TRICYCLOHEXYLTIN HYDROXIDE JMPR 1973
Explanation
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.
TOXICOLOGICAL STUDIES
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
1973.
TABLE 1. SUMMARY OF ADDITIONAL ACUTE TOXICITY STUDIES
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.,
1973).
Comments
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
animals.
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.
TOXICOLOGICAL EVALUATION
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.
RESIDUES IN FOOD AND THEIR EVALUATION
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 "µg/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 µg to 6.8 µg 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.µg/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.
Appraisal
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 µg/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.
RECOMMENDATIONS FOR TOLERANCES, TEMPORARY TOLERANCES OR
PRACTICAL RESIDUE LIMITS
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
(days)
Citrus 2 0
Tea (manufactured) 2 14
Practical residue limits
0.2 ppm in meat; 0.05 ppm in milk (fat basis).
FURTHER WORK OR INFORMATION
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.
Desirable
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.
REFERENCES
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
Corporation.
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):
881-885
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)