360. Carbophenothion (Pesticide residues in food: 1976 evaluations)

CARBPHENOTHION JMPR 1976

Explanation

Carbophenothion was evaluated at the 1972 JMPR (FAO/WHO 1973).
Temporary tolerances were recommended for various fruits, nuts,
vegetables, meat (fat), milk (fat), and olive oil. The tolerances
are expressed as carbophenothion but apply to total residues
including parent, its sulfoxide and sulfone and their corresponding
oxygen analogs. Further work on plasma cholinesterase depression
and a reproduction study were required for evaluation by the 1976
Joint Meeting. At the 1975 (Eighth) Session of the Codex Committee
on Pesticide Residues, the delegation of the Netherlands requested
re-evaluation of carbophenothion by the 1976 Joint Meeting.

EVALUATION FOR ACCEPTABLE DAILY INTAKE

Since the additional data required by the 1972 Joint Meeting
were not available and there was no indication of intent to provide
these data, the previously allocated temporary ADI was withdrawn.

RESIDUES IN FOOD AND THEIR EVALUATION

Country statements for the 1976 Joint Meeting were received
from Australia, the Netherlands, and the United Kingdom. The
information provided on current national uses of carbophenothion
did not indicate a need for additional maximum residue limits for
crops beyond those recommended by the 1972 Meeting. No additional
data from supervised residue trials were available. The country
statements included some information of interest on current use
patterns, national tolerances and residue chemistry.

USE PATTERN

Information provided by the responding countries on current
use patterns are shown in Table 1.

FATE OF RESIDUES

A submission from the United Kingdom reported research
relating to injury to geese from the use of carbophenothion as a
seed dressing on cereals. This use was subsequently withdrawn from
certain areas in the U.K. The report included some collateral
studies which were of interest with regard to possible residues in
human foods. Carbophenothion and four esterase inhibiting
degradation products were found at significant levels within the
roots and bulbs of wheat grown from treated seeds, suggesting that
carbophenothion has some systemic activity. Residues in the leaves
were, however, very low. The identified inhibitors were
carbophenothion sulphone, carbophenothion sulphoxide and the
corresponding oxygen analogue and oxygen analogue sulphone. (Brown
and Torpey, 1976).

TABLE 1. National use patterns of carbophenothion

Pre-harvest
Application interval National⁽¹⁾
Country Crop Rate (days) tolerances (mg/kg)

Australia fruits 0.05% emul. spray 21 1
vegetables 2 kg/ha 21 1

cattle, sheep 0.1% emul. spray 14(pre- 1 (fat basis)
slaughter)

pasture, forage 0.05% emul. spray 7(cutting or 0.1 milk and⁽²⁾
grazing) milk products
(fat)

Netherlands prunes, peaches 14.75% before bloom 0.01⁽²⁾
grapes aerosol and after
(under glass) 0.06 g/m³ harvest

⁽¹⁾ Maximum residue limits or tolerances as reported to the 1976 meeting.

⁽²⁾ Tolerance represents a change from national tolerances listed in 1972
monograph (FAO/WHO, 1973b).

A laboratory experiment in the same report disclosed photolysis
products after exposure to sunlight and UV radiation. In addition to
the alteration products found in wheat seedlings, carbophenothion oxon
and the insecticide ethion were identified after 130 hours' exposure
to sunlight. (Machin et al., 1976). UV radiation at 254 nm produced
four other related organophosphorus products. The experiments did not
show whether, under field conditions, any of these compounds would
constitute a significant part of the terminal residue on crops.

METHODS OF RESIDUE ANALYSIS

A comprehensive discussion of the methods available for
carbophenothion and its oxidative metabolite residues in foods appears
in the 1972 evaluation of this pesticide (FAO/WHO 1973b).

Certain advances in carbophenothion methodology were called to
the attention of the 1976 meeting. Jennings et al. (1975) describe
an improved method for carbophenothion in avian tissues in which
extraction with diethyl ether is followed by an alumina column
clean-up. Alternative determinative steps specified in this method are
TLC, GC with flame photometric detection and GC/MS. Brown and
Weerasinghe (1976) further improved extraction of the oxidation
products by substituting methanol for diethyl ether and modifying the
chromatographic clean-up. The U.S. Food and Drug Administration
multi-residue method for organophosphorus insecticides (FDA Pesticide
Analytical Manual, Vol. I) will detect carbophenothion, the oxygen
analogue, and the carbophenothion sulphone metabolites.

APPRAISAL

Three countries responded to requests for information for the
re-evaluation of carbophenothion by the 1976 Joint Meeting. There was
no indication that the scope of carbophenothion uses has increased
since the 1972 evaluation. No additional data from supervised residue
trials were available. There was no new information on residue
chemistry which would justify any changes in the previously
recommended maximum residue limits. Some new information on the nature
of carbophenothion residues and on analytical methods was evaluated.

EVALUATION

Because the further information required by the 1972 Joint
Meeting has not been supplied, the temporary ADI and temporary maximum
residue limits then recommended are withdrawn. In the absence of an
ADI, the temporary limits are converted to guideline levels.

FURTHER WORK OR INFORMATION

REQUIRED (before an acceptable daily intake can be allocated and
maximum residue limits can be recommended)

1. Studies to substantiate the marked species difference in
sensitivity to plasma cholinesterase depression.

2. An adequate reproduction study.

DESIRABLE

1. Further elucidation of the nature of the terminal residues on
crops, particularly as to possible presence under field
conditions of photolysis products reported by Machin and
coworkers.

REFERENCES

FAO/WHO. 1972 Evaluations of some pesticide residues in 1973
foods. FAO/AGP/1972/M/9/1.

Brown, P.M. & Torpey, C.L. Determination of carbopheniothion
1976 residues in wheat plants grown from
carbophenothion-treated seeds. Pest Infestation
Control Laboratory, Ministry of Agriculture,
Fisheries and Food, unpublished.

Brown, P.M. & Weerasinghe, D.K. Evaluation, development and
1976 application of methods for extraction and analysis
of carbophenothion and its metabolites from avian
tissues. Unpublished report, Pest Infestation
Control Laboratory, U.K., Ministry of Agriculture,
Fisheries and Food.

Jennings, D.M., Bunyan, P.J., Brown, P.M., Stanley, P.I., & Jones,
1975 F.J.S. Organophosphorus poisoning; a comparative
study of the toxicity of carbophenothion to the
Canada Goose, the Pigeon and the Japanese Quail.
Pestic. Sci., 6:245-257.

Machin, A.F., Quick, M.P., & Norman, I.M. Unpublished.
1976

Stanley, P.I., Brown, P.M., Martin, A.D., Steed, L.C., Westlake,
1976 G.E., Howells, L.C. & Machin, A.F. The avian
toxicology of carbophenothion. Pest Infestation
Control Laboratory and the Central Veterinary
Laboratory, Ministry of Agriculture, Fisheries and
Food, unpublished.

    See Also:
       Toxicological Abbreviations
       Carbophenothion (ICSC)
       Carbophenothion (WHO Pesticide Residues Series 2)
       Carbophenothion (Pesticide residues in food: 1977 evaluations)
       Carbophenothion (Pesticide residues in food: 1979 evaluations)
       Carbophenothion (Pesticide residues in food: 1980 evaluations)
       Carbophenothion (Pesticide residues in food: 1983 evaluations)