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)