** Evaluation in CCPR periodic review programme
RESIDUE AND ANALYTICAL ASPECTS
Chlorfenvinphos was evaluated for residues by the JMPR in 1971 and 1984 and is now being reviewed in the CCPR periodic review programme. It is a contact and soil-applied organophosphorus insecticide used for the control of various pests on a range of vegetable, cereal and oilseed crops. A use for cattle dipping was also reported.
The Meeting received information on physico-chemical properties of the technical material, metabolism, environmental fate in soil, methods of residue analysis, approved use patterns, supervised residue trials, animal transfer studies, the fate of residues during food processing, monitoring data and national MRLs.
Data on metabolism in humans, rats, dogs, lactating cattle, potatoes, cabbage, maize, carrots and onions were reviewed; in all cases the main residue was chlorfenvinphos. These studies, as well as those on the environmental fate, were old and briefly reported with limited experimental detail. No data on the mobility of chlorfenvinphos in soil were submitted.
Analyses of crop and soil samples for chlorfenvinphos and its metabolites were based on GLC with FP, EC or NP detection. Only limited data on validation of the methods were presented. No information was provided on the stability of residues in stored analytical samples.
Data on residue trials on a number of crops were submitted. Several of the reports of the trials lacked important experimental details or were poorly presented. The Meeting estimated maximum residue levels for onion, head cabbage, cauliflower, carrot, parsnip and rape seed, but these estimates were based mainly on trials in which the duration of sample storage before analysis was not reported.
Summary data on residues in lettuce and lamb's lettuce grown as rotational crops indicated that significant residues may occur in rotational crops after soil applications of chlorfenvinphos.
In studies of ruminant grazing and external treatment, measurable residues were found only in samples of 'fat'.
Data on domestic preparation and processing indicated that most of the residue in carrots is associated with the top of the carrot including the crown.
The Meeting agreed that in view of the lack of studies according to modem standards on metabolism, the stability of residues in stored analytical samples, the mobility of chlorfenvinphos in soil and the residues found in following crops, the estimated maximum residue levels could not be recommended as MRLs. For any future consideration of MRLs, the submission of data on such studies would be needed. The Meeting recommended the withdrawal of the existing CXLs.
FURTHER WORK OR INFORMATION
1. The following physico-chemical properties of the pure active ingredient: vapour pressure, melting point, octanol/water partition coefficient, solubility in organic solvents, solubility in water, specific gravity.
2. If significant residues occur in relevant feed items, a study of metabolism and distribution in a lactating ruminant and/or in laying poultry carried out according to modem standards in which treatment is made through oral ingestion.
3. Data on metabolism in a ruminant after the external application of chlorfenvinphos to support the reported approved dipping use in Australia.
4. Plant metabolism and translocation studies carried out according to modem standards.
5. Studies on the stability of pesticide residues in representative analytical samples stored for at least two years. These would help to support data evaluated by the Meeting on residue trials for which the duration of sample storage was not reported.
6. Studies to assess the nature and levels of residues in representative rotational crops other than lettuce and lamb's lettuce.
7. If significant residues are found in animal feed, a transfer study on ruminants according to modem standards (see 1993 JMPR report, Section 2.7).
8. A study of the mobility of chlorfenvinphos in soil, including leaching, adsorption and desorption, according to modem standards.
9. Copies of the product labels supporting the information submitted on GAP.
10. The full reports of the rotational crop studies on lamb's lettuce and lettuce.