RESIDUE AND ANALYTICAL ASPECTS
Information was provided to the 1995 and 1996 Meetings on the use of bifenthrin as a stored grain protectant. The 1996 Meeting recommended MRLs for wheat and milled commodities related to this use. It was suggested at the CCPR that the CXLs for animal products might be affected by revised GAP for cereals.
The 1996 JMPR listed the following information as desirable in connection with the use of bifenthrin as a grain protectant.
Validation of the analytical method for recoveries of bifenthrin residues from bread at the levels occurring in practice and at the LOD.Information on the degree of extraction of bifenthrin residues from bread by the current procedure.
Information on national registrations and MRLs for bifenthrin covering its use on stored grain.
Information on the fate of bifenthrin during the commercial mailing of barley treated with it post-harvest. The studies should simulate the commercial process. (From 1995 JMPR).
No additional information was available on the analytical method for bifenthrin residues in bread.
Croatia and Romania have issued temporary registrations for the treatment of stored grain with bifenthrin.
The results of a barley making trial were made available. It suggested that bifenthrin residues decreased substantially during the mailing process but the study was defective because no barley samples were taken for analysis at the time the malting commenced.
The Meeting received additional data from trials with bifenthrin on stored grain. Bifenthrin residues are generally persistent during storage.
The recommendations of the 1992 JMPR for MRLs for bifenthrin in cattle fat, kidney, liver, meat and milk were based on the assumption that levels of bifenthrin in the diet of cows were unlikely to exceed 2 ppm, on the basis of a feeding study in which bifenthrin was fed at 5 ppm for 28 days. The 1995 Meeting recommended MRLs of 0.5 mg/kg in wheat and 2 mg/kg in wheat bran because of the post-harvest use on wheat. Because these levels do not exceed the level of 2 ppm in the feed on which the 1992 recommendations were based no change to the draft MRLs for cattle commodities is needed.
In a study of metabolism in laying hens (1992 JMPR) bifenthrin constituted 51.5% of the total residue in abdominal fat of 1.0 mg/kg produced by a feeding level of 40 ppm. In a feeding study on laying hens also reported in 1992 birds were fed for 28 days at 0.25 ppm.
Total residues at the limit of detection of 0.01 mg/kg were detected only in fat, suggesting that the residue of bifenthrin in fat was 0.005 mg/kg. Bifenthrin residues in the eggs were 0.002-0.004 mg/kg.
The current CXLs for bifenthrin in chicken fat and the fat of chicken meat are 0.05* mg/kg, which should be adequate for a feed level of 2.5 ppm bifenthrin if the proportionality between levels in the feed and fat is the same as in the trial. The current CXL for bifenthrin in eggs is 0.01* mg/kg, which should be adequate for a feed level of 0.6-1.2 ppm bifenthrin.
The draft MRL for bifenthrin in wheat (to cover post-harvest use) is 0.5 mg/kg, and the STMR is 0.255 mg/kg. The current CXLs for chicken eggs, fat, meat and edible offal should be adequate for chickens consuming bifenthrin-treated wheat, which can be a major part of a poultry diet.
The 1996 Meeting estimated maximum residue and STMR levels for bifenthrin in bran produced from post-harvest-treated wheat of 2 and 0.89 mg/kg respectively. Bran may constitute 50% of the poultry diet; at this level the CXLs for chicken fat, meat and offal should be adequate. The CXL for eggs is probably adequate. It is at the LOD and its adequacy depends on assumptions about the proportion of bran in the poultry diet.
The Meeting made no recommendations to change the existing CXLs or draft MRLs for bifenthrin.
The Meeting noted that the data submitted had not provided the information which the 1995 and 1996 Joint Meetings needed to recommend MRLs for stored grains, except wheat, and their products.
Future submissions of data should meet the requirements of the FAO Manual on the Submission and Evaluation of Pesticide Residues Data for the Estimation of Maximum Residue Levels in Food and Feed. The studies should be valid and supply the information listed in the 1995 and 1996 Evaluations.
FURTHER WORK OR INFORMATION
Desirable
1. Validation of the analytical method for recoveries of bifenthrin residues from bread at the levels occurring in practice and at the LOD.2. Information on the degree of extraction of bifenthrin residues from bread by the current procedure.
3. Information on national registrations and MRLs for bifenthrin covering its use on stored grain.
4. Valid studies on the fate of bifenthrin during the malting of barley treated with it post-harvest. The studies should simulate the commercial process.
