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Adverse Effects
Abstracts

ACTIVITY: Fungicide (azole)

CAS Name: 1-[[bis(4-fluorophenyl)methylsilyl]methyl]-1H-1,2,4-triazole

Structure:

1993 FAO/WHO JOINT MEETING ON PESTICIDE RESIDUES Geneva, 20-29 September 1993

PESTICIDE RESIDUES IN FOOD
REPORT OF THE 1993 JOINT FAO/WHO MEETING OF EXPERTS

4.24 FLUSILAZOLE (165)

RESIDUE AND ANALYTICAL ASPECTS

Flusilazole was previously reviewed for residues by the 1989, 1990 and 1991 Meetings. The present Meeting reviewed information provided in response to the 1991 JMPR requirement for additional GAP and residue data to confirm the 0.1 mg/kg temporary estimate for peaches and nectarines, and information listed as desirable on grapes, details of wheat grain freezer storage studies, stability of metabolites in freezer-stored grain samples, hen metabolism, metabolites in grain processed fractions and soil studies. Additional residue data on pome fruit, grapes and cereals (although there were no outstanding residue data requirements on these commodities) and new data on sugar cane were also provided.

Fate of residues in animals. Several reports on hen metabolism were provided. Some had been submitted before and some, including the requested study by Smyser, were new. Only the Smyser report included data in need of review by the Meeting.

The report basically combines and summarizes information in two previously reviewed reports and provides further clarification of the residues of metabolites, especially in terms of the percentage of the total radioactivity in poultry tissues and eggs, for both the phenyl and triazole labels. It confirms previous JMPR conclusions that bis(4-fluorophenyl)(methyl)silanol (IN-F7321, the methyl silanol) and 4-fluorophenyl(methyl)silanediol are the predominant residues in poultry tissues and eggs arising from the phenyl-labelled compound and that triazole is the main residue from the triazole label, except in fat where flusilazole is the primary residue from the triazole label.

The report does not effectively answer questions raised by the 1989 and 1991 Meetings concerning differences in residues found between ruminant and poultry metabolism and feeding studies. The Meeting noted and agreed with the 1991 JMPR conclusion that these differences probably result largely from the more detailed residue characterization and identification in the poultry studies than in the ruminant studies. The Meeting also agreed with the 1991 JMPR that although all questions have not been completely answered, the nature of the residue in animal products can be considered to be reasonably well understood in view of the low residues expected (especially for flusilazole) in animal products.

Soil dissipation. The Meeting reviewed the final report of a 3-year soil dissipation study (4 applications per year) for which an interim report was reviewed by the 1989 JMPR. It confirms the 1989 observations that over 92% of the radioactivity is confined to the top 8 cm of soil over the test period, and that the predominant residues in this segment are flusilazole and its silanol metabolite IN-F7321. The author cites statistical evaluation of the data to support the view that residues will reach a steady level at 57% of yearly application levels after repeated application levels under worst-case conditions.

The report cites the steady-state conclusion, the strong adsorption to the top layers of soil, the lack of residues exceeding 0.01 mg/kg in the 24-36 cm soil depths and the weak leaching potential indicated in other studies as evidence that residues in ground water were unlikely. While the data indicate that over 92% of the radioactivity remains in the top 8 cm of the silt loam soil investigated, and indeed that residue levels are extremely low in the 24-36 cm depths, it also shows an increasing penetration by low levels of radioactivity over the test period in this soil type. The identity of these residues in the deeper soil segments was not indicated.

While the adsorption of this persistent pesticide to soil is strong, the 1989 JMPR had noted that uptake of low residue levels can occur in rotational crops and that the leaching potential would be less for silt loams (as in this study) than for more sandy soils. Because the silt loam study was under worst-case conditions (bare ground, repeated applications) and was consistent with reassuring findings of a number of other relevant studies, the Meeting accepted that ground water residues from silt loam soils were unlikely.

Freezer storage stability. Instead of details of a previous 36.5-month study for the parent compound only, the Meeting was provided with a new 11-month freezer storage study of flusilazole and its metabolites in wheat grain and straw. While the results suggest that about 30% of 0.3 mg/kg residues of the parent compound and its phenyl metabolites in grain and straw are lost after various storage intervals up to 11 months, the variability in the recoveries of freshly fortified samples indicates that the apparent losses are probably as much the result of analytical variability as actual storage losses. The Meeting concluded that the data demonstrated adequate stability of flusilazole and the metabolites IN-7321, 1,1,3,3-tetrakis(4-fluorophenyl)-1,3-dimethyldisiloxane (IN-G7072), 2-fluoro-5-[(4-fluorophenyl)(methyl)(1-H-1,2,4-triazol-1-ylmethyl)silyl]phenol (IN-37722) and 2-fluoro-5-[(4-fluorophenyl)(hydroxy)(methyl)silyl]phenol (IN-37738) (presumably unconjugated) over 11 months under the conditions of the study.

The 11-month storage interval compares with sampling-to-laboratory-receipt intervals ranging from 2 to 15 months in cereal grain trials from which data were reviewed by the 1989 JMPR. The Meeting did not know the actual sampling-to-analysis intervals for the data reviewed in 1989, although according to the 1989 monograph all samples were generally stored at -20¡C.

Cereals. The original 1989 JMPR estimates of maximum residue levels of 0.1 and 2 mg/kg respectively for cereal grains and straws or fodders (dry) were based on maximum residues of 0.07 mg/kg in grain and 1.7 mg/kg in straw. Although there were no outstanding requirements for additional supervised trials data, the Meeting received extensive additional cereal grain, plant, forage and straw data from Europe and North America. Because no need for MRL revisions was indicated, the Meeting only briefly summarized the submitted data on grain and straw. It concluded that there was no need to revise the recently adopted limits of 0.1 mg/kg in the grains and 2 mg/kg in the straws and fodders (dry) of barley, rye and wheat at present. This conclusion may need to be reconsidered at a future Meeting in the light of future GAP information.

Cereal grain processing. The 1991 JMPR reviewed a wheat processing study submitted in response to a 1989 requirement. While no concentration in milled fractions was observed, samples were not analysed for metabolites (especially IN-F7321) and such analysis had been recorded as desirable. A barley grain processing study provided to the Meeting confirmed that no concentration of flusilazole or the major metabolite IN-F7321 occurred in milling fractions.

Grapes. Limited additional information on GAP in Europe and Australia and additional grape data submitted in response to the 1991 requests showed maximum residues reflecting GAP of 0.22 mg/kg compared to the recently adopted CXL of 0.5 mg/kg. A delegation to the CCPR had suggested that a 0.2 mg/kg limit was sufficient. The Meeting confirmed the 1989 JMPR conclusion that residues were unlikely to exceed 0.3 mg/kg.

Pome fruit. Additional GAP information and residue data did not require a revision of the current 0.2 mg/kg limit.

Stone fruit. The 0.1 mg/kg limit for peaches and nectarines recommended by the 1991 JMPR was temporary pending the submission of additional GAP and residue data. It had been based on data from New Zealand and France and GAP from New Zealand and Spain. The Meeting received information on current GAP from Spain, France, Greece (pending) and Italy, and residue data on nectarines from France and on peaches from Australia, Italy, Greece, and the United States. French apricot data were also provided as supporting information. No GAP information was available for Australia or the United States. One to 4 applications at 3-4 g ai/hl and a PHI of 7 to 10 days appears to be usual for countries with established GAP, although in two cases the maximum number of permitted applications was not indicated.

At a 7-day PHI, the new French data or those summarized by the 1991 JMPR which reflect GAP rates showed maximum residues of flusilazole per se in peaches of 0.09 mg/kg (1991) or 0.08 mg/kg (1993), except in one trial in the 1993 submission where a residue of 0.55 mg/kg after 8 days was reported from 9 applications at GAP rates. Maximum apricot residues reflecting GAP rates were 0.08 mg/kg after 7 days. Maximum residues in the US trials were 0.09 mg/kg at a 2.4 g ai/hl spray concentration after 7 or 14 days (0.2 mg/kg after 5 days) and 0.3 mg/kg at a 4.8 g ai/hl rate after 12 days. At a pending GAP rate, maximum residues after 7 days in the Greek trials were 0.09 mg/kg. Residues were not detected in the Australian or Italian trials (<0.05 mg/kg and <0.01 mg/kg respectively), but that is not unexpected in view of the long PHIs and the type of application. The Meeting concluded that a 0.5 mg/kg limit was supported for peaches. Observing that GAP for apricots and nectarines is similar to that for peaches, the Meeting concluded that the available data could also mutually support 0.5 mg/kg limits for apricots and nectarines at a 7-day PHI.

Limited data for plums and cherries were insufficient to recommend MRLs.

Sugar cane. No residues (<0.02 mg/kg) were detected in the juice from plants grown after dip treatments of sugar cane sets at fivefold application rates. No stalks were analysed. The Meeting concluded that the data were inadequate to support a limit for sugar cane.

FURTHER WORK OR INFORMATION

Desirable

1. Submission of analytical method AMR-115-85 cited in Du Pont, 1993, Vol. 1, exhibit 6. Submission of validation information to permit estimation of limits of determination is desirable.

2. On completion, submission of the soil dissipation report AMR-791-87 (Fujinari, 1988). The interim report was reviewed by the 1989 JMPR.