METHOMYL JMPR 1976
Explanation
Methomyl was evaluated in 1975 by the Joint Meeting on
Pesticide Residues. Complete toxicological data were not made
available to the Meeting and an ADI could not be allocated. In the
absence of an ADI no recommendations could be made for maximum
residue limits, but guideline levels were recommended for various
commodities and are summarized in Annex 1 of the Report of the 1975
Meeting (FAO/WHO, 1976). Further work required by the 1975 Meeting
included development of a suitable regulatory method and residue
data from countries other than the U.S.A. The U.S. manufacturer
submitted information for evaluation by the 1976 Meeting on
residues, analytical methods, maximum residue limits and labelling
(Dupont, 1976). Country statements were received from the
Netherlands and Australia.
In the absence of relevant data, toxicological evaluation of
this compound was postponed.
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
In addition to information on new use patterns submitted by
the basic manufacturer (Dupont, 1976), country statements
describing national use patterns were received from Australia and
the Netherlands. Table 1 summarizes the new use patterns called to
the attention of the 1976 Meeting.
RESIDUES RESULTING FROM SUPERVISED TRIALS
New residue data from Australia, the Netherlands and the
U.S.A. were made available to the Meeting. Data from the
Netherlands were on tomatoes and peppers. Australia submitted data
on maize, sweet corn, tomatoes, cauliflower, cabbage, peaches,
apples, and cherries. The U.S. dossier included collards, hops,
tobacco and garden vegetables (the latter from W. Germany). The new
data generally support the 1975 guideline levels. The residue
studies supporting changes in or additions to the 1975 guideline
levels are detailed in this monograph. All residue values are
expressed as methomyl but the analytical method determines total
residues of methomyl plus the oxime metabolite S-methyl
thioacethydroximate (1-(methylthio) acetaldehyde oxime).
Asparagus
The available data on asparagus are from trials at 10
locations in the U.S.A. (Dupont, 1975). Registered uses in that
country permit a dosage of 1 kg a.i./ha, repeated as necessary,
with a 1 day pre-harvest interval (PHI). The Meeting has not
received any information on use patterns in other countries.
Initial deposits from the permitted dosage are in the range 1-2
mg/kg. Residues on the following day are usually < 1 mg/kg but
occasionally exceed this level. The unique harvesting practice for
asparagus involves cutting emerging spears every 2 or 3 days and
thus requires a short (1 day) PHI. A guideline level of 2 mg/kg
would be adequate.
Grapes
The only available data are from 11 locations in the U.S.
(Dupont, 1975) and show residues in the range 0.4 to 4.8 mg/kg on
harvested grapes treated under the registered use pattern (1 kg
a.i./ha - 1 day PHI). Australia requires a 2 day PHI. The data
indicate a need for a 5 mg/kg guideline level.
Peaches, nectarines
A guideline level of 1 mg/kg for nectarines was recommended by
the 1975 Joint Meeting (FAO/WHO, 1976). Apparently a guideline level
for peaches was inadvertently omitted. Approved Australian practice
provides for use on peaches and nectarines at a spray concentration of
22.5 g a.i./100l with a 1 day waiting period. Australian data made
available to the 1976 Meeting show initial residues of 0.93 and 1.3
mg/kg from the recommended (1x) and 2x application rates in "flesh of
peaches". U.S. data indicate residue levels of 6 to 7 mg/kg on whole
fruit one day after a 1/2x treatment and residues of the order of 5
mg/kg persisting into the fourth day. Nectarines exhibited a similar
residue pattern in the U.S. data (Dupont 1975). On the basis of
residues on the whole raw commodity it was concluded that a guideline
level of 5 mg/kg would be appropriate for both peaches and nectarines.
This level is based on a 4 day pre-harvest interval.
Green peas
The only available residue data are from U.S. field trials.
Methomyl is used on peas in the U.S. at the rate of 1 kg a.i./ha, 2
applications, with a 1 day waiting period for pea harvest, 5 days for
vines being fed to livestock, and 10 days for pea vine hay. In
Australia the use of sprays at 0.025 - 0.05% with a 1 day waiting
period is permitted. Supervised trials in the U.S. show residues of
0.02 to 0.4 mg/kg in shelled peas and 0.12 to 4.6 mg/kg in filled pods
at the specified 1 day PHI and recommended dosages. This suggests that
separate guideline levels of 0.5 mg/kg for shelled green peas and 5.0
mg/kg for peas in the pod would be adequate.
TABLE 1. National use patterns for methomyl, 1976
Application Pre-harvest Interval Other
Country Crop Rate (a. i.) Formulation (days) Restrictions
Netherlands tomatoes 0.1% spray 25% WP 3
(glasshouse)
peppers " " 3
Australia apples 35-45 g/100 l 25% sol. 1
nectarines 25 g/100 l " 1
peaches 25 g/100 l " 1
cherries " 2
leafy veg. 250-500 g/ha " none
potatoes 300-450 g/ha " none
tomatoes 35-45 g/100 l " none
lucerne " 1
peppers " 1
eggplant " 1
beans 25 g/100 l " 1
soybeans 300 g/ha " 3
citrus " 2
grapes " 2
TABLE 1. (Cont'd.)
Application Pre-harvest Interval Other
Country Crop Rate (a. i.) Formulation (days) Restrictions
cottonseed 25% sol. -
rapeseed " 2
peas 25-50 g/100 l " 1
U.S.A. asparagus 0.5-1.0 kg/ha Water 1
(as needed) sol.
field & 0.25-0.5 powder Do not feed
popcorn kg/ha and animals within
liq.sol. 3 days after
application
green peas 0.5-1.0 kg/ha " 1 livestock
(2 applications) feeding-3 days
vine, 14 days
hay
sugar beets 8-1.0 kg/ha " 7 do not feed tops
(3 applications) to livestock
New Zealand cereals 7
pasture 7
tomatoes 2
beans 2
cabbage, 7
cauliflower
TABLE 1. (Cont'd.)
Application Pre-harvest Interval Other
Country Crop Rate (a. i.) Formulation (days) Restrictions
New Zealand lettuce,
potatoes,
raspberries 2
United hops 0.3-0.8 kg/ha 25% WP none
Kingdom (as needed)
Snap beans
The data on snap beans (succulent) show residues at harvest in
the range 0.06 to 1.4 mg/kg one day after a treatment at 1.0 kg
a.i./ha. Residues had decreased to 0.03 - 0.30 mg/kg by the second and
third day. Information made available through country statements
indicates that New Zealand requires a 2 day waiting period while
Australia and the U.S. require 1 day. A guideline level of 2 mg/kg
would accommodate all these use patterns.
Hops
Data from trials at five locations in the United Kingdom were
made available (Dupont, 1976). Multiple applications at exaggerated
dosages resulted in residues ranging from < 0.02 to 1.2 mg/kg when
the last application was made one week before harvest. The sample was
presumably dried hops. The approved use in the U.K. permits repeated
applications at 0.3 - 0.8 kg/ha.
Collards
New data on collards (Dupont, 1976) showed some unusually high
residue values, e.g. 123 mg/kg one day after a 1 kg/ha application; 56
mg/kg after 7 days; 12 mg/kg at 10 days, and 5 mg/kg at 14 days. The
residue values from the four trial sites exhibited no particular
pattern, which may be typical for the broad leaf vegetables. A
guideline level of 5 mg/kg would be consistent with the 1975
recommendation on spinach. The data indicate the need for a 14 day
PHI.
Garden vegetables and vegetables under glass
The results of a series of residue trials in Fed. Rep. of Germany
were made available to the 1976 Meeting. They are summarized in Table
2.
METHODS OF RESIDUE ANALYSIS
The further development of available analytical methods for
residues to make them suitable for regulatory use was required by the
1975 Joint Meeting. The gaschromatographic method of Pease and
Kirkland (1968), modified by the use of a flame photometric detector
(Pease, 1969) has been used successfully for regulatory purposes in
some laboratories but others have experienced difficulties. It was
concluded that the method could not be recommended without reservation
for regulatory purposes until these difficulties had been resolved.
NATIONAL TOLERANCES
National tolerances or maximum residue limits reported to the
Meeting are shown in Table 3.
APPRAISAL
Toxicology data were not adequate to support an ADI when methomyl
was evaluated by the Joint Meeting in 1975, but sufficient residue
information was available to permit the Meeting to record guideline
levels. The supplementary information submitted to the 1976 Meeting
includes country statements from the Netherlands and Australia, as
well as a dossier from the basic manufacturer (Dupont).
TABLE 2. Methomyl residues resulting from 1 application of 225 g/ha (Fed. Rep. of
Germany
Crop Residue, mg/kg, at interval, days, after treatment
0 3 5 7 10 14
cauliflower (head) 0.94 0.06 0.04 0.03 0.01 <0.01
" (leaves) 2.38 0.29 0.03 0.02 <0.01 <0.01
radishes 0.46 0.16 0.08 0.20 0.08 0.08
radishes, under glass 0.14 0.78 0.81 0.98 1.06 0.22
cucumbers 0.15 <0.01 0.02 0.02 0.01 <0.01
tomatoes <0.01 0.02 0.02 <0.01 <0.01 <0.01
tomatoes, under glass 0.19 0.07 0.07 0.02 0.02 0.05
cabbage 0.38 0.02 0.02 0.01 0.01 0.01
lettuce (under glass) 3.20 2.7 1.8 2.3 1.2 0.29
carrots 0.09 <0.02 <0.02 <0.02 <0.02 <0.02
onions <0.01 <0.01 0.02 0.08 <0.01 <0.01
spinach 9.06 0.86 0.91 0.16 0.01 0.02
TABLE 3. National tolerances or maximum residue limits
reported to the Meeting
Country Crop Tolerance or maximum
residue limit, mg/kg
Netherlands tomatoes 0.05
peppers 0.05
Australia apples 1
nectarines 1
peaches 1
cherries 1
leafy veg. 1
potatoes 1
tomatoes 1
Australia lucerne exempt
peppers (1) 1
eggplant (1) 1
beans (1) 1
soybeans (1) 1
citrus (1) 1
grapes (1) 1
cottonseed (1) 0.2
rapeseed (1) 1
U.S.A. asparagus 2
field & popcorn 0.1 (grain)
green peas 10 (vines)
5 (peas)
New Zealand cereals 0.2
pasture 0.2
tomatoes 0.2
beans 0.2
cabbage, 0.2
cauliflower,
lettuce,
potatoes,
raspberries 0.2
(1) Provisional tolerances
The new material includes useful information on national use
patterns, national tolerances, and additional supervised trials from
countries other than the U.S.A. This information was designated as
"required" by the 1975 Meeting.
A requirement for the development of an analytical method
suitable for regulatory use has not been fully satisfied. It was
concluded that the GC (flame photometric) method of Pease would serve
this purpose in laboratories where it had been validated, but could
not be recommended without reservation.
Some data on the decline of residues in storage and processing
were furnished in response to the request made in 1975.
In the light of new information on national use patterns,
tolerances and supervised residue trials, some revisions are made to
the guideline levels recorded by the 1975 Meeting.
EVALUATION
The guideline levels recorded by the 1975 Meeting are reaffirmed
or are amended as listed below. Several new guideline levels are also
noted.
Interval on which
Commodity Guideline level (mg/kg) guideline is based
(days)
Collards1/ 5 14
Grapes 5 2
Nectarines 5 4
Peas (in pod)1/ 5 1
Peaches1/ 5 4
Asparagus 2 1
Snap beans 2 1
Peas (shelled) 0.5 1
1/Additional to 1975 levels.
FURTHER WORK OR INFORMATION
REQUIRED (before an acceptable daily intake can be allocated and
maximum residue limits can be recommended)
1. Submission of full toxicological data.
DESIRABLE
1. Development of an improved analytical method for regulatory
purposes.
2. Further information on the decline of methomyl residues in
storage or in processing.
3. Further information on national use patterns and residue data
from countries other than Australia, the Netherlands, and the
U.S.A.
REFERENCES
Dupont Information on methomyl insecticide. E.I. DuPont de Nemours
1975 & Co. (Inc.), Wilmington, Delaware, U.S.A.,
September, 1975.
Dupont Information on methomyl insecticide. E.I. DuPont de Nemours
1976 & Co. (Inc.), Wilmington, Delaware, U.S.A., July,
1976.
FAO/WHO Pesticide residues in food. WHO Technical Report Series
1976 No. 592; FAO Plant Production and Protection
Series No. 1.
Pease, H.L. and Kirkland, J.J. Determination of methomyl residues
1968 using microcoulometric gas chromatography. J. Agr.
Food Chem. 16:554-557.
Pease, H.L. Modification of the published gas chromatographic
1969 method for determination of methomyl residues: Use
of a flame photometric detector.
See Also:
Toxicological Abbreviations
Methomyl (EHC 178, 1996)
Methomyl (HSG 97, 1995)
Methomyl (ICSC)
Methomyl (WHO Pesticide Residues Series 5)
Methomyl (Pesticide residues in food: 1977 evaluations)
Methomyl (Pesticide residues in food: 1978 evaluations)
Methomyl (Pesticide residues in food: 1986 evaluations Part II Toxicology)
Methomyl (Pesticide residues in food: 1989 evaluations Part II Toxicology)
Methomyl (JMPR Evaluations 2001 Part II Toxicological)