PESTICIDE RESIDUES IN FOOD - 1979
Sponsored jointly by FAO and WHO
Joint meeting of the
FAO Panel of Experts on Pesticide Residues
in Food and the Environment
WHO Expert Group on Pesticide Residues
Geneva, 3-12 December 1979
Carbophenothion was evaluated in 1972. The temporary ADI allocated on
that occasion was withdrawn in 1976 because required information on
toxicological studies to substantiate marked species differences in
sensitivity to plasma cholinesterase inhibition and an adequate
reproduction study had not been provided. In 1977, when some
additional information had become available, the Meeting confirmed the
previously listed need for further information and re-allocated the
temporary ADI at a lower level.
The 1977 Meeting recorded a desirability for the results from further
studies on residues in crops. The 11th Session of the CCPR, when
considering the temporary MRLs for apples and pears suggested by the
Meeting, asked for the figures to be reevaluated in the light of new
These aspects are covered in this monograph addendum.
The Meeting re-evaluated a previously reported study in man in which
it was incorrectly stated that five people were administered
carbophenothion at a dose of 0.8 mg/kg body weight/day for 30 days.
This study, reviewed in 1972, gave rise to the questions relating to
species sensitivity. Upon reevaluation, this problem was resolved.
In the study no significant alteration in plasma or RBC cholinesterase
activity was reported at the dose level of 0.8 mg/man/day.
In light of the re-evaluation and in consideration of the previous
evaluation, the Meeting allocated an acceptable daily intake, as
Level Causing No Toxicological Effect
Rat: 3 ppm in the diet, equivalent to 0.15 mg/kg body weight
Dog: 0.02 mg/kg body weight
Man: 0.8 mg/man/day, corresponding to 0.01 mg/kg body weight
Estimate of Acceptable Daily Intake for Man
0-0.0005 mg/kg body weight
RESIDUES IN FOOD AND THEIR EVALUATION
Preharvest on apples and pears
Country Rate Pre-harvest
USA Up to 1.25 lb 30 30
RESIDUES RESULTING FROM SUPERVISED TRIALS
Considerable residue data for carbophenothion on apples and pears,
representing several states, were received from the United States
(Stauffer). Determination was by cholinesterase inhibition. Because
of the late arrival at the Meeting, much of these data were not in a
format for inclusion in the monograph in tabular form. However, data
which could not be readily tabulated in tabular form were presented in
a residue decline curve form after adjusting to the U.S. dosage of 20
oz/A. A half-life of 30 days on apples was indicated by the
analytical method used.
For those data which could not be readily tabulated the estimated
maximum residues from the decline curves at 30 days is summarized
Data which could be readily tabulated are summarized in Table 1. The
above estimates together with the high value of 0.85 in Table 1 at 29
days demonstrate that the proposed 0.5 mg/kg temporary MRL is too low.
FATE OF RESIDUES
A study on the metabolism of phenyl-14C carbophenothion in orange
trees was received (McBain, et al, 1971) but did not arrive in time
for evaluation at this Meeting. This information will be evaluated at
the next scheduled evaluation of this compound.
TABLE 1. Residues of Carbophenothion on Apples and Pears (U.S.A. 1956/57)
CROP Application Residues in mg/kg, at intervals (days) after applicationsa
Locality rate formulationd 0 1-3 5-7 12-13 14-15 21-25 27-31
Cal. 20 4-F 1.3 0.64 0.71 0.61 0.56
20 25-W 0.89 0.59 0.54 0.51 0.45
N.Y. 24 2.2 0.70 0.50 0.40
Wash. 32 4-F 2.9, 2.3 1.8 0.74
16 2-D 0.17 0.2, 0.13 0.09
Wash. 32 4-F 3.1, 1.8 1.2
Cal. 20 4-F 1.7 1.76 0.15
7.3 1.6 0.67b
2.4 2.3 1.5 0.85c
24 4-F 1.9 1.3 .64 0.50
1.1 .89 .37 0.28
8 4-F 1.6
4 4-EV 1.0
a Uncorrected for controls
b 27 days (control 0.65 ppm apparent carbophenothion)
c 29 days (control 0.02 ppm)
d 4-F is an emulsion; 4-EV is an emulsifiable concentrate; 25-W is a wettable
EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION
No new data were available.
NATIONAL MRLs REPORTED TO THE MEETING
Additional residue data from the use of carbophenothion on apples and
pears were received from the U.S.A. as promised at the 11th Session of
the CCPR. Also received was a metabolism study for orange trees
submitted in response to a request from the 1977 Meeting for further
elucidation of the structure of terminal residues on crops. The
metabolism study arrived too late to permit evaluation at this Meeting
and is reserved for the next scheduled review of this compound.
The additional data for carbophenothion on apples and pears were
determined by cholinesterase inhibition and indicate that the current
0.5 ppm temporary MRL is too low. Even the meagre data on which basis
the current 0.5 ppm limit was made suggests that residues could be 0.7
ppm at 30 days after application according to good agricultural
practice (1972 Evaluations).
The additional data indicate that residues could exceed even 1 ppm
when determined by cholinesterase inhibition. However, the high
values and variability of controls on apples from the use of the
cholinesterase method almost certainly result in apparent residues
greater than actual, as could be elucidated by residue data from
current analytical methods.
It is recommended that the previous recommendation on apples and pears
be revised to the following:
Commodity MRL (mg/kg)*
Apples, pears 1
FURTHER WORK OR INFORMATION
1. Studies on identity and relative toxicity of metabolites.
*Residues refer to the sum of carbophenothion, its sulphoxide and
sulphone, together with their corresponding oxygen analogues.
2. Additional residue data for carbophenothion on apples and pears
resulting from good agricultural practice in the USA and other
countries and determined by current analytical methods.
3. Additional information listed as desirable by the 1977 meeting.
McBain, J.B., Wren J.P. and Menn, J.J. Metabolism of (Phenyl-14C)
Carbophenothion by Orange Trees. (1977) Unpublished data submitted by
Stauffer - Chemical S.A., 25 rue des Carboubiers, 1227 Carouge,
Stauffer. Section D, residue data on apples and pears from US
Petition No.120 and as submitted with Dec. 23, 1957 labels to US
regulatory agencies. Made available by Stauffer Chemical Company,
1200 S. 47th St. Richmond, CA, 94804.