This acaricide was evaluated by the FAO/WHO Joint Meeting of
    Experts in 1970 (FAO/WHO, 1971b). The estimate of the temporary
    acceptable daily intake for man made at that meeting was 0-0.0075
    mg/kg body weight and a request was made for more information to be
    made available by 1973.1 Further information on the effect of the
    compound on copper balance, on the production of cysts in the liver
    and the pituitary gland, on body weight in relation to food intake and
    on the significance of the brown discolouration on the serosa of the
    intestine has been provided and is discussed, together with other
    relevant new data, in this monograph addendum.


    Special studies on reproduction

         Groups of 12 male and 24 female bobtail quail were fed for 20
    weeks on diets containing 0, 5 and 20 ppm tricyclohexyltin hydroxide.
    Determination of body weights, food consumption, numbers of eggs laid
    and embryonated, numbers of live three week-old embryos normal
    hatchlings and 14-day-old survivors and of measurement of egg shell
    thickness revealed no differences attributable to treatment with the
    test compound (Fink, 1973).

    Acute toxicity

         The results of additional acute toxicity studies are summarized
    in Table 1.

    1 A temporary tolerance of 2 ppm was recommended for apples and pears
    with the notation of five requirements for additional work by June



    Species              Sex     Route      LD50       Reference

    Bobwhite quail       M       Oral       390        Shellenberger, 1971

    Bobwhite quail       F       Oral       300        Shellenberger, 1971

    Japanese quail       M       Oral       255        Shellenberger, 1971

    Japanese quail       F       Oral       280        Shellenberger, 1971

    Table 1 (cont'd)

    Species              Sex     Route      LD50       Reference

    Mouse                M       Oral       970        Shirasu, 1970

    Mouse                F       Oral       1 150      Shirasu, 1970

    Rat                  M       Oral       143        Shirasu, 1970

    Rat                  F       Oral       85         Shirasu, 1970

    Dog                          Oral       >800a      Noel et al. 1971

    Monkey                       Oral       >800a      Noel et al. 1971

    Cat                          Oral       >800a      Noel et al. 1971

    a Vomited after dosing. Vomiting occurred with doses above
        approximately 25 mg tricyclohexyl tin/kg body weight.

    Short-term studies

    Mouse. Groups of 10 male and 10 female mice were fed on diets
    containing 25, 50, 100, 200, 400, 800 and 1600 ppm tricycle hexyltin
    hydroxide for three months. Two similarly sized control groups were
    used. The 1600 ppm dietary level killed all mice in four to seven
    days. Over half of the 800 ppm group died in 5-25 days, the remainder
    surviving for 90 days. Death followed severe weight loss and
    diarrhoea, gastro-enteritis and degenerative changes in the liver and
    kidneys. Weight gain was normal in the 25 ppm group but depressed in
    females of the 50 ppm group and both sexes at higher dosage levels.
    Initially the intake of food was decreased with diets containing
    higher concentrations of the test compound but the intake returned to
    normal levels after two to three weeks. Food intake was unaffected at
    the 25 and 50 ppm dietary levels. Female mice receiving 800 ppm
    tricyclohexyltin hydroxide became slightly anaemic but other groups
    showed no haematological abnormalities. Treatment did not affect urine
    composition or renal concentrating power. Relative organ weights were
    normal for test groups other than the 800 ppm group, which had larger
    liver and smaller ovary weights compared with controls. Four of the
    nine mice surviving the 800 ppm dietary level showed pronounced
    formation of lacunae (? vacuolation) in the liver. Shrinkage or
    disappearance of follicles was seen in all three mice of the 800 ppm
    group and eight of the 10 on 400 ppm diet. Mice receiving 200 ppm or
    less were normal in this respect. The no-effect level in this study
    was 25 ppm in the diet, equivalent to a daily intake of 3.8 mg/kg
    (Shirasu, 1970).

    Rat. Groups of 10 male and 10 female rats were fed diets containing
    25, 50, 100, 200, 400 and 800 ppm tricyclohexyltin hydroxide for three
    months. Two similarly sized control groups were used. Only one male
    and one female rat on 800 ppm diet survived for 90 days, the remainder
    dying between six and 50 days. Nine of 20 rats on 400 ppm diet
    survived treatment. One male animal on 200 ppm diet and another on the
    100 ppm diet died but all others survived. Deaths followed severe
    weight loss and diarrhoea and autopsy showed death was associated with
    desquamation of epithelial cells and inflammation of the submucosa of
    the intestine and mild degenerative changes in the kidneys and liver.
    Weight gain was depressed in all test groups of females but males on
    25 ppm diet grew normally. Initially the intake of food was decreased
    with the higher dietary contents of test compound but, unlike mice, no
    sign of tolerance to the diet occurred. No abnormalities were found in
    the blood or urine of treated rats and renal concentrating ability
    appeared unchanged. The relative weights of heart, liver and kidneys
    were higher in the 800 ppm groups than in controls. One male and one
    female rat surviving 800 ppm diet showed pronounced formation of
    lacunae (? vacuoles) in the liver and male rats on 400 ppm diet showed
    some degenerate hematic cells (associated with eosinophilic cytoplasm
    and shrinkage of nuclei). Both rats surviving 800 ppm diet showed
    biliary duct inflammation and one male and one female hyper trophy of
    the biliary duct. Almost all rats in the 200 ppm and higher dosage
    groups showed slight biliary duct cell hypertrophy. The ovaries of
    rats were not affected like those of mice (Shirasu, 1970).

    Dog. Groups of four male and four female dogs were fed for 90 clays
    on diets containing tricyclohexyltin hydroxide at levels adjusted to
    provide 0, 1.5, 3 and 6 mg of test compound/kg/day. Dogs receiving 3
    and 6 mg/kg/day showed a significantly reduced rate of body weight
    gain. The weight gain of the 1.5 mg/kg group was also below that of
    controls but not significantly go. No changes attributable to
    treatment were found in food consumption or in the results of
    haematological investigations and serum and urine analyses, in
    relative organ weights and in the results of examining organs and
    tissues histologically. No dog died during the study. Loose stools
    were noted among dogs receiving 6, 3 and 1.5 mg/kg/day after three,
    six and nine weeks respectively. Clear fluid was found in the
    peritoneal cavity of seven of the eight dogs receiving 6 mg/kg/day of
    tricyclohexyltin hydroxide; no explanation was found for this
    (Calandra, 1970).

         Groups of two male and two female dogs were fed for 90 days on
    diets containing tricyclohexyltin hydroxide at levels adjusted to
    provide 0, 1 and 3 mg of test compound/kg/day. No significant changes
    in body weight or food intake occurred and treated animals remained in
    good health. Organs appeared normal at autopsy and organ weights of
    test animals were within normal limits. The analyses for copper in
    serum obtained during weeks 1, 9, 12 and 13 of the test showed that
    there were considerable variations in the levels of serum copper in
    all groups. The levels of total copper excreted over a 24-hour period
    in urine collected before the trial and during weeks 1, 5, 9 and 12 of
    the trial also showed wide variations. The copper content of liver

    obtained at autopsy and of serum and urine samples were not
    significantly different in control and test animals (Humiston et al.,


         A recent study has satisfactorily established that the copper
    concentration of blood and liver and the daily urinary copper
    excretion were not altered in dogs fed on diets providing up to 3 mg
    tricyclohexyltin hydroxide/kg/bw/day.

         The histological appearance of the liver and pituitary cysts
    reported to occur in rats receiving up to 12 mg tricyclohexyltin
    hydroxide/kg body weight in the diet for two years has been reviewed
    by the author of the study. The pituitary cysts were of a type
    commonly seen in rats and their incidence was not increased by
    treatment. Some of the liver cysts were parasitic in origin. It was,
    however, noted by the Meeting that some of the lesions previously
    described as cysts in liver had been reclassified as adenomas and that
    these occurred in both male and female animals receiving the two
    highest dosage levels of tricyclohexyltin hydroxide. The cysts
    occurring in animals fed on lower dosage levels were not reviewed.
    Although it was claimed that hepatic adenomas appeared at maturity in
    the strain of rat used no such adenomas were, in fact, seen in control

         The compound is highly irritant and doses of more than 25 mg/kg
    body weight produce vomiting in those species capable of vomiting.
    Histological changes consistent with gastroenteritis were seen in
    animals which received the substance orally. However, whether the
    decreased weight gain was associated with this or due to diminished
    food intake or to other factors, has not been clarified.

         No further explanation of the brown discolouration of the
    intestinal serosa in dogs exposed to the compound has been offered
    although it is stated that this change did not involve tissues deep to
    the serosa. The phenomenon has not been found in dogs in two
    three-month studies in which dosage levels up to 6 mg/kg/day were fed.


    Level causing no toxicological effects

         Dog: level in the diet adjusted to give 0.75 mg/kg bw.

    Estimate of temporary acceptable daily intake for man

         0-0.007 mg/kg bw.a

    a The ADI of 0-0.0075 mg/kg bw established in 1970 has been rounded
    off as for Section 2.4 of FAO/WHO 1974a, Techn. Rep. Ser., No. 545.


         A detailed discussion on the fate of tricyclohexyltin hydroxide
    in plants, soils, and animals may be found in the monograph resulting
    from the 1970 evaluation (FAO/WHO, 1971). A similar monograph on the
    related phenyltin compounds on page 327 of the same reference is also
    of interest. Several alteration products are known The progression of
    degradation has been shown as:

    parent -> dicyclohexyltin oxide -> monocyclohexylstannoic acid-> Sn+4
    (Cy3Sn OH) (Cy2Sn O)                   (Cy Sn O2H)

         Residues on fruits are generally characterized as persistent
    surface residues, with little penetration of fruit. The proportions of
    parent and alteration products are a function of weathering time but
    residues of tricyclohexyltin hydroxide predominate at any given time.
    The complex residues resulting from use of the compound are determined
    by a number of analytical methods which measure variously, inorganic
    tin, organic tin, total tin, or specifically the parent, and
    dicyclohexyl and monocyclohexyltin hydroxide. The analytical methods
    have been used interchangeably in some of the supervised trials
    referenced below, and a careful distinction must be made as to which
    component of the residue is reported.

    Use pattern

    1.   Citrus. Wettable powder sprays at concentrations of 15 to 33
    g/100 l applied at the rate of 0.4 to 1.7 kg/ha are used. Information
    on frequency of treatments was not available. Pre-harvest intervals
    range from 0 to 35 days depending on the country and spray schedule.

    2.   Tea. Wettable powder sprays at concentration 15 to 33 g/100 l
    at rate of 0.4 to 1.7 kg/ha are used. Frequency of treatment was not
    indicated but the pre-harvest interval is usually 14 days.

    3.   Cucumbers, gherkins, melons, bell peppers, tomatoes (green
    house only). 0.1% spray with three-day pre-harvest interval.

    Residues resulting from supervised trials

    1. Citrus. The data are contained in seven unpublished reports
    submitted by the Dew Chemical Company. The reports are referenced here
    as Getzendaner and Corbin, 1971; Corbin, 1973; Westlake and Gunther,
    1970; Goto and Kishi, 1973; Anon., 1970a and Anon., 1970b.

         In summary, the reports include 15 different field experiments in
    various citrus areas of the United States of America and Japan, on
    oranges, tangerines, grapefruit, limes and lemons, with analyses of
    either whole fruit, peel, edible pulp, or juice.

         As noted above, some analyses are reported in terms of total tin,
    some as organotin, and some analyses were specifically for
    tricyclohexyltin hydroxide. The values obtained for total tin are
    invariably higher, approximately 5 ppm in peel and 0.1-0.2 ppm in
    juice. However, since the tolerance for the tin compounds does not
    include inorganic tin, these values are relatively unimportant as an
    index to an appropriate tolerance. Since it has been shown that
    residues on the citrus are predominantly the parent compound, the
    values for "organotin" and the specific analyses for tricyclohexyltin
    hydroxide are considered to be roughly equivalent. The data show
    initial deposits of "organotin" or tricyclohexyltin hydroxide on whole
    fruit to approximately 1-1.5 ppm. Decline of residues over the period
    of the experiments (usually 0-28 days) was minor. Data indicate
    varietal differences, lemons and limes being significantly lower in
    residues than oranges, grapefruit, and tangerines. Since smaller fruit
    tend to incur larger residues due to surface/volume relationships the
    apparent varietal differences may be due to vagaries of the
    experiment. Most trials included multiple treatments (up to six) but
    no correlations were apparent on residue level effects.

         The pre-harvest interval which ranges from 0-35 days in various
    countries is of diminishing importance in view of the fact that
    residue decline rate is not significant and residues at zero day did
    not exceed 2 ppm.

         It may be concluded that residues of organotin or
    tricyclohexyltin hydroxide per se would not exceed 2 ppm on whole
    fruit or 0.1 ppm in edible pulp or juice.

    2. Tea. Data are available on manufactured tea (the dried tea of
    commerce) and the brewed beverage. Since uncured green tea leaves do
    not move in channels of commerce it is appropriate that recommended
    tolerances for tea be on manufactured tea. All data are from Japan in
    an unpublished report submitted by Dew Chemical Company (Goto and
    Akazaki, 1973).

         Four field trials are described in which one or two applications
    at the recommended maximum concentration (33 g/100 l) of wettable
    powder spray were made. Samples were taken at 14, 21 and 28 days.
    Residues of "tricyclohexyltin hydroxide" in manufactured tea ranged
    from 0.2 to 1.1 ppm. Again, there was no significant decline of
    residues over the period of the trial.

         The analytical results are expressed as "tricyclohexyltin
    hydroxide". The analytical procedures followed (Goto and Akasaki,
    1973) appear to be a modification of a published method (Getzendaner
    and Corbin, 1972) which is discussed below. The procedure used on

    fired tea would measure only tricyclehexyltin hydroxide. The procedure
    followed on the beverage tea appears to omit the alcoholic KOH
    treatment of the hexane fraction and would probably measure the
    dicyclohexyltin hydroxide and parent tricyclohexyltin hydroxide. The
    omission would probably not introduce any significant deviation since
    other data indicate that tricyclohexyltin hydroxide comprises
    practically all of the residue.

         Residues in the beverage were expressed in terms of "g/12 g
    percolate" and in percentage of transfer from dried tea to percolate.
    A reading of the experimental procedure (Goto and Akazaki, 1973) would
    indicate that the column heading refers to a percolate portion of
    unspecified volume derived from 12 g of dried tea (rather than 12 g of
    beverage). The 12 g is apparently derived from dietary statistics that
    12 g of dried tea produces 0.72 litres of beverage tea; which is
    considered the maximum normal daily intake.

         Residues in the percolate ranged from 0.8 g to 6.8 g per
    portion. The data could be interpreted to indicate a maximum daily
    intake of about 7 jug/day. The data on brewed tea, however, were
    obtained from tea bearing less than the proposed tolerance level. For
    the purpose of estimating possible human intake, it would be
    reasonable to apply the percentage extraction factors to the tolerance
    level. Per cent conversion from dried tea to beverage ranged from 23.1
    to 62% (average 42.5%). Dried tea bearing the tolerance level could
    therefore on the average contribute 10.0.g/day to the diet.

    3. Vegetables under glass (Netherlands). Available data in support
    of these uses are very meagre. There is an indication that the
    organotins may be used for field treatments of vegetables in other
    countries. Before giving further consideration for tolerances to cover
    this specialized use, it would be advisable to have additional
    information on uses of tricyclohexyltin hydroxide in other countries
    and additional data from supervised residue trials.

    4. Meat and milk. In the 1970 Joint Meeting (FAO/WHO, 1971) it was
    concluded that the limited feeding of apple and pear pulp would not
    produce detectable residues in meat or milk. A problem was recognized
    in the monograph on the triphenyltin compounds on page 354 of the same
    reference in which it was recommended that the fresh foliage of
    treated crops not be fed to livestock. Of the crops under
    consideration at the 1973 joint Meeting, only citrus occupies an
    important position as a livestock feed. Data indicate a concentration
    of two to four fold in the manufacture of dried citrus pulp
    (Getzendaner and Corbin, 1971). Citrus pulp might therefore contain up
    to 8 ppm. The pulp is incorporated in beef and dairy cattle rations in
    amounts up to 3076 of the diet in some countries, and could contribute
    about 2.5 ppm to the total diet. Cattle feeding studies (at 10 ppm)
    show that, after adjusting for the diet factors, 0.15 ppm in liver,
    0.1 ppm in kidney, and <0.1 in muscle and fat might be predicted.
    Residues in milk would be >0.05 ppm (fat basis). The data would
    support a recommendation for PRLs of 0.2 ppm in meat and 0.05 ppm in
    milk fat.

    Methods of residue analysis

         The monograph of the 1969 Joint Meeting included a survey of the
    methods available at that time. A recommendation was made for the
    development of an analytical procedure capable of distinguishing
    between the tricyclohexyltin and other organotin compounds.

         The basic manufacturer has made available a specific EC-GC method
    for tricyclohexyltin hydroxide, using a TLC clean-up and determination
    as the tricyclohexyltin chloride (Kutschinski, 1972a). The method has
    been validated on orange juice and muscle, liver and kidney with minor
    differences in extraction clean-up. The method has rather poor
    sensitivity by present standards (0.1 ppm), low recoveries were
    obtained from the animal tissues (30-60%, average 40%), and with
    respect to the procedure for meat it is described a qualitative test.
    It would appear to be a delicate analytical method, requiring extreme
    attention to technique. Nevertheless, in view of its possible
    regulatory use at tolerance level (2 ppm) it would satisfy the
    stipulation in the 1970 Joint Meeting recommendations regarding a
    specific method.

         Another method capable of determining individually the
    tri-di- and moncyclohexyltin compounds has in the meantime been
    published (Getzendaner and Corbin, 1972). The method employs a
    complex extract partitioning scheme for separation of the tin
    residues with final measurement in all cases by the colorimetric
    toluene-3, 4-dithiol method.

         Corbin (1973b) has published a rapid spectrophotometric method
    for tin employing pyrocatechol violet which may be substituted for the
    final determinative stop in the above methods.

    In soil

         The fate of tricyclohexyltin hydroxide in soils was discussed in
    the 1970 monograph. A question has since been raised as to whether the
    compound would be converted to a methyl derivative in soils. A report
    of an investigation into this possibility (Kutchinski, 1972b) has been
    made available. The study showed that such conversion does not occur
    in soils under either aerobic or anaerobic conditions.

    National tolerances (commodities under consideration only)a

    Citrus: United States of America, 2 ppm with no limitations.

    Tea: none.

    a National tolerances are as received by the Joint Meeting and are
    not represented here to be complete or official.

    "Vegetables":  Israel, 1 ppm with seven-day pre-harvest interval;
                   Netherlands, 1 ppm with three-day pre-harvest interval.

    Accepted uses in nations where tolerances are not required

    Citrus:  Brazil, no pre-harvest interval; New Zealand, 35-day
             pre-harvest interval; Taiwan, no pre-harvest interval.

    Tea:  none.

    "Vegetables": France, seven-day pre-harvest interval;
                  United Kingdom, 28-day pre-harvest interval.


         Recommendations for a temporary tolerance of 2 ppm for
    tricyclohexyltin hydroxide on apples and pears were made by the 1970
    Joint Meeting, with requirements for certain additional toxicity
    studies and a requirement that a specific analytical method be
    developed to determine tricyclohexyltin in the presence of the
    triphenyl tin compounds.

         Specific analytical methods which satisfy the 1970 requirement
    have been submitted by the basic manufacturer.

         Information deemed desirable on the occurrence of the acaracide
    on fruit in commerce has not become available.

         Information was received on the nature, level and occurrence of
    residues of tricyclohexyltin hydroxide on citrus and tea
    (manufactured) and certain vegetables grown under glass. The residue
    data and information on use patterns on vegetables was inadequate.

         Beverage tea brewed from manufactured tea containing the
    tolerance level of 2 ppm is calculated to contribute 10.0 g/day to
    the human diet. Additional trace levels may be contributed to the diet
    through meat and milk from animals fed rations containing dehydrated
    citrus pulp.


         The following tolerance and practical residue limits are
    recommended in addition to the 2 ppm temporary tolerance for apples
    and pears recommended in 1970.

                                       Interval on which
    Crop                     ppm       tolerance is based
    Citrus                   2         0

    Tea (manufactured)       2         14

    Practical residue limits

         0.2 ppm in meat; 0.05 ppm in milk (fat basis).


    Required by 1977

    1.   A long-term carcinogenicity study to elucidate the significance
         of the occurrence of adenomas in rats.

    2.   A study of the factors that lead to the diminished weight/gain in
         animals fed on diets containing tricyclohexyltin hydroxide.


    1.   Further validation and study of the specific method of Kutchinski
         to determine its suitability as a regulatory method.

    2.   Additional residue data and information on use patterns for those
         vegetables on which the information was found inadequate at the
         1973 Joint Meeting.

    3.   Data on the occurrence of tricyclohexyltin residues on apples and
         pears moving in commerce.


    Anon. (1970a) The results of tests on the amount of residue remaining
    after application. Unpublished report from Dow Corporation

    Anon. (1970b) Results of Plictron residue analysis in apples and
    citrus. Unpublished report of Tokyo University of Agriculture and
    Technology, Japan, submitted by Dow Corporation

    Calandra, J.C. (1970) Ninety-day subacute oral toxicity study of
    tricyclohexyltin hydroxide in beagle dogs. Unpublished report of
    Industrial Bio-Test Laboratories, submitted by Dow Chemical

    Corbin, H.B. (1973a) Analyses of lemons for residues of organotin.
    Unpublished report of M & T Chemicals Inc., Rahway, N.J.

    Corbin, H.B. (1973b) Rapid and selective pyrocatechol violet method
    for tin. Anal. Chem. 45(3):  534-537

    FAO/WHO (1971) 1970 Evaluations of some pesticide residues in food.  
    AGP: 1970/M/12/1

    Fink, R. (1973) One-generation reproduction study-bobwhite quail 
    DOWCO 213. Unpublished report of Hazelton Laboratories, submitted by
    Dow Chemical Corporation.

    Getsendaner, M.E. and Corbin, H.B. (1971) Residue study of citrus
    fruits from trees treated with Plictran(R) miticide. Unpublished
    report of Dow Chemical Co. and M & T Chemicals Inc., U.S.A.

    Getsendaner, M.E. and Corbin, H.B. (1972) Residues on apples and pears
    from use of Plictran miticide. J. Agric. and Food Chem. 20(4):

    Goto, S. and Kishi, T. (1973) Residue data for citrus. Unpublished
    report of the Institute of Environmental Toxicology and Yamomoto
    Noyaka Co. Ltd., Japan.

    Goto, S. and Akazaki, K. (1973) Residue data for tea. Unpublished
    report from the Institute for Environmental Toxicology and Kumaj
    Chemical Industry, Inc., Japan

    Humiston, C.G., Wade, C.E., Kociba, R.J., Jewett, G.L. and Krokosky,
    J.A. (1973) A 90-day dietary feeding study with tricyclohexyltin
    hydroxide in male beagle dogs. Unpublished report of Chemical Biology
    Research submitted by Dow Chemical Corporation, U.S.A.

    Kutschinski, A.H. (1972) Method ACR 72.11. Gas chromatographic a
    method for the determination of tricyclohenyltin hydroxide in orange
    juice. Unpublished report Dow Chemical Co., USA.

    Kutschinski, A.H. (1972b) Investigation of the possibility of
    conversion of tricyclohexyltin hydroxide to dicyclohexyl methyl tin
    hydroxide in soil. Unpublished report of Dow Chemical Co., U.S.A.

    Noel, P.R.B., Heywood, R. and Squires, P.F. (1970) PLICTRAN acute oral
    dosage experiments in dogs, monkeys, and cats. Unpublished report of
    Huntingdon Research Centre, submitted by Dow Chemical Corporation

    Shollenberger, T.E. (1971) Acute toxicological evaluations of
    DOWCO(R) 213 and PLICTRAN(R) 50W miticide with bobwhite and
    Japanese quail. Unpublished report of Gulf South Research Institute
    submitted by Dow Chemical Corporation

    Shirasu, Y.  (1970) Test report on the subacute toxicity of an 
    insecticide "DOWCO" 213. Unpublished report of The Physical and
    Chemical Research Unit, Japan, submitted by Dow Chemical Corporation.

    Westlake, W.E. and Gunther, F.A. (1970) Residues of tin on and in 
    oranges and citrus pulp cattlefeed resulting from spray applications
    of Plictran(R). Unpublished report of University of California.


    See Also:
       Toxicological Abbreviations
       Tricyclohexyltin Hydroxide (AGP:1970/M/12/1)