466. Carbophenothion (Pesticide residues in food: 1979 evaluations)

PESTICIDE RESIDUES IN FOOD - 1979

Sponsored jointly by FAO and WHO

EVALUATIONS 1979

Joint meeting of the
FAO Panel of Experts on Pesticide Residues
in Food and the Environment
and the
WHO Expert Group on Pesticide Residues
Geneva, 3-12 December 1979

CARBOPHENOTHION

Explanation

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that occasion was withdrawn in 1976 because required information on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
information.

These aspects are covered in this monograph addendum.

Toxicological Comments

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
follows.

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

Use Pattern

Preharvest on apples and pears

Country Rate Pre-harvest
Interval (days)

USA Up to 1.25 lb 30 30
a.i./A

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
below:

Estimated

Formulation Estimated
Maximum
Residue (mg/kg)

4-F 1.1
4-EV 1.6
25W 1.6

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

In Plants

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 applications^a
Locality rate formulation^d 0 1-3 5-7 12-13 14-15 21-25 27-31
oz. ai/A

APPLES

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

PEARS

Wash. 32 4-F 3.1, 1.8 1.2
Cal. 20 4-F 1.7 1.76 0.15
7.3 1.6 0.67^b
2.4 2.3 1.5 0.85^c
24 4-F 1.9 1.3 .64 0.50
1.1 .89 .37 0.28
Oz./100 gal
8 4-F 1.6
1.8
0.95
4 1.2
4 4-EV 1.0
8 1.8
2.4
2.5

^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

None reported.

APPRAISAL

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.

RECOMMENDATIONS

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

Desirable:

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.

REFERENCES

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,
Geneva, Switzerland.

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.

    See Also:
       Toxicological Abbreviations
       Carbophenothion (ICSC)
       Carbophenothion (WHO Pesticide Residues Series 2)
       Carbophenothion (Pesticide residues in food: 1976 evaluations)
       Carbophenothion (Pesticide residues in food: 1977 evaluations)
       Carbophenothion (Pesticide residues in food: 1980 evaluations)
       Carbophenothion (Pesticide residues in food: 1983 evaluations)