CYHEXATIN JMPR 1974
Explanation
The 1970 JMPR (FAO/WHO, 1971) recommended temporary tolerances of
2 mg/kg for cyhexatin (under the name of tricyclohexyltin hydroxide)
on apples and pears. Inorganic tin and organotin degradation products
are not included in the tolerance. The 1973 JMPR recommended
additional tolerances of 2 mg/kg in citrus and manufactured tea, and
practical residue limits of 0.2 mg/kg in meat and 0.05 mg/kg in milk
fat. The 1974 Meeting of the Codex Committee on Pesticide Residues
(CCPR) referred to the Joint Meeting a question as to whether the
proposed limit of 2 mg/kg in fruits was too high and requested from
the Joint Meeting a proposal for tolerances on cucumbers, gherkins,
tomatoes, melons and bell peppers on the basis of data requested from
governments.
RESIDUES IN FOOD AND THEIR EVALUATION
RESIDUES RESULTING FROM SUPERVISED TRIALS
1. Apples and pears
Some new data from the Netherlands on apples suggest that
residues in apples resulting from approved use patterns in that
country would probably not exceed the national tolerance of 1 mg/kg.
The use pattern in the Netherlands is 0.4-0.5 kg a.i./ha wettable
powder sprays with a 28 day pre-harvest interval (PHI). Data available
to the 1970 JMPR however showed that dosages of 0.42 - 1.68 kg a.i./ha
are approved in other countries, with pre-harvest intervals as short
as 2 days. A re-examination of the data on which the 1970 JMPR
recommendations were based shows that a 2 mg/kg maximum limit is
required for the residues likely to result from the uses practiced in
countries other than the Netherlands.
2. Gherkins
The only country responding to the request for data was the
Netherlands. Treatments of gherkins in that country are principally
limited to glasshouse culture. The residue data submitted are adequate
to show that residues in glasshouse gherkins would not exceed 1 mg/kg,
the national tolerance.
3. Cucumbers, melons, bell peppers, tomatoes
Again, the only country responding to the request for data was
the Netherlands, with the exception of two residue trials on tomatoes
from the Republic of South Africa. All uses on these commodities in
the Netherlands are under glass. The use pattern is 0.25 to 0.4 kg
a.i./ha with a 3 day PHI. The data on cucumbers, tomatoes, and bell
peppers indicate that residues under glasshouse conditions would not
exceed 0.5 mg/kg, the national tolerance. No data were made available
on melons but the Meeting concluded that residue data on cucumbers
could be translated to melons of the muskmelon or cantaloupe variety.
All of the data from the Netherlands is expressed as cyhexatin
and based on measurements of total tin. The residue values are
therefore somewhat larger than those which would be obtained by
methods which determine only organotin.
The Republic of South Africa submitted information that there is
a national tolerance of 2 mg/kg for cyhexatin on tomatoes in
conjunction with a registered use pattern of 0.7 kg a.i./ha with a 3
day PHI (outdoor use). The residue data show that a 2 mg/kg tolerance
would be required to cover residues resulting from outdoor use under
South African conditions. The South African data did not indicate the
specific residues covered by the tolerance nor those determined by the
analytical method employed in the study.
APPRAISAL
The 1974 CCPR has referred to the Joint Meeting a question
regarding the need for the previously recommended 2 mg/kg tolerance
for cyhexatin on apples and pears and a request for proposals from the
Joint Meeting for tolerance on cucumbers, gherkins, tomatoes, melons
and bell peppers on the basis of data requested from governments.
Response to the request for information was obtained only from the
Netherlands and the Republic of South Africa, the latter referring
only to two trials on tomatoes.
The Joint Meeting concluded that the previously recommended
2 mg/kg tolerances on apples and pears could not be reduced because
use patterns currently registered in countries other than the
Netherlands show a need for that level.
The Netherlands proposal for tolerances on cucumbers, gherkins,
bell peppers, melons, and tomatoes is based on glasshouse uses only.
Residue data submitted by the Netherlands support a tolerance of
1 mg/kg on gherkins and 0.5 mg/kg on cucumbers, melons, bell peppers
and tomatoes for the glasshouse uses.
The 1973 JMPR considered a similar proposal from the Netherlands
but could not recommend tolerances at that time because of inadequate
residue data and inadequate information on outdoor uses on the same
crops in other countries.
Tolerances are not usually recommended to cover only a highly
specialized use in one country when there is reason to believe that
other agricultural uses are practiced in other countries. However, the
response to the request to other governments for information on
cyhexatin uses from the 1974 CCPR would indicate that there is no
great interest in such uses other than on tomatoes in the Republic of
South Africa.
The Joint Meeting therefore concluded that a recommendation for
tolerances on the subject crops (other than tomatoes) could be made
with the limitation that the tolerances are intended to cover
glasshouse uses only.
The data from South African outdoor use on tomatoes would justify
a tolerance of 2 mg/kg on that crop, that level being also adequate to
cover glasshouse uses.
RECOMMENDATIONS
The following maximum residue limits are for cyhexatin excluding
organic degradation products and inorganic tin.
TOLERANCES mg/kg
Apples, pears, citrus, tomatoes,
tea (manufactured) 2
Gherkins 1
Cucumbers, melons, bell peppers
(Glasshouse use only) 0.5
PRACTICAL RESIDUE LIMITS
Meat 0.2*
Milk and milk products (fat basis) 0.05*
*Level at or about the limit of determination
REFERENCES
FAO/WHO (1971). 1970 Evaluations of some pesticide residues in food.
AGP/1970/M/12/1; WHO/Food Add./71.42.