PESTICIDE RESIDUES IN FOOD - 1984
Sponsored jointly by FAO and WHO
EVALUATIONS 1984
The monographs
Data and recommendations of the joint meeting
of the FAO Panel of Experts on Pesticide Residues
in Food and the Environment and the
WHO Expert Group on Pesticide Residues
Rome, 24 September - 3 October 1984
Food and Agriculture Organization of the United Nations
Rome 1985
PHORATE
Explanation
Phorate was evaluated by the Joint Meeting in 1977, 1982 and
1983. 1/ Guideline levels were recorded in 1977. When a temporary ADI
was established in 1982 these were converted to temporary MRLs.
At the 16th Session of the CCPR, questions were raised on the
limits for hops, lettuce, milk, peanuts and potatoes. Clarification of
the commodity description "maize (green)" was also requested.
The CCPR at its 14th Session asked the JMPR to consider amending
the definition of the residue, currently "sum of phorate, its oxygen
analogue, and their sulphoxides and sulphones, expressed as phorate",
to exclude the oxygen analogue.
The meeting received new information on uses of phorate, and
results from supervised trials in South Africa on maize, potatoes and
wheat.
The new data are reviewed in this addendum, and the question of
the CCPR are considered in the "Appraisal".
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
Information has been provided from Canada and South Africa on
approved uses of phorate (Table 1).
RESIDUES RESULTING FROM SUPERVISED TRIALS
Trials were carried on in South Africa on maize, potato and wheat
plants (Table 2). Residues corresponding to good agricultural practice
in South Africa are underlined. Residues were determined as the sum of
phorate and its oxidised metabolites, expressed as phorate. The limit
of determination for residues in maize and wheat was 0.05 mg/kg and in
potatoes 0.1 mg/kg.
Maize. Residues were determined in the whole plant and in the cob
(in the dough state). Residues were observed up to 32 days after
treatment but none were detected in the plant or cob after the
approved withholding period of 60 days.
Potato. Residues were observed 79 days after treatment, but not
after the required withholding period (90 days).
1/ See Annex 2 for FAO and WHO documentation.
Table 1. Approved uses of phorate
Country Commodity Approved application Application Limitations
rate. a.i.
Canada Beans 1.1-2.25 kg/ha Soil treatment in At planting time
(gran. 10-15%) rows to the side only. No feeding to
of the seeds animals within 60
days after treatment
Rutabaga 4.5 kg - 9.0 kg/ha Soil treatment, band
(gran. 10-15%) 5 cm below soil surface At planting time only
or band spreading
Potato 2.25 kg - 3.25 kg/ha Soil treatment in - " -
(gran. 10-15%) furrows or bands on
each side of the row
Maize 0.55-1.1 kg/ha Soil treatment in
(field and (gran. 10-15%) band placed 1-2.5 cm - " -
sweet) over seeds
100 g/1000 m row Band spraying - " -
Lettuce 1.1 kg/ha Soil treatment in
(gran. 10-15%) band in sides of - " -
the row
South Maize 5 g/100 m, plant row Soil treatment in At planting time only.
Africa (gran. 10%) planting furrow Withholding period
60 days.
Potato 2-3 kg/ha - " - At planting time only
(gran. 10%) Withholding period
90 days
Table 1. (continued)
Country Commodity Approved application Application Limitations
rate. a.i.
Cabbage 11-21 g/100 m - " - At planting time only
plant row Withholding period
(gran. 10%) 56 days
Wheat 3.5 g/100 ml - " - ) At planting time only
plant furrow ) Withholding period
(gran. 10% ) 90 days
)
1.5 kg/ha Soil treatment ) No feeding to
(gran. 10% Overall treatment ) animals
Table 2. Residues of phorate from supervised trials in South Africa
Crop Application Residue,mg/kg,at interval(days/after treatment (mean of duplicate determinations)
(Location) method and
rate (a.i.) 0 10 20 30 40 50 60 70 80 90 100 110
Maize In planting furrow
Leslie at planting 0.35 0.95 <0.02 <0.02 <0.02 <0.02
Gran. 5 g/100m (cob)
(Bethal) 10 g/100m 2.8 0.95 0.11 0.04 <0.02 <0.02
(cob)
5 g/100m <0.02 <0.02 <0.02
(cob)
10 g/100m 0.06 <0.02 <0.02
(cob)
(Viljoenskroon) 5 g/100m 0.35 <0.02 <0.02
(cob)
10 g/100m 0.75 0.03 <0.02
(cob)
Potato In planting furrow
2 kg/ha <0.1
3 kg/ha 0.15 <0.1
Wheat In planting furrow <0.05 0.9 0.09 <0.05
(plants) 1.66 g/100m
3.33 g/100m 3.3 0.5 <0.05 <0.05
6.66 g/100m 4.4 7.0 1.6 0.07
Wheat (plants). Residues were detected up to 42 days after
treatment at the recommended dosage and up to 91 days at double
dosage. No residue was observed at the approved dosage and 90-day
withholding period.
DEFINITION OF THE RESIDUE
Almost all the data on which the residue evaluations were based
were obtained after oxidation of all the components of the residue to
the sulphone of the oxygen analogue. In the few cases where the
compounds included in the definition were determined individually, all
except the oxygen analogue have been detected. The transient existence
of the oxygen analogue can be assumed.
The analytical methods used to generate the residue data preclude
an estimate of the proportions of the individual components
contributing to the residue. Although it appears that the oxygen
analogue could be excluded, its exclusion would not simplify the
analytical procedure and could complicate the problems of enforcement
in cases where the total residue found exceeds the MRL. It is
concluded that the definition of the residue should not be changed.
APPRAISAL
New information on use patterns and on residues in maize,
potatoes and wheat plants resulting from supervised trials was
evaluated. No changes in previously estimated maximum residue levels
in these crops were required.
The 16th CCPR had asked the Joint Meeting to clarify the term
"maize (green)". Since the original residues data referred to the
whole maize plant, the commodity description should be changed to
"maize fodder".
It had been suggested at the 16th CCPR that neither the data made
available to the 1977 JMPR on dried hops nor the analytical method
used, supported a limit of 0.1 mg/kg. The meeting realized that, owing
to the difficulties in the analysis of this crop, the limit of
determination in the trials was about 0.2 mg/kg. An increase in the
temporary MRL for dried hops to 0.2 mg/kg is therefore recommended.
The meeting also reconsidered the data on peanuts and lettuce. As
none of the data referred exactly to good agricultural practice in the
countries in which the trails were performed, or adequate information
on GAP in those countries was not available, the meeting was of the
opinion that the proposed limits were the best estimates.
It had been suggested that the limit for milk should be lowered
from 0.05 to 0.02 mg/kg. As the limit of determination on which the
trials were based was about 0.05 mg/kg, this is not possible.
A delegation to the 16th CCPR was of the opinion that the limit
for potatoes should be raised from 0.05 to 0.5 mg/kg, and that data
submitted from the U.S.A. had not been taken into consideration by the
1977 JMPR. The meeting reconsidered the original data and realized
that the U.S.A. data had been taken into consideration, but only a few
residues had been higher than 0.05 mg/kg. Furthermore, those data were
old and residues had been determined by the cholinesterase-inhibition
method, while all new data based on analysis by GLC, including the
data supplied to this meeting from South Africa, showed residues well
below 0.05 mg/kg. For these reasons the meeting maintained its
original estimate.
The possibility of simplifying the residue definition was
considered. The analytical methods normally used involve converting
the residue to the sulphone of the oxygen analogue and preclude an
estimate of the proportions of the individual components contributing
to the residue. When, exceptionally, the residue components have been
separately determined, all except the oxygen analogue have been found.
Although it appears that the oxygen analogue could be excluded, its
exclusion would not simplify the analytical procedure and could
complicate the problems of enforcement in cases where the total
residue found exceeds the MRL. It is concluded that the definition of
the residue should not be changed.
RECOMMENDATIONS
The following maximum residue levels were estimated and
recommended as suitable for use as temporary MRLs.
Commodity TMRL, mg/kg
maize fodder 0.05 (no change in TMRL)
(description changed from
"maize (green)"
hops, dried 0.2 (increased from 0.1)
It is recommended that the definition of the residue should not
be changed.
See Also:
Toxicological Abbreviations
Phorate (ICSC)
Phorate (Pesticide residues in food: 1977 evaluations)
Phorate (Pesticide residues in food: 1982 evaluations)
Phorate (Pesticide residues in food: 1985 evaluations Part II Toxicology)
Phorate (Pesticide residues in food: 1994 evaluations Part II Toxicology)
Phorate (Pesticide residues in food: 1996 evaluations Part II Toxicological)