PARATHION-METHYL JMPR 1978
Explanation
Parathion-methyl was reviewed in 1968, 1972 and 1975 (FAO/WHO
1969b, 1973b, 1976b). The 1975 Meeting required oral studies on
teratogenesis and on reproduction in species appropriate to such
tests to be carried out by 1978. In addition, the following
information was considered desirable.
1. Adequate long-term studies in at least one
mammalian species.
2. Information on current use patterns in various
countries on crops for which no
recommendations are made and on residue levels
resulting from such uses.
Some of the information has been submitted and is evaluated
below.
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
Parathion-methyl is a general-purpose insecticide in several
countries although it is slowly being replaced by the newer
insecticides. Application is at 0.02 - 0.05% concentrations at
rates of 350 g/ha to 1 kg/ha. The compound, being already a
commodity product, is considered one of the more widely used
insecticides world-wide. National use patterns, especially in
tropical countries, are therefore still important.
In Australia, specific uses include the following.
1. Orchard crops, Parathion-methyl is applied at concentrations
of 20-50 g/100 l (0.02-0.05%) to control aphids, jassids,
coddling moth, light brown apple moth, oriental fruit
moth and scale insects with application being made
throughout the season. A pre-harvest interval of 14 days
is recommended.
2. Field and vegetable crops. Parathion-methyl is applied at 33
33 g/100 l (0.03%) or at 350 g/ha to control aphids,
bugs, caterpillars and mites. Application is made at
10-14 days intervals or as required throughout the
growing season. The pre-harvest interval is 14 days.
3. Cotton. Parathion-methyl is applied at 350-700 g/ha, in
convenient concentrations, to control cluster
caterpillars, loopers, aphids and mites. Applications are
made when the pests are first seen. The pre-harvest
interval is 14 days.
4. Tobacco. Application is at 52 g/100l (0.05%) in admixture
with DDT (0.1%) to control budworms, leaf miners and
loopers. It is applied weekly or as required.
RESIDUES RESULTING FROM SUPERVISED TRIALS
In soybeans
Soybeans treated with an emulsifiable formulation of
Parathion-Methyl at 1.1 and 2.2 kg ai/ha in the United States in
1968 showed no detectable residues of paraoxon-methyl,
parathion-methyl or nitrophenol 16-37 days after the last
application. Parathion-methyl residues were detected in beans plus
pods with applications 1-14 days before harvest, but the oxon was
not detected and p-nitrophenol was detected only at 1 day after
application (Table 1).
In soybean forage
Residue determinations were conducted on field-treated samples
of soybean forage from three locations in the United States. At 1.1
kg ai/ha residues were below 1.0 mg/kg after 5 days. Residues of
paraoxon-methyl could not be detected (< 0.05 mg/kg) while
p-nitrophenol was generally below 0.2 mg/kg (Table 2).
In cottonseed
Residues were determined in field-treated samples of
cottonseed from 12 locations. The detectable residues were below
0.2 mg/kg paraoxon-methyl, parathion-methyl and p-nitrophenol in
mature cottonseeds from cotton treated with emulsifiable
formulations at rates up to and including 1.375 kg ai/ha. The
interval between the last application and harvest ranged from 18 to
74 days.
ULV application of parathion-methyl at 0.83 kg/ha gave no
detectable residues in the mature cottonseeds.
In various crops in Finland
The residues of parathion-methyl from supervised trials on
several crops in Finland are shown in Table 3. Residues are
generally low at the pre-harvest intervals adopted.
In green beans
Low-level residues were obtained in a recent series of residue
trials in the Philippines. Insecticides were applied weekly at 1.0
and 2.0 kg ai/ha two weeks after emergence; the latter is double
the recommended rate. On the basis of the established MRL of 1
mg/kg for vegetables in general, a two days pre-harvest interval
may be adequate for tropical climates (Table 4).
TABLE 1. Parathion-methyl and p-nitrophenol residues in field-treated soybeans
in USA 1/, 2/
Rate Days after Residue, mg/kg
Location (kg ai/ha) Application Parathion-methyl p-nitrophenol
Sweethome,
Ark. 1.1 1 14.6 0.1
15.8 0.1
2.2 1 40.0 0.2
36.2 0.1
1.1 5 3.7 ND2/
3.25 ND
2.2 5 6.0 ND
5.8 ND
1.1 7 1.9 ND
2.2 ND
2.2 7 2.7 ND
2.6 ND
1.1 14 1.1 ND
1.1 ND
2.2 1.9 ND
1.8 ND
1.1 16 ND ND
ND ND
2.2 ND ND
ND ND
1/ Paraoxon-methyl was sought in all samples but not detected.
2/ Sample consists of bean plus pod.
3/ ND = < 0.02 mg/kg parathion-methyl
< 0.05 mg/kg paraoxon-methyl
< 0.05 mg/kg p-nitrophenol
TABLE 2. Parathion-methyl and p-nitrophenol residues in field-treated soybean forage
in USA 1/
Rate Days after Residue, mg/kg
Location (kg ai/ha) application Parathion-methyl p-nitrophenol
Stoneveille,
Miss 1.1 1 2.6, 2.8 0.2, 0.2
2.2 6.2, 6.6 0.7, 0.6
1.1 5 0.5, 0.4 0.1, 0.1
2.2 1.0, 1.1 0.2, 0.2
1.1 7 0.4, 0.4 0.1, 0.1
2.2 0.8, 0.9 0.1, 0.1
1.1 14 0.3, 0.3 ND2/,0.1
2.2 0.6, 0.6 Nd, 0.1
1.1 21 ND ND
2.2 0.08,0.08 ND
Charleston,
Ill. 1.1 17 ND ND
2.2 ND ND
Charleston,
Ill. (dry forage) 1.1 22 0.03,0.02 ND
2.2 0.03,0.03 ND
Albany,
Ga. 1.1 19 ND ND
2.2 ND ND
1/ Paraoxon-methyl was sought in all samples but not detected.
2/ ND = < 0.02 mg/kg parathion-methyl
< 0.05 mg/kg paraoxon-methyl
< 0.05 mg/kg p-nitrophenol
TABLE 3. Residues of parathion-methyl from supervised trials in Finland
Crop Rate and Interval from Residues, mg/kg
formulation last application
to harvest days
blackcurrant 1.0 g/bush, dust 22 washed 0.05
unwashed 0.05
pea 150 g/ha, dust 29 pea ND (<0.05)
pod ND (<0.05)
pea 150 g/ha, dust 22 pea ND
pod ND
pea 150 g/ha, dust 15 pea ND
pod ND
pea 150 g/ha, dust 8 pea ND
pod ND
cauliflower 150 g/ha, dust 21 washed ND (<0.05)
unwashed ND
sugar beet 150 g/ha, dust 28 washed roots ND (<0.03)
tops 0.09
sugar beet 150 g/ha, dust 21 washed roots ND (<0.03)
tops 0.6
sugar beet 150 g/ha, dust 6 washed roots 0.04
tops 0.6
cabbage 150 g/ha, dust 28 inner cabbage ND (< 0.05)
whole cabbage ND
cabbage 150 g/ha, dust 21 inner cabbage ND
whole cabbage ND
cabbage 150 g/ha, dust 14 inner cabbage 0.08
whole cabbage 0.08
cabbage 150 g/ha, dust 7 inner cabbage 0.18
whole cabbage 0.18
sugar beet 300 g/ha 1 0.5
sugar beet 300 g/ha 2 0.34
TABLE 3. (Cont'd.)
Crop Rate and Interval from Residues, mg/kg
formulation last application
to harvest days
sugar beet 300 g/ha 3 0.15
sugar beet 300 g/ha 4 0.12
sugar beet 300 ha 7 0.04
sugar beet 300 g/ha 9 0.04
sugar beet 90 g/ha 126 washed ND (<0.005)
sugar beet 90 g/ha 126 washed ND
TABLE 4. Residues of parathion-methyl in green beans, Philippines 1978
Residues (mg/kg) at intervals (days) after last application
No. of Application rate
trials (kg ai/ha)
emulsion concentrate 0 1 2 3 5 7
2 1 kg ai/ha
× 5 1.30 0.39 0.13 0.02 ND = ND =
< 0.01 < 0.01
2 2 kg ai/ha
× 5 2.53 1.07 0.57 0.06 ND ND
In cabbage
No detectable residues (< 0.01 mg/kg) were observed with the
recommended pre-harvest interval of 1 week.
FATE OF RESIDUES
No data were available.
RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION
In a market basket survey in 1970 in Australia, parathion-methyl
residues were not determined specifically but the total
organophosphorus (OP) residues found did not exceed 0.5 mg/kg in any
of the foods examined. Some 240 samples were analysed and only 32
contained any OP residues, of which only 3 exceeded 0.2 mg/kg.
Residues of parathion methyl have occasionally been detected in
vegetables sampled routinely in a continuous national residues survey
programme. In general, these do not exceed 0.1 mg/kg. For example, in
a 12 month period (1977-1978) 5 of 105 samples had residues higher
then 0.1 mg/kg; these samples were localized and were indicative of
applications in excess of the recommended rates.
Market basket survey results from New Zealand are shown in Table
5. Of 462 samples, only 30 contained parathion-methyl. All of the 5
samples of leafy vegetables found positive had residues considerably
lower than the established MRLs; but 11 citrus-fruit and one
stone-fruit samples had residues at or about the MRL for fruits of
0.2 mg/kg.
NATIONAL MAXIMUM RESIDUE LIMITS REPORTED TO THE MEETING
Australia reported national maximum residue limits as follows.
Cottonseed, fruits, vegetables 1 mg/kg
Cottonseed oil 0.05 mg/kg
APPRAISAL
The 1975 Joint Meeting considered information desirable on
current use patterns and residue levels in various countries on crops
for which no recommendations had been made. Australia submitted data
on use patterns on orchard crops, field and vegetable crops, cotton
and tobacco. The pre-harvest interval is generally 14 days. Residue
data were submitted by Monsanto Co. on soybeans, soybean forage and
cottonseed and by Finland on a range of crops. Only low residues, if
any could be detected 14 days after application. With cabbage and
green beans under tropical conditions, degradation is rapid so that
the established MRL is not likely to be exceeded with good agriculture
practice.
TABLE 5. Residues of parathion-methyl found in random sampling at the retail level
in New Zealand
Year Crop No. of No. of
sample positive Residues found (mg/kg)
tested samples Range Average
1970 Leafy vegetables 15 2 0.3 0.3
1971 Leafy vegetables 54 1 0.1
1972 Leafy vegetables 48 0 - -
1973 Leafy vegetables 40 1 - 0.15
1971 Root vegetables 48 0 - -
1972 Root vegetables 46 1 0.26
1973 Root vegetables 32 0
1970 Pip fruit 2 0.05 0.05
1971 Pip fruit 9 3 0.04 - 0.02 0.03
1972 Pip fruit 24 - - -
1973 Pip fruit 27 0 - -
1972 Stone fruit 17 1 0.25
1971 Citrus 18 4 0.5 - 0.01 0.2
1972 citrus 20 4 1.4 - 0.01 0.2
1973 Citrus 32 7 0.4 - 0.01 0.2
1975 Fruit (fresh) 16 2 0.007 - 0.003 0.005
Fruit (canned) 16 2 0.008 - 0.002 0.005
In two national residue survey programmes (in Australia and New
Zealand), parathionmethyl has seldom been detected, and never at
levels exceeding established MRLs.
RECOMMENDATIONS
No changes or additions to existing temporary MRLs are
recommended.
FURTHER WORK OR INFORMATION
Desirable
1. Data on use patterns especially in tropical countries.
REFERENCES
Australia Report from the Codex Contact Point, Australia on
(1978) parathion-methyl.
Conkin, R.A. Methyl parathion residue study. Contribution to the
(1978) FAO/WHO Joint Meeting on Pesticide Residue, Rome,
1978, by Monsanto Agricultural Products Co.,
U.S.A.
Magallona, E.D. Report from the Codex Contact Point, Philippines,
(1978) on parathion-methyl.
New Zealand Report from the Codex Contact Point, New Zealand, on
(1978) parathion-methyl.
See Also:
Toxicological Abbreviations
Parathion-methyl (FAO/PL:1968/M/9/1)
Parathion-methyl (WHO Pesticide Residues Series 2)
Parathion-methyl (WHO Pesticide Residues Series 5)
Parathion-methyl (Pesticide residues in food: 1979 evaluations)
Parathion-methyl (Pesticide residues in food: 1980 evaluations)
Parathion-methyl (Pesticide residues in food: 1984 evaluations)
Parathion-methyl (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)