       Iyatomy (1980)
                                 F        Oral                 3900
    Rat         Wistar           F        Oral (fasted)        > 5000            95.1       Flucke (1980)
    Rat         NR               M        Oral                 > 5000            96.7       Heimann (1981)
                                 M        Oral (fasted)        > 5000
    Rat         NR               M        Oral (fasted)        4800              99.1       Mihail (1982a)
    Rat         NR               M        Oral (fasted)        4800              97.1       Mihail (1982b)
    Rat         NR               M        Oral                 > 5000            NR         Heimann (1983a)
    Rat         NR               M        Oral (fasted)        > 5000            97.6       Heimann (1984a)
    Mouse       NMRI             M        Oral (fasted)        4500              96.5       Thyssen & Kimmerle (1977a)
                                 F        Oral (fasted)        4200
    Mouse       NR               M        Oral                 3500              95.0       Iyatomy (1980)
                                 F        Oral                 3200
    Dog         Beagle           M/F      Oral (fasted)        > 5000            95.0       Hoffmann (1981a)
    Sheep       Blackface        M/F      Oral                 ~ 1000            95.0       Hoffmann (1981b)

    Rat         Wistar           M/F      Dermal               > 5000            96.5       Thyssen & Kimmerle (1977a)
    Rat         NR               M/F      Dermal               > 5000a           95.0       Iyatomy (1980)
    Mouse       NR               M/F      Dermal               > 5000            95.0       Iyatomy (1980)
    Rabbit      New Zealand      M/F      Dermal               > 2000            94.9       Hixson (1979)

    Rat         Wistar           M/F      Inhalation 1 h       > 720             96.5       Thyssen & Kimmerle (1977a)
    Rat         Wistar           M/F      Inhalation 4 h       > 550             96.5       Thyssen & Kimmerle (1977a)
    Rat         Wistar           M/F      Inhalation 5 x 4 h   > 380             96.5       Thyssen & Kimmerle (1977a)
    Ratb        Sprague-Dawley   M/F      Inhalation 4 h       > 1200            95.7       Shiotsuka (1987)

    Table 1. (continued)

                                                                                                                        
    Species     Strain           Sex      Route                LD50 or LC50      Purity     Reference
                                                               (mg/kg bw or      (%)
                                                               mg/m3 air)
                                                                                                                        

    Rat         Wistar           M        Intraperitoneal      1200              96.5       Thyssen & Kimmerle (1977a)
                                 F        Intraperitoneal      720
    Rat         NR               M        Intraperitoneal      700               95.0       Iyatomy (1980)
                                 F        Intraperitoneal      560
    Mouse       NR               M        Intraperitoneal      570               95.0       Iyatomy (1980)
                                 F        Intraperitoneal      610

    Rat         NR               M/F      Subcutaneous         > 1000            95.0       Iyatomy (1980)
    Mouse       NMRI             M/F      Subcutaneous         > 5000            96.5       Thyssen & Kimmerle (1977a)
    Mouse       NR               M/F      Subcutaneous         > 1000            95.0       Iyatomy (1980)
                                                                                                                        

    NR, not reported; M, male; F, female; A, diastereomer A; B, diastereomer B 
    a  Slight local irritation present
    b The study was conducted in compliance with good laboratory practive
    

    this study complied to a certain extent with OECD guideline 408; at
    the time the study was performed, compliance with GLP was not
    compulsory. 

         Doses of 100 mg/kg per day and higher had a dose-related adverse
    effect on body-weight development. At 300 mg/kg per day, behavioural
    disturbances (isolation from the other animals, dirty coat) and hair
    loss were observed in the female rats; however, all females had normal
    behaviour near the end of the treatment period. Animals at this dose
    had moderate leukocytosis, and females had reduced haemoglobin and
    thrombocyte counts. Increased alkaline phosphatase activity was
    observed only in the females. The relative liver weights of animals of
    each sex at 100 mg/kg bw per day and above were increased. At
    300 mg/kg bw per day, the absolute liver weights were elevated and the
    absolute weights of the heart, kidneys, adrenals, and ovaries
    depressed in female rats at the termination of treatment. The relative
    weights of the thyroid and testes in males and of the spleen in
    females were also elevated, whereas the relative weights of the heart,
    adrenals, and ovaries were depressed in females. Hyperkeratoses and
    parakeratoses, distended epithelial cells, slight inward growth of the
    papillary body, and cellular infiltration in the epithelial and
    subepithelial layers were observed histopathologically in the
    forestomachs of four female animals at 300 mg/kg bw per day that were
    sacrificed at the end of treatment. The appearance of the digestive
    tract was unexceptional at the end of the recovery period., and all of
    the changes in the rats at the high and intermediate doses had
    likewise reverted. The NOAEL was 30 mg/kg bw per day (Thyssen &
    Kaliner, 1977).

         Groups of 20 male and 20 female Sprague-Dawley rats were given
    bitertanol (purity, 95%) at doses of 0, 100, 400, or 1600 ppm, equal
    to 7, 28, and 110 mg/kg bw per day in males and 7.4, 30, and 110 mg/kg
    bw per day in females, for 28 days. The test procedures complied to a
    certain extent with OECD guideline 407; at the time the study was
    performed, compliance with GLP was not compulsory. Half of the animals
    were sacrificed and examined after four weeks, whereas the other half
    were observed without treatment for a further four weeks. 

         The dose of 400 ppm had an adverse effect on body-weight
    development and food intake, and an adverse effect on the red blood
    cell population was seen from decreases in the haematocrit and
    haemoglobin readings. The relative liver weight was slightly elevated
    in animals of each sex. Those at 1600 ppm had ataxia, reduced food
    intake and body weight, and depressed red blood cell parameters
    (haemoglobin, haematocrit, erythrocyte count), with a simultaneous
    increase in the reticulocyte count. A slight increase in the serum
    cholesterol concentration and a significant increase in the relative
    liver weight were found in animals of each sex. Histopathological
    examination revealed weak irritation of the gastric mucosa and
    slightly altered ovaries, adrenals, and pituitaries. All of the
    observed effects were reversible within the four-week recovery period.
    The NOAEL was 100 ppm, equal to 7 mg/kg bw per day (Hatanaka et al.,
    1981).

         Bitertanol (purity, 90.2%) was administered to groups of 20 male
    and 20 female Wistar rats at concentrations of 0, 150, 600, or 2400
    ppm, equal to 12, 48 and 300 mg/kg bw per day in males and 13, 58, and
    310 mg/kg bw per day in females, for three months. This study was
    conducted before enactment of prevailing regulatory guidelines;
    however, the procedures complied to certain extent with OECD guideline
    408. 

         Although appearance and behaviour were unaffected at doses up to
    600 ppm, 2400 ppm caused decreased motility and reduced food intakes.
    Dose-related growth retardation was observed in females at 600 and
    2400 ppm and in male animals at all concentrations; however, the 150
    ppm dose decreased body weights only temporarily. The dose of 2400 ppm
    had adverse effects on various haematological parameters, including
    reduced erythrocyte and leukocyte counts, decreased haemoglobin
    content and haematocrit reading, increased reticulocyte counts, a
    relative increase in the polymorphonuclear leukocyte count, and a
    relative decrease in the lymphocyte count. The changes in clinical
    chemical parameters of the blood also found at this concentration were
    elevated alkaline phosphatase, aspartate aminotransferase, and
    glutamate dehydrogenase activities in the female animals. The blood
    protein level was slightly depressed and the cholesterol level
    slightly elevated. The finding of increased liver weight in females at
    2400 ppm also indicated an effect on the liver. The NOAEL was 150 ppm,
    equal to 12 mg/kg bw per day (Bomhard & Löser, 1978).

         In a supplementary study, bitertanol (purity, 90.8%) was
    administered to groups of 15 male and 15 female Wistar rats at
    concentrations of 0, 30, 100, or 300 ppm, equal to 2.5, 8.1, and 25
    mg/kg bw per day in males and 3.3, 10, and 32 mg/kg bw per day in
    females, for three months. The method used in this study complied to a
    certain extent with OECD guideline 408; at the time the study was
    performed, compliance with GLP was not compulsory.

         The appearance, behaviour, and mortality rate were unaffected at
    all concentrations. At 300 ppm, the rats gained less weight than the
    controls. Haematological, clinical chemical, gross and
    histopathological examination, and urinary analyses provided no
    evidence of adverse effects. The NOAEL was 100 ppm, equal to 8 mg/kg
    bw per day (Krötlinger et al., 1978).

         In a further study, bitertanol (purity, 95%) was administered to
    groups of 15 male and 15 female Sprague-Dawley rats at concentrations
    of 0, 40, 200, or 1000 ppm, equal to 3.1, 16, and 82 mg/kg bw per day
    in males and 3.6, 19, and 88 mg/kg bw per day in females, for three
    months. Five males and five females were subjected to urinary,
    haematological, and clinical chemical determinations. The method used
    in this study complied to a certain extent with OECD guideline 408; at
    the time the study was performed, compliance with GLP was not
    compulsory. 

         The dose of 200 ppm retarded weight gain in male and female
    animals and slightly increased the activities of alkaline phosphatase
    and aspartate aminotransferase in the serum of females. The dose of
    1000 ppm reduced body-weight gain and decreased food and water intakes
    in animals of each sex. The erythrocyte count was also depressed, and
    the reticulocyte count elevated in male and female animals. In
    addition, the leukocyte and thrombocyte counts were elevated, and the
    haemoglobin content and haematocrit reading were decreased in females.
    Elevated lactate dehydrogenase, aspartate aminotransferase, and
    alkaline phosphatase activities and a slightly elevated cholesterol
    concentration were found in the serum of females. The absolute weights
    of the liver and spleen were increased in females and the relative
    weights in males and females. The following lesions were found
    histopathologically in animals of each sex: increased swelling and
    fatty degeneration of hepatocytes, hyperkeratoses of the oesophageal
    and gastric mucosal epithelium and/or erosions of the glandular
    stomach, swelling, and fatty degeneration of adrenal cortical cells.
    Isolated bile-duct proliferation was also seen in females. The NOAEL
    was 40 ppm, equal to 3 mg/kg bw per day (Yonemura et al., 1981).

         Groups of 10 male and 10 female Wistar rats were exposed to
    bitertanol at mean analytically determined concentrations of 18, 63,
    or 200 mg/m3 air for 6 h per day, five days per week for three weeks.
    Only the head and nose of the animals were exposed, under dynamic
    conditions, and the inhaled bitertanol was dissolved in a 1:1 blend of
    ethanol:polyethylene glycol 400.The method used in this study complied
    to a certain extent with OECD guideline 412; at the time the study was
    performed, compliance with GLP was not compulsory.  

         The concentrations of 18 and 63 mg/m3 air were tolerated by male
    and female rats with no observed effect. Exposure to 200 mg/m3 air
    caused deterioration of the general condition of female rats, and the
    growth of male rats in this group was significantly decreased.
    Although the relative weights of the lung, liver, kidney, and adrenal
    in males and females at the high concentration were sometimes higher
    than control values, no evidence of damage due to exposure to
    bitertanol was seen histopathologically. The NOAEL was 63 mg/m3 air
    (Mihail & Kimmerle, 1977).

     Dogs

         Groups of four male and four female beagles received bitertanol
    (purity, 90.2%) at a dose of 0, 1, 5, or 25 mg/kg bw per day in
    gelatin capsules. The method used in this study complied to a certain
    extent with OECD guideline 409; at the time the study was performed,
    compliance with GLP was not compulsory. 

         Doses of 5 mg/kg bw per day and above led to signs of
    dose-related adverse effects on the skin and mucous membranes. The
    effects on the skin were manifested by increased reddening, with local
    inflammation, desquamation, and hair loss; and those on the mucous
    membranes by increased reddening and slight inflammatory phenomena in
    regions of the oral cavity (gingiva) and eyes (conjunctiva). They were

    evident histologically as slight broadening of the epithelial layer of
    the skin and slightly enhanced cornification in some cases. Evidence
    for superficial involvement of the cornea (keratitis), apparently
    resulting from conjunctival irritation, was observed in a few animals
    at 25 mg/kg bw per day. The behaviour of the controls and treated
    animals was similar; in contrast, the food intake and body-weight
    development of animals at the high dose showed an adverse effect. The
    results of laboratory tests indicated treatment-related interference
    with liver function (elevated alkaline phosphatase and alanine
    aminotransferase activities) in dogs at 5 and 25 mg/kg bw per day.
    Elevated  N-demethylase activity and an increase in the cytochrome
    P450 concentration in liver homogenates were found in the high-dose
    group at study termination. The weights of the thymus in females at
    25 mg/kg per day and of the prostate (relative at 5 mg/kg per day and
    both relative and absolute at 25 mg/kg per day) were statistically
    significantly lower than those of the controls. The changes in
    prostate weights correlated with dose-related histopathological
    findings of retarded development. The NOAEL was 1 mg/kg bw per day
    (Hoffmann & Schilde, 1979).

         In view of the dermal phenomena observed in the previous study,
    tests were performed to determine whether they represented a
    sensitization effect. Beagle dogs were first treated orally 10-42
    times with 35 or 70 mg/kg bw bitertanol, which led to marked
    irritation and dermal lesions, particularly in the area of the head.
    After a treatment-free interval of four to six weeks, when the lesions
    had healed, the animals were treated with a dose of 1.75 mg/kg bw,
    previously found to induce no reaction, for 14 days. Hair loss and a
    slightly increased incidence of reddened gingiva were determined in
    isolated animals only at termination of treatment. The study gave no
    evidence for sensitization, and the delay in development of the effect
    specifically argues against such an effect (Hoffmann, 1977).

         No evidence for sensitization was found in a study in which
    beagles were exposed to a concentration of 28.8 mg/m3 air for 4 h per
    day, five days per week for three weeks, left untreated for 10 days,
    and subsequently re-exposed to a concentration of 47.1 mg/m3 air for
    one week. All dogs tolerated the exposures with no signs, and no
    evidence was found for either an irritating effect on visible mucous
    membranes or for a Type I (immediate anaphylactic type) allergy
    (Thyssen & Kimmerle, 1977b). 

     Cats

         Groups of three male and three female cats weighing 2-3 kg
    received whole-body exposure to aerosols of bitertanol (active
    ingredient, 95.8%) in a 3-m3 inhalation chamber for 6 h per day for
    four weeks (20 x). The mean analytically determined bitertanol
    concentration was 27 mg/m3 air. Analysis of the generated aerosols
    showed that more than 90% of the aerosol particles had a mass-related
    and more than 99% a particle-related aerodynamic diameter smaller than
    5 µm. The exposed animals were compared with negative controls (air)

    and positive controls (dichlozoline, 28 mg/m3 air). The animals were
    observed over a recovery period of 12 weeks after termination of the
    exposure. Their eyes were examined with an ophthalmoscope before
    exposure and each week throughout the four-week exposure and the
    recovery period and for gross and histopathological alterations at the
    end of the study. The method used complied with OECD guideline 412; at
    the time the study was performed, compliance with GLP was not
    compulsory. 

         The exposed cats tolerated the treatment with no signs of
    toxicity, damage to the eyes, or cataractogenesis. Under comparable
    experimental conditions, the animals exposed to dichlozoline showed
    signs of lenticular opacity (cataracts), starting from the end of the
    second week of exposure. Lenticular opacity that had not reverted up
    to the end of the recovery period was observed in all animals of this
    group at the end of the second week of the recovery period. Cats
    exposed to bitertanol had no cataracts (Pauluhn et al., 1983).

     Rabbits

         Groups of six male and six female New Zealand rabbits received
    applications of bitertanol (purity, 95.8%) in an aqueous suspension
    (0.5 ml) at concentrations of 0, 50, or 250 mg/kg bw on the intact or
    abraded dorsal and lateral skin for 6 h per day, five times per week
    for three weeks. The method used in this study complied to a certain
    extent with OECD guideline 411; at the time the study was performed,
    compliance with GLP was not compulsory. 

         Bitertanol had no apparent effect on the appearance, behaviour,
    body weight, or survival of the rabbits. Transient erythema developed
    on the exposed areas, initially on abraded skin but later on intact
    skin. There was no effect on skin-fold thickness or on haematological,
    clinical chemical, or urinary parameters. At necropsy, there were no
    gross pathological findings. Histopathological examination showed
    slight epidermal thickening only in exposed areas of all treated
    animals. Preparations of liver showed no evidence of induction of
    microsomal  N- or  O-demethylation or cytochrome P450 content. The
    dermal application had no effect on any of the parameters
    investigated. The NOAEL was 250 mg/kg bw (Heimann & Vogel, 1984).

     (c)  Long-term  studies of toxicity and carcinogenicity

     Mice

         Bitertanol (purity, 94-95%) was administered to groups of 50 male
    and 50 female CF1/W74 mice at doses of 0, 20, 100, or 500 ppm, equal
    to 2, 25, and 130 mg/kg bw per day in males and 7, 37, and 180 mg/kg
    bw per day in females, for two years. The study was conducted before
    enactment of prevailing regulatory guidelines; however, the test
    procedures complied to a certain extent with OECD guideline 453 but
    with no attempt to monitor ocular changes. 

         Behaviour, feed consumption, mortality, and haematological
    parameters were not affected by treatment. In animals at 500 ppm, body
    weights were reduced and serum alkaline phosphatase activity was
    significantly elevated; females at this dose had an increased
    incidence of enlarged and greenish-coloured livers at necropsy. The
    liver weights were also increased, particularly in the female mice,
    and the livers had increased numbers of eosinophilic foci. No evidence
    was found for a carcinogenic effect at any concentration, which
    extended into the toxic range. The NOAEL was 100 ppm, equal to 25
    mg/kg bw per day (Bomhard & Löser, 1981a).

     Rats

         Bitertanol (purity, 94% in weeks 1-18; 95% from week 19) was
    administered to groups of 50 male and 50 female SPF Wistar rats at
    doses of 0, 20, 100, or 500 ppm, equal to 1, 4.9, and 26 mg/kg bw per
    day in males and 1.3, 6.6, and 34 mg/kg bw per day in females, for two
    years. The study was conducted before the enactment of prevailing
    regulatory guidelines; however, the test procedures complied to a
    certain extent with OECD guideline 453. 

         The 500 ppm concentration led to retarded growth in animals of
    each sex. Ocular changes were not recorded. Haematological, blood
    chemical, and urinary parameters were not significantly affected, and
    the mortality rate was not adversely influenced. No treatment-related
    effects were seen on organ weights or the gross or microscopic
    appearance of the tissues. In particular, the type, location,
    incidence, and time to occurrence of the tumours observed in the
    treated groups were comparable to the control findings and to the
    spontaneous findings for this strain of rat. The NOAEL was 100 ppm,
    equal to 4.9 mg/kg bw per day (Bomhard & Löser, 1981b).

     Dogs

         Groups of four male and four female beagle dogs received
    bitertanol (purity, 95-97.3%) in the diet at concentrations of 0, 10,
    40, or 160 ppm, equal to 0.3, 1.2, and 4.9 mg/kg bw per day, for two
    years. The method used in this study complied to a certain extent with
    OECD guideline 452; at the time the study was performed, compliance
    with GLP was not compulsory. 

         Although the control dogs gained more weight than did treated
    dogs, there was no association with treatment. A good nutritional
    status was maintained by dogs in all groups, and there was no
    significant difference between groups in food or water consumption. No
    abnormalities were seen in selected reflexes, body temperature, or
    pulse rate; however, three of eight dogs at the high dose developed
    bilateral cataracts. Urinary and haematological examinations conducted
    at approximately three-month intervals revealed no abnormalities,
    although serum alanine aminotransferase and alkaline phosphatase
    activities were increased at 40 and 160 ppm. At necropsy, the mean
    liver weight of dogs at the high dose was markedly increased.
    Histological examination showed mild to moderate vacuolation of the

    adrenal zona reticularis epithelia at doses at and above 40 ppm. The
    NOAEL was 10 ppm, equal to 0.3 mg/kg bw per day (Hoffmann & Gröning,
    1983).

         Groups of six male and six female beagles were fed diets
    containing 0, 3, or 25 ppm bitertanol (purity, 96.3-96.7%) for 12
    months, equal to 0.1, 1, and 7.6 mg/kg bw per day. A further group was
    maintained on a diet containing 200 ppm bitertanol for 20 months to
    permit continued ophthalmoscopic examination. The method used in this
    study complied to a certain extent with OECD guideline 452; at the
    time the study was performed, compliance with GLP was not compulsory. 

         Treatment had no apparent effect on behaviour, appearance, or
    nutritional status, and food consumption and body-weight gain were
    also unaffected. Pulse rates, body temperature, and selected reflexes
    were unchanged. Ophthalmoscopy, conducted on animals at 0, 3, or 25
    ppm at three-month intervals, showed no changes; however, one dog at
    the high dose developed severe bilateral lenticular cataracts, which
    were observable from week 58. Four other animals had slight lenticular
    opacification by week 85. Dogs in this group also had signs of
    conjunctivitis, with nasociliary discharge and incrustation.
    Intermittent increases in serum alanine aminotransferase, glutamate
    dehydrogenase, and alkaline phosphatase activities were also seen in
    the dogs at the high dose. Other clinical chemical, haematological,
    and urinary parameters were unaffected by treatment. At necropsy,
    there were no gross abnormalities. The weights of the adrenals of the
    dogs at the high dose were apparently greater than those of controls,
    and lipoid vacuolation was observed in the zona reticularis epithelia.
    The NOAEL was 25 ppm, equal to 1 mg/kg bw per day (Hoffmann & Vogel,
    1983).

     (d)  Genotoxicity 

         No genotoxic or mutagenic potential of bitertanol was found in
    lower organisms or in mammalian cells or systems  in vivo or
     in vitro. The results of assays for the genotoxicity of bitertanol
    are summarized in Table 2.

     (e)  Reproductive toxicity 

    (i)  Multigeneration reproductive toxicity

         The effect of bitertanol (purity, 95.0%) on fertility, lactation
    performance, and pup development was examined in a three-generation
    study in Long-Evans FB 30 rats with two litters per generation. The
    test substance was administered throughout the study period at
    concentrations of 0, 20, 100, or 500 ppm, equivalent to 1, 5, and 25
    mg/kg bw per day. Each of the mating groups consisted of 10 male and
    20 female rats. The animals were five to six weeks old at the
    beginning of the study and were treated for 70 days before the first
    mating. The F3b generation pups and their parents (F2b generation)
    were sacrificed and examined histopathologically after a four-week
    lactation period. The method used in this study complied to a certain


        Table 2. Results of assays for the genotoxicity of bitertanol
                                                                                                                                    

    Test system         Test object                          Concentration          Purity     Results      Reference
                                                                                    (%)
                                                                                                                                    

    In vitro
    Reverse mutationa   S. typhimurium TA98, TA100,          4-2500 µg/plate        93.7       Negative     Herbold (1979)
                        TA1535, TA1537

    Reverse mutationa   E. coli WP2 hcr-                     1-5000 µg/plate        95.0       Negative     Shirasu et al. (1981)
                        S. typhimurium TA98, TA100, 
                        TA1535, TA1537, TA1538

    Forward mutationa   Mouse lymphoma L5178Y tk +/-         1-25 µg/mlb            95.0       Negative     Bootman & Rees
                                                             1-20 mg/mlc                                    (1983)

    DNA repaird         B. subtilis H17 rec+, M45 rec-       20-5000 µg/disc        95.0       Negative     Shirasu et al. (1981)

    DNA repaira,d       E. coli W3110 pol A+; P3470 pol A-   0.1-33.3 mg/plate      95.0       Negative     Riach (1981)

    Aneuploidy          Sordaria brevicollis                 0.1-5.0 mg/L           95.0       Negative     Bond & McGregor (1981)

    Cytogenetic         Chinese hamster lung cells           3.3 × 10-6-3.3 × 10-4  97.1       Negative     Sasaki (1987)
    alterationsa,d                                           mol/Lb 
                                                             1.0 × 10-5-1.0 ×.10-3  
                                                             mol/Lc

    In vivo
    Micronucleus        NMRI mice                            2 × 1000 mg/kg bw      93.7       Negative     Herbold (1978a)
    formation                                                2 × 2000 mg/kg bw

    Dominant lethal     Male NMRI mice                       1000 mg/kg bw          93.7       Negative     Herbold (1978b)
    mutation
                                                                                                                                    

    a With and without exogenous metabolic activation
    b Without exogenous metabolic activation
    c With exogenous metabolic activation
    d Conducted in compliance with good laboratory practice and to a certain extent with OECD guidelines 
    

    extent with OECD guideline 416; at the time the study was performed,
    compliance with GLP was not compulsory.

         No adverse effects were seen on appearance, behaviour, or
    mortality in any group or generation. Bitertanol at a concentration of
    20 ppm in the diet did not affect reproductive performance.
    Administration of 100 or 500 ppm led to reductions in pup survival
    rates during the lactation period in several matings and to pups with
    lower birth weights. At 100 ppm, retarded pup growth was also seen in
    the F2a and F2b generations. At 500 ppm, general retardation of
    growth was seen. The NOAEL was 20 ppm, equivalent to 1 mg/kg bw per
    day (Löser & Eiben, 1981).

    (ii)  Developmental toxicity

     Rats

         Groups of 20-23 Long-Evans rats were given bitertanol (purity,
    96.5%) orally at doses of 0, 10, 30, or 100 mg/kg bw per day on days
    6-15  post coitum. The method used in this study complied to a
    certain extent with OECD guideline 414; at the time the study was
    performed, compliance with GLP was not compulsory. The body-weight
    gain of dams at 30 or 100 mg/kg bw per day was significantly reduced
    during treatment and throughout the gestation period for those at 100
    mg/kg bw per day. Resorption rates, fetal deaths, placental weights,
    and sex ratio were unaffected by treatment; however, fetal weights
    were significantly reduced at 100 mg/kg bw per day and significant
    fetal stunting occurred at doses of 30 mg/kg bw per day and higher. At
    100 mg/kg bw per day, skeletal ossification was retarded, and a
    significantly increased incidence of malformations was observed, which
    included cleft palate, hydrocephalus, malformed tails, dysplasia, and
    synostosis of the ribs. A simple case of hydrocephalus occurred at 30
    mg/kg bw per day. The NOAEL was 10 mg/kg bw per day (Machemer, 1977).

         Groups of 22 or 23 Sprague-Dawley rats were given bitertanol
    (purity, 96%) orally at doses of 0, 10, 25, or 65 mg/kg bw per day on
    days 6-15  post coitum. The study was conducted in compliance with
    GLP standards and with OECD guideline 414. Reduced weight gain was
    seen in dams at daily doses of 25 mg/kg bw and higher, which persisted
    throughout the gestation period in those at 65 mg/kg bw per day. The
    number of corpora lutea, implantation rates, resorption rates, live
    fetuses, sex ratio, and fetal and placental weights were unaffected by
    treatment. An increased incidence of a fourteenth (lumbar) rib
    relative to controls was observed at daily doses of 25 mg/kg bw (32%
    incidence) and 65 mg/kg bw (70% incidence). No teratogenic effects
    were observed. The NOAEL was 10 mg/kg bw (Nagumo et al., 1987).

         Pregnant Wistar rats were given single oral doses of 100, 500, or
    1000 mg/kg bw bitertanol on day 9, 10, 11, or 13 of gestation. The
    doses were calculated to represent 1/5, 1/10, and 1/50 of the reported
    LD50 value of 5000 mg/kg bw. The method used complied to a limited
    extent to OECD guideline 414. The largest deviation was the short
    application period; no information was given on compliance with GLP.

    The study was available only in abstract form and is therefore of only
    limited value for risk evaluation. Bitertanol induced congenital
    anomalies when given on day 9, 10, or 11 at 500 or 1000 mg/kg bw. The
    malformations consisted of microcaudia and acaudia and, in rare cases,
    exophthalmus, hypognathia, and cleft palte. The NOAEL was 100 mg/kg bw
    (Vergieva, 1990).

         In two studies, groups of 25 Long-Evans rats were exposed to
    bitertanol (purity, 93.7%) by inhalation for 4 h per day on days 6-15
     post coitum at a mean analytical concentration of 0, 2.9, 6.4, or 22
    mg/m3 air in one study and 0, 27, 60, or 120 mg/m3 air in the other.
    The method used complied to a certain extent with OECD guideline 414;
    at the time the study was performed, compliance with GLP was not
    compulsory. No adverse effects were observed on dams exposed at any
    concentration, but the average fetal weights were reduced
    significantly by exposure to 120 mg/m3. Fetuses with below-average
    weights were found increasingly at aerosol concentra-tions greater
    than 22 mg/m3 air, without a clear dose-response relationship.
    Implantation rates, resorption rates, placental weights, and sex ratio
    were unaffected by treatment. No embryolethal or teratogenic effects
    were observed. The NOAEL was 22 mg/m3 air (Machemer & Thyssen, 1979).

     Rabbits

         Twelve Himalayan rabbits, were given bitertanol (purity, 96.7%)
    at daily oral doses of 0, 10, 30, or 100 mg/kg bw on days 6-18
     post coitum. The method used complied to a certain extent with OECD
    guideline 414; at the time the study was performed, compliance with
    GLP was not compulsory. The dose of 100 mg/kg bw led to reduced weight
    gain and isolated clinical signs, such as reduced food intake,
    diarrhoea, and blood in the urine; one dam died on day 29
     post coitum. This dose also resulted in increased embryonal and
    fetal mortality and reduced fetal and placental weights, and three
    individual malformations occurred, which deviated from those seen in
    controls in their nature (epignathus, pulmonary hypoplasia, and
    aplasia) but not in their number. The NOAEL was 30 mg/kg bw per day
    (Roetz, 1982).

         Groups of 15 Himalayan rabbits were given bitertanol (purity,
    93.9%) at daily oral doses of 0, 10, 30, or 100 mg/kg bw on days 6-18
     post coitum. The method complied to a certain extent with OECD
    guideline 414; at the time the study was performed, compliance with
    GLP was not compulsory. Treatment had no effect on the behaviour,
    appearance, or body-weight gain of the dams. At 100 mg/kg bw per day,
    a significantly higher resorption rate and reduced numbers and weights
    of fetuses were seen, and the number of malformed fetuses was
    increased, with rare types of malformation such as cleft palate and
    pigeon chest. The NOAEL was 30 mg/kg bw per day (Schlüter, 1983).

         Groups of 16 fertilized chinchilla rabbits were given bitertanol
    (purity, 96.9%) at a daily oral dose of 0, 10, 50, or 250 mg/kg bw on
    days 6-18 of gestation. Because of the very high rate of post-
    implantation loss at 250 mg/kg bw per day, doses of 0 and 150 mg/kg bw

    per day were used in a supplementary study. The study was conducted in
    compliance with OECD guideline 414 and with GLP standards. A
    dose-related reduction in food consumption was seen in dams at > 50
    mg/kg bw per day. The dose of 250 mg/kg bw per day significantly
    reduced body weights from day 7 to the end of the experiment and
    significantly reduced corrected body-weight gain. One dam at 150 mg/kg
    bw per day and two at 250 mg/kg bw per day died during the study.
    Isolated hair loss and enlarged and heavier livers at necropsy were
    observed in dams at the high dose. A dose-related increase in the rate
    of post-implantation losses was observed at > 150 mg/kg bw per day.
    Two dams at 150 mg/kg bw per day and 13 at 250 mg/kg bw per day
    completely resorbed their embryos, and the fetuses at these doses
    showed dose-related reductions in body weight and a dose-related
    increased in the incidence of incompletely or unossified phalangeal
    nuclei and calcanei. The NOAEL was 50 mg/kg bw per day (Becker et al.,
    1987).

     (f)  Special studies 

         As the studies in this section were published in the open
    literature, the level of detail needed for full evaluation was not
    available.

    (i)  Effects on the central nervous system

         The effect of bitertanol on the central nervous system was
    examined in pharmacological screening tests in mice and rats, which
    included tests for potentiation of anaesthesia in mice (hexobarbital
    sleep period), stimulation of spontaneous motility in mice, an Irwin
    behaviour test in mice, the novel box response in rats, the open field
    test in mice, and a test for reserpine ptosis in mice. In these
    investigations, bitertanol was administered as a single oral dose of
    0.075, 0.6, or 4.8 mg/kg bw. The results showed a slight stimulating
    effect of bitertanol on the central nervous system in mice, but no
    specific pharmacological effects, such as potentiation of amphetamine
    effects or antagonism to reserpine ptosis, were determined (Polacek,
    1983).

         In a pharmacological test programme, groups of 10 male mice were
    given a single oral dose of 0.02, 0.2, 2, 20, or 200 mg/kg bw
    bitertanol. The highest dose significantly increased spontaneous motor
    activity, with marked effects when treatment was given during the dark
    period. In mice treated with 20 mg/kg bw per day, motor activity
    tended to increase but not significantly, and lower doses had no
    effect. No further effects on behaviour were observed at any dose
    (Kaneto, 1986a). In a further test, male mice received bitertanol at 1
    or 100 ppm for one week or one month. No increase in spontaneous motor
    activity and no potentiating effect in amphetamine-pretreated animals
    were seen after repeated dosing (Kaneto, 1986b).

         In a study designed to determine whether bitertanol has similar
    behavioural effects on the fixed-interval response rate and motor
    activity of rats, doses of 10-300 mg/kg bw were given
    intraperitoneally to rats maintained under a multiple fixed-interval
    1-min schedule of reinforcement. Intermediate doses increased the
    response rates and disrupted response patterning in both
    fixed-interval components. The same doses of bitertanol did not
    increase motor activity (Allen & MacPhail, 1983).

         In rats placed in an actographic device designed for continuous
    measurement of the locomotor component of spontaneous motor activity,
    bitertanol increased motor activity at 200 mg/kg bw after
    administration either orally or intraperitoneally. The activity peaks
    at the low dose of 100 mg/kg bw coincided with normal night and
    morning activity maxima (Frantik et al., 1996).

         One the basis of previous results showing that acute exposure to
    the triazole fungicide triadimefon affects central nervous system
    catecholamines and induces a transient syndrome in rats that consists
    of hyperactivity and stereotyped behaviour, a study was designed to
    determine whether this type of toxicity is characteristic of other
    triazoles. Dose-effect functions were determined for 14 triazoles or
    structurally related pesticides, including bitertanol, in adult male
    Long-Evans rats. All of the chemicals were administered orally in corn
    oil. Hyperactivity was measured for 2 h in figure-eight mazes. Only
    triadimefon and triadimenol induced hyperactivity, suggesting a very
    rigid structure-activity relationship for the hyper-activity syndrome.
    The absence of an effect of bitertanol may be due to steric hindrance
    of benzene-ring substitution for the halogen on the benzene-ring
    structure of triadimefon and/or triadimenol. Alternatively, bitertanol
    may lack halogen substituents on the benzene rings and thus be less
    polarized. The lack of activity of bitertanol is probably not due to
    differences in absorption kinetics (Crofton, 1996).

    (ii)  Toxicity in combinations

         Acute tests were performed to determine whether bitertanol has
    superadditive (potentiating) effects when administered in combination
    with triadimenol, captan, fuberidazole, or dodine. At the time the
    studies were performed, OECD methods were not available and compliance
    with GLP was not compulsory. The study involved administration of
    single equitoxic oral (with triadimenol, captan, or fuberidazole) or
    intraperitoneal (with dodine) doses of the active ingredients to male
    rats. A factor greater than 1 between observed and expected LD50
    values indicates a superadditive effect. Bitertanol plus triadimenol,
    bitertanol plus fuberidazole, and bitertanol plus dodine had no
    superadditive effects but only additive toxic effects (Mihail, 1982b;
    Flucke, 1980; Heimann, 1984b). In contrast, the active ingredient
    combination of bitertanol plus captan had slightly superadditive
    action, with a potentiation factor of 1.9 (Mihail, 1982a).

    (iii)  Effect on the liver

         Groups of 10 male and 10 female Wistar rats received bitertanol
    (purity, 95.8%) suspended in distilled water with Cremorph EL by
    gavage at doses of 0, 30, 100, or 300 mg/kg bw per day for 14 days. On
    sacrifice, blood was collected for detailed haematological and
    clinical chemical testing, and liver samples were taken for detailed
    histopathological and enzyme studies. During treatment, 1/10 female
    rats at the intermediate dose and 9/10 at the high dose showed hair
    loss, and some lost weight, while females at the low dose had reduced
    body-weight gain in comparison with control animals. Female rats also
    had a dose-related tendency to mild thrombocytosis, which was
    significant at the intermediate and high doses. Serum gamma-glutamyl
    transpeptidase activity and bilirubin concentration were slightly
    increased in females at the high dose. There were no gross
    pathological findings at necropsy. The liver weights tended to be
    increased at the intermediate and high doses, especially in females.
    Slight-to-moderate bile-duct proliferation with peribiliary
    infiltration of monocytes or polynucleocytes was seen histologically
    in animals at the intermediate and high doses. These changes were
    sometimes accompanied by parenchymal Councilman bodies or, more
    occasionally, mitoses. The hepatocytes of animals at the high dose
    were occasionally swollen, with finely granular cytoplasm. Little
    fatty infiltration was seen. The results of studies  in vitro were
    consistent with induction of hepatic microsomal enzymes, as the
    cytochrome P450 content increased in a dose-related manner, especially
    in males. Aminopyrene  N-demethylase activity was increased in males
    and females at the high dose and in males at the intermediate dose,
    while  O-demethylase activity was increased in males at the
    intermediate and high doses and in females at the high dose. The
    hepatic triglyceride content was not affected by treatment. Bitertanol
    thus caused mild hepatotoxicity, with modest induction of hepatic
    microsomal activity in rats at 100 and 300 mg/kg bw per day. The NOAEL
    was 30 mg/kg bw per day (Mihail & Luckhaus, 1985).

    3.  Studies on metabolites

    (a)  1-(Triazol-1-yl)-1-(4'-phenylphenoxy)-3,3-dimethylbutan-2-one
         (plants, soil)

         1-(Triazol-1-yl)-1-(4'-phenylphenoxy)-3,3-dimethylbutan-2-one, a
    keto analogue of bitertanol, has very little acute toxicity in rats
    when given orally or dermally. It induced signs of effects on the
    central nervous system, with initial sedation and respiratory
    disturbances and later stimulation. The highest technically
    administrable oral dose, 1750 mg/kg bw, caused no deaths. A dermal
    dose of 5000 mg/kg bw and the highest dose administered by inhalation
    (dynamic dust nebulization) were tolerated with no observed signs. The
    LC50 value in male and female rats was > 500 mg/m3 air after a 1-h
    exposure or a 4-h exposure, respectively. In rabbits, the compound was
    slightly irritating to the skin only after contact for 24 h and was
    mildly irritating to the mucous membranes of the eyes (Thyssen &
    Kimmerle, 1978).

    (b)  Bitertanol benzoic acid (soil)

         Bitertanol benzoic acid had little acute toxicity when given
    orally. The highest administered dose, 5000 mg/kg bw, was tolerated by
    fasted male rats with no observed signs or deaths (Heimann, 1983b).
    The compound was not mutagenic to  Salmonella typhimurium in the
    presence of an exogenous metabolic activation system (Herbold, 1983).

    (c)  1,2,4-Triazole (photodegradation, soil) 

         1,2,4-Triazole has moderate or low acute toxicity when given
    orally (LD50 value, 1600 mg/kg bw in males and females) or dermally
    (LD50 values, 4200 mg/kg bw in males and 3100 mg/kg bw in females).
    At high oral and dermal doses, the compound had effects on the central
    nervous system. In tests of inhalation of air enriched with vapours of
    the test substance, male rats and mice tolerated exposure for 4 and
    6 h, respectively, with no observed signs. No dermal irritation was
    observed on rabbits exposed for 24 h or on the skin of five male
    volunteers exposed for 8 h. 1,2,4-Triazole was strongly irritating to
    the mucous membranes of the rabbit eye (Thyssen & Kimmerle, 1976).

         Groups of 15 male and 15 female rats were given 1,2,4-triazole
    (purity, 99.6%) at a dose of 0, 100, 500, or 2500 ppm for three
    months. The study was conducted before enactment of prevailing
    regulatory guidelines, but the test procedures complied to a certain
    extent with OECD guideline 408. Treatment at 2500 ppm resulted in a
    temporary decrease in food intake, a reduction in body weight, and
    transient, slight palmospasms in isolated animals. Significant
    reductions in the haemoglobin, haematocrit, mean corpuscular volume,
    and mean corpuscular haemoglobin values in male rats at 2500 ppm
    indicated an effect on the blood. In this group, slight to moderate
    fat accumulation was found in the cells of the liver parenchyma in
    three of 15 males, which was attributed to the treatment. The NOAEL
    was 500 ppm, equal to 38 mg/kg bw per day (Bomhard et al., 1979).

         1,2,4-Triazole at concentrations of 10-5000 µg/plate did not
    induce point mutations in  Salmonella typhimurium TA1535, TA1537,
    TA98, or TA100, with or without metabolic activation (Poth, 1989).

         In two studies, groups of 25 fertilized Wistar rats were given
    daily oral doses of 1,2,4-triazole (purity, 95.3% and 94.0%,
    respectively) on days 6-15 of gestation at  doses of 0, 10, 30, or 100
    mg/kg bw in one study and 0, 100, or 200 mg/kg bw in the other. The
    studies were conducted in compliance with GLP standards and OECD
    guideline 414. Maternal toxicity was indicated by decreased weight
    gain of dams at 100 and 200 ppm relative to those in the control
    group. Reduced fetal weights, retarded osteogenesis, and increased
    numbers of runts were found at > 100 mg/kg bw per day. An increased
    resorption rate was found in dams at 200 mg/kg per day, but the rate
    of fetuses with retarded ossification was not increased. The types and
    incidences of the malformations observed in this group (including
    cleft palate and malformed extremities) indicate that 1,2,4-triazole

    has teratogenic potential. The NOAEL was 30 mg/kg bw per day (Renhof,
    1988a,b).

    4.  Observations in humans

         No health impairment was observed in male or female employees
    engaged in formulating bitertanol and using the customary safety
    precautions, who had regular medical examinations (Miksche, 1981).

         Slight, transient prurient reddening of the forearms, which
    regressed spontaneously after a few days, developed in rare, isolated
    cases after direct dermal contact during packaging of a powder of the
    pure active ingredient. Unequivocal differentiation between an
    allergic dermal reaction and mechanical-toxic skin irritation was not
    possible. There was no tendency to relapse (Faul, 1986).

    Comments

         After oral administration bitertanol is rapidly and extensively
    absorbed (about 84%) and distributed. Excretion is also rapid (rats,
    almost complete within 72 h) and occurs mainly in the faeces (about
    90%) by biliary excretion, owing to the lipophilic nature of the
    parent substance. The liver and kidneys are the main sites of tissue
    accumulation in both male and female rats. Although some statistically
    significant sex-related differences were seen, they were of minor
    physiological importance. The substance has a relatively low rate of
    dermal penetration. The metabolic profile was similar at the various
    doses tested. The main metabolic pathways are hydroxylation of the
    phenyl ring in the  para position and oxidation of the  tert-butyl
    moiety, leading to bitertanol alcohol and the corresponding carboxylic
    acid; metabolites derived from the two pathways combined were also
    observed. The metabolites occur in both free and conjugated forms. The
    parent compound was not detected in urine or bile. There was no
    toxicological concern with regard to the metabolic profile in plants.

         Bitertanol had very low acute toxicity in rats, mice, and dogs
    when given orally and after dermal application or by inhalation. It
    was of moderate to low toxicity in rats and mice after intraperitoneal
    injection. Females appeared to be slightly more sensitive than males,
    but only in some studies. This was perhaps due to slightly different
    absorption characteristics in animals of the two sexes, as seen after
    oral administration. In view of the toxic signs (including respiratory
    disturbances, sedation, spasms, and tremor) and the findings of the
    pharmacological screening tests, it may be inferred that bitertanol
    has central nervous system activity; however, no specific
    pharmacological effects, such as potentiation of amphetamine action,
    antagonism of reserpine ptosis, or an effect on hexobarbital
    anaesthesia, were observed.

         Bitertanol induces no, or only very slight, dermal irritation. It
    induces slight to moderate reactions of the ocular mucosa but has no
    effect on the cornea or iris. No evidence for a sensitizing effect was
    observed in any study

         Bitertanol has been classified by WHO as unlikely to present an
    acute hazard in normal use (WHO, 1996).

         In medium- and long-term tests for toxicity, the liver is
    regarded as the main toxicological target organ in dogs and rats at
    doses of 1.2 and 28 mg/kg bw per day and above, respectively. Liver
    weight was found to be the most sensitive indicator. Corresponding
    patterns of disruption of liver function were observed in rats and
    dogs. The activities of the transaminases, alkaline phosphatase, and
    glutamate dehydrogenase in the serum were increased. In addition, a
    rise in cholesterol level was observed in several studies in rats at
    doses of 61 mg/kg bw per day and above. The ability of bitertanol to
    induce mixed-function oxidases was verified in both species. It is
    therefore likely that the effect on weight is essentially due to
    hypertrophy of the endoplasmic reticulum in hepatocytes at doses of
    100 mg/kg bw per day and above. Morphological changes in the liver
    were seen only at relatively high doses and consisted of hepatocytic
    swelling, bile-duct proliferation, perilobular fatty degeneration,
    eosinophilic foci, and fibrous structures. The induced effects
    corresponded to toxic liver damage with bile-duct involvement.

         Evidence for haemotoxicity was found at doses of 28 mg/kg bw per
    day and above in rats; this may be classified as an effect on the
    peripheral red blood cell population. The decreases in erythrocyte
    count, haemoglobin concentration, and packed cell volume and the
    compensatory rise in the reticulocyte count argue for this
    interpretation. No evidence was found for damage to the haematogenic
    organs.

         Slight increases in the leukocyte count were also seen in a few
    studies in rats at doses of 61 mg/kg bw per day and above. The
    increased leukocyte counts are probably attributable to inflammatory
    processes, since the increase occurred in studies and at doses at
    which inflammatory processes were also observed. Hyperkeratosis of the
    oesophageal epithelium and glandular stomach and/or erosions of the
    glandular stomach as well as parakeratosis of the stomach wall were
    observed in rats. The histopathological picture included distended
    epithelial cells, slight inward growth of the papillary body, and
    cellular infiltration of the epithelial and subepithelial layers in
    the affected animals. These changes are probably attributable to
    irritation of the mucous membranes by the active ingredient.

         Effects on the skin were observed in dogs, sheep and rats. The
    effects in dogs at doses of 5 mg/kg bw per day and above consisted of
    reddening, with localized inflammation, desquamation, and hair loss,
    and increased reddening and slight inflammatory phenomena in the
    mucous membranes of the oral cavity and eyes. Histological examination
    showed broadening of the epithelial layer, enhanced cornification, and
    minor erosions. The dermal effects were apparently accompanied by
    pruritus. The keratitis observed in dogs was considered to be
    secondary to conjunctivitis. Hair loss was also observed in rats and
    sheep, which occurred after administration of bitertanol by capsule or

    gavage at doses of 300 mg/kg per day and above; this was considered to
    be a systemic effect.

         Pathological changes were seen in the adrenals of dogs and rats
    at 1.2 and 81 mg/kg bw per day and above, respectively, consisting of
    swelling and fatty degeneration of the adrenal cortical cells,
    particularly in the zona reticularis and zona fasciculata. These
    alterations were considered to be due to inhibition of sterol
    biosynthesis by triazole derivatives. It is highly probable that this
    effect, which also represents the biological, antimycotic action of
    the substance, leads to an effect on corticoid metabolism with
    corresponding morphological effects in the cells of the adrenal
    cortex.

         In feeding studies in dogs, lenticular opacity seen at doses of
    4.9 mg/kg bw per day and above were considered to be related to
    treatment. No lenticular alterations attributable to administration of
    bitertanol were seen in any other study or species. The exact
    mechanism of the cataractogenesis resulting from long-term
    administration of triazole fungicides is presently unknown. The ocular
    lens undertakes its own de-novo synthesis of cholesterol, which is
    isolated from lipoproteins circulating in the blood; other substances
    that inhibit cholesterol synthesis can induce cataracts.

         No evidence for any carcinogenic potential of bitertanol was
    found in long-term studies of toxicity and carcinogenicity in rats and
    mice treated in the diet. The highest doses tested were 130 mg/kg bw
    per day in mice and 26 mg/kg bw per day in rats.

         In a series of studies, bitertanol had no genotoxic potential in
    lower organisms or in mammalian cells or systems  in vitro or
     in vivo.

         In a three-generation study of reproductive toxicity in rats,
    adverse effects on the pups (reductions in survival rates during the
    four-week lactation period, reduced weight at birth, and retarded
    growth) were observed at parentally toxic doses of 100 or 500 ppm,
    equivalent to 5 or 25 mg/kg bw per day. The NOAEL was 1 mg/kg bw per
    day.

         In studies of developmental toxicity, treatment with bitertanol
    led to several embryotoxic and teratogenic effects, depending on the
    animal species, route of administration, and dose. In rats, an oral
    dose of 10 mg/kg bw per day was tolerated with no observed effect.
    Doses of 25 mg/kg bw per day and above led to retardations and
    variations (e.g. increased incidence of the 14th rib). Malformations
    were observed at an oral dose of 100 mg/kg bw per day, which was
    clearly maternally toxic. Exposure of pregnant rats to concentrations
    of 27 mg/m3 air and above by inhalation resulted in retardation
    effects; no malformations were observed. In rabbits, doses of 50 mg/kg
    bw per day and above were maternally toxic; fetotoxic effects were
    seen at doses of 100 mg/kg bw per day and above. Teratogenic effects
    were observed in Himalayan rabbits at 100 mg/kg bw per day, while in

    the second strain tested (Chinchilla), even a dose of 250 mg/kg bw per
    day did not lead to malformations.

         The ADI established at the 1988 Meeting of 0-0.01 mg/kg bw, based
    on a combined NOAEL of 1 mg/kg bw per day from the two-year and the
    one-year study in dogs, was maintained. The ADI is supported by the
    NOAEL of 20 ppm (equivalent to 1 mg/kg bw per day) in a
    three-generation study in rats.

         An acute RfD was not allocated because bitertanol has been
    classified by WHO as unlikely to present an acute hazard in normal use
    and it has not shown any specific adverse effects (teratogenicity,
    neurotoxicity) after single doses 100 times the lowest relevant NOAEL
    in long- and short-term studies that were used to establish the ADI.
    Therefore, the Meeting concluded that the acute intake of residues is
    unlikely to present a risk to consumers.

    Toxicological evaluation

     Levels that cause no toxic effects

         Mouse:    100 ppm, equal to 25 mg/kg bw per day (toxicity in a
                   two-year study of toxicity and carcinogenicity)

         Rat:      100 ppm, equal to 4.9 mg/kg bw per day (toxicity in a
                   two-year study of toxicity and carcinogenicity)
                   20 ppm, equivalent to 1 mg/kg bw per day (reproductive
                   and parental toxicity in a three-generation study) 
                   10 mg/kg bw per day (maternal and developmental
                   toxicity in a study of developmental toxicity)

         Dog:      1 mg/kg bw per day (overall NOAEL in one-year and
                   two-year studies of toxicity)

         Rabbit:   50 mg/kg bw per day (maternal and developmental
                   toxicity in a study of developmental toxicity)

     Estimate of acceptable daily intake for humans

         0-0.01 mg/kg bw

     Estimate of acute reference dose 

         Not allocated (unnecessary)

     Studies that would provide information useful for continued 
     evaluation of the compound

         Further observations in humans

        List of end-points relevant for setting guidance values for dietary and non-dietary exposure
                                                                                                 

     Absorption, distribution, excretion, and metabolism in mammals

    Rate and extent of oral absorption         Commenced immediately, about 84% absorbed
    Dermal absorption                          About 10%
    Distribution                               Highest concentrations in liver and kidneys
    Potential for accumulation                 None
    Rate and extent of excretion               About 90% excreted with bile, 10% with urine
    Metabolism in animals                      No parent compound in bile or faeces; extensively 
                                               metabolized to 14 metabolites (ring 
                                               monohydroxylation, ring dihydroxylation, aryl 
                                                O-methylation, aliphatic hydroxylation, aliphatic 
                                               oxidation to carboxylic acids, and ether cleavage) 
    Toxicologically significant compounds      Parent compound
    (animals, plants and environment)

     Acute toxicity

    Rat: LD50, oral                            > 5000 mg/kg bw
    Rat: LD50,, dermal                         > 5000 mg/kg bw
    Rat: LC50, inhalation                      > 550 mg/m3 (4 h)
    Skin irritation                            Not irritating
    Eye irritation                             Not irritating
    Skin sensitization                         Not a sensitizer (Magnussen & Kligman test)

     Short-term toxicity

    Target/critical effect                     Liver, red blood cells, adrenals, digestive tract
    Lowest relevant oral NOAEL                 Dog: 90 days: 1 mg/kg bw per day
    Lowest relevant dermal NOAEL               Rabbit: 3 weeks; 250 mg/kg per day
    Lowest relevant inhalation NOAEL           Rat: 3 weeks,  63 mg/m3

     Genotoxicity                               No genotoxic or mutagenic potential

     Long-term toxicity and carcinogenicity
    Target/critical effect                     Liver
    Lowest relevant NOAEL                      Dog: 1 year and 2 years: 1 mg/kg bw per day
    Carcinogenicity                            No evidence of carcinogenic potential

     Reproductive toxicity

    Reproductive target/critical effect        Reproductive effects (reduced litter size, pup 
                                               growth rate, and pup survival) at parentally toxic 
                                               doses
    Lowest relevant reproductive NOAEL         Rat: 1 mg/kg bw per day

    Developmental target/critical effect       Fetotoxic and teratogenic effects at maternally 
                                               toxic doses
    Lowest relevant developmental NOAEL        Rat: 10 mg/kg bw per day

    Neurotoxicity/Delayed neurotoxicity        No relevant effects

    Other toxicological studies                Induction of hepatic microsomal activity

    Medical data                               No health impairments observed in employees 
                                               subjected to regular medical examinations

    Summary                 Value                  Study                   Safety factor
    ADI                     0-0.01 mg/kg bw        1 and 2 years in dogs   100
    Acute reference dose    None allocated 
                            (unnecessary)
                                                                                                 
    
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    See Also:
       Toxicological Abbreviations
       Bitertanol (Pesticide residues in food: 1983 evaluations)
       Bitertanol (Pesticide residues in food: 1984 evaluations)
       Bitertanol (Pesticide residues in food: 1987 evaluations Part II Toxicology)