PESTICIDE RESIDUES IN FOOD - 1984 Sponsored jointly by FAO and WHO EVALUATIONS 1984 The monographs Data and recommendations of the joint meeting of the FAO Panel of Experts on Pesticide Residues in Food and the Environment and the WHO Expert Group on Pesticide Residues Rome, 24 September - 3 October 1984 Food and Agriculture Organization of the United Nations Rome 1985 CYPERMETHRIN Explanation Cypermethrin was reviewed by the MJPR in 1979, 1981 and 1982 and MRLs have been recommended on a wide range of crops and on meat and milk. 1/ Data on residues in tea have now been evaluated. RESIDUES IN FOOD AND THEIR EVALUATION USE PATTERN Cypermethrin is used for the control of insect pests of tea in Malawi, Indonesia and experimentally in southern India. The main pests of tea that are susceptible to cypermethrin are thrips, Helopeltis antonii, H. febriculosa, H. schoutedeni and H. theivora, as well as the lepidopterous pests, the tea tortrix (Homona coffearia) , slug caterpillar (Thosea sinesis), Darma trima, nettle grub (Setora nitrens), tea leaf roller (Gracillaria theivora), and Laspeyresia leucostoma. Application rates and timing of applications are influenced to some extent by the pest. Thus, thrips and Helopeltis require rates of from 25 g a.i./ha, whereas up to 40 g may be needed for some of the lepidopterous pests. More than one treatment may be needed each season, but never more than one treatment between pickings; the preharvest interval is typically a minimum of five days. RESIDUES RESULTING FROM SUPERVISED TRIALS Tea Most of the data available were obtained from Malawi in a series of trials carried out in late 1981 (Bosio, 1982a). Studies were carried out at four locations, three with China tea and one with Indian. Plot sizes were 100 sq.m. and treatments were applied at the rates of 10, 20 or 40 g a.i./ha. The number of treatments was 1, 2, 3 or 7 with generally about a month between each application, except in the case of the three-application experiment where the interval between applications was about two weeks. The tea was harvested at various intervals after treatment. The leaves were then dried and processed and sent to the laboratory. The intervals between the last application and harvest ranged from 1 to 29 days, although in practice the minimum preharvest interval (PHI) in Malawi is about five days. The dry tea samples were analysed for residues of cypermethrin and the results are given in Table 1. 1/ See Annex 2 for FAO and WHO documentation. TABLE 1. Residues of Cypermethrin in Tea from Supervised Trials, Malawi Trial Application Residues (mg/kg in dry leaves) after preharvest interval (days) No. No. Rate (g a.i./ha) 1 3 5 7 10 14 20 29 5 1 10 9.2 3.5 2.3 0.2 20 16 7.3 4.3 0.2 40 24 12* 9.7 0.7* 6 2 10 5.7 1.8 0.5 0.1 20 10 4.0 0.7 0.1 40 11 8.1 1.0 0.1 7 3 20 4.3 1.7 0.4 0.2 0.03 8 7 20 4.6 2.1 0.3 0.1 0.01 * Samples used for further investigations concerning metabolites. 1 See Annex 2 for FAO and WHO documentation. The results show that with a PHI of five days, cypermethrin residues were below 20 mg/kg in every case. The concentrations were not noticeably affected by the number of applications, but the rate of application and the PHI were both important factors, particularly the latter. Two samples of dry tea were also obtained from Indonesia (Bosio, 1980). The tea was treated three times at weekly intervals with 10 g a.i./ha and sampled six days after the last application. The samples, which arrived in the laboratory 12 days after harvest, were analysed as for the Malawi samples. The residues reported were low, being 0.10 and 0.15 mg/kg dry tea. As described in the 1979 Evaluations (FAO/WHO 1980b), cypermethrin degrades in biological systems, primarily by hydrolysis of the ester linkage, to give the cyclopropane carboxylic acid (CPCA; WL 4476) and 3-phenoxybenzoic acid (3-PBA; WL 44607). The amide analogue of cypermethrin (WL 47133) formed by hydrolysis of the cyano group without breakage of the ester link has also been reported as a metabolite, but only a minor one. In other crop commodities, none of these metabolites has been detected but they have occurred in tea. Thus, two samples of dry tea from one of the Malawi trials, those marked with an asterisk in Table 1, were analysed for the presence of metabolites (Bosio, 1982b). The results are given in Table 2. In both samples, the CPCA moiety was found. In the sample with higher residue concentrations there was a small amount of 3-PBA, although neither sample contained detectable levels of the amide compound. TABLE 2. Residues of cypermethrin metabolites in dry tea leaves (mg/kg) Parent 3 PBA CPCA Amide 12 0.13 1.1 <0.03 0.7 <0.05 0.45 <0.03 Residues of pesticides in tea are significant to the consumer only insofar as they occur in the tea when it is drunk. To estimate the concentration of cypermethrin likely to occur in tea infusions, all the tea samples from the Malawi experiments were used to brew tea and the infusions analysed for cypermethrin content. The dry tea (6 g) was infused with 360 ml boiling water, allowed to stand for five minutes and then strained off. The infusions were analysed as for the dry tea with the very low limit of determination of 0.01 ug/l. Data for those samples giving residues above the 0.01 ug/l in the brewed tea are summarized in Table 3. Only very low concentrations occurred in the infusions, the highest being about 0.25 ug/l from two samples of dry tea with 11 and 8 mg/kg cypermethrin residue. Cypermethrin was not detected (limit of determination 0.01 ug/l) in any infusions made from dry tea with a residue of less than 1 mg/kg cypermethrin. The percentage extracted into the infusion was extremely small, as would be expected from the lipophilic nature of cypermethrin. In no case did the percentage of cypermethrin extracted into the infusion exceed 0.2 percent. The average value based on the results in Table 3 was 0.1 percent. The two samples from Indonesia were also used to make infusions, but as would be expected from the very low concentrations of cypermethrin in them, no residues were found in the infusions. (In this earlier work, the limit of determination was much higher at 0.2 ug/l.) Infusions were also made from the two dry tea samples from Malawi that were analysed for metabolites, using methodology comparable to that employed for the dry tea. The results are shown in Table 4. Thus, the process of brewing tea is relatively effective for the extraction of residues of the CPCA metabolite, as distinct from residues of the parent compound. Although a low concentration of 3-PBA was detected in the higher residue sample of dry tea, none was detected in the corresponding infusion. No amide compound was detected in the infusion. APPRAISAL In response to requests made at the sixteenth Session of the CCPR by several countries, the meeting reviewed earlier residues data on lettuce, grapes, peaches, nectarines and pome fruit (1979, 1981 and 1982 evaluations). The meeting accepted that harvest intervals for grapes were likely to be 14 days or longer and agreed that the estimate of the maximum residues level could be revised to 0.5 mg/kg. The only residue exceeding 0.5 mg/kg at 14 days was from a trial in Canada, a country for which there is no submitted good agricultural practice. This change enabled the meeting to propose a group MRL of 0.5 mg/kg for small fruits and berries to replace separate limits for gooseberries, raspberries, strawberries, grapes and currants (black, red and white). The data on peaches (nectarines were added by extrapolation from the data on peaches) indicate that, at the highest doses included in GAP and with intervals of 14 days, the levels can exceed 1 mg/kg. The meeting, therefore, confirmed its earlier estimate of 2 mg/kg for peaches and nectarines. Similarly, the meeting confirmed its estimate of 2 mg/kg as the maximum residue level for pome fruit and lettuce if an interval of 7 days is used as a basis for GAP. TABLE 3. Residues of cypermethrin in tea infusions made from dry leaves with known cypermethrin content Residue Trial In dry In tea Percentage No. tea infusion extracted 1 (mg/kg) (µg/l) 15 9.2 0.02 0.01 16 0.04 0.01 24 0.10 0.02 12 0.08 0.03 9.7 0.04 0.02 6 5.7 0.14 0.1 1.8 0.09 0.2 10 0.15 0.1 4 0.06 0.1 11 0.24 0.1 8.1 0.24 0.2 7 4.3 0.07 0.1 1.7 0.04 0.1 8 2.1 0.03 0.1 1 On basis of 1 µg/l equivalent to 0.05 mg/kg dry tea; average percentage extracted = 0.1. TABLE 4. Residues of cypermethrin metabolites in tea infusions Residues in infusion (µg/l) Calculated equivalent in dry tea (mg/kg) Parent 3PBA CPCA Amide Parent CPCA 0.08 <0.01 11 <0.05 0.005 0.7 <0.01 <0.01 2.8 <0.05 - 0.2 New data on cypermethrin residues in tea enabled the meeting to estimate a maximum residue level of 20 mg/kg in dry leaves (the commodity in trade). Only 0.1 percent of the residue is extracted into the tea infusion. After reviewing some of the previous proposals for cypermethrin the meeting agreed to propose several changes. The definition of kidney beans (in pod) should be replaced by beans (with pod) at the same level. The meeting also proposed that an estimate of 0.05 mg/kg for legume oilseeds should replace separate estimates of 0.02 mg/kg for peanuts and 0.05 mg/kg for soybeans. The level of 0.05 mg/kg was identified as at or about the limit of determination for all commodities except milk. The meeting noted that: (1) the MRL of 0.5 mg/kg for peppers, proposed by the 1981 JMPR, was recorded in the evaluations of that year as applying separately to sweet peppers and chilli peppers, and (2) that the 1981 report referred to "coffee beans" and the evaluations to "coffee (dried beans)". The meeting agreed that the correct commodity descriptions are "peppers" and "coffee beans". The proposal of 0.2 mg/kg for milk products was withdrawn to accord with decisions made at the 15th Session of the CCPR on these processed foods. RECOMMENDATIONS The following MRLs were estimated and recommended as suitable for use. Commodity MRL Preharvest interval on (mg/kg) which MRL is based (days) Small fruits and berries 0.05 14 (replacing separate limits for grapes, currants, gooseberries, raspberries and strawberries) Tea 20 - Further changes in MRLs or commodity descriptions were recommended: - Replace kidney beans (in pod) by beans (with pod) at the same level; - Replace peanuts, 0.02 mg/kg, and soybeans, 0.05 mg/kg, by legume oilseeds, 0.05 mg/kg; - Withdraw proposed MRL for milk products of 0.2 mg/kg. All MRLs at 0.05 mg/kg should be indicated as at or about the limit of determination. (The MRL for milk, 0.01 mg/kg, should not be so indicated.) REFERENCES Bosio, P.G. Report BEGR. 80.038 submitted by Shell Chimie to FAO. 1980 (Unpublished) Bosio, P.G. Report BEGR. 82.097 submitted by Shell Chimie to FAO. 1982 (Unpublished) Bosio, P.G. Report BEGR. 82.106 submitted by Shell Chimie to FAO. 1982b (Unpublished)
See Also: Toxicological Abbreviations Cypermethrin (EHC 82, 1989) Cypermethrin (HSG 22, 1989) Cypermethrin (ICSC) CYPERMETHRIN (JECFA Evaluation) Cypermethrin (PIM 163) Cypermethrin (Pesticide residues in food: 1981 evaluations) Cypermethrin (Pesticide residues in food: 1982 evaluations) Cypermethrin (Pesticide residues in food: 1983 evaluations)