FENCHLORPHOS JMPR 1972
Explanation
This insecticide was previously evaluated in 1968 (FAO/WHO, 1969) at
which time an acceptable daily intake and temporary tolerances were
recommended. Five requirements for further work or information were
set forth. Since the previous evaluation, additional data and
information have become available.
At the Sixth Session of the Codex Committee on Pesticide Residues it
was requested that further consideration be given to this compound by
the FAO/WHO Joint Meeting on Pesticide Residues in the light of new
use patterns and new residue data.
RESIDUES IN FOOD AND THEIR EVALUATION
FULFILLMENT OF REQUIREMENTS
In the following paragraphs, the numbers refer to the corresponding
requirement laid down by the 1968 Joint Meeting.
1. Extension of use on fruit and vegetables
There is no anticipated extension of use on fruits or vegetables
beyond those few commodities currently registered (such as
bananas for importation into the United States of America and
Canada), and there would be no need for international tolerances
for this type of application.
2. Animal use pattern and resultant residues from countries other
than the United States of America and the United Kingdom
Data in the form of registered labels and tables of registered
uses did not indicate a use pattern in Canada or residues in
animals significantly different from that in the United States.
Supervised trials in Lebanon (Kowar, 1968) in which dairy cattle
were treated with one application each at levels of 0.38 and
0.75% fenchlorphos had initial milk residues of about 1.8 ppm one
day after treatment (high rate). By four days after application,
no residues were detectable in milk.
3. Residue levels in raw agricultural products moving in commerce
No Information was available.
4. Residue levels found in total diet studies in countries other
than the United States
Out of 462 subsamples analysed in the total diet survey in
England and Wales (Abbott, 1970) only one had positive residues
of fenchlorphos (at 0.09 ppm).
5. Evaluation of methods of analysis for regulatory purposes
Since the 1968 Joint Meeting, several new methods of analysis
have been developed. One in support of the registration of
fenchlorphos is based on an adaptation of the procedure of
Claborn (1965) and utilizes electron capture gas chromatography
(Dow, 1967).
The method has been validated down to 0.01 ppm for fenchlorphos
and to 0.1 ppm for the total metabolites in animal tissues.
A method for determining fenchlorphos and its oxygen analogue in
tissues of cattle has recently been published (Ivey, 1971), which
utilizes flame photometric gas chromatography and can detect
0.002 ppm fenchlorphos and 0.005 ppm of the oxygen analogue.
Recoveries were 75-95% for fenchlorphos and 80-100% for the
oxygen analogue. Since fenchlorphos is listed as one of the
compounds detectable by the multi-residue gas chromatographic
method of analysis of Abbott et al. (1970), that method is
recommended for regulatory use.
For confirmation, a gas chromatographic method with thermionic
detection appears suitable (Watts, 1969). The paper describes
retention times and response data on three different GLC columns.
EVALUATION OF NEW RESIDUE DATA
A large amount of data was available on residues in fat of cattle,
sheep, and pigs, in poultry, and eggs, and in milk from a wide variety
of applications. Table 1 summarizes those data and reflects the
maximum residues found among all of the applications tested.
The data in Table 1 indicate that for cattle and sheep (and by
extrapolation, goats) the possibility exists for residues in fat to
exceed 7 ppm, but it would never exceed 10 ppm at the recommended
withdrawal interval. The previously recommended tolerances for meat
(fat basis) of 7.5 ppm should therefore be increased to 10 ppm for
cattle, sheep and goats. However, the data further indicate that
residues in fat of pigs would rarely exceed 2 ppm and residues in
poultry would not exceed 0.01 ppm; therefore, the tolerances should be
lowered accordingly.
TABLE 1 Residues of fenchlorphos in fat of cattle, sheep and pigs
Animal Ronnel Days Maximum Recommended
(route of (mg/kg/day withdrawal residue in withdrawal
application) × days) before fat or milk prior to
slaughter (ppm) slaughter
(days)
Cattle (oral, 18 × 7 1 43 10
in capsule) 8 6.7
15 0.51
Cattle (oral 15 × 22 1 31 10
mineral feed) 7 8.5
27 <0.05
Cattle (oral 8.76 × 14 0 9.5 10
mineral feed) 10 0.40
21 0.026
28 0.001
35 <0.001
Cattle (spray, 1.0% 7 7.5 14
aqueous) 14 1.6
21 0.7
35 <0.05
Sheep (dip, 0.5% 7 51 28
1 time, aqueous) 14 30
21 14
28 9
Pigs (sprays 0.5% 8 0.66 0
aqueous) (100 mg/kg) 14 0.21
21 0.20
28 0.13
Poultry (litter, 0.5% 42 <0.005 (in mixed muscle)
water spray) 60 <0.005 (in mixed muscle)
Dairy cattle 17.6 × 7 1 0.029 in milk 10
(oral, 32P 2 0.041 "
labelled feed 3 0.064 "
additive) 7 0.092 "
8 0.072 "
9 0.064 "
10 0.043 "
TABLE 1 (Cont'd.)
Animal Ronnel Days Maximum Recommended
(route of (mg/kg/day withdrawal residue in withdrawal
application) × days) before fat or milk prior to
slaughter (ppm) slaughter
(days)
Dairy cattle 0.5% 0.3 0.120 in milk 7
(spray, aqueous) 1 application 1 0.210 "
3 0.144 "
5 0.052 "
10 0.006 "
17 0.001 "
21 <0.001 "
The data for milk residues indicate that a low probability exists for
values in excess of 0.04 ppm. However, it was considered desirable to
change the previous recommendation for the commodity whole milk to
milk and milk products (fat basis), in order to indicate where the
residue would be found (fat) and to accommodate milk products. Using
the accepted factor of 25 (representing 4% butterfat) the calculated
residue in milk (fat basis) would be 1.25 ppm. This figure should be
rounded off to 2 ppm to reflect the degree of sampling error expected
at such low levels and to conform to the current practice of
recommending values to only one significant figure in these
monographs.
APPRAISAL
The five items of further work or information required by the 1968
Joint Meeting are considered to have been met. There was no indication
of a need to include recommendations for tolerances on fruit and
vegetables. The use pattern appears to be about the same throughout
the world. Total diet studies in England and Wales have not shown a
significant incidence of residues of fenchlorphos in food. Existing
multi-residue methods of analysis are suitable for regulatory purposes
and are recommended.
Consideration of new data on residues likely to occur in meat, milk
and eggs from a wide variety of new application procedures on
livestock and poultry has shown that a higher tolerance is required
for fat of meat of cattle, goats and sheep, but that lower tolerances
would suffice for poultry and fat of meat of pigs.
The previously recommended tolerance on whole milk of 0.04 ppm was
changed to 2 ppm in milk and milk products (fat basis), which is
equivalent to 0.08 ppm in whole milk, on the basis of the new data
examined.
RECOMMENDATIONS
TOLERANCES
The temporary tolerances in effect until 1972 are replaced by the
following tolerances, which include the oxygen analogue.
ppm
Fat of meat of cattle, goats and
sheep 10
Fat of meat of pigs, milk and milk
products (fat basis) 2
Eggs (shell free) 0.05
Poultry 0.01*
* at or about the limit of determination
FURTHER WORK OR INFORMATION
None
REFERENCES
Abbott, D.C., Crisp, S., Tarrant, K.R. and Tatton, J.O'G. (1970)
Pesticide residues in the total diet in England and Wales, 1966-1967.
III. Organophosphorous pesticides residues in the total diet. Pestic.
Sci., 1: 10-13.
Claborn, H.V. and Ivey, M.C. (1965) Determination of O,O-dimethyl
O-2,4,5-trichlorophenyl phosphorothioate in animal tissues and milk.
J. Agr. Food Chem., 13: 353-354.
Dow Chemical U.S.A. (1968) Gas chromatographic determination of
Ronnel, O,O-dimethyl-O-(2,4,5-trichlorophenyl) phosphorothioate,
and Ronnel phenolic metabolites in animal tissues. AGR. 68.15, 1968.
(unpublished)
FAO/WHO. (1969) 1968 evaluations of some pesticide residues in food.
FAO/PL:1968/M/9/1; WHO/Food Add./69.35.
Ivey, C. and Claborn, H.V. (1971) Gas-liquid chromatographic
determination of ronnel (O,O-dimethyl-O-2,4,5-trichlorophenyl
phosphorothioate) and the oxygen analogue of Ronnel (dimethyl
2,4,5-trichlorophenyl phosphate) in tissues of cattle. J. Agr. Food
Chem., 19(6): 1256-1258.
Kowar, S., Bostonian, J. and Badawi, S. (1968) Insecticidal residues
in the milk of dairy cows treated for control of ectoparasites. J.
Dairy Sci., 51(7): 1023-1025.
Watts, R. and Storherr, R.W. (1969) Gas chromatography of
organophosphorus pesticides: Retention times and response data on
three columns. J. Ass. off. analyt. Chem., 52(3): 513-521.