PESTICIDE RESIDUES IN FOOD - 1981
Sponsored jointly by FAO and WHO
EVALUATIONS 1981
Food and Agriculture Organization of the United Nations
Rome
FAO PLANT PRODUCTION AND PROTECTION PAPER 42
pesticide residues in food:
1981 evaluations
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
Geneva, 23 November-2 December 1981
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome 1982
CYPERMETHRIN
Explanation
Cypermethrin was evaluated by the 1979 JMPR,* and a temporary ADI
was estimated at that time. Lack of data on tissue residue storage and
release and on human experience with cypermethrin were instrumental in
making this temporary. Further toxicological data were required on
potential bioaccumulation of cypermethrin and/or its metabolites in
adipose tissue and on humans exposed to the pesticide, especially
those with a high level of occupational exposure. Such data were
submitted to this Meeting for evaluation.
Temporary maximum residue limits were recommended for several
crops in 1979 and the Meeting considered that further information was
desirable on residue data on known fruits from supervised trials,
selective surveys of residues in crops known to have been treated
under practical circumstances, and use patterns for animal health use
and residues in foods of animal origin deriving from the recommended
application.
At the 13th Session of the Codex Committee on Pesticide residues,
the appropriateness of the MRLs for wheat and alfalfa was questioned.
Since cypermethrin was evaluated by the JMPR in 1979, new data
have become available. These are summarized in this monograph and
cover the following categories: new food crop uses, including coffee,
fruiting vegetables with edible peel, nectarines and apricots;
additional data for crops previously evaluated by the JMPR, including
wheat grain, cherries and plums; and residue data on fodder crops,
cattle tissues and milk.
DATA FOR THE ESTIMATION OF ACCEPTABLE DAILY INTAKE
BIOCHEMICAL ASPECTS
Absorption, distribution, biotransformation and excretion
Rats
The fate of orally administered cis- and trans-isomers of
cypermethrin was studied in rats at levels of 1 to 5 mg/kg, using
three forms of radio labelling, e.g. benzyl-14C; cyclopropyl-14C and
cyano-14C (Crawford et al 1981). Radioactivity derived from the
* See Annex II for FAO and WHO documentation.
benzyl-14C and cyclopropyl-14C labelling was rapidly eliminated,
mostly in the urine. Tissue residues were generally very low, e.g.
0.01 µg/g in brain, with the exception of fat (about 1 µg/g). Residues
derived from the cis-isomer tended to be higher them those derived
from the trans-isomer. The rate of depletion of the residues derived
from (benzyl-14C)-cis-cypermethrin was rapid (t 1/2 was less than
about 1 day) from all tissues except fat (t 1/2 of 11 to 12 days).
This residue consisted largely of unchanged cis-cypermethrin. The
rapid elimination of cypermethrin from rats is due primarily to the
efficient cleavage of the ester bond giving rise to polar metabolites,
which are further oxidized and conjugated before excretion (Crawford
et al 1981).
The kinetics of cypermethrin in the blood of rats following
single oral doses of 2 mg/kg and 200 mg/kg in male and female Wistar
rats utilizing 14C-benzyl-, and 14C-cyclopropyl-labelled cypermethrin
(50:50 of cis:trans) have been described (Climie 1980). In the low
dose studies (2 mg/kg) the half-lives for the elimination of
radioactivity from the blood of rats following an oral dose of
14C-labelled cypermethrin were:
14C-benzyl label: male, 2.78 h; female 4.36 h.
14C-cyclopropyl label: male, 4.30 h; female, 4.74 h.
The mean peak blood concentrations of cypermethrin equivalents
derived from the benzyl label were 1.8 and 1.4 µg/ml, both at about
3 h after dosing for male and female rats respectively. The equivalent
figures from the cyclopropyl label study were 0.7 and 0.6 µg/ml at
about 3 and 3 to 4 h after dosing respectively. This difference could
be attributed to a rapid clearance of the labelled chemical from the
body or to inter-animal variation. The mean peak plasma concentrations
of cypermethrin in the benzyl-labelled study were 0.19 and 0.18 µg/ml
for male and female rats respectively. The equivalent figures for the
cyclopropyl label were 0.04 and 0.02 µg/ml. The difference between the
two studies can only be accounted for by inter-animal variation.
The high dose studies with 200 mg/kg (50:50 of cis:trans) showed
a high inter-animal variation. Each animal behaved differently from
the others, both with respect to the toxic effect of the compound and
to the amount of labelled chemical in the blood at any given time. The
mean peak blood concentrations of cypermethrin equivalents from the
benzyl-label were 41.9 and 39.7 µg/ml at about 16 and 23 h after
dosing for females and male rats respectively. The equivalent figures
from the cyclopropyl study were 6.7 and 10.3 µg/ml blood at about 8
and 24 h respectively. The peak plasma concentration of cypermethrin
equivalents in the cyclopropyl metabolite study for female rats,
however, occurred at 24h and not at 8h after dosing. The mean peak
plasma concentrations of cypermethrin in the benzyl labelled study
were 5.4 µg/ml for both male and female rats. The equivalent figures
for the cyclopropyl label were 0.43 and 0.42 µg/ml for male and female
rats respectively (Climie 1980).
The elimination of radioactivity after a large (200 mg/kg)
single oral dose of radio-labelled cypermethrin (50:50 of cis:trans)
to groups of male and female rats was rapid (Logan 1980). Cypermethrin
was partially absorbed and rapidly metabolized, principally by
ester cleavage, to give the cyclopropanecarboxylic acid and the
3-phenoxybenzyl moiety, which was excreted mostly as the
sulphate conjugate of 3-(4'hydroxyphenoxy) benzoic acid. The
cyclopropanecarboxylic acid was transformed mainly to the ester
glucuronide prior to elimination. The overall excretion of
cypermethrin and its metabolites was very rapid, with more than 75% of
the dose in the case of males and 85% in the case of females being
eliminated within three days. The residues in the tissues at seven
days were low with, on average, less than 1% of the total dose being
retained in the whole body. The residues in fat were the highest of
all tissues (21 to 14 µg/g) but they were considerably less than 100
times as large as the residues found in fat when rats were dosed at
about 2 mg/kg (Crawford and Hutson 1977; Crawford 1977), and suggests
than an appreciable portion of the dose was not absorbed.
The presence of a large proportion of the dose as untransformed
cypermethrin in the faeces, 26 to 51%, is a further indication of the
poor absorption of this insecticide at this dose level. The absorbed
cypermethrin, however, was rapidly cleaved at the ester bond to
produce 2,2-dimethyl-3-(2', 2'-dichlorovinyl)cyclopropane carboxylic
acid and a 3-phenoxy-benzoyl moiety that was mostly further
metabolized by oxidation at the 4' position. The resultant phenol
was almost totally conjugated with sulphate, the identical result to
that observed in low dose studies (Crawford and Hutson 1977). The
4'-hydroxy sulphate forms the major aryl metabolite (16% of the dose)
with 3-phenoxybenzoic acid as the second most important (5%). The
other identified aryl metabolites are 3-(4 -hydroxyphenoxy) benzoic
acid (1%) and the glycine conjugate, N-(3-phenoxybenzoyl) glycine
(1%).
The cyclopropyl acid is almost exclusively conjugated as the
ester glucuronide (30% of the dose in males, 47% in females) with some
free acid (twice as much trans as cis) being found in the urine (4%)
together with traces of the trans-hydroxymethyl cyclopropyl acids
(2%).
The bioaccumulation of radioactivity in the rat was investigated
following 28 consecutive daily oral doses of (14C)-cypermethrin
(50:50 of cis: trans) at a dose level of 2 mg/kg bw/day (Hall
et al 1980).
Twenty-four hours after the 28th daily dose, the tissue
distribution of radioactivity was similar in male and female rats. The
highest mean concentrations of radioactivity were found in fat (4 100
and 5 100 ng equivalents of (14C-cypermethrin/g tissue in males and
females respectively), skin (636 and 712 ng equivalents/g of tissue),
gastrointestinal tract (547 and 578 ng equivalents/g tissue), liver
(566 and 672 ng equivalents/g tissue), kidney (495 and 535 ng
equivalents/g tissue), adrenal glands (913 and 665 ng equivalents/g
tissue) and ovaries (710 ng equivalents/g tissue).
Low mean concentrations were found in heart (67.6 and 88.7 ng
equivalents/g tissue in males and females respectively), spleen
(64.2 and 63.6 ng equivalents/g tissue), muscle (35.2 and 51.7 ng
equivalents/g tissue) and bone (72.8 and 44.4 equivalents/g tissue).
There was no detectable radioactivity in the brain of female rats and
only a very low concentration in that of males (mean = 13.4 ng
equivalents/g tissue). Of the individual organs examined, the highest
residual radioactivity was found in the gastrointestinal tract
(mean = 6 405 ng equivalents/g tissue), liver, (mean = 5 820 ng
equivalents/g tissue) and kidney (mean = 795 ng equivalents/g tissue).
The high concentration of radioactivity found in fat, skin,
ovaries and adrenal glands is consistent with the lipophilic nature of
cypermethrin. The pyrethroid group of insecticides is known to undergo
extensive metabolism in mammals (Casida and Ruzo 1980) resulting in
metabolites of a less lipophilic nature that will therefore be more
rapidly excreted than the parent compound.
The accumulation of radioactivity in the liver and kidney found
in this study is consistent with these processes of metabolism and
excretion. High levels of radioactivity were also found in the
gastrointestinal tract, reflecting its role in absorption. The
remaining tissues that were studied accumulated less radioactivity,
the lowest levels being located in the brain (Hall et al 1980).
A bioaccumulation study was undertaken to establish the rate of
extent of accumulation of cypermethrin-derived 14-C label in a
selected range of tissues during a daily oral dosing regime and also
the rate of elimination of any 14C-residues following the attainment
of steady state tissue levels. Sixty female rats were dosed orally
with 14C-benzyl-labelled cypermethrin (50:50 of cis: trans), 2 mg/kg
(2 µCi/kg) bw, in maize oil (2 ml/kg) for up to 70 consecutive days. A
group of treated (3) and untreated (1) animals were sacrificed at
prescribed intervals during the dosing regime in order to monitor the
rate and extent of bioaccumulation of 14C-radioactivity in liver,
kidney, adipose tissue (fat), blood (whole blood and plasma), skin and
ovaries (Jones 1981).
The elimination of radioactivity from fat demonstrated biphasic
characteristics. This was associated with a rapid elimination of
residues of trans-cypermethrin coupled with a slower elimination of
the cis-isomer. These elimination characteristics did not allow a
simple half life value for elimination of radioactivity from fat to be
calculated. However, as the relative proportions of cis- and trans-
isomers in fat were monitored from day 70 of the study, it was
possible to determine the independent half lives for both isomers. At
the termination of dosing, the relative proportions of cis-and trans-
isomers in fat were 88.25% to 11.75%. The half lives of elimination of
cis- and trans-cypermethrin from fat were calculated by linear
regression analysis to be 18.24 and 3.43 days respectively.
Daily dosing was continued for 70 consecutive days, by which
time the extent of bio-accumulation of radioactivity in each
tissue analysed had been shown to reach a plateau. The extent of
accumulation, expressed as µg equivalents of cypermethrin per gram of
tissue (as mean ± S.D. values from a group of 3 rats), was: liver
0.97 ± 0.31; kidneys 0.65 ± 0.24; fat 3.91 ± 0 25, blood 0.35 ± 0.13;
plasma 0.64 ± 0.28; skin 1.86 ± 0.14 and for each ovary 0.03 ± 0.01 µg
equivalents. Such levels of radioactivity in ovaries were similar to
background values.
In addition, the degree of accumulation of 14C-label in the
sciatic nerve was determined by analysing nerves isolated from treated
animals given 56 to 70 daily doses of cypermethrin. The extent of
accumulation of radioactivity did not exceed 0.05 µg equivalents of
cypermethrin per nerve, representing a level of radioactivity similar
to the background value.
Following the termination of dosing, the remaining groups of
treated and untreated rats were sacrificed at prescribed intervals
during a period of 50 days. Tissue residue levels of radioactivity
were monitored and the rate of elimination of 14C-label from each
tissue was determined. After the cessation of dosing the liver, kidney
and blood 14C-residue levels fell rapidly and reached control
background levels within 29, 8 and 15 days respectively. With regard
to skin, a much slower elimination of radioactivity was observed, with
half of the radioactivity being eliminated by 18.7 days after dosing
(Jones 1981).
Dog
The metabolites derived from a single oral dose of
(14C-cyclopropyl) cypermethrin (1:1 cis/trans-WL 43467), administered
orally to two male beagle dogs, have been studied. The rapid
elimination of cypermethrin in dogs was due to the efficient cleavage
of the ester linkage of both the cis- and trans-isomers and the
urinary excretion of the cyclopropane carboxylic acid moiety, largely
as its glucuronic acid conjugate. This metabolite comprised 18% and
51% of the respective doses administered to dogs 1 and 2. Absorption
of the orally administered cypermethrin was not complete, i.e. 65.6%
of the dose was excreted as unchanged cypermethrin in the faeces of
dog 1 and 32.1% in the faeces of dog 2.
The results of this study confirmed those derived from a similar
study in which dogs were dosed with (14C-aryl) cypermethrin, in that
most of the excreted metabolites were ester-cleavage products of
cypermethrin. Whereas the 3-phenoxybenzyl moiety was mostly
hydroxylated in the 4'-position before excretion, most of the
cyclopropane carboxylic acids (cis- and trans-) were excreted without
further metabolism other than glucuronide conjugation (Crawford and
Croucher 1979).
The results of these studies show that the metabolic fate of
cypermethrin in dogs is similar to that in rats and mice with the
following exceptions: absorption from the gut is limited and somewhat
erratic, and hydroxylation reaction(s) do not occur as readily as in
rats and mice (Crawford and Croucher 1979).
Cow
The metabolic fate of (14C-benzyl)cypermethrin (cis-47% and
trans-53%) (49.4 mg), administered orally to one lactating cow twice a
day for 7 days, has been elaborated. This dosage was equivalent to
approximately 10 ppm of cypermethrin in the total diet. Milk, urine
and faeces were collected daily and the animal was sacrificed 16h
after the last dose. A second control cow was fed an untreated diet
over this period.
Elimination and ingestion of radioactivity were in balance at
about day 4 after the start of dosing. Urine and faeces were equally
the major routes of elimination. Although the metabolites in the urine
and faeces were not analysed in this study, it was noted that the
major urinary metabolite of the 3-phenoxybenzyl moiety of the related
insecticide permethrin in the cow has previously been identified as
N-(3-phenoxybenzoyl)glutamic acid (Gaughan et al 1978). Although
radioactivity was detected in milk, it was equivalent to only about
0.03 µg of cypermethrin/ml (<0.2% of the ingested dose) and was
located mostly in the lipophilic component (cream or butterfat).
Radioactive residues retained in the tissues were generally low
and were in the order: liver > kidney > fat > blood > muscle.
Tissue residues (expressed as µg cypermethrin/per g tissue) were liver
0.21; kidney 0.11; renal fat 0.1; subcutaneous fat 0.08; blood
0.04 and muscle 0.01. The major residue in liver and kidney was
N-(3-phenoxybenzoyl)glutamic acid. Another polar metabolite was
detected in both liver and kidney and, although not identified,
it was suggested that it could be an acid-label conjugate of
3-(4'-hydroxyphenoxy)benzoic acid. Unchanged cypermethrin formed only
a very small proportion of the residue in liver and kidney. Residues
in lean muscle could not be identified as they were very low (Hutson
1980.
A study designed to examine the residue transfer into milk and
tissues of Fresian cows following oral administration of cypermethrin
was reported. Three groups of three Fresian cows were fed for up to
29 consecutive days on a diet containing 0.2, 5.0 or 50 mg/kg of
cypermethrin (calculated on a whole diet, e.g. grass, nuts, plug, hay,
basis). (Cypermethrin used was of 78.5% purity, isomer ratio: cis A
21.7%; cis B 21.6%; trans C19.1% and trans D 16.1%.) At the end of the
treatment period, two cows from each group were slaughtered. The
remaining cow from each group was fed an untreated diet for a further
7 to 8 days before being slaughtered. No effects on milk yields or
general health of the animals were observed throughout the period of
the trial.
Cypermethrin residues found in the milk did not accumulate and
declined rapidly when feeding of treated diet ceased. Levels
correlated well with dose rate. Residues resulting from the 0.2 mg/kg
dose rate remained <0.005 mg/kg and reached mean plateau values of
0.021 and 0.249 mg/kg for the 5.0 and 50 mg/kg groups respectively.
Cypermethrin residue levels in tissues were generally in the
order peritoneal fat > subcutaneous fat > kidney > muscle> liver,
and these again correlated well with dose level. Cows from the two
lower dosage groups had tissue residues that were around or below the
limit of determination of 0.01 mg/kg in all but the fat of the
5.0 mg/kg group, which contained 0.09 to 0.34 mg/kg. Cypermethrin
residue levels in the tissues of the high rate group ranged from
<0.05 mg/kg in liver samples, approximately 0.5 mg/kg in muscle and
kidney samples and up to approximately 5.0 mg/kg in a peritoneal fat
sample.
Examination of the isomer ratios of cypermethrin residues in milk
and fat showed some cis enrichment compared to the cypermethrin
originally incorporated into the diet.
The residue levels of two major metabolites of cypermethrin,
namely 3-(2,2-dichloro-vinyl)-2,2-dimethylcyclopropane carboxylic acid
(DCVA) and 3-phenoxybenzoic acid (3-PB acid) have been quantitatively
measured in the milk and tissues of dairy cows fed for up to 29 days
on a diet containing 50 mg/kg of cypermethrin (Swaine and Saprets
1980b), Analysis was also carried out on the milk and tissues of a cow
that was returned to untreated diet for seven days following the
treatment period. Residue levels of both metabolites in milk were
extremely low; measurable residues at about the limit of determination
of the methodology used (e.g. 0.01 mg/kg) were found in only isolated
samples and none were found in the post-treatment "recovery" period.
Tissue analysis indicated residue levels in different organs in the
general order liver - kidney > muscle > fat, with the maximum
metabolite residues not exceeding 0.5 mg/kg. Residue levels in the
"recovery" cow were significantly lower, indicating that the
metabolites were readily excreted (Swaine and Sapiets 1980a).
A two-year feeding study has been carried out in which beagle
dogs, groups of four males and four females, were fed diets containing
0, 3, 30, 300 and (initially) 1 000 ppm of WL 43467 (cypermethrin).
When severe signs of intoxication were observed in the groups fed
1 000 ppm WL 43467, this top dose level was reduced to 750 ppm, and
when signs of intoxication persisted it was further reduced to 600 ppm
of the insecticide.
The results of the study were as follows:
1. Signs of intoxication consisted of licking and chewing of
the paws, a stiff high-stepping gait, whole body tremors, head
shaking, incoordinate ataxia and, in some cases, convulsions. Some
dietary inappetence was observed in males fed 1 000 ppm WL 43467.
These signs were observed in the group fed 1 000 ppm and 750 ppm, but
not when the dietary level of WL 43467 was reduced to 600 ppm. No
signs of intoxication were observed in groups of dogs fed 3, 30 and
300 ppm WL 43467.
2. A reduction in body Weight was observed in the top dose
group males in the main feeding study. This is considered to be a
consequence of the dietary inappetence observed early in the study
when the dogs were fed 1 000 ppm WL 43467. No effect on body weight
(attributable to feeding of the compound) was observed in dogs fed 3,
30 and 300 ppm WL 43467.
3. Significant but small differences between controls and
treated dogs were observed randomly throughout the study. Sodium
levels in the blood plasma of male dogs at the 600 ppm treatment level
showed a significant decrease in some weeks, but were always within
the normal physiological range. Three dogs tended to have high
alkaline phosphatase activity throughout most weeks of the study, this
made the 300 ppm treatment level in male dogs significantly higher
than in controls. This effect was not observed at 600 ppm. No similar
effect was observed in female dogs. This observation was not therefore
considered to be of toxicological significance. Overall, no
significant differences were detected in clinical chemistry and
haematological estimations that could be attributed to the feeding of
WL 43467 for two years.
4. No compound-related pathological abnormalities were found. A
small number of minor organ weight changes were found in intermediate
dose groups, but were not considered to be due to the feeding of dogs
with WL 43467 for 2 years (Shell Research Ltd. 1980d).
Special studies on exposure of spray applicators
A study was carried out in humans at the Institut de Recherches
du Coton et des Textiles Exotiques (IRCT), Bouake, Ivory Coast, after
hand-held ULV application to cotton of the pyrethroid Ripcord (WL
43467) during one season of spraying.
The operators were 7 indigenous Africans. Six of them had no
previous pesticide application history; One had very limited
experience. They sprayed the formulation EF 4922 (25 g Ripcord/l in
a 50/50 (v/v) hexylene glycol and Shellsol AB mixture) on an area of
1 ha at the rate of 2 l/ha in 6 spray sessions at fortnightly
intervals under the supervision of IRCT staff. In a seventh spray
session, the same amount was sprayed under the supervision of the
Exposure Monitoring Group. The operators wore their normal clothes and
no special protective devices were used.
Exposure to Ripcord was monitored by collecting the total amount
of urine passed during the first 24 h after each spray session and the
determination of the excretion levels of the urinary metabolite trans
WL 44776 3-(2,2-dichlorovinyl-2,2-dimethyl-cyclopropane-1-carboxylic
acid). In many samples the excretion was below the limit of detection,
indicating a low level of absorption. Skin contamination and
inhalational exposure were monitored only in the seventh spray
session. Skin and inhalational measurements did not correlate well
with the urinary excretion. Inhalational exposure was about 1% of skin
exposure. Skin exposure, as measured with aluminum foil, reflected the
working procedures. It was concluded that exposures were low, in
particular when the spraying recommendations are observed. The
absorption was calculated to be substantially less than the equivalent
of an oral dose of 1 mg Ripcord per spray session.
General medical and extensive clinical and neurological
examinations, blood biochemistry and peripheral nerve function tests
(including the trigeminal nerve) did not show abnormalities either
before or after the series of 6 spray sessions nor after the seventh
spray session. In some electroneurophysiological tests (motor
conduction velocity, slow fibre conduction velocity and cornea reflex)
a statistically significant change within the normal range appeared to
exist for the group of sprayers between pre- and post-exposure
measurements. There is no evidence that these changes are compound
related; they probably reflect seasonal variations.
The general conclusion is that under the conditions of this study
the application of Ripcord caused no detectable adverse health effects
(Prinsen and Van Sittert 1979).
Transient facial sensory symptoms following exposure to
synthetic pyrethroids (e.g. cypermethrin, permethrin, fenvalerate
and fenpropathin) in some workers has been reported (LeQuesne
et al 1980). Among 23 workers exposed to synthetic pyrethroids,
19 had experienced one or more episodes of abnormal facial sensation
that developed between 30 min and 3 h after exposure and persisted
for 30 min to 8 h. There were no abnormal neurological signs and
electrophysiological studies were normal in the arms and legs. It was
concluded that the symptoms are most likely to be due to transient
lowering of the threshold of sensory nerve fibres or sensory nerve
endings following exposure of the facial skin to pyrethroids, similar
to the phenomena that have been described following exposure of animal
nerves to pyrethroids (Wouters and van den Bercken 1978).
Skin sensations experienced by those handling cypermethrin or
other pyrethroids are believed to arise by repetitive firing of
sensory nerve terminals in the skin. It is said to be a strictly local
effect, which may occur as soon as the pyrethroid concentration on or
in the skin reaches a certain level and is not considered as a sign of
general intoxication (provided the pyrethroid does not reach the blood
in any significant concentration). A possibility exists, however, that
repeated occurrence of intense repetitive firing can perhaps
eventually lead to dysfunction of sensory nerve terminals and sense
organs and finally to degeneration of sensory nerve fibres (van den
Bercken 1980).
Special studies on photodecomposition
The decomposition of a number of pyrethroids, e.g. cypermethrin,
fenvalerate, NRDC 161, permethrin, phenothrin and S-3206 on glass by
radiation of 305 nm has been reported (Barlow et al 1977). A
comparison of permethrin and cypermethrin (e.g. insecticide half lives
of 4.5 and 1.9 days respectively) indicates that the presence of an
alpha-cyano group in the alcohol reduces stability, while the
phenothrin-permethrin pair illustrates the stabilizing effect of
chlorines replacing the methyl groups in the acid position of the
molecule (Barlow et al 1977).
RESIDUES IN FOOD
USE PATTERN
Recommendations for the use of cypermethrin on peaches, wheat and
maize covered in this document were described in papers submitted to
the 1979 JMPR. Corresponding information for those crops discussed
herein, and not previously considered by the JMPR, are listed in
Table 1.
TABLE 1. Recommendations for the use of cypermethrin on crops and in animal treatment
Crop Pest Application rate (g/ha) PHI1
Cucumber Trialeurodes vaporariorum 50-80 1-2 days
Aubergine Epilachna sp. 50 "
Leucinodes orbonalis 60
Pepper Heliothis sp. 30-50 "
Gnorimoschema sp. 50-75
Coffee Leucoptera coffeella 10-15 3 weeks
37.5-70
Sorghum2 Diatraea sp.
Euxoa sp. 35-70
Heliothis armigera 30-50
Busseola fusca 70-80
Chilo partellus 50-70
Spodoptera frugiperda 50-75
Contarinia sorghicola 40
Autoba silicula 40
Alfalfa2 Colias lesbia 60
Spodoptera frugiperda 60-70
Acyrthosiphon 30
Animal Pest Application rate (mg/l)
Cattle HaematoDia irritans 900 mg/1-200 ml/animal =
(Buffalo fly) 180 mg/animal
WHP - meat 3 days
milk nil
Boophilus microplus 100 mg/l as dip
(Cattle tick)
Haematobia irritans " "
WHP - meat - 3 days
milk - nil
Sheep Linognathus ovillus 18 g/l
Linognathus pedalis WHP- 7 days
Damalinia ovis
(Sheep lice)
Melophagus ovinus
(Sheep ked)
1 Interval shown is current minimum required for good agricultural practice;
2 Owing to the nature of uses, PHIs tend to be indeterminate.
RESIDUES RESULTING FROM SUPERVISED TRIALS
New food crop uses
Fruiting vegetables with edible peel
The available residue data are summarized in Table 2. In some
instances, crops were grown in greenhouses but, where comparable
outdoor data are available, it may be seen that residue levels for
cypermethrin, resulting from the two situations, were similar. As can
also be seen from Table 2, residue levels for cucumbers and sweet
peppers were not very different for the two crops, even where a large
number of applications were made at frequent intervals. Results from a
single trial with eggplants are included in Table 2, as this crop is
within the same vegetable classification group. The residue levels
reported indicate that levels are likely to be generally similar to
those for cucumbers and sweet peppers and for all three crops are
unlikely to exceed 0.5 mg/kg following recommended treatments. Data
for chilli peppers are also included in Table 2. These data tend to be
somewhat higher than those for the other crops in this group mentioned
previously; residues up to 1 mg/kg were found at harvest 1 week after
treatment.
Coffee
Residue data have been obtained from a number of trials in
Brazil. Although treatment according to recommendations gave rise to
residues in the whole cherries (Imperial Chemical Industries 1981c) of
up to 0.10 mg/kg, no residues (limit of determination of 0.01 mg/kg)
were found in samples of coffee beans obtained from either 'green' or
air-dried cherries. These latter and other data on beans are given in
Table 3. As coffee is exported only as dried, 'green' beans, without
the skin or flesh of the fruit, it is considered that residues are
unlikely to occur in the exported commodity at levels in excess of
0.05 mg/kg.
Peach, nectarine and apricot
Some additional data on peaches, obtained since the 1979
evaluation, are summarized in Table 4. These support the MRL proposed
by the 1979 JMPR. The close similarity between nectarines and
peaches suggests that residue data obtained for peaches could be
applied equally well to nectarines (both are Prunus persicae
varieties). Moreover, the latter fruit have somewhat smoother skins,
are likely to retain less spray deposit than peaches and, hence,
contain somewhat lower residues. The very close physical similarity of
apricots to peaches also suggests that apricots could also be covered
by peach residue data.
TABLE 2. Residues of cypermethrin in fruiting vegetables with edible peel
Application Time References
Rate Between PHI Residues
Crop Variety Country Formulation (g/ha) No. treatment (Days) (mg/kg)
Cucumber Evadan Denmark 10% EC 67 2 10 days 1 0.03 Shell Chimie
(glasshouse) 3 0.02 S.A. 1980a
7 0.02
Amazone Germany 10% EC 60 3 2 weeks 0 0.07
1 0.05 ibid 1980b
3 0.10
4 0.04
7 0.02
Uniflora Germany 10% EC 60 3 2 weeks 0 0.05 ibid
1 0.03
3 0.02
4 0.02
7 <0.01
Sandra Germany 10% EC 60 3 2 weeks 0 0.05
1 0.07 ibid
3 0.05
4 0.05
7 0.03
Corona The Netherlands 10% EC 125 3 1 week 0 0.02,
0.04 ICI 1981c
3 0.01,
0.01
7 0.01,
0.01
14 0.01,
0.01
TABLE 2. (con't)
Application Time References
Rate Between PHI Residues
Crop Variety Country Formulation (g/ha) No. treatment (Days) (mg/kg)
Cucumber Hokus Germany 10% EC 60 3 2 weeks 0 0.02 Shell Chimie
(outdoor) 1 0.04 S.A. 1980b
3 0.01
4 <0.01
7 <0.01
Hokus Germany 10% EC 60 3 2 weeks 0 0.05
1 0.07 ibid
3 0.04
4 0.03
7 0.02
Mervita Germany 10% EC 60 3 2 weeks 0 0.03
1 0.01 ibid
3 <0.01
4 <0.01
7 <0.01
Pepper Sweet Canada 40% EC 70 9 4-6 days 1 0.28 ibid 1978a
(Stoddons 3 0.25
select) 7 0.22
14 0.19
Sweet Canada 25% EC 35 5 1 1/2-4 wks 1 0.02 ICI 1981c
(Emerald 4 0.02
Giant) 7 0.03
14 0.02
22 <0.01
TABLE 2. (con't)
Application Time References
Rate Between PHI Residues
Crop Variety Country Formulation (g/ha) No. treatment (Days) (mg/kg)
Pepper Sweet Canada 25% EC 50 5 1 1/2-4 wks. 1 0.01 ICI 1981c
(Emerald 4 0.02
Giant) 7 0.02
14 0.01
22 0.01
Sweet Canada 25% EC 50 1 - 1 0.09 ibid
(Emerald 3 0.08
Giant) 7 0.11
Chilli India 10% EC 50 1 - 7 0.50 Shell Chimie
14 0.23 S.A. 1980c
75 1 - 7 0.76 ibid
14 0.54
100 1 - 7 1.00 ibid
14 0.59
Eggplant Long France 40% EC 112 1 - 2 0.10 ibid 1976a
Black 7 0.04
15 0.01
TABLE 3. Residues of cypermethrin in coffee
Application
Rate PHI Residues References
Crop Part Country Formulation (g/ha) No. (Days) (mg/kg)
Coffee Dried Brazil 40% EC 5 1 4 weeks <0.01 Shell Chimie
beans 16 weeks <0.01 S.A. 1980d
10 1 4 weeks <0.01
16 weeks <0.01
Dried Brazil 40% EC 10 1 1 month <0.01 ibid 1981a
beans
Beans ex Brazil 25% EC 10 1 1 day <0.01
dried 3 days <0.01 ICI 1981c
cherries 6 days <0.01
17 days <0.01
31 days <0.01
Beans ex Brazil 25% EC 10 1 1 day <0.01 ibid
green 3 days <0.01
cherries 6 days <0.01
17 days <0.01
31 days <0.01
Brazil 25% EC 20 l 1 day <0.01 ibid
3 days <0.01
6 days <0.01
17 days <0.01
31 days <0.01
Brazil 25% EC 40 1 1 day <0.01 ibid
3 days <0.01
6 days <0.01
17 days <0.01
31 days <0.01
TABLE 4. Additional residue data for cypermethrin in peaches
Application Time References
Rate Between PHI Residues
Variety Country Formulation (g/ha) No. treatment (Days) (mg/kg)
Redhaven Canada 20% WP 140 4 2-4 0 0.34, 0.38, 0.38 Shell Chimie S.A.
0.51, 0.60 1980e
3 0.31, 0.36, 0.36
0.38, 0.48
7 0.21, 0.23, 0.24
0.25, 0.38
Loring Canada 20% WP 140 5 2 0 0.42, 0.52, 0.52 ibid 1981b
7 0.35, 0.26
140 4 2 14 0.17, 0.25, 0.19
7 0.34, 0.20
21 0.04, 0.15
Loring Canada 12.5% 60 4 3-31/2 1 0.25 ICI 1981c
3 0.15
8 0.06
14 0.09
100 4 3-31/2 1 0.32
3 0.23
8 0.15
14 0.15
120 4 3-3 1/2 1 0.72
3 0.38
8 0.44
14 0.21
TABLE 4. (con't)
Application Time References
Rate Between PHI Residues
Variety Country Formulation (g/ha) No. treatment (Days) (mg/kg)
Dixired France 5% EC 30 1 - 1 0.04 Shell Chimie
7 0.03 S.A. 1980f
14 0.02
Additional data on certain crops already reviewed
The following residue data complement data already considered by
the 1979 JMPR.
Cherry and plum
A summary of recent data on cherries is given in Table 5. As
cherries were considered together with plums by the 1979 JMPR, new
data on plums are also presented (Table 6). These new data are
compatible with those available in 1979.
Wheat
New residue information on wheat grain has been obtained from
trials in Europe and Canada and is summarized in Table 7. It can be
seen that several figures are near to 0.1 mg/kg. As these data were
derived from experiments with rather low treatment rates (use against
aphids rather than the less sensitive pests) it is not, therefore,
possible to be reasonably assured that maximum levels arising from
current recommendations will fall below 0.1 mg/kg.
Cottonseed
In addition to the extensive data considered in 1979, further
information has been provided from more recent supervised trials in
the USA. Multiple applications of cypermethrin were made in 1979 and
in 1980 with commercial type spray equipment at a total of twelve
cotton fields. The sites were distributed among nine States coast to
coast California, Arizona, Texas, Louisiana, Arkansas, Mississippi,
Alabama, Georgia and North Carolina - and at six of the sites
cypermethrin was applied by air. Some trial programmes included 24%
and 36% EC formulations. Up to 16 applications were made at rates up
to 0.13 kg a.i./ha/application. Higher application rates were also
used in some of the trials (Table 8). Cotton was harvested 13 to 74
days after the last application (Ussary 1980, 1981).
Residue samples normally consisted of approximately 1 kg of
mature crop. Samples of bolls, separated from burrs in the field,
were shipped frozen to the analytical laboratory, where they were
transferred immediately on arrival to a freezer maintained at -18°C.
Samples were ginned, milled and analysed by gas-chromatography using
an electron capture detector (as reviewed at the 1979 Meeting).
The US label involves spraying at 0.07-0.13 kg a.i./ha, with up
to sixteen applications per season and with a minimum pre-harvest
withholding interval of 14 days. The results of this residue trial
programme are shown in Table 8. There was no obvious difference in
residue levels yielded by 24% and 36% EC formulations under similar
circumstances (Table 8) (Ussary 1980, 1981).
TABLE 5. Residues of cypermethrin in cherries
Application Time References
Rate Between PHI Residues
Variety Country Formulation (g/ha) No. treatment (Days) (mg/kg)
Rubin Germany 10% EC 0.01% 3 2 weeks 0 1.3 Shell Chimie, S.A.
(150 g/ha) 4 0.80 1980h
7 0.40
10 0.29
14 0.17
Germany 8% WP 0.008% 3 2 and 1 week 0 1.3 ibid 1981 c
(120 g/ha) 4 0.6
7 0.54
10 0.27
14 0.22
Schatten Germany 8% WP 0.008% 3 2 and 1 week 0 0.47
Morelle (120 g/ha) 4 0.39
7 0.25
10 0.18
14 0.08
Rubin Germany 8% WP 0.008% 3 2 and 1 week 0 2.0
(120 g/ha) 4 0.70
7 0.35
10 0.25
14 0.11
TABLE 6. Residues of cypermethrin in plums, Fed. Rep. of Germany1
Application Time Residues
Rate between PHI
Variety Formulation2 (g/ha) No. treatments (days) (mg/kg)
Auerbacker 8% WP 120 5 2-3 weeks 0 0.08
7 0.07
14 0.06
21 0.05
Ortenberg 8% WP 120 5 2-3 weeks 0 0.04
7 0.02
14 <0.01
21 <0.01
Hauszwetsche 8% WP 120 5 2-3 weeks 0 0.1
7 0.09
14 0.08
21 0.06
1 Reference-Shell Chimie S.A. 1981d;
2 Cypermethrin was applied in admixture with fenbutatin oxide in all these experiments.
TABLE 7. Residues of cypermethrin in wheat grain
Application Time (days) Residues
Rate between PHI
Country Variety Formulation (g/ha) No. treatments (days) (mg/kg) Reference
Canada Neepawa 40% EC 28 1 - 10 0.04,0.05 Shell Research
24 0.04,0.03,0.03 Ltd. 1981e
49 0.02,0.08,<0.01
3 24 and 14 10 0.05,0.07,0.01
28 1 - 20 0.03,0.03,0.02,0.02
32 0.03,0.02,0.01,0.02
57 0.03,<0.01,0.01,0.01
3 24 and 12 20 0.07,0.08
28 1 - 20 0.02,0.02,0.03
32 0.02,0.03,0.03,0.03
57 <0.01,<0.01,<0.01,<0-01
3 24 and 12 20 0.03,0.03,0.04,0.04
28 1 - 32 0.05,0.05,0.06,0.05
40 0.03,0.02,0.03,0.03
62 0.02,0.01,0.02,0.02
3 22 and 9 32 0.08,0.09,0.07,0.12
Denmark 10% EC 50 1 - 42 <0.01 Shell Chimie
10% EC 50 1 - 42 <0.01 S.A. 1981d
UK 25% EC 30 1 - 18 <0.01
32 <0.01 ICI 1981c
60 1 - 18 <0.01
32 <0.01
TABLE 8. Residues of cypermethrin on cottonseed, 1979 and 1980 USA field trials1
Cypermethrin (mg/kg)3
Trial No. Formulation Application Days after
Rate last application 0.07 0.09 0.11 0.13 0.26 0.53
and location Type No. (gal/acre) to harvest Check kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha
38AZ 79-006 24% EC 10 26 14 <0.05 <0.05
Yuma, AZ
38AZ79-005 24% EC 11 5 14 <0.05 <0.05
Yuma, AZ 36% EC 11 5 14 <0.05
(aerial) 24% EC 11 5 74 <0.05 <0.05
36% EC 11 5 74 0.07
28GA79-003 24% EC 11 13.5 66 <0.05 0.05
Smithville,GA
28GA79-004 24% EC 12 5 61 <0.05 0.05
Smithville,GA 24% EC 12 5 61 <0.05
(aerial)
29MS79-014 24% EC 6 12.9 72 <0.05 <0.05
Greenwood, MS
06AR79-008 24% EC 5 8 40 <0.05
Scott, AR
20TX79-009 24% EC 7 7.3 55 <0.05 <0.05
Still Store, TX
EU1-79-03 24% EC 5 19.6 64 <0.05 <0.05
Goldsboro, NC 36% EC 5 19.6 64 <0.05
24% EC 5 19.6 64 <0.05
TABLE 8. (con't)
Cypermethrin (mg/kg)3
Trial No. Formulation Application Days after
Rate last application 0.07 0.09 0.11 0.13 0.26 0.53
and location Type No. (gal/acre) to harvest Check kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha
EU1-70-04 24% EC 5 19.6 64 <0.05
Goldsboro, NC
45AL80-008 36% EC 16 10.2 14 <0.01 0.05 0.01
Shorter, AL 24% EC 16 10.2 14 <0.01
42AZ80-004 36% EC 16 32 14 0.08 0.13 0.11
Peoria, AZ 24% EC 16 32 14 0.02
38AZ80-011 36% EC 16 5 14 0.02
Yuma, AZ (air)
41CA80-007 36% EC 16 20 13 0.31 0.52
Visalia, CA 24% EC 16 20 13 <0.01 0.13
28GA80-021 36% EC 16 10 14 <0.01 0.02
Athens, GA
28GA80-023 36% EC 16 4 14 0.01
Cochran, GA (air)
36LA80-010 36% EC 16 5 14 0.01
Jonesville, LA
(air)
29MS80-002 36% EC 16 6 16 0.07 0.16
Glen Allan, MS
TABLE 8. (con't)
Cypermethrin (mg/kg)3
Trial No. Formulation Application Days after
Rate last application 0.07 0.09 0.11 0.13 0.26 0.53
and location Type No. (gal/acre) to harvest Check kg/ha kg/ha kg/ha kg/ha kg/ha kg/ha
29MS80-003 36% EC 16 2 16 <0.01 0.01
Glen Allan, MS
(air)
43MS80-023 36% EC 16 8.2 31 <0.01 0.03 0.13
Rocky Mounts, NC
33TX80-002 36% EC 16 3 14 <0.01 0.05
Wilson, TX (air)
33TX80-009 36% EC 16 41 14 <0.01 0.05 0.16
Lorenzo, TX
1 Reference - Ussay 1980, 1981
2 US gallons/acre = 9.3 litres/hectare
3 values corrected for analytical recovery.
Data relating to the use of cypermethrin-treated crops as animal
feed
The crop commodities likely to be the main source of cypermethrin
residues in animal feed are fodder crops and legume crops. Although
other components of animal feed, such as cottonseed cake or dried
fruit pomace, may contain residues of cypermethrin, these will be
either at low levels, or the product will form only a relatively small
proportion of the total daily ration, so that residues in feeds from
these sources will not be the determining factor in considering
maximum residue limits.
Residue data for fodder crops including straw are given in Table
9 (recommendations for the use of cypermethrin and data on residues in
grain components of the crops have previously been examined by the
JMPR in 1979). Data for legume crops (alfalfa) are given in Table 10.
The data cover a wide range of levels, depending on crops and
conditions. However, as cattle may be given feed prepared shortly
after treatment, it would seem that estimates of maximum levels that
could occur in feed should be estimated from the higher residues
arising from short pre-harvest intervals.
From the information available, therefore, it is considered that
residues in animal feed components are unlikely to exceed 10 mg/kg in
total diet but will, in most instances, be considerably below this
level.
FATE OF RESIDUES
In animals
Cow
Studies have been undertaken to investigate the fate of
cypermethrin in cattle and to establish at what level of residues in
meat or milk could arise as a result of feeding crop products treated
with cypermethrin as cattle feed. Separate experiments have been
carried out using both radio-labelled material and technical
(unlabelled) cypermethrin. In these experiments feeding levels
corresponding to between 0.2 and 50 mg/kg of the total daily ration
have been used to investigate the fate and magnitude of residues which
could occur following the use of feed components containing residues
at various levels.
Trials carried out in Australia (Australia 1981) with
cypermethrin emulsion designed for spraying cattle as protection
against buffalo fly involved the application of 200 ml of spray
containing 1 g/l cypermethrin (i.e. 200 mg/animal), the recommended
TABLE 9. Residues of cypermethrin in fodder crops
Application Time
Rate between PHI Residues Reference
Crop Crop part Country Formulation (g/ha) No. treatments (days) (mg/kg)
Maize Stems USA EC 30 1 - 4 2.6 ICI 1981c
7 0.92
14 0.89
60 1 - 4 6.9
7 2.0
14 2.6
Husks 30 1 - 4 0.54
7 0.37
14 0.23
60 1 - 4 1.1
7 0.54
14 0.62
Whole plant S. Africa 20% EC 15 1 - 1 0.11 ibid
2 0.06
4 0.07
16 <0.05
32 0.20
30 1 - 1 0.12
2 0.06
4 0.13
8 0.08
16 0.13
32 0.07
TABLE 9. (con't)
Application Time
Rate between PHI Residues Reference
Crop Crop part Country Formulation (g/ha) No. treatments (days) (mg/kg)
Stalks and leaves Canada 40% EC 50 5 4-7 days 9 0.83 Shell Chimie
(at maturity) 70 5 4-7 days 9 1.80 S.A. 1980g
Stems and leaves Canada 40% EC 50 5 5 days 1 1.7 Shell Research
(at maturity) 3 1.4 Ltd. 1981a
14 0.7
Husks Canada 40% EC 50 5 5 days 1 0.92 ibid
3 0.65
14 0.25
Green maize Fed. Rep. of 10% EC 100 1 - 0 2.9 Shell Chimie
Germany 7 1.1 S.A. 1979a
14 0.15
10% EC 100 1 - 0 1.9 ibid
7 0.5
14 0.12
Green maize Fed.Rep. of 10% EC 100 1 - 0 2.7 ibid
Germany 7 2.2
14 0.51
Green maize S. Africa - 120 1 - 14 0.8 Shell Research
Ltd.1977a
240 1 - 14 2.0
TABLE 9. (con't)
Application Time
Rate between PHI Residues Reference
Crop Crop part Country Formulation (g/ha) No. treatments (days) (mg/kg)
Wheat Straw Canada 40% EC 140 1 - 13 8.5 Shell Chimie
20 5.4 S.A.1977a
27 1.9
Green plant Canada 40% EC 140 0 6.5 ibid 1977b
6 4.3
0 7.3
6 4.3
13 3.8
0 8.1
6 4.5
13 2.8
20 1.9
Green plant UK 25% EC 30 1 - 18 0.67 ICI 1981c
32 0.58
60 1 - 18 1.3 ibid
32 0.64
Straw UK 25% EC 30 1 - 18 1.5
32 1.2
60 1 - 18 1.8
32 1.7
TABLE 9. (con't)
Application Time
Rate between PHI Residues Reference
Crop Crop part Country Formulation (g/ha) No. treatments (days) (mg/kg)
Sorghum Whole plant S. Africa 20% EC 15 1 - 1 0.88 ibid
4 0.67
30 1 - 1 3.1
2 2.2
4 2.4
8 2.1
16 1.8
32 1.5
Sorghum Heads S. Africa 20% EC 40 1 - 0 0.76 Shell Research
1 0.78 Ltd. 1980a
2 0.61
4 0.60
8 0.37
70 1 - 0 1.2 ibid
1 0.82
2 0.55
4 0.74
8 0.79
140 1 - 0 1.5 ibid
1 1.4
2 1.2
4 1.2
8 1.4
TABLE 9. (con't)
Application Time
Rate between PHI Residues Reference
Crop Crop part Country Formulation (g/ha) No. treatments (days) (mg/kg)
Australia 20% EC 80 1 - 0 1.7 ibid 1980b
3 1.3
7 1.7
14 1.2
160 1 - 0 2.3 ibid
3 2.7
7 2.3
14 2.2
S. Africa 20% EC 30 1 - 1 0.47 ICI 1981c
2 0.58
4 0.49
8 0.82
16 0.44
32 0.70
TABLE 10. Residues of cypermethrin in legume animal feeds
Application Time
Rate between PHI Residues Reference
Crop Country Formulation (g/ha) No. Treatments (Days) (mg/kg)
Alfalfa Canada 4% EC 28 1 - 1 2.00,2.50 Shell Research
Green 2 0.12,0.19 Ltd.1981b
8 0.4
Hay USA 24% EC 25 2 26 days 41 0.73 ICI 1981c
61 0.64
101 0.8
50 2 26 days 41 1.6
61 1.8
101 1.8
Green USA 24% EC 70 1 - 23 0.51,0.55,0.45 ibid
36 0.82,0.10
140 1 - 23 0.21,1.4
36 0.30,1.8,1.0 ibid
Green USA 24% EC 25 2 26 days 12 0.68 ibid
72 0.37
50 2 26 days 12 0.95
72 0.74
1 includes 3 days drying time, dry matter content 65.7%
2 Dry matter content 33.3%.
rate, or various higher rates up to 500 ml of a 1.5 g/l emulsion
(i.e. 750 mg/animal) to dairy cows from which milk was collected 7 and
24 h later.
The only residues detected were in 2 of 6 milk samples taken 7 h
after spraying the cows with 750 mg cypermethrin, i.e. 3.75 times the
recommended rate of application. No residues were found in samples
from cows treated at the recommended rate or at 2.5 times the
recommended rate of application or in any samples collected 24 h after
spraying.
Trials were carried out with cypermethrin prepared as a dip
against cattle tick and buffalo fly and containing 75 mg/l of dip wash
(Australia 1981). Six dairy cows were dipped, and milk collected 1, 3
and 7 days later was analysed for cypermethrin. Low concentrations of
cypermethrin, 0.002 to 0.010 mg/l were found in milk taken up to 3
days after treatment, with a mean value of 0.003 mg/l. By the end
of the 7 days, the residues had declined to below the limit of
determination (0.002 mg/l). A second dipping 8 days after the first
did not produce any evidence of accumulation of cypermethrin from the
cow in the milk.
In a third study (Australia 1981), in which a cypermethrin spray
designed to control buffalo fly was applied to dairy cows at the rate
of 100 mg/l and 200 mg/l (200 ml/animal), cypermethrin residues were
found to range up to 0.035 mg/kg one day after treatment in butterfat.
They then decreased slowly over a period of 10 to 13 days. The details
are given in Tables 11 and 12.
Fifteen cattle were treated by dipping in cypermethrin at the
recommended concentration of 75 mg/l (Australia 1981). Three of the
animals were subjected to a second dipping 8 days later. Three animals
were slaughtered on each of days 1, 3, 4, 7 and 14 following dipping.
Those on day 14 were the 3 that had been dipped a second time on day
8.
A commercial dairy herd was treated with an overall spray at the
rate of 200 ml/animal. The solution had a concentration of 1 g/l. One
litre samples were taken from the bulk milk vat at 1, 3, 7, 10 and 13
days post-treatment. The samples were kept frozen until analysed. The
results are given in Table 12.
Samples of omental fat, perirenal fat, muscle, liver and kidney
were taken from each animal and analysed for cypermethrin by a
method sensitive to 0.01 mg/kg. The highest residue detected was
0.02 mg/kg in omental fat from two animals 3 and 4 days after dipping,
respectively. There was no evidence that the first dipping caused any
build-up of cypermethrin in cattle tissues. Liver, kidney and muscle
contained no detectable residues.
TABLE 11. Mean cypermethrin residues in butterfat samples
Residue (mg/kg)
Animal
number Day 0 Day 1 Day 3 Day 7 Day 10 Day 13
am pm am pm am am pm pm
14 ) treatment 0.013 0.018 0.035 0.022 0.024 0.019 <0.01
118 ) 0.1% a.m. 0.024 0.026 0.028 0.025 0.032 - <0.01
267 ) <0.01 0.026 0.024 0.022 0.022 0.035 <0.01
Bulk vat 0.01 as pre-treatment sample
TABLE 12. Cypermethrin residues in butterfat samples taken from bulk milk vat
Residue (mg/kg)
Day 0 Day 1 Day 3 Day 7 Day 10 Day 13
am pm am pm am am pm pm
Bulk ) <0.011 0.028 0.046 0.032 0.021 0.019 0.024 <0.01
Vat )
Samples )
1 Pre-treatment.
Twenty four cattle were sprayed with 200 ml cypermethrin emulsion
containing 100 mg/l and 200 mg/l cypermethrin (12 with each rate -
recommended rate and 2 × recommended rate). Three animals from each
group were slaughtered on days 1, 3, 7, 10 and 13 after spraying.
Those slaughtered on day 13 were first sprayed a second time on day 8.
Samples of omental fat, perirenal fat, liver, kidney and muscle were
analysed for cypermethrin by methods sensitive to 0.005 mg/kg in
liver, kidney and muscle and 0.01 in fat. The only residues detected
were in omental fat and perirenal fat from animals sprayed twice at
the double rate and slaughtered 7 days following the second treatment.
The residue level in these samples ranged up to 0.036 mg/kg (4 times
the limit of sensitivity) (Australia 1981).
Experiments using radio-labelled cypermethrin were carried out
on separate occasions in which cattle were given feed concentrate
containing cypermethrin equivalent to 0.2, 5.0 and 10.0 mg/kg in
the total daily feed (Shell Research Ltd. 1978a, 1979a, 1980c).
Measurement of radioactivity in urine and faeces showed that the major
excretory route was into the urine and only small amounts were
excreted in the milk. A small proportion of the ingested cypermethrin
remained in the body at the end of the feeding period. Details of the
studies on milk and tissues are described.
At the 0.2 mg/kg feeding level, two lactating cows were given
treated feed concentrate (containing cypermethrin, 14 C-benzyl
labelled) twice daily over a 3-week period. The radioactivity present
in whole milk over this time ranged from 0.0003 mg/l to 0.0012 mg/l
cypermethrin equivalents. 60-70% of this radioactivity was present in
the cream and totalled about 0.5% of the cypermethrin fed to the
animals.
At the end of the 3-week feeding period, the animals were
slaughtered and samples of tissue examined. Levels were below
0.001 mg/kg cypermethrin equivalents in blood, muscle and brain. In
subcutaneous fat, renal fat, liver and kidney, residues were present
in small amounts up to 0.012 mg/kg cypermethrin equivalents.
In order to complement information from the 0.2 mg/kg experiment,
5 mg/kg radio-labelled cypermethrin (labelled in either the benzyl or
cyclopropyl ring) was fed daily to cows over a 7-day period. Rates of
intake and excretion of radioactivity were similar after 3 to 4 days,
after which levels in whole milk ranged between 0.009 mg/l and
0.013 mg/l radioactivity, in terms of cypermethrin equivalents.
At the end of the test feeding period the animals were
slaughtered and the tissues examined. The following results were
obtained (expressed as cypermethrin equivalents). These were similar
for either labelled position.
Muscle < 0.04 mg/kg
Fat 0.01-0.10 mg/kg
Liver and kidney 0.05-0.13 mg/kg
An experiment using a single animal given 10 mg/kg 14C-benzyl-
labelled cypermethrin in feed, also over a 7-day period, was carried
out with the objective of developing further information on the nature
of some of the major components of residues in fat, liver and kidney.
Total residues in tissues were as anticipated from the previous
experiments (muscle 0.01 mg/kg, fat 0.08 to 0.10 mg/kg, liver and
kidney 0.21 and 0.11 mg/kg and milk levels 0.01 to 0.03 mg/kg).
Further studies on the nature of the compounds present showed
that residues in tissue fat and in milk consisted almost entirely of
cypermethrin, whereas in liver and kidney they were largely of
3-phenoxybenzoic acid conjugated with glutamic acid. In these latter
tissues, there were also indications of the presence of small amounts
of unchanged cypermethrin and 4-hydroxy-3-phenoxybenzoic acid.
Experiments with non-labelled material were carried out using
three feeding levels 0.2, 5.0 and 50 mg/kg in the daily diet over a
4-week period. Analyses of tissues and milk for cypermethrin were made
and gave the results shown in Tables 13 and 14 (ICI 1981a, b).
These data show that residues of cypermethrin in muscle were
at or below the limit of determination of 0.01 mg/kg at a feeding
level of 5 mg/kg or less and that similar levels were present in
liver and kidney. Following feeding at the higher level of 50 mg/kg,
cypermethrin residues in these tissues varied between 0.02 mg/kg and
0.45 mg/kg, but were mostly below 0.2 mg/kg, apart from kidney.
Residues of cypermethrin in fat were, as expected, higher than in
other tissues and were roughly in proportion to the feeding rate with
cypermethrin. Levels ranged from at or near the limit of determination
at a feeding level of 0.2 mg/kg to 0.10 to 0.34 mg/kg at 5 mg/kg and
2.3 to 5.3 mg/kg at a feeding rate of 50 mg/kg.
Comparison of the levels present in feed with those in fat
shows that even at the high rate of feeding (50 mg/kg) the level of
cypermethrin in fat was seldom more than one tenth of the level in the
feed.
In milk, residues were below the limit of determination of
0.005 mg/kg in whole milk at the lowest feeding rate, but at the two
higher levels ranged as follows:
Feeding level Range of data
5 mg/kg 0.008 - 0.037 mg/kg
50 mg/kg 0.15 - 0.49 mg/kg
TABLE 13. Cypermethrin residues in cow tissues
Cypermethrin residue (mg/kg)-duplicate analysis
Feeding rate Cow
(mg/kg) No. Muscle Fat Liver Kidney
adductor pectoral cardiac subcutaneous peritoneal
0.2 4 <0.01, 0.01 <0.01, 0.01 <0.01, 0.01 <0.01, 0.01 0.01, 0.01 <0.01,<0.01 <0.01, 0.02
0.2 5 <0.01,<0.01 <0.01,<0.01 <0.01,<0.01 0.01, 0.01 0.02, 0.02 <0.01,<0.01 0.01,<0.01
0.2 61 <0.01,<0.01 <0.01,<0.01 <0.01,<0.01 0.01,0.01 0.01, 0.01 <0.01, 0.01 <0.01,<0.01
5.0 7 <0.01, 0.01 <0.01,<0.01 0.01, 0.01 0.16, 0.17 0.34, 0.32 <0.01,<0.01 0.01, 0.03
5.0 8 <0.01,<0.01 0.01,<0.01 0.01, 0.01 0.09, 0.10 0.20, 0.17 <0.01, 0.01 0.03, 0.01
5.0 91 <0.01,<0.01 0.02, 0.01 0.02, 0.01 0.16, 0.15 0.25, 0.21 <0.01,<0.01 0.02, 0.01
50 10 0.07, 0.08 0.09, 0.09 0.13, 0.11 2.3 ± 0.242 2.7, 2.8 0.05, 0.04 0.27, 0.25
50 11 0.16, 0.16 0.47±0.052 0.11, 0.11 4.1 3.3 5.3, 5.2 0.02, 0.02 0.45, 0.43
50 121 0.06, 0.05 0.09, 0.09 0.09, 0.08 2.1, 1.9 1.6, 1.5 <0.01, <0.01 0.07, 0.08
Control 3 <0.01,<0.01 <0.01,<0.01 <0.01 <0.01 <0.01 <0.01 <0.01
1 Animal was allowed a seven-day recovery period; 2 mean and standard deviation obtained from seven independent analyses.
TABLE 14. Cypermethrin residues in milk
Cypermethrin residues (mg/kg) in bulked am and pm samples
Feeding
Rate Cow Pre-
(mg/kg) Number treatment
Day - 1 Day 1 Day 3 Day 5 Day 10 Day 15 Day 21 Day 25 Day 28 Day 29 Day 30 Day 32 Day 34 Day 36
4 <0.005
5 <0.005
0.2 6 <0.005 <0.005 <0.005 <0.005 <0.005
Group B <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005
7 0.022
8 0.025
5.0 9 0.034 0.010 <0.005 <0.005 <0.005
Group C <0.005 <0.005 0.021 0.037 0.016 0.021 0.016 0.015 0.015 0.008
10 0.177
11 0.3921
± 0.06
50 12 0.492 0.142 0.017 0.016 0.012
Group D <0.005 <0.005 0.231 0.152 0.223 0.207 0.202 0.211 0.204
TABLE 14. (con't)
Cypermethrin residues (mg/kg) in bulked am and pm samples
Feeding
Rate Cow Pre-
(mg/kg) Number treatment
Day - 1 Day 1 Day 3 Day 5 Day 10 Day 15 Day 21 Day 25 Day 28 Day 29 Day 30 Day 32 Day 34 Day 36
1
Control 2
3 <0.005 <0.005
Group A <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005
1 Mean and standard deviation obtained from six replicate analyses.
At the conclusion of the 4-week feeding period one animal in each
group was retained on a cypermethrin-free diet for a further 7 days.
The results of the analysis of the milk and tissues from these animals
showed that cypermethrin excretion in milk fell rapidly during this
extra period without cypermethrin. There was also a fall in tissue
residue levels, particularly in liver and kidney, which fell below the
limit of determination in liver, even in the case of the animal fed at
50 mg/kg.
Samples from animals fed at 50 mg/kg were also analysed for
DCVA, 3-(2,2-dichlorovinyl) -2,2-dimethylcyclopropane carboxylic acid,
and 3-phenoxybenzoic acid. These data are summarized in Table 15.
The levels of 3-phenoxybenzoic acid were low (below 0.05 mg/kg) in
muscle and fat, but were higher in liver and kidney ranging up to
0.26 mg/kg. Residues of DCVA were higher in most tissues than those of
3-phenoxybenzoic acid, generally by a factor of 3 to 4, but were
similar in the case of liver.
In milk, residues of both metabolites were at or below the limits
of determination of 0.01 to 0.02 mg/l. As expected, levels of the
metabolites, as in the case of the parent compound, fell during the
subsequent feeding period of 7 days on a cypermethrin-free diet. These
data are compatible with the results of the experiments using radio-
labelled material, bearing in mind that analyses were carried out for
specific products and that feeding was for more extended periods.
The crop data reviewed indicate that residue levels in cattle
feed components may occasionally approach 10 mg/kg, although in most
cases they would be considerably below this level. In general,
therefore, it is felt that residue levels averaged over the whole diet
would seldom be above 5 mg/kg.
From the information cited on cattle feeding experiments it may,
therefore, be concluded that residues of cypermethrin in products of
animal origin from stock given feed prepared from cypermethrin-treated
crops are not likely to exceed the following:
Carcass fat 0.2 mg/kg
Muscle 0.05 mg/kg
Liver and kidney 0.2 mg/kg
Whole milk 0.05 mg/kg
Sheep
Six sheep were dipped in a cypermethrin dip containing 25 mg/l
cypermthrin (1.5 × recommended rate) and samples were collected
from 3 sheep following slaughter the next day and from the other
3 slaughtered 7 days after dipping. Residues were detected only in
sheep slaughtered one day after treatment. The highest residue level
TABLE 15. Levels of cypermethrin, DCVA and 3-phenoxybenzoic acid in milk and tissues of cows receiving
55:45 cis: trans cypermethrin at 50 ppm in the diet for 28-29 days
Levels (µg/g)
Treatment
Regime Residue Muscle Fat
Milk adductor pectoral cardiac subcutaneous peritoneal Kidney Liver
50 ppm in Cypermethrin 0.15-0.231 0.07-0.16 0.09-0.49 0.11-0.13 2.3 -4.1 2.7 -5.3 0.25-0.45 0.02-0.05
diet for DCVA <0.011 0.04-0.07 0.05-0.016 0.19-0.21 0.03-0.05 0.04-0.06 0.42-0.44 0.13-0.22
28-29 days 3-phenoxybenzoic
acid <0.02 0.01-0.02 0.02 0.05 0.02 0.03-0.04 0.12-0.15 0.13-0.26
As above, Cypemethrin 0.01 0.05-0.06 0.09 0.08-0.09 1.9 -2.1 1.5 -1.6 0.07-0.08 <0.01
then a DCVA <0.01 0.02 0.03 0.04 <0.01 <0.01 0.06 0.04
further 3-phemoxybenzoic
7 days on acid <0.01 0.01 0.03 0.03 0.02 0.01 0.02 0.07
untreated
diet
1 Plateau levels.
was 0.51 mg/kg in liver. Residues in muscle and fat from the same
animals were 0.18 mg/kg. The limit of determination in liver and
muscle was 0.005 mg/kg and in fat 0.01 mg/kg (Australia 1981).
In plants
In 1979 the Meeting considered the degradation of cypermethrin in
plants, especially cotton, lettuce and apples. Most of these studies
involved radio-labelled compound. Since then the results of studies on
apples, pears, maize and potatoes have become available.
Trials were carried out in Canada during 1978 (Shell Research
Ltd. 1979 b,c,d,e) in which an EC formulation of cypermethrin was
applied to apple trees, pear trees, maize and potatoes and residue
levels in the crops were measured at harvest (Table 16).
TABLE 16. Cypermethrin found in various crops at harvest
Application Interval after last
Crop treatment at which
No. Rate samples were taken
Apple 1 70 12 weeks
7 150 8 weeks
Pear 2 70 12 weeks
4 30 5 weeks
Maize 3 75 3 days
5 70 7 days
Potato 4 150 7 days
Samples from each crop were analysed for three plant metabolites:
3-phenoxybenzoic acid (free and conjugated); 2,2-dimethyl-3-
(2,2-dichlorovinyl)cyclopropane-carboxylic acid (free and conjugated);
and alpha-amino-3-phenoxybenzyl-2, 2-dimethyl-3-(2,2-dichlorovinyl)
cyclopropanecarboxylate, either by high performance liquid
chromatography (HPLC) with UV detection, gas chromatography/mass
spectography or gas chromatography with electron capture detection. No
detectable residues of any of the metabolites were found in the
samples when analysed by a method with a limit of determination of
0.05 mg/kg.
NATIONAL MAXIMUM RESIDUE LIMITS
National maximum residue limits reported to the Meeting are shown
in Table 17.
TABLE 17. National maximum residue limits reported to the Meeting
Country Commodity MRL PHI
(mg/kg) (days)
Australia fat of meat of cattle 0.1 3
fat of meat of sheep and goats 0.02 3
milk and milk products (fat basis) 0.1 -
cottonseed 0.2 14
cottonseed oil 0.02 -
soybean 0.05 14
soybean oil 0.1 -
stone fruit (except cherries) 1.0 14
navy beans 0.05 7
mung beans 0.05 7
S. Africa cottonseed 0.05 28
maize 1.5 28
Yugoslavia grape 0.5 28
pear 0.5
Fed. Rep.of Germany maize 5 49
EVALUATION
COMMENTS AND APPRAISAL
Cypermethrin, although not well absorbed from the gastro-
intestinal tract, appears generally to be rapidly metabolized and
excreted from the body with little potential for accumulation in
tissues.
Data were available on exposure of spray applicators, which
were considered to satisfy the requirements of the previous JMPR.
The exposure was monitored by measurements of the metabolite
3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid in the
urine.
A two-year feeding study in beagle dogs was also evaluated and a
no-effect level of 300 ppm in the diet was determined.
Since cypermethrin was first evaluated in 1979 a considerable
amount of additional data have been made available to the Meeting.
This includes information on new and extended uses on a variety of
crops and on livestock. Residue data from many supervised residue
trials on peaches, cherries, plums and wheat grain (pre-harvest) have
confirmed the MRLs recommended in 1979.
Residue data on cucumbers, sweet peppers, chilli peppers,
eggplants, coffee, alfalfa and other animal feeds have enabled the
Meeting to recommend additional MRLs. The Meeting proposes that the
MRL for nectarines should be the same as for peaches and that the
limit for cypermethrin residues in cottonseed should be increased.
The recommendation concerning wheat, questioned at the 13th
Session of the CCPR, has been confirmed. The Meeting considers that,
in view of the evidence of residues regularly approaching 0.1 mg/kg
(0.08 etc.) and the problems known to occur in sampling and analysing
cereal grains for residues such as cypermethrin, it would be prudent
not to reduce the limit to 0.1 mg/kg but to retain the previous
recommendation of 0.2 mg/kg knowing that most of this residue will be
removed with the bran in the processing of the cereal grain for
consumption.
The new evident available to the Meeting enables it to better
define the residue in alfalfa and to recommend a new limit based in
the dry (12% moisture) commodity.
Extensive studies on the spraying, dipping and feeding livestock
with cypermethrin have provided a new basis for recommending MRLs in
foods of animal origin. Cypermethrin is virtually insoluble in water
and it partitions preferentially into animal fats. The Meeting
therefore proposed MRLs based on the concentration likely to be found
in the fat of meat and milk.
Level causing no toxicological effect
Rat: 100 ppm in the diet, equivalent to 5.0 mg/kg bw/day
Dog: 300 ppm in the diet, equivalent to 7.5 mg/kg bw/day
Estimate of acceptable daily intake for man
0 - 0.05 mg/kg bw
RECOMMENDATIONS OF RESIDUE LIMITS
The following new and amended maximum residue limits are
recommended based on the pre-harvest intervals indicated below. The
limits refer to the sum of the isomers of the parent compound in the
portion of the sample to be analysed as described by CCPR.
3. Results of ongoing studies on residues in soybeans.
Pre-harvest
interval on which
Commodity MRL (mg/kg) recommendation
was based
Cucumber 0.2 1
Sweet pepper 0.5 1
Chilli pepper 0.5 1
Eggplant 0.2 1
Coffee (dried beans) 0.05 -
Nectarine 2 7
Cottonseed 0.21 14
Carcass meat 0.22 nil
Meat by-products 0.2 nil
Milk 0.01 nil
Milk products (fat basis) 0.2 nil
Alfalfa 5 (dry weight basis) 14
Maize fodder 5 (dry weight basis) 14
Wheat straw 5 (dry weight basis) 14
Sorghum fodder 5 (dry weight basis) 14
1 Increase from recommendation made in 1979;
2 the figure applies to carcass fat.
FURTHER WORK OR INFORMATION
Desirable
1. Mutagenicity studies on the metabolite 3-(2,2-dichlorovinyl)-
2,2-dimethyl-cyclopropane-carboxylic acid.
2. Results of ongoing studies on the level and fate of cypermethrin
in poultry and eggs following feeding at levels representing possible
residues in poultry feed.
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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: 1982 evaluations)
Cypermethrin (Pesticide residues in food: 1983 evaluations)
Cypermethrin (Pesticide residues in food: 1984 evaluations)