Propoxur was evaluated by the JMPR in 1973, 1977, 1981, 1983 and 1991. At the 1994 CCPR, several delegations expressed the opinion that the MRLs recommended by the 1991 JMPR for head lettuce and potatoes were based on very old data. The manufacturer stated that new data on potatoes would be available for the 1996 JMPR and that additional studies were scheduled for lettuce. New data from supervised trials on these commodities were provided to the Meeting, together with information on GAP, analytical methods and monitoring surveys.
Analytical methods
Analyses in the new supervised trials were by HPLC with on-line derivatization and fluorometric detection. This method allows the determination of both propoxur and its metabolite 2-hydroxy-propoxur (2-OH-propoxur).
Recoveries from lettuce and potatoes were 86-95% for propoxur and 84-93% for 2-OH-propoxur and the limits of determination were 0.02 mg/kg in potatoes and 0.04 mg/kg in lettuce.
The method was considered suitable for use in supervised trials and for enforcement.
Field trials data
The Meeting evaluated newly submitted data from supervised trials on lettuce and potatoes and re-evaluated data reviewed by earlier Meetings in the light of current GAP. The Meeting agreed not to estimate STMRs for these commodities until a periodic review was undertaken, since CXLs exist for many commodities and metabolic studies were not submitted to the Meeting.
Lettuce. Six supervised trials in The Netherlands in 1963 and 1971 under glass were reported in the 1973 JMPR monograph. The residues were 0.9-20.2 mg/kg at 0-13 days and 0.5-0.8 mg/kg at 14-17 days from single applications of 0.6-0.9 kg ai/ha. The details of the trials were not clear and the treatments did not match current glasshouse GAP in The Netherlands (0.15-0.30 kg ai/ha for WP and 0.40-0.60 kg ai/ha for EC, PHI 14 days from March to September and 21 days from October to February, 2 applications).
Eight supervised field trials carried out in Germany during 1961-1964 were reported in the 1991 JMPR monograph. Samples were analysed by a very old colorimetric method and details of 4 trials (0.3-0.75 kg ai/ha, one application, 0-18 days PHI) were not clear. In the other 4 trials the conditions (0.15 or 0.6 kg ai/ha, one application, 0-8 days PHI) were not comparable with GAP in Germany (0.18-0.24 kg ai/ha, 0.03-0.04 kg ai/hl, 2 applications, 7 days PHI) or The Netherlands (0.20-0.40 kg ai/ha, one application, 14 or 21 days PHI). The trials data could not be used for evaluation.
In three field trials in 1975, reported in 1991, the conditions (0.24 kg ai/ha, 0.04 kg ai/hl, 3 applications, 0-9 days PHI) were comparable to German GAP except in the number of applications and the residues were 0.01, 0.2 and 0.3 mg/kg at 7 days PHI. The Meeting considered that the effect of the number of applications would not be significant because propoxur residues were observed to decrease rapidly during the first 7 days after application.
In 1991, supervised trials were carried out at four locations in Germany according to German GAP with the current HPLC analytical method. The residues of propoxur were 0.05, 0.07, 0.10 and 0.13 mg/kg, and of 2-hydroxy-propoxur <0.04 mg/kg in each trial.
The Meeting used the three 1975 and four 1991 German trials to estimate maximum residue levels. The residues were 0.01, 0.05, 0.07, 0.10, 0.13, 0.2 and 0.3 mg/kg.
The Meeting estimated a maximum residue level of 0.5 mg/kg for propoxur in head lettuce to replace the existing CXL of 3 mg/kg.
Potatoes. Seven supervised trials in Germany in 1971-1975 were reported in the 1991 monograph. Although most of these trials were at higher dose rates or shorter PHIs than required by GAP in Germany and The Netherlands, all of the residues were below the limit of determination of 0.1 mg/kg.
In 1994, supervised trials were carried out at six locations in Germany according to German GAP (0.24 kg ai/ha, 1 application, 14 days PHI). Analyses by the new HPLC analytical method showed propoxur and 2-hydroxy-propoxur residues to be below the limit of determination (0.02 mg/kg).
The government of Poland provided data on three supervised trials to the Meeting. The trials were in 1993 and 1994 and according to GAP (0.3-0.5 kg ai/ha, 2 applications, 7 days PHI). The residues were below the limit of determination (0.01 or 0.02 mg/kg). The Meeting concluded that adequate data on propoxur residues in potatoes determined by a modem method of analysis with an LOD of 0.02 mg/kg were now available.
The Meeting estimated a maximum residue level of 0.02* mg/kg for propoxur in potatoes to replace the existing CXL (0.1* mg/kg).
Monitoring data
In monitoring in Poland for propoxur in 1994, 731 samples of apples, white cabbages, carrots, cauliflowers, celery, sour cherries, black, red and white currants, bulb onions, parsley, potatoes and tomato (glasshouse) were analysed. No residues were found in any samples except two of white cabbage at 0.1 and 0.3 mg/kg, but information on the LOD was not available. The detection frequency was 0.3% for all samples and 1.8% for white cabbage. The residues found in white cabbage were below the national MRL (vegetables: 3 mg/kg).
Comprehensive monitoring was carried out in The Netherlands from 1991 to 1994 on 9810 samples of apples, bananas, celery, cucumbers, currants, egg plant, endive, leeks, lettuce, plums, raspberries, strawberries, sweet peppers and wheat. The overall detection frequency was 0.81% and the detection frequency for individual commodities ranged from 0.3% for cucumbers and lettuce to 40% for leeks. The mean residues in all crops were below the national MRL (fruit and vegetables 3 mg/kg, other food commodities <0.05 mg/kg).
