1. The 1996 Meeting agreed that guidance was required on the estimation of maximum residue levels and STMRs for products of animal origin to aid in the preparation of future JMPR evaluations and to improve the transparency of the procedures. The Meeting agreed that this guidance should supersede the recommendation made in the report of the FAO Panel Workshop1, which met in the Hague in April 1996.
1 Anon 1996. Report of an informal workshop on data evaluation in the estimation of dietary intake of pesticide residues for the JMPR. The Hague, Netherlands, April 1996.
2. The present Meeting recognized that it is appropriate to use a different residue value for the estimation of acute intake from that used for the estimation of chronic intake. For chronic dietary exposure the York Consultation2 had developed the concept of using the median residues from supervised field trials (STMRs) to represent the most likely residue level if the pesticide is used according to maximum GAP conditions. However, the scope for the estimation of a median residue for products of animal origin directly from the feeding trials is limited, since usually only one or very few feeding studies are available at an appropriate level.
2 Anon 1996. Report of an Joint FAO/WHO Consultation on the Revision of the guidelines for the estimation of dietary intake of pesticide residues. York, UK, May 1995.
3. The Meeting agreed that the problems of estimating STMRs and maximum residue levels for products of animal origin are different from those of estimating these values for crop commodities from supervised residue trials. For example, the main residue in feed items may be a metabolite and this may need to be taken into account. The Meeting concluded therefore that this recommendation of the Workshop, although providing useful guidance, would not be appropriate in all situations.
4. The Meeting noted that the continuous consumption of feed items containing residues at the MRL is unlikely and therefore recognized that the magnitude of the residues in animal products following the consumption of treated feed items would depend on the rate at which the compound reached a steady state in tissues, milk and eggs. The residues of some compounds transfer into milk or eggs fairly rapidly, whereas those of other compounds do not reach a plateau unless dosing is sustained for 1-2 weeks or more.
5. The Meeting agreed that in deciding which dosing level to use from feeding studies on farm animals, account must be taken of whether the dosing levels in the feeding studies are expressed on a wet or a dry weight basis. The Meeting recommended that reports of future feeding studies should record the feeding levels primarily on a dry weight basis. It agreed that interpolation between dosing levels from the feeding studies was appropriate in cases where reasonable linearity of the relation between residue level and dosing level could be assumed (where three or more dosing levels show reasonable linearity), whereas extrapolation substantially beyond the range of dose levels was not appropriate.
6. The Meeting agreed that maximum residue levels and STMRs for products of animal origin should normally be derived as shown below and summarized in Table 1.
a) For compounds which reach a plateau rapidly in milk or eggs.Maximum residue levels should be calculated from the MRL for each feed item, the maximum feed incorporation rates and the highest residues determined in the milk, eggs and tissues in the feeding studies.
STMRs should be calculated from the STMR for each feed item, the maximum feed incorporation rates and the mean residues determined in the milk, eggs and tissues in the feeding studies.
b) For compounds which reach a plateau slowly in milk or eggs.
Maximum residue levels should be calculated from the STMR for each feed item, the maximum feed incorporation rates and the highest residues determined in the milk, eggs and tissues in the feeding studies.
STMRs should be calculated from the STMR for each feed item, the maximum feed incorporation rates and the mean residues determined in the milk, eggs and tissues in the feeding studies.
In deciding between options a) and b), the persistence of the residue in the feed items should be taken into account.
7. The Meeting recommended that worked examples should be developed in time for the 1998 JMPR.
Table 1. Summary of procedures for the estimation of maximum residue levels and STMRs for products of animal origin when residues are transferred from feed items.
|
|
Residue reaches plateau rapidly |
Residue reaches plateau slowly |
||
|
Max. Residue level |
STMR |
Max. residue level |
STMR |
|
|
Feed item residue level |
MRL |
STMR |
STMR |
STMR |
|
Feed incorporation rates |
maximum |
maximum |
maximum |
maximum |
|
Feeding study residue level |
highest |
mean |
highest |
mean |
