WHO Pesticide Residues Series, No. 1
1971 EVALUATIONS OF SOME PESTICIDE RESIDUES IN FOOD
THE MONOGRAPHS
The evaluations contained in these monographs were prepared by the
Joint Meeting of the FAO Working Party of Experts on Pesticide
Residues and the WHO Expert Committee on Pesticide Residues that met
in Geneva from 22 to 29 November 1971.1
World Health Organization
Geneva
1972
1 Pesticide Residues in Food: Report of the 1971 Joint Meeting of
the FAO Working Party of Experts on Pesticide Residues and the WHO
Expert Committee on Pesticide Residues, Wld Hlth Org. techn. Rep.
Ser., No. 502; FAO Agricultural Studies, 1972, No. 88.
These monographs are also issued by the Food and Agriculture
Organization of the United Nations, Rome, as document AGP-1971/M/9/1.
FAO and WHO 1972
CHLORFENVINPHOS
IDENTITY
Chemical name
2-chloro-1-(2,4 dichlorophenyl) vinyl diethyl phosphate.
Synonyms
chlorfenvinfos, "Supona" (R), "Birlane" (R)
Structural formula
Chlorfenvinphos exists in two geometric isomeric forms: alpha (=cis)
isomer and ß (=trans) isomer. In the ß (=trans) isomer the vinyl
chlorine atom is opposite to the substituted aryl ring.
The technical material contains not less than 92% of total isomers; a
typical sample contains 9.7% w/w cis-and 83.8% trans-isomer. The alpha
isomer is less insecticidally active than the ß isomer.
Other information on identity and properties
(a) Composition of technical chlorfenvinphos
Analysis of a typical sample of technical chlorfenvinphos gave
the following results:
Component %w
Chlorfenvinphos, cis-isomer (alpha isomer) 9.7
Chlorfenvinphos, trans-isomer (beta isomer) 83.8
1-(2,4-dichlorophenyl)vinyl diethyl phosphate 1.1
2,2 dichloro-1-(2,4-dichlorophenyl) vinyl diethyl
phosphate 3.8
2-chloro-1(3,4-dichlorophenyl) vinyl diethyl phosphate
(cis plus trans isomers) 0.9
alpha, 2,6-trichloroacetophenone 0.6
alpha, alpha, 2,6-tetrachloroacetophenone 0.1
100.0
(b) Physical and chemical properties of technical chlorfenvinphos
Physical state: Liquid at 25°C
Colour: Amber
Odour: Mild chemical
Melting point: -19 to -23°C
Boiling point: 167-170°C at 0.5 mm Hg
Vapour pressure: 1.7×10 mm Hg at 25°C
Specific gravity: 1.36 at 15.6°/15.6°C
Refractive index: n25°C : 1.5272
D
Inflammability: Non-flammable
Solubility: Miscible with aceton, xylene, alcohol,
Kerosene, propylene glycol and Korn oil.
Sparingly soluble in water
Stability: Stable when stored in glass or
polyethylene-lined steel containers
Compatibility: Can be used with most pesticides in
common use
Hydrolysis rate: Half-life in water at 38°C is greater
than 400 hours at pH 9.1, and greater
than 700 hours at pH 1.1
EVALUATION FOR ACCEPTABLE DAILY INTAKE
Biochemical aspects
Absorption, distribution and excretion
Six male and six female rats given an oral dose of 2 mg/kg
(3.0 µci/mg) C14-labelled chlorfenvinphos (labelled in the vinyl
moiety) excreted 51.9-77.4% of the C14 in urine within 24 hours. An
additional 6.1-25.6% was excreted during the next 24 hours. Faecal
elimination comprised 11.2% of the C14, and a further 1.4% was
excreted via the lungs within 96 hours. The total dose was eliminated
within 96 hours (Hutson et al., 1967).
Two male and two female dogs were given capsules orally containing 0.3
mg/kg (8 µCi) of C14-labelled chlorfenvinphos. 86% (82.6-91.4%) and
4.1% of the administered C14 was eliminated in urine and faeces
respectively within 24 hours (Hutson et al., 1967).
Administration of 25-30 mg/kg orally to young rats resulted in
detection of unchanged chlorfenvinphos in peripheral blood. A dog
receiving 88 mg/kg orally showed similar concentrations of unchanged
chlorfenvinphos in peripheral blood at similar time intervals (Hutson
and Hathway, 1967).
The estimated half-life of chlorfenvinphos in the body fat of the
rabbit is about 1 day (Hunter, 1964).
Following intramuscular injection of C14-labelled chlorfenvinphos
(647 µCi, 233 mg) into a lactating cow, only 0.2% of the
radio-activity appeared in the milk, mainly in the first two milkings.
75% of this C14 was secreted as unchanged chlorfenvinphos (Hunter,
1969a).
Oral administration of C14-labelled chlorfenvinphos (35.1 µCi,
12.5 mg) to an adult man resulted in rapid elimination of the C14 in
the urine, 72% of the dose being excreted in 4-1/2 hours, and 94%
within 24 hours (Hutson, 1969).
Biotransformation
In rats, oral administration of 2 mg/kg, C14-labelled
chlorfenvinphos is followed by complete metabolism of the
chlorfenvinphos. Urinary metabolites comprise
2-chloro-1-(21,41,dichlorophenyl) vinyl ethyl hydrogen phosphate
(32.3% of administered C14,
[1-(21,41dichlorophenyl) ethyl ß-D-glucopyranosid] uronic acid
(41.0% of administered C14), 2,4-dichloromandelic acid (7.0% of
administered C14), 2,4-dichlorophenylethanediol glucuronide (2.6% of
administered C14), and 2,4-dichlorohippuric acid (4.3% of
administered C14) (Hutson et al., 1967).
In dogs receiving 0.26 mg/kg C14-labelled chlorfenvinphos complete
metabolism also occurred. The urinary metabolites were present in
different proportions as follows:
2-chloro-1-(21,41 dichlorophenyl) vinyl ethyl hydrogen phosphate,
69.6%; [1-(21,41-dichlorophenyl) ethyl ß-D-glucopyranosid]
uronic acid, 3.6%; 2,4-dichloromandelic acid, 13.4%;
2,4-dichloro-phenylethanediol glucuronide, 2.7%. The
2,4-dichlorohippuric acid was not detected (Hutson et al., 1967).
In the lactating cow following 0.58 mg C14-labelled
chlorfenvinphos/kg injected intramuscularly, the 0.2% radioactivity
found in milk contained 75% unchanged chlorfenvinphos; together with
small amounts of 2,4-dichloroacetophenone, 1-(2,4-dichlorophenyl)
ethanol, and 2,4-dichloromandelic acid. Urinary metabolites comprised
1(2,4-dichlorophenyl) ethanol and 1(2,4-dichlorophenyl) ethanediol.
The glucuronides of these compounds were not detected (Hunter, 1969a).
In man, five metabolites were identified in the urine following a
single oral dose of 12.5 mg C14-labelled chlorfenvinphos. These were
2-chloro-1-(2,4-dichlorophenyl) vinyl ethyl hydrogen phosphate
(23.8%), 2,4-dichloro-mandelic acid (23.9%),
[1-(2,4-dichlorophenyl) ethyl ß-D-glucopyranosid] uronic acid,
2,4-dichlorophenyl-ethanediol glucuronide, and 2,4-dichlorobenzoyl
glycine (Hutson, 1969).
Effects on enzymes and other biochemical parameters
In vitro incubation with dog, rabbit and rat liver slices show the
conversion rates of chlorfenvinphos to
2-chloro-1-(21,41-dichlorophenyl) vinyl ethyl hydrogen phosphate
were 88:24:1 respectively. The enzyme was associated with the
microsomal fraction of rabbit liver homogenate, and possessed the
properties of a hydroxylase, the reaction being an oxidative
0-deethylation (Donninger et al., 1966). In addition, a soluble
de-0-methylation fraction has been isolated from the supernatant
fraction, whose activity is lost after dialysis.
Glutathione appears to act as the methyl acceptor for the soluble
enzyme. Enzyme activity, in similar amounts was found in mouse, rat,
and pig livers (Hutson et al., 1967).
I50 values following incubation with blood of various mammalian
species were 1.6 × 10-6, 1.4 × 10-5, 3.0 × 10-3, 3.9 × 10-6,
4.0 × 10-4, 86.3 × 10-4 for "true" cholinesterase and 1.0 ×
10-14, 6.3 × 10-4, 5.6 × 10-12, 7.0 × 10-5, 1.0 × 10-14 and
1.0 × 10-14 for "pseudo" cholinesterase for mouse, rat, guinea pig,
rabbit, dog, and man respectively (Brown, 1964).
Incubation of chlorfenvinphos with mouse liver slices caused an
increase in anti-"true" cholinesterase activity which reached a peak
at 30 minutes and was still elevated at 45 minutes. Chlorfenvinphos
concentration decreased 29.8% in 30 minutes. In rat, anti-"true"
cholinesterase activity declined sharply throughout the 45 minutes of
incubation. Chlorfenvinphos concentration decreased 37.8%. In dog,
there was an initial drop of anti-"true" cholinesterase activity for
10 minutes, followed by rapid recovery. Percentage decrease of
chlorfenvinphos was only 10.9% (Brown, 1964).
TOXICOLOGICAL STUDIES
Special studies
Reproduction
Four groups of 30 male and 20 female rats were fed 0, 30, 100 or 300
ppm in the diet through three generations, the second litters of each
generation being used as parents for the next generation. Males were
rotated three times during each breeding sequence of 20 days.
Autopsies were performed on parent rats, and on F1-3/b weanlings.
Plasma and erythrocyte cholinesterase levels were measured in F2b
generation 30-week-old adults (0, 30 and 100 ppm levels) and in F3b
siblings at 0 and 30 ppm three weeks after weaning. After weaning of
F3b rats, F2b females fed 30, and 100 ppm diets were cross-mated with
rats on 0 ppm diet, to produce F3c litters. Body-weight for all parent
generations was reduced at all dose levels. No offspring on the 300
ppm diet survived beyond the F1 generation. Fertility was unaffected
in the Fo generation; reduced at 100 and 300 ppm in the F1/b
generation; and also reduced at 30 ppm in the F2/b generation.
Viability and lactation indices were reduced at 100 and 300 ppm in all
matings; and at 30 ppm in the F1/b and F3/b litters, lactation index
was reduced. In the F2/b 30 ppm female × control male cross, fertility
index was still reduced (fertility index 25%). A reverse cross
(control females × 30 ppm males) resulted in a fertility index of 42%.
Vaginal smears of 0, and 30 ppm females were normal. Plasma and
erythrocyte cholinesterase levels were depressed in F2/b adults, at 30
and 100 ppm, and in F3/b weanlings at 30 ppm (Ambrose et al., 1970).
Four groups of 10 male and 20 female rats were fed 0, 1, 5, or 15 ppm
in the diet through three generations, of two litters/generation.
Parent animals commenced on treated diet at weaning in the Fo animals.
During mating, two males were exposed to each female over a 14-day
period. F3/b weanlings were autopsied. The only adverse effects were
reduction in body-weight of F1/b pups at 1 ppm, and of F1/b adult
males at 1 and 5 ppm (Eisenlord et al., 1967).
Neurotoxicity
Groups of adult hens were injected i.p. daily for 10 days (or until
death) with 0 (5 hens), 100 (6 hens), 150 (3 hens), and 200 (4 hens),
or 300 (2 hens) mg/kg/dose in 20% ethanol-80% propylene glycol
solution. Two further groups of three hens received 100, or 200 mg/kg
together with 1 mg atropine sulphate/kg. The hens were autopsied 20
days after the last dose. All doses induced symptoms of cholinesterase
depression, and all groups suffered mortalities. Atropine did not
protect against the lethal effects. Survivors (5 hens at 100, 2 at
150, and 1 at 200 mg/kg) showed no behavioural or histopathologic
signs of neurological damage (Ambrose et al., 1970).
Potentiation study
Studies on the acute LD50 of chlorfenvinphos in combination with
other pesticides show that mild potentiation occurred with Guthion;
and strong potentiation with Diazinon, Malathion, methyl Parathion,
and Ronnel. No potentiation occurred with Vapona, Ciodrin, Bidrin,
Co-Ral, Delnav, Dibron, Dimethoate, Disyston, EPN, Ethion, OMPA,
Parathion, Phosdrin, Phosphamidon, Sevin, Systox or Trithion (Kehoe,
1963).
Acute oral toxicity of metabolites
Metabolites
Compound Species LD50 (mg/kg) Reference
2-chloro-1-(21, 41-dichlorophenyl)-vinyl Hutson et
ethyl hydrogen phosphate Rat >1 000 al., 1967
Compound Species LD50 (mg/kg) Reference
2,4-dichloromandelic Hutson et
acid Rat >1 000 al., 1967
2,4-dichlorophenacyl Hutson et
chloride Rat 1 450 al., 1967
Acute toxicity
Technical compound
Species Route Solvent LD50 (mg/kg) Reference
Mouse Oral Arachis oil 133 - 155 Hunter, 1964
Mouse Oral DMSO 150 - 200 Hutson and Hathway, 1966
Mouse Oral Polyethylene 117 Pickering, 1965
glycol
Mouse i.p. Polyethylene 37 Hutson and Hathway,
glycol 1966
Rat Oral Arachis oil 9.6 - 39.0 Ambrose et al., 1970
Gaines, 1969, Virginia
Medical College, 1962,
Hunter, 1964
Rat Oral DMSO 10 - 15 Hutson and Hathway, 1966
Rat Oral Polypropylene 10.9 - 13.3 Hunter, 1964
glycol
Rat Oral Polyethylene 23.8 Pickering, 1965
glycol
Rat Oral Propylene 10.8 Virginia Medical
glycol College, 1962
Rat i.v. Lipomul 1% 6.6 Ambrose et al., 1970
Rat i.p. Polyethylene 8.5 Hutson and Hathway, 1966
glycol
Rat Dermal Xylene 30-108 Gaines, 1969,
Pickering, 1965
Species Route Solvent LD50 (mg/kg) Reference
Guinea-pig Oral Undiluted 125 - 250 Hutson and Hathway, 1966
Brown 1965
Guinea-pig s.c. Undiluted 500 Brown, 1965
Rabbit oral Arachis oil ca 300 Ambrose et al., 1970
Rabbit oral Undiluted 500 - 1 000 Hutson and Hathway, 1966
Brown, 1965
Rabbit Dermal Undiluted 412 - 4 700 Ambrose et al., 1970
Hunter, 1964
Witherup and Schlecht.
1963
Dog Oral Corn oil >12 000 Ambrose et al., 1970
Dog i.v. Lipomul 1% 50.5 Ambrose et al., 1970
Chicken Oral Polyethylene 36.6 Pickering, 1965
(1 week) glycol/water
Chicken i.p. Polyethylene 23.1 Pickering, 1965
(1 week) glycol/water
Hen Oral Polyethylene 240 Pickering, 1965
glycol/water
Hen Oral Undiluted 44 - 62.5 Brown, 1965
Sheep Abomasal AR395/water 71.3 Pickering, 1965
Calves Abomasal AR395/water 20 Pickering, 1965
Symptoms in all recorded cases were typical of anticholinesterase
activity.
Short-term studies
Six groups of 10 male and 10 female weanling rats were observed for
five weeks during which base-line plasma and erythrocyte
cholinesterase values were determined on five males and five females
per group. The rats were then fed 0, 3, 10, 30, 100, or 1000 ppm
chlorfenvinphos in the diet for 12 weeks. Plasma and erythrocyte
cholinesterase was measured after 1, 2, 4, 6, 8, 10 and 12 weeks. All
rats in excess of five males and five females/group were sacrificed
after 12 weeks; the remainder being returned to normal diet for
further cholinesterase studies after 1 and 4 weeks. These animals were
autopsied after four weeks' withdrawal. Growth was depressed in both
sexes at 1000 ppm, a slight reversal of the effect being apparent
during the withdrawal period. Significant plasma and erythrocyte
cholinesterase-depression occurred at 30 ppm and above, and sporadic
depression was observed at 10 ppm. Plasma cholinesterase recovery was
complete in one week at all levels except females at 1000 ppm where
recovery was complete after four weeks' withdrawal. Erythrocyte
cholinesterase activity recovered in four weeks, except in males
previously fed 100 and 1000 ppm diets. Spleen organ/body-weight ratios
were decreased in females at 30 and 100 ppm and kidney weights in both
sexes at 30 ppm in rats sacrificed at 12 weeks only (Ambrose at al.,
1970).
Three groups of 35 male and 35 female rats were fed 0, 1 or 3 ppm in
the diet for three months. Plasma cholinesterase was marginally
depressed at 3 ppm (Virginia Med. Coll., 1963).
Four groups of two male and two female mongrel dogs were observed for
five weeks during which time plasma and erythrocyte cholinesterase
values were determined. The dogs were then fed 1, 10, 100, or 1000 ppm
for 12 weeks. Cholinesterase determinations were made at 1, 2, 4, and
10 and 12 weeks, when 1 dog/sex/group was sacrificed. The remaining
dogs were returned to basic diets for eight weeks prior to sacrifice.
Cholinesterase activity was determined at 1, 2, 4, and 8 weeks post
dosing. Plasma cholinesterase was depressed at all dose levels.
Erythrocyte cholinesterase depression was sporadic. By eight weeks
post treatment, recovery trends were apparent for plasma
cholinesterase activity, but not for erythrocyte cholinesterase
activity (Ambrose et al., 1970).
Four groups of beagle dogs were fed 0 (5 male and 5 female), 0.5
(3 male and 3 female), 1.0 (4 male and 2 female) or 3.0 (1 male and 1
female) ppm in dry diet for 16 weeks. The only effect was a decrease
of between 14 and 24% in plasma cholinesterase when the 0 and 3 ppm
levels were compared (Walker, 1965).
Four groups of two male and two female beagle dogs were fed 0, 30, 200
or 1000 ppm in the diet for two years, at which time survivors wore
autopsied. One control dog was sacrificed in a moribund state at 97
weeks. Plasma cholinesterase activity was depressed during the first
39 weeks of the study at all dose levels. However, the lack of
significant depression does not appear to be due to recovery, but to a
drop in the plasma cholinesterase activity of the controls.
Erythrocyte cholinesterase activity was significantly depressed at the
1000 ppm level during the first 12 weeks, and again at 79 weeks
(Ambrose et al., 1970).
Long-term studies
Five groups of 30 male and 30 female weanling rats were fed 0, 10, 30,
100 or 300 ppm in diet for 104 weeks. At least 4 rats/sex/group were
sacrificed at 13 weeks. The 300 ppm male survivors were sacrificed at
95 weeks, and all other survivors at 104 weeks. Bodyweight of females
on 100 and 300 ppm diets was depressed from 26 weeks to almost the
termination of the study. Plasma and erythrocyte cholinesterase
activity was reduced in all groups throughout the study, with the
exception of male rats at 10 ppm during the second year.
Organ/body-weights for female rat spleen were depressed at 300 ppm at
13 weeks only, and male liver-weight ratio was increased at 100 ppm at
104 weeks. There was no increase in tumour incidence. (Ambrose et al.,
1970)
Observations in man
Dermal exposure on the forearms of 11 adult males of 5-10 mg/kg of
chlorfenvinphos for up to four hours, in three formulations (80% and
24% E.C. and 25% WP + water) resulted in chlorfenvinphos detection in
whole blood. Only the 24% E.C. caused plasma cholinesterase depression
(Hunter, 1969).
In vitro studies on human blood indicate that 50% cholinesterase
depression require 1.1 × 10-8, or 4.9 × 10-7 concentrations for
plasma and erythrocyte respectively (cf 1.1 × 10-8, and 1.6 × 10-8
for paroxon) (Larson, 1964).
Comments
Information is available on the metabolism of chlorfenvinphos in rat,
dog and man. Over 90% of an administered dose is excreted in these
species within 24 hours.
Acute toxicity studies are available in three species and short and
long-term studies are available in rats and dogs as well as
multi-generation reproduction studies in rats. There appear to be
considerable species differences in acute toxicity. In the short-term
rat study the Meeting assumed that the description "disseminated
granulomatous inflammatory processes" referred to changes attributable
to non-specific respiratory diseases to which laboratory rats are
prone. Some sporadic depression of red blood cell cholinesterase was
noted in dogs but there was no consistent depression of plasma
cholinesterase at 1 ppm. The 0.05 mg/kg bodyweight level was
considered to be of no toxicological effect in both species and an
acceptable daily intake was established on the basis of these studies.
TOXICOLOGICAL EVALUATION
Level causing no toxicological effect
Rat -1 ppm in the diet equivalent to 0.05 mg/kg body-weight per day
Dog -1 ppm in the diet equivalent to 0.05 mg/kg body-weight per day
Estimate of acceptable daily intake for man
0-0.002 mg/kg body-weight per day.
FURTHER WORK OR INFORMATION
Desirable
1. Clarification of differences in acute toxicity between species.
2. Further information on the depression of red blood cell
cholinesterase levels in dogs.
RESIDUES IN FOOD AND THEIR EVALUATION
Use pattern
Chlorfenvinphos is a non-systemic organo-phosphorus insecticide which
is used against soil-borne and foliage insects in both agricultural
and horticultural crops and against ectoparasitic insects, ticks and
mites on livestock.
Pre-harvest applications
Main uses are for the control of various root flies in root
vegetables, e.g. carrots, potatoes, radishes, in brassicas and onions;
for the control of Colorado beetle and other foliage pests on
potatoes. The material is used as a seed dressing, soil or foliar
application in cereal crops, e.g. wheat, corn and rice.
Chlorfenvinphos is widely used in the following countries: Australia,
France, Federal Republic of Germany, Hungary, Japan, Netherlands,
United Kingdom and the following tables summarise the recommendations
in accordance with good agricultural practice on crops and together
with the more important insect pests concerned.
Livestock uses
Chlorfenvinphos is widely used for the control of ectoparasites of
livestock (e.g. ticks, itch mites, lice, blowfly, screw worm),
especially on sheep and beef cattle; it is only occasionally used on
dairy cattle. On meat producing animals it is normally applied more
than seven days before slaughter; rather shorter intervals are
observed rarely, the minimum interval is two days before slaughter.
When used on dairy cattle the material is used directly after the
morning milking; the interval between application and next milking
will then be about seven hours. Chlorfenvinphos is used both on cattle
and sheep against ectoparasites mainly as a dip (0.05% a.i.) but it
may also be applied as a saturation spray of similar strength.
Main areas of use, on sheep: Australia, New Zealand, United Kingdom,
South Africa; on cattle: South Africa, South and Central America,
Kenya.
In some countries, a.o. France, the material is used as a residual
spray (0.05%-0.1% a.i.) for the control of flies in dairy barns.
Post-harvest treatments
Chlorfenvinphos is not recommended for post-harvest use on
agricultural commodities.
Other uses
Chlorfenvinphos is also used in the sphere of public health and
municipal control programmes, a.o. against housefly,
Musca domestica; stablefly, Stomoxys calcitrans; German cockroach,
Blatella germanica; and mosquito larvae, Culex sp.
Residues resulting from supervised trials
Residue data are available from supervised trials carried out in
different countries on food crops grown under various conditions and
on livestock, using various rates of application and various
pre-harvest or pre-slaughter intervals.
In most cases, normal dosage rates were applied in accordance with
label recommendations; the data from these trials on crops are
summarized in Tables I, II and III. However, in some experiments
higher dosages were also included; the results are summarized in
Tables IV and V.
In the more recent trials, samples were analysed for residues of both
the cis-and trans-isomers of chlorfenvinphos, and where appropriate,
these values are given in the tables. In all other cases the results
of the analyses are given as the sum of the cis- and trans-isomers of
chlorfenvinphos. Since field studies have she" that metabolites of
chlorfenvinphos at detectable levels occur rarely in food crops,
livestock and livestock products, no further reference will be made to
them in this section (see section on Fate of Residues).
APPLICATIONS TO SOIL, SEED OR ROOT, AT OR NEAR SOWING OR PLANTING TIME
Crop Main pests Recommended Time of Application
dosage application method
Brassicas Cabbage root up to 2 kg at or near as a drench,
i.e. Cabbage fly: a.i./ha planting root dip or
Brussels Chortophila granular soil
sprouts, brassicae application in
Swedes, the row
Turnips and
other
Brassica's
Carrots, Carrot rust 2-4 kg a.i. before or as granular or
parsnips, fly: /ha at sowing spray appl., in
celeriac and Psilla rosae the row or
celery broadcast
Radishes Radish fly: 2-4 kg a.i. before granular appl.,
Chortophila /ha sowing in the row or
brassicae and
Ch. cilicrura
Potatoes Potato 2-4 kg a.i. before granular appl.,
weevil: /ha planting in the row or
Phyrdenus broadcast
muriceus
Onions and Onion fly: 3-5 kg a.i. before as granular or
lettuce Hylemia /ha sowing or spray appl., in
antiqua planting the row or
broadcast
Wheat Wheat bulb fly: 80 g a.i./ at sowing as seed
Leptohylemia 100 kg dressing
hylemia seed
coarctata
APPLICATIONS TO SOIL, SEED OR ROOT, AT OR NEAR SOWING OR PLANTING TIME (continued)
Crop Main pests Recommended Time of Application
dosage application method
Maize Frit fly: 1-2 kg a.i. at or near as granular or
(corn) Oscinella /ha sowing spray appl.
Frit over the seed
Rootworms: row
Diabrotica
spp.
Peanuts soil-borne 2-4 kg/ha prior to band treatment
insects pegging with granulars
APPLICATIONS DURING CROP GROWTH
Crop Main pests Recommended Type of Recommended
dosage application interval
between
(last)
application
and harvest
in days
Potatoes Colorado 0.125-0.25 kg foliar spray 7-21
beetle: a.i./ha
Leptinotarsa repeated if
decemlineata necessary at
2-3 week
interval
Potato tuber 0.2-0.4 kg foliar spray 21
moth: a.i./ha
Phtorimaea
operculella
Tomatoes, Phtorimaea 0.25-1 kg foliar spray 14
Aubergines spp. a.i./ha
Carrots, Plutella 0.25-1 kg foliar spray 30
Cauliflower, maculipennis, a.i./ha
Radish, Pieris spp.
Swedes, Aphis spp. 0.5-2 kg
Onions a.i./ha dust
Rice Stem borers 0.25-0.5 kg foliar spray 30*
Chilo spp. a.i./ha
Tryporyza spp. 1 kg a.i./ha granular 30*
application
to paddy water
* Normally applications for borer control are made only in the early development
of the crop, and only occasionally up until 30 days before harvest.
The following conventions have been employed in presenting the data:
1. All application rates refer to active ingredient.
2. lbs/acre has been regarded as being essentially equivalent to
kg/ha.
3. Mean values have been calculated on the basis that samples
without detectable residues contained residues at half the limit
of detection.
TABLE I. RESIDUES OF CHLORFENVINPHOS FOUND FOLLOWING RECOMMENDED SOIL TREATMENTS
Crops Range of dosage Pre-harvest No. of No. of alpha and beta
rates in interval trial sites results chlorfenvinphos
kg a.i./ha* (weeks) in ppm
range
Brussels sprouts 2.5-5 17 1 4 < 0.05
Broccoli 2.5-5 11-17 1 4 < 0.04
Cabbage 2.5-5 11-20 5 9 < 0.005-0.03
Cauliflower 1-2.5 7-17 3 4 0.02-0.10
Swedes 2.5 14-18 1 2 < 0.05
Turnips 1.0-4.0 10-16 3 4 < 0.02-0.04
Potatoes 2.0-4.0 16-27 3 5 < 0.01-0.08**
Carrots 2.0-4.0 14-48 7 17 < 0.01-0.35
Celery 1.0-2.0 13-19 2 4 0.03-0.2
Radish 2.0-4.0 4-9 3 6 < 0.02-0.05
Wheat grain 3.8 43 1 2 < 0.02
Maize grain 1.5-4.0 10-16 3 4 < 0.04-0.05
Peanuts (shelled) 2.0-4.0 11-31 8 11 < 0.05
Mushrooms 50-170 ppm 4 1 3 < 0.01
* Except where stated otherwise.
** One result only.
TABLE II. RESIDUES OF CHLORFENVINPHOS AFTER FOLIAR APPLICATION ACCORDING TO THE RECOMMENDATIONS
Crops Range of dosage No. of Pre-harvest No. of No. of Sum of alpha and beta
rates in applications interval trial sites results chlorfenvinphos
kg a.i./ha (weeks) in ppm
range
Cauliflower 1.0 3 7 1 1 < 0.05
Swedes 2.5 1 14-18 1 2 < 0.05
Carrots 0.5-2.0 1-6 2-7 2 4 < 0.02-0.18
Radish 2.0 1 2.5 1 1 < 0.02
Potatoes 0.15-0.6 1-8 0.5-16 5 10 < 0.01-0.02
Sweet potatoes 0.67 3 10 1 2 < 0.02
Tomatoes 0.25-1 1-6 1-11 4 16 < 0.01-0.06
Aubergines 0.25 1-3 5-11 3 12 < 0.01
Onions 1.0 1 4 1 1 < 0.02
Maize grain 1.0-1.2 2 6-14 1 2 < 0.01
Rice (polished) 0.36-0.40 1-4 5-12 8 14 < 0.02-0.04
Cotton seed 0.25-2.0 1-7 5-13 3 9 <0.02-<0.05
TABLE III. RESIDUES OF CHLORFENVINPHOS FOUND FROM RECOMMENDED TREATMENTS OTHER THAN SOIL OR FOLIAR TREATMENTS
Crop Type Range of dosage Pre-harvest No. of No. of Chlorfenvinphos residues
application rated interval trial sites results sum of alpha and beta isomers
(weeks) in ppm range
Cauliflower root dip 0.05-0.10% 13 1 4 10.05
Celery root drench 17-18 mg/plant 11-16 2 2 0.2-0.49
Radish root drench 2.4 kg/ha 26 1 2 < 0.02
Wheat grain seed dressing 80-100 kg seed 37-43 2 5 < 0.02
TABLE IV. RESIDUES OF CHLORFENVINPHOS FOUND FOLLOWING SINGLE SOIL TREATMENTS AT RATES HIGHER THAN RECOMMENDED
Crop Range of dosage Pre-harvest No. of No. of Chlorfenvinphos residues
rates in interval trial sites results in ppm
kg a.i./ha (weeks) range
Cabbage 8 16 1 1 0.01
Carrots 5-8 17-30 4 9 <0.01-0.12
Onions 6 22-26 3 3 < 0.01
Potatoes 90 26 1 1 0.27
Radish 8 8-9 1 3 <0.02-0.05
Cauliflower 4-5 11-20 2 3 <0.005-0.02
TABLE V. RESIDUES OF CHLORFENVINPHOS FOUND FOLLOWING TREATMENTS AT RATES HIGHER THAN RECOMMENDED OR AT SHORTER
INTERVALS TO HARVEST
Crop Range of dosage Pre-harvest No. of No. of Chlorfenvinphos residues
rates in interval trial sites results in ppm
kg a.i./ha (weeks) range
Rice polished 0.6-3.0 2.5-12 10 50 <0.02-0.20
4. The following abbreviation has been used: a.i. - active
ingredient.
Residues resulting from supervised trials - livestock
Mutton
Cheviot ewes, four years old and recently shorn, were dipped in 0.05
and 0.1% chlorfenvinphos (i.e. once and twice the recommended dosage).
A third group was sprayed with 0.2% chlorfenvinphos emulsion.
From each group two animals were slaughtered 3, 7, 14 and 21 days
after treatment. Residues of chlorfenvinphos were determined in
omental, perirenal and pericardial fat. On no occasion chlorfenvinphos
residues in the fat exceeded 0.10 ppm. After observing a seven-day
pre-slaughter interval residues in the fat of animals dipped in 0.05
and 0.1% chlorfenvinphos varied between (0.003 and 0.093 ppm (one
animal). Chlorfenvinphos was only found in the fat and not in other
organs or non-fatly tissues such as liver, spleen, adrenals, kidney,
heart, lung, uterus, ovaries, brain, subcutaneous tissues and muscle
(Robinson et al., 1966).
Eight Dorset Dawn lambs (4 shorn and 4 unshorn), 3-4 months old, were
dipped in chlorfenvinphos 0.05% (recommended dosage). Residues of
chlorfenvinphos were determined in omental, perirenal, pericardial and
subcutaneous fat, from animals slaughtered three and seven days after
treatment. The upper limit was 0.02 ppm (Shell Res., 1965).
Beef
Beef cattle were sprayed with 32P-labelled chlorfenvinphos in 0.05,
0.25 and 0.5%. Residues were detected in tissues other than fat only
when animals were sprayed at 5x and 10x the recommended rate of
application of 0.05% (Ivey et al., 1966).
In a more detailed study (Ivey et al., 1966) cattle were sprayed with
0.1% chlorfenvinphos emulsion (= 2x the now recommended dosage) either
12 times at weekly intervals or six times at intervals of two weeks.
Residues were determined with a GLC method (Claborn et al., 1965) in
omental fat of animals slaughtered seven days resp. 14 days after a
weekly or two-weekly treatment. In the first series the
chlorfenvinphos residues ranged between 0.009 and 0.245 ppm (one
animal). In most of the samples the residues were <0.16 ppm. In the
second series, where animals were slaughtered 14 days after a
two-weekly treatment the residues in the fat varied between <0.005
and 0.18 ppm. In fat from animals slaughtered two weeks after the last
weekly or two-weekly sprays no residues of chlorfenvinphos could be
determined (limit of determination <0.003 ppm).
Decreasing the interval between last application and slaughter tended
to increase the residue levels. In an experiment on nine young beef
steers treated up to 13 times at weekly intervals with the recommended
dosage and currently used application methods (spray concentration
varying between 0.03 and 0.05%) the mean residue in omental fat of
animals slaughtered two days after last application was 0.07 ppm with
an upper figure in one sample of 0.11 ppm; with a pre-slaughter
interval of seven days the mean level was 0.012 ppm (upper limit
0.026) in subcutaneous fat and 0.006 (upper limit 0.01) in omental fat
(Shell Res., 1968).
For higher bath or spray concentrations residues were higher, roughly
in proportion of the dosage used, where other factors were comparable,
although higher concentrations are normally not used or recommended.
There is no evidence of accumulation of chlorfenvinphos residues in
the fat of treated animals in cases where a number of consecutive
weekly treatments were applied (Ivey et al., 1966).
In addition to meat animals, chlorfenvinphos is also recommended for
the treatment of dairy cattle. Experiments have been carried out in
which milking cows were treated according to the recommended dosage
and to excessive dosages (5-7 times the recommended rate of 0.05%
chlorfenvinphos) and milk analysed at intervals after treatment.
Residues were highest when the treatment was given shortly before
milking.
Milk sampled five hours after one application of 9 gram a.i./cow (5-7
times the recommended rate) contained 0.105 ppm chlorfenvinphos (on
whole milk), whereas a bulk sample of morning and evening milk of next
day milking contained 0.013 ppm. Three, resp. five days after the
treatment, residues of chlorfenvinphos in the bulked milk were 0.002
and 0.00005 ppm/whole milk (Claborn, 1965a).
When applied as a spray mist after each morning milking according to
the recommended dosages, the minimum residues found were 0.001
ppm/whole milk (range <0.005-0.001) (Claborn et al., 1965b).
Roberts et al. (1961) compared with 32P chlorfenvinphos the residues
in milk after using two different methods of application. 5 g
chlorfenvinphos per cow was either brushed in with an aqueous spray
(400 ml) or sprayed with 60 ml xylone solution, containing 5 g
lanoline as sticker after the morning milking. Residues were measured
as total extracted radio-activity in the morning milk of nine
following days.
In an intensive spray regime cattle were treated weekly. The interval
between application and first milking was resp. 1-1/2, 4 and 7 hours.
From the samples analysed average residues figures for the milk
production of a week period were included. For the interval of 4 resp.
1-1/2 hour the average residue in the milk of a week was about 0.01
ppm. The corresponding figure for a seven-hours interval was about
0.005 ppm. After treatments with a double dosage the levels were
approximately proportionally higher. The residues were highest in milk
from the first milking after treatment, but fell rapidly thereafter.
With the recommended levels the figures for the first milking for the
two shortest intervals were 0.056 and 0.053 respectively, and for the
seven-hour interval 0.02 ppm. It is this first figure which dominates
the means for the whole week, since at the next milking (next morning)
levels had fallen by about 5-7 times and by the third day were barely
distinguishable from the controls (Shell Res., 1969a).
CHLORFENVINPHOS IN MILK FROM TWO DIFFERENT TREATMENTS
OF 5 g CHLORFENVINPHOS PER COW
Time after Chlorfenvinphos residues* total
application radio-activity basis: morning milk only
400 ml 60 ml
Aqueous spray Xylene spray
8 hours 0.037 0.02
1 day 0.019 0.009
2 days 0.017 0.005
3 days 0.010 0.003
5 days 0.003 0.002
7 days 0.001 0.0008
9 days 0.001 0.0008
* Adjusted for 4% butterfat.
Residues of chlorfenvinphos which could arise in milk when cows are
fed with feed containing chlorfenvinphos, were studied at the North
Carolina University (1965). Dairy cattle were fed 1, 10 or 50 ppm of
chlorfenvinphos in their total diet for a period of two weeks. The
residues of chlorfenvinphos and of 2,2', 4'-trichloroacetophenone in
the milk of cows fed at the 1 and 10 ppm levels, were so close to the
background levels, that little significance could be attached to the
levels measured. Only with chlorfenvinphos levels of 50 ppm in the
total feed, milk residues were detectable; at this level residues of
chlorfenvinphos in whole milk were about 0.02 ppm.
Residues of 2,2', 4'-trichloroacetophenone were also reported in milk
from animals fed at this high level. In one case they reached 0.05 ppm
in the whole milk. Thus, the occasional residues of chlorfenvinphos
(max. 0.14 ppm) detected in samples of maize stover and silage, would
not produce significant levels of chlorfenvinphos in milk taken from
cows, which had been fed with a diet containing maize stover or
silage, from maize treated according to the recommendations (Shell
Chem., 1963-64, Reports on residues in maize).
Fate of residues
General comments
Although radio-labelled studies suggest that
1-(2,4-dichlorophenyl)-ethan-1-ol and its sugar conjugate, together
with much smaller amounts of desethyl-chlorfenvinphos might occur in
treated crops, field studies have shown that their occurrence at
detectable levels is rare. Likewise in milk from treated cows only
extremely low levels of these products have been detected.
In soils
The breakdown pathways of chlorfenvinphos were studied in the
laboratory in glass jars containing clay, loam, sand and peat soil
treated with a relatively high dosage level, 15 ppm 14C
chlorfenvinphos (corresponding with more than 15 kg a.i./ha (Beynon et
al., 1967).
After four months' storage at 22°C the following radio-labelled
compounds were detected in the moist soils: unchanged chlorfenvinphos,
1.0-4.7 ppm; 1-(2,4-dichlorophenyl) ethan-1-ol, 0.06-1.0 ppm;
2,4-dichloroacetophenone, 0.1-0.5 ppm; desethyl chlorfenvinphos,
0.1-0.2 ppm; salts or conjugates of desethyl chlorfenvinphos, 0.05-0.6
ppm. No other breakdown products were detected. From these studies the
breakdown path shown in Fig. 1 was proposed.
The results of analyses of various field soils (Beynon et al., 1966)
treated with chlorfenvinphos at dosage rates of 4 and 8 lb a.m./acre
(recommended rate and double rate) showed that the initial half-life
of chlorfenvinphos in soils varied from 2 to 12 weeks in mineral soils
depending on soil type, formulation and dosage level. In one peat soil
a half-life of 16-23 weeks was reported. These half-lives would
probably have all been much shorter but for exceptionally dry
conditions which occurred during the season when these experiments
were carried out (1964).
Further experiments (Beynon et al, 1968b) indicated that after
application of about the recommended dosage (4-6 lb a.m./acre)
residues of 1-(2,4-dichlorophenyl)-ethan-1-ol and
2,4-dichloroacetophenone did not exceed 0.2 ppm by the end of the
season. There was no evidence for the conversion of the trans-isomer
of chlorfenvinphos.
In plants
Chlorfenvinphos may be applied either directly to soil for soil pest
control, or to the aerial parts of plants for foliage pest control.
Studies have been carried out to study the breakdown of
chlorfenvinphos in crops grown in treated soil (Beynon et al., 1967)
and in crops sprayed directly (Beynon et al., 1968).
FIGURE 3;V071pr13.BMP
In cabbage grown in the greenhouse in soil treated at a rate
corresponding to 3-4 kg a.i./ha of 14C-chlorfenvinphos, no residues
of chlorfenvinphos, nor of its breakdown products could be detected in
the edible parts of the plant (hearts and outer leaves). Onions and
carrots in the same experiment, however, contained unchanged
chlorfenvinphos as the principal residue (0.07-0.12 ppm), and small
amounts of a compound which was probably a salt or conjugate of
desethyl chlorfenvinphos. The amounts were too small for positive
identification.
After application of 14C-chlorfenvinphos to the foliage of potatoes,
cabbage and maize in a glasshouse, half of the parent compound
disappeared from the foliage within 2-3 days. The major breakdown
product was 1-(2,4-dichlorophenyl)-ethan-1-ol, as in soils. Whereas
this remains in the free state in soils, it occurs mainly as a sugar
conjugate in crops. Traces of the desethyl chlorfenvinphos were
detected, but generally at only 1% of the corresponding residue of the
conjugated ethan-1-ol. Residues of the breakdown products tended to
reach levels above those of the remaining chlorfenvinphos, five days
after foliar application to maize, 12 days after application to
cabbage, and 30 days after application to potatoes. Nevertheless the
half-life of the total residue (parent and breakdown products), in so
far as this concept can be applied to all products together, was not
more than 5-7 days. Residues were detectable only in treated foliage;
there was no evidence of translocation of any radio-activity from
treated leaves to untreated parts of the plant.
After the radio-labelled studies, analytical methods were developed
for unlabelled desethyl chlorfenvinphos, the ethan-1-ol and its sugar
conjugate and field experiments conducted with unlabelled
chlorfenvinphos. A summary of the results is given underneath (Beynon,
Davies et al., 1966; Beynon et al., 1968; Shell Res., 1967, residues
in carrots etc.).
In milk
To study the partition of chlorfenvinphos breakdown products in milk a
small Friesian cow weighing about 400 kg was injected intramuscularly
with 233 mg of 14C-chlorfenvinphos shortly after milking at 10 a.m.
(Shell, 1969). Milk samples were taken at 4 p.m. on the same day and
on subsequent days from milkings at 10 a.m. and 4 p.m. until the fifth
day.
TABLE
RESIDUES OF THE METABOLITE, 1-(2,4-DICHLOROPHENYL)-ETHAN-1-OL IN CROPS
Crop Country Type of Crop part Residues of Residues of
application chlorfenvinphos ethan-1-ol (ppm)
(ppm) (total of
cis- plus Free Conjugated
trans-isomers)
Carrots Holland Soil - 3.8 < 0.05
France Soil - 0.08 < 0.05 < 0.05
Potatoes U.K. Foliar Tubers < 0.02 < 0.10
Brazil Soil Whole 0.08 0.05 < 0.05
Brazil Soil Peeled 0.03 < 0.05 < 0.05
Onions Germany Soil - < 0.02 < 0.05
Leeks Germany Soil - < 0.01 < 0.05
Radishes Germany Soil - 0.05 < 0.05
Celery U.K. Soil - 0.02 < 0.05
Tomatoes S. Africa Foliar - 0.06 < 0.05 < 0.05
Maize France Foliar - < 0.01 < 0.10
Rice Thailand Foliar Polished < 0.02 < 0.05 < 0.05
Thailand Foliar Straw 0.65 < 0.05 < 0.05
Thailand Foliar Polished < 0.02 < 0.05 < 0.05
Thailand Foliar Unpolished 0.03 < 0.05 < 0.05
Thailand Foliar Bran < 0.02 < 0.05 < 0.05
Thailand Foliar Straw 2.7 < 0.05 < 0.05
Philippines Foliar Unpolished 0.02 < 0.08 < 0.08
Philippines Foliar Straw 0.07 0.16 < 0.08
Using the first milk sample taken after the injection (sample with
highest radio-activity) the fat fraction was separated from protein
and whey, and total radio-activity in the milk was distributed as
follows:
DISTRIBUTION OF RADIO-ACTIVITY BETWEEN 3 MILK FRACTIONS
Fraction Percentage total radio-activity in milk
Fat 83.1
Protein 4.1
Whey 12.8
To identify the breakdown products, fat from the first milk samples
after the injection was extracted; aliquots of the extract were added
to 20 mg of the reference compounds 1-9 (q.v.) and the mixture
streaked onto a T.L.C. plate and developed. The amounts of
radio-activity associated with each reference compound (expressed as
ppm of each compound) are shown below.
CHLORFENVINPHOS AND METABOLITES FOUND IN MILK FAT AFTER ADMINISTRATION BY
INTRA-MUSCULAR INJECTION
Metabolite Metabolite ppm expressed on
number whole milk basis
1 Chlorfenvinphos 0.0485
2 2,4-dichlorophenacyl chloride 0.0008
3 2,4-dichloroacetophenone 0.0023
4 1-(2,4-dichlorophenyl) ethanol 0.0014
5 1-(2,4-dichlorophenyl) ethandiol none detected
6 2,4-dichloromandelic acid 0.0011
7 2,4-dichlorobenzoic acid <0.0014
8 1-(2,4-dichlorophenyl) 2-chloro-ethanol 0.0004
9 des-ethyl chlorfenvinphos 0.0007
Compounds responsible for less than 2% of the total radioactivity in
the extract were difficult to identify with certainty, since such
levels of radio-activity were close to the background activity level.
Although the levels were not strictly related to levels arising from
use of the recommended application, the data serve to show that
breakdown products occur at much lower levels than chlorfenvinphos
itself; the highest level being that of the 2,4-dichloroacetophenone
which occurred at only one-twentieth that of the level of the parent
chemical.
Some examination of the radio-activity in the whey was also made.
Twenty per cent. was extracted at neutral pH and was probably
unchanged chlorfenvinphos. A further 23% was extracted at pH 2 and
considered likely to be due to either metabolites 6 or 9.
The second milk sample, taken the morning after the administration
contained 0.011 total activity (calculated as ppm chlorfenvinphos);
the unchanged chlorfenvinphos gave rise to 60% of the total
radio-activity, thus the metabolites together corresponded with 0.004
ppm chlorfenvinphos equivalent.
In meat
Studies by Robinson et al. (1966), Shell (1965) and Ivey et al. (1966)
have demonstrated the absence of the most likely metabolite of
chlorfenvinphos, i.c. 2,2', 4'-trichloroacetophenone, in the body fat
and organs of sheep and cattle. In these trials, chlorfenvinphos had
been applied to the cattle and sheep as dip or spray, at dosage rates
up to twice the recommended level. The limits of determination of the
analytical methods were 0.001-0.01 ppm.
Effect of storage and processing
The process of washing, peeling (either mechanical or chemical) and
blanching during industrial canning procedures reduced residues of
chlorfenvinphos from 0.20 to 0.25 ppm in fresh carrots to below the
limit of determination (c.q. 0.01 ppm). The peeling of the carrots was
the most effective step in removing any residues of chlorfenvinphos
(Biston et al., 1969).
Analyses of peeled and unpeeled potatoes have also demonstrated that
residues of chlorfenvinphos are mainly concentrated in the peel;
peeling removes 60-75% of the chlorfenvinphos present (Shell Res.,
1968, 1970).
The effect of boiling in a vegetable mash on residues of
chlorfenvinphos is shown in the Report of the Government Chemist 1967.
Forty-six per cent. of chlorfenvinphos was hydrolized during boiling
for 30 min in a potato mash, while 74% was hydrolized in a cabbage
mash in the same time. No new compounds which could be detected by
G.L.C. were found.
In rice, treated according to the recommended rate, residue levels of
chlorfenvinphos decreased from 0.19-0.20 to 0.04-0.05 after boiling
and 0.06-0.07 after frying (Shell Chemie, 1971).
Methods of residue analysis
Residues of chlorfenvinphos can be determined by a non-specific enzyme
inhibition cholinesterase method, or by a specific gas-liquid
chromatographic procedure. The non-specific method should, in general,
only be used where it can be shown that no pesticide other than
chlorfenvinphos has been applied to the crop.
Enzymatic inhibition
Although enzyme inhibition cholinesterase methods are nonspecific, it
has been found that the results obtained with this technique are in
good agreement with those obtained with the specific gas-liquid
chromatographic method, and it can therefore be inferred that none of
the degradation products are cholinesterase inhibitors. An enzyme
inhibition technique for determination residues of chlorfenvinphos is
described by Beynon et al. (1966). The limit of determination is 0.02
ppm.
Gas chromatographic methods
A gas chromatic method of analysis for chlorfenvinphos is the method
of choice based on accuracy, specificity, sensitivity and speed. The
following scheme for analysis has proved successful in analysing soil
and crops (Beynon et al., 1966). Crop samples are extracted by
maceration with 30% v acetone in petroleum spirit, while soil samples
are extracted by end-over-end tumbling with 20% acetone in petroleum
spirit. The extracts are analysed by gas-liquid chromatography using
an electron capture detector. If natural products extracted from the
crops and soils interfere with the analysis, the extract should be
subjected to clean-up by column chromatography. With this technique
the cis- and trans-isomers of chlorfenvinphos can be separated, and
measured separately, if required. Using this procedure, mean
recoveries are 95% from soils at the 0.20-1.0 ppm level, and 100% from
crops at the 0.05-0.10 ppm level. The limit of determination of
chlorfenvinphos with this method is 0.02 ppm. Chlorfenvinphos is
thermally stable under the G.L.C. conditions used in this method
(column temperature of 188°C or below), and no decomposition has been
observed.
Gas-liquid chromatographic methods have successfully been employed in
detecting residues of the metabolites of chlorfenvinphos in crops and
soils: 2,4-dichloroacetophenone, limit of determination 0.01 ppm;
2,4-dichlorophenacyl chloride, 0.01 ppm; free
1-(2,4-dichlorophenyl)ethan-1-ol, 0.10 ppm; and conjugated
1-(2,4-dichlorophenyl)ethan-1-ol, 0.10 ppm (Beynon at al., 1968). The
determination of chlorfenvinphos by flame photometric gas
chromatography with virtually no clean-up can be accomplished by the
general procedure described by Beroza and Bowman (1968).
A gas-liquid chromatographic method has been used for the
determination of chlorfenvinphos residues in animal tissues and milk
(Claborn and Ivey, 1965), which depends on the conversion of
chlorfenvinphos to 2,2', 4'-trichloroacetophenone and the subsequent
determination of the ketone by G.L.C. The amounts detectable with this
method are 0.005 ppm of chlorfenvinphos and 0.003 ppm of
trichloroacetophenone in tissues and 0.0001 and 0.0006 respectively in
milk.
A different G.L.C. residue method was used by Robinson for the
determination of chlorfenvinphos in milk. The limit of detection in
whole milk with this method is 0.0003 ppm.
Note: It should be recognized that in practical use the levels of
detection mentioned to some extent depend on the samples, and
variation up or down inevitably occurs.
National tolerances
The following table lists some of the national tolerances for
chlorfenvinphos (expressed as the sum of cis- and trans-isomer)
established at this time.
Country Crop Tolerance, ppm
Belgium Fruits, vegetables (excl. potatoes) 0.1
Carrots and other root vegetables 0.4
Germany Potatoes, turnips, maize, celery,
cabbage, onion, radish,
horseradish, cucumbers 0.1
Carrots 0.4
Italy Cabbage, carrots, potatoes 0.5
Netherlands Fruit, vegetables (excl. carrots) 0.1
Potatoes 0.05
Carrots 0.4
Switzerland Cabbage 0.03
Yugoslavia All crops No residue
Appraisal
Chlorfenvinphos is a non-systemic organo-phosphorus insecticide which
is used on a considerable scale in many countries on a relatively wide
range of crops and on livestock animals.
Main uses are as soil, seed or plant root treatment against soil borne
insects, especially root-flies and foliar treatments against foliage
pests such as Lepidopterous larvae, beetles, etc. It is used on
livestock, especially on sheep and beef cattle, mainly as a dip or a
spray against ectoparasites i.e. ticks, mites, lice, blowfly and screw
worm; it is only occasionally used on dairy cattle.
Technical chlorfenvinphos contains no less than 92% of alpha and
ß isomer (typical sample 9.7% alpha isomer and 83.8% ß isomer). The
impurities in the technical material are known ; the main component is
2,2-dichloro-1-(2,4-dichlorophenyl) vinyl diethyl phosphate (about
3.8%).
Chlorfenvinphos is used in different formulations, emulsifiable
liquid, wettable powder, dust and granular. The rates of uses range
from 1 to 5 kg a.i. when applied to soil or roots and 0.125-1 kg
a.i./ha applied as foliar application. On sheep, beef cattle and
occasionally on dairy cattle, chlorfenvinphos is used as a dip (circa
0.05% a.i.) or as a spray of the same strength.
The residue data available were obtained from many different countries
and regions with different climatical conditions and, with a few
exceptions, they are representative for likely conditions of good
agricultural practice and veterinarian practice. Information is
available on the fate of chlorfenvinphos residues in soil, in plants
and in products of animal origin.
The residues which may occur in food either from plant or animal
origin, after observing the recommended directions of use and the
recommended pre-harvest and pre-slaughter intervals, consist largely
of chlorfenvinphos itself. Breakdown products, which could be
identified in radio-labelled studies and confirmed with other relevant
methods of analysis occur in very low levels under normal limits of
determination.
Little information is available on chlorfenvinphos residues in foods
in commerce.
A number of methods for residue analysis based on gas-chromatographic
procedures are available which enable specific determination of the
parent chemical and main metabolites. Recommendations are given for
the most appropriate extraction procedures in food products of animal
and plant origin.
The limit of determination in soil and plant material is respectively
0.01 ppm for chlorfenvinphos, and the metabolites 2.4
dichloroacetophenone, and 2.4 dichlorophenacyl chloride; 0.1 ppm for
free and the conjugated 1-(2.4 - dichlorophenyl) ethan-1-ol.
A gas-liquid chromatographic method is available for the determination
of chlorfenvinphos residues in animal tissues and in milk and milk
products depending on the conversion of chlorfenvinphos to 2, 2',
4'-trichloroacetophenone and the subsequent determination of the
ketone by G.L.C. Limits of detection are 0.005 0.005 ppm of
chlorfenvinphos and 0.003 ppm of trichloroacetophenone in animal
tissues and 0.0001 ppm and 0.0006 ppm in milk and milk products
respectively.
Gas chromatic procedures as mentioned are available for the
determination of residues of alpha and ß chlorfenvinphos, which can be
adapted for regulatory purposes as required.
RECOMMENDATIONS FOR TOLERANCES
The following tolerances, given as the sum of alpha and ß
chlorfenvinphos are recommended.
Since the residues in animals, in tissues other than fat, were
detected only with animals which were sprayed at 5 to 10 times the
recommended rate, the tolerances are recommended only on a fat basis.
In milk, most of the residue (at least 83%) occurs in the butter fat
and therefore the tolerances are expressed on a fat basis. The
tolerance figures for milk and milk products are also given on the
assumption that blending will take place before milk enters in
commercial channels.
Food commodity Recommendation Basis of
for tolerance recommendation
(sum of alpha and beta) (pre-harvest
chlorfenvinphos interval
in ppm weeks)
Brassicas (except cauliflower)
i.e. Brussels sprouts, cabbage,
broccoli, swedes, turnips 0.05 swedes 14 x
Cauliflower 0.1 4-7 x
Carrots, celery 0.4 2-7 x
Potatoes, sweet potatoes 0.05 1-4 x
Radish (incl. horseradish) 0.1 2-5 x
Tomatoes 0.1 1-4 x
Aubergines 0.05 5-10 x
Onions, leeks 0.05 4 x
Cereals i.e. maize grain,
rice (raw and polished), maize, x
wheat grain 0.05 rice 5-12 (wheat)
Food commodity Recommendation Basis of
for tolerance recommendation
(sum of alpha and beta) (pre-harvest
chlorfenvinphos interval
in ppm weeks)
Peanut (shelled) 0.05 x
Mushroom 0.05 x
Cotton seed 0.05 5-13
Meat on fat basis 0.2 0.5-1*
Milk and milk products,
on a fat basis 0.2 **
* Period between application and slaughter.
** Weekly sprays on cattle, 4-7 hours between application
and first milking.
x Entries marked x refer to applications to the soil or plant
root prior to, or at, planting or sowing.
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cotton seed (1964 rep. RES 63-156); maize (1963 rep. RES 62-43,
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