WORLD HEALTH ORGANIZATION FOOD AND AGRICULTURE ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE ORGANISATION POUR L'ALIMENTATION
ET L'AGRICULTURE
VBC/DS/84.51
ORIGINAL: ENGLISH
DATA SHEET ON PESTICIDES No. 51
PERMETHRIN
CLASSIFICATION:
Primary use: Insecticide
Secondary use:
Chemical group: Pyrethroid
It must be noted that the issue of a Data Sheet for a
particular pesticide does not imply endorsement of the pesticide by
WHO or FAO for any particular use, or exclude its use for other
purposes not stated. While the information provided is believed to
be accurate according to data available at the time when the sheet
was compiled, neither WHO nor FAO are responsible for any errors or
omissions, or any consequences therefrom.
The issue of this document does Ce document ne constitue pas une
not constitute formal publication. Il ne doit faire
publication. It should not be l'objet d'aucun compte rendu ou
reviewed, abstracted or quoted résumé ni d'aucune citation sans
without the agreement of the l'autorisation de l'Organisation
Food and Agriculture des Nations Unies pour
Organization of the United l'Alimentation et l'Agriculture
Nations or of the World Health ou de l'Organisation Mondiale de
Organization. la Santé.
1. GENERAL INFORMATION
1.1 COMMON NAME: Permethrin (ISO, BSI, ANSI)
1.1.1 Identity:
IUPAC: 3-phenoxybenzyl (1RS)-cis,trans-3-(2,2-dichlorovinyl)-
2,2-dimethylcyclopropanecarboxylate
CAS No. 1: (3-phenoxyphenyl)methyl (1RS)-cis,trans-3-(2,2-
dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate
CAS Reg. No.: 52645-53-1
Molecular formula: C12H20O3
Molecular weight: 391.29
Structural formula:
1.1.2 Synonyms: Acion(R); AI3-;29158; Ambush(R); AMbushfog(R); BW-21-7;
CO-Opex(R); Ectiban(R); Eskmin(R); FMC 33297; Indothrin(R);
Kafil(R); Matadon(R); NIA 33297; NRDC 143; Outflank; OMS-1821;
Perthrine(R); Picket(R); Picket G(R); Pounce(R); Perigen(R);
Pramex(R); PP557; Qamlin(R); R86557; Stockade(R); Stomoxin(R);
S-3151; SBP-1513; Talcord(R); WL43479.
1.2 SYNOPSIS: Permethrin is a composite synthetic pyrethroid; a broad
spectrum, non-cumulative pesticide; and, a fast acting neurotoxin
with good contact, limited stomach and no fumigant action. It is
moderately stable in the environment and has good residual action
on inert surfaces. Permethrin is nonsystemic in plants; of low
mammalian toxicity,, and is readily metabolized with immediate
loss of toxicity.
1.3 SELECTED PROPERTIES
1.3.1 Physical characteristics - The pure isomers are colourless
crystals at ambient temperatures changing to a clear, pale
yellow, viscous liquid above the melting points of 63-65°C for
the cis isomers and 44-47°C for trans isomers. The boiling point
is 200°C/0.01 mmHg. The technical product is a viscous, brown
liquid which may partially crystallize at ambient temperatures
and is completely liquid above 60°C. The technical products boil
at 210-220°C/0.05 mmHg. The specific gravity is 1.190-1.272 at
20°C.
1.3.2 Solubility - at 20°C, less than 0.1 mg/l water
at 30°C, 0.2 mg/l water
+450.0 g/l acetone
+450.0 g/l cyclohexanone
+450.0 g/l ethanol
+450.0 g/l xylene
+450.0 g/l chloroform
it is soluble in or mixable with most organic solvents except
ethylene glycol.
1.3.3 Stability - Permethrin has good stability on plant surfaces
under severe conditions of temperature, humidity and solar
radiation but it is relatively unstable in most soils.
In solution it is stable under neutral and acidic pHs but
relatively unstable in alkaline conditions.
1.3.4 Vapour pressure - at 20°C, cis isomer 2 x 10-9 kPa
trans isomer 1 x l0-9 kPa
1.4 AGRICULTURE, HORTICULTURE AND FORESTRY
1.4.1 Common formulations -
Agronomic uses: Emulsifiable concentrates (100-500 g
a.i./l); fogging solutions (50 g/l) ; ULV concentrates
(50- 470 g/l) .
Veterinary uses: Emulsifiable concentrates (25-200 g
a.i./l) and dusts (2.5-10 g a.i./kg). For plant use the
cis:trans isomer ratio is 40:60 or higher, a lower ratio of
25:75 is available for use on animals and on animal shelter
surfaces.
1.4.2 Susceptible pests - Permethrin is effective, at low doses, as
an ovicide, larvicide and adulticide; and, as a repellent and
a feeding suppressor against a wide variety of insect
ectoparasites of plants and animals. It is particularly
effective against members of the Lepidoptera, Coleoptera,
Diptera and Heteroptera orders. However, as a lipophilic
substance lacking fumigant action it is not usually effective
against aphids, systemic parasites and soil pests except by
direct contact application. Mites, cockroaches, locusts
and grasshoppers are well controlled at high dose levels.
In addition to biting insects, other arthropod ectoparasites
such as ticks are well controlled on animals.
1.4.3 Use pattern - Permethrin is used in the protection of a wide
variety of field crops (cotton, tobacco, hops, fruits and
vegetables), in greenhouses, market gardens and vineyards.
Successful use in large-scale silviculture programmes is under
review. Permethrin may be applied from ground or from air
dispensers to field crops. It may be sprayed on plants in
enclosed areas and on inert surfaces for quick knockdown or
repellent effect or used as a dip or spray for animals. Some
biting insects are well controlled for several weeks by simply
applying the formulation to one or two dominant members of a
small herd (10-30 animals).
1.4.4 Unintended effects - Permethrin is not phytotoxic when used as
recommended, rapid degradation in soils, aquatic environment and
low mobility limit adverse effects on non-target organisms. It
is very toxic to bees.
1.5 PUBLIC HEALTH PROGAMMES
1.5.1 Common formulations - See 1.4.1, also available in hand held
aerosol and fogging formulations; as a transparent emulsion; and,
in a variety of formulations in combination with several other
active ingredients including, bioallethrin, copper sulfate,
dichlorvos, pirimicarb, pirimiphos-methyl, tetramethrin and
triforine.
1.5.2 Susceptible pests - Pemethrin is effective in the control of
several insect vectors of disease, ticks, ants, mosquitos, lice,
fleas, blackflies, tsetse fly, domestic flies and other pests
which contaminate food and water sources.
1.5.3 Use pattern - Most commonly permethrin is used as a spray or
fogging treatment of surfaces, buildings, plants, confined spaces
or larval habitats. Permethrin is very effective as a direct
contact poison or as a residual substance. It has been
experimentally absorbed onto fabric with good effect retained
after the fabric was washed. Permethrin has also been effective
when used as a low concentration dusting powder directly on
humans against body lice in experimental trials.
1.6 HOUSEHOLD AND INDUSTRIAL USE
1.6.1 Common formulations - See 1.4.1; also available in hand held
aerosol sprays or fogging devices; as a transparent emulsion;
and, in a variety of formulations in combination with several
other active ingredients including bioallethrin, copper sulfate,
dichlorvos, pirimicarb, pirimiphos-methyl, tetramethrin and
triforine.
1.6.2 Susceptible pests - See 1.5.2; Permethrin is also effective
against termites and woodboring beetles, silverfish, bed-bugs,
cockroaches, crickets and other undesirable arthropods.
1.6.3 Use pattern - Permethrin may be used as a space or surface spray;
as a residual film on inert surfaces, in fabrics and on exposed
wood. It is used for its knockdown and kill properties and as
a repellent.
2. TOXICOLOGY AND RISKS
2.1 TOXICOLOGY - MAMMALS
2.1.1 Absorption route - Permethrin is readily absorbed from the
gastrointestinal tract; minimally through the intact skin, in
non-polar solvents more rapidly than in aqueous solutions; and,
by inhalation of dust and fine spray mist.
2.1.2 Mode of action - Permethrin is a neurotoxin which acts directly
on neuron membranes. It prolongs sodium ion permeability during
the excitatory phase of the action potential thus effecting
repetitive activity in the sensory and motor pathways. The parent
compound is the neurotoxic agent.
2.1.3 Excretion - The metabolism of permethrin has been extensively
studied in rats and mice and in lactating cows and goats. The
two sets of cis and trans isomers are metabolized by liver
microsomal esterases and oxidases; however, the sequence of
enzyme activity and the relative contribution of each enzyme are
quite variable among the isomers and within animal species for
individual isomers. A concise and thorough review has been
published by D. R. Hutson (Prog. Drug. Metab., 3; Chap. 4, p.
215, 1979). The trans isomer metabolism is dominated by
hydrolysis whereas the cis isomers are less easily hydrolised and
more toxic. Oxidase activity in both isomers involves
stereospecific oxidation of the acid moiety,
cyclopropanecarboxylic acid; oxidation of the alcohol moiety, 3-
phenoxybenzyl alcohol (3-PB alc) to 3-phenoxybenzoic acid
(3-PBA); and hydroxylation of the alcohol moiety at positions
4', 6 and to a limited extent at position 2. Trans isomers are
excreted more rapidly than the cis isomers and excretion of the
acid radioisotope label is more rapid than that of the alcohol.
Hydrolysis resistance is associated with low urinary (45-55%)
and high faecal excretion of the cis isomers whereas trans
isomers are primarily eliminated in urine (81-90%). The major
excretion products of the alcohol moiety in both isomers are 4'-
HO-3-PBA sulfate in rats; 4'-HO-3-PBA (trans) and 6-HO-3-PBA
cis) sulfates in mice; and, N-(3-phenoxybenzoyl) glutamate in
cows. These, along with the cyclopropanecarboxylic acid
glucuronides and 3-PBA glucuronides are the primary excretion
products in most of the species studied. In rats the metabolism
of racemic permethrin is very rapid, some 42 metabolites have
been identified none of which have known toxic effects.
Elimination is rapid, following a single oral dose of a racemic
mixture over 50% of the radioactive lable was excreted within 48
hours. It is completely eliminated within 8 to 12 days of
administration.
2.1.4 Toxicity, sinple dose - The toxicity of the racemic mixture
varies with the cis/trans ratio and the characteristics of the
vehicle uged. In general the cis isomers are the most toxic and
non-polar carriers increase the toxicity of both isomers.
Oral LD50:
Rat (M) 430 mg/kg b.w.; racemic permethrin in corn oil
Rat (F) 470 mg/kg b.w.; racemic permethrin in corn oil
Mouse (M, F) 3 150 mg/kg b.w.; 1R, trans-permethrin
Mouse (M, F) 96 mg/kg b.w.; 1R, cis-permethrin
Mouse (M, F) +5 000 mg/kg b.w.; 1S, cis/trans-permethrin
Mouse (M) 310 mg/kg b.w.; racemic cis/trans = 75/25
Mouse (M) 470 mg/kg b.w.; racemic cis/trans = 50/50
Mouse (M) 1 620 mg/kg b.w.; racemic cis/trans = 25/75
Mouse (M) 490 mg/kg b.w.; racemic permethrin in corn oil
Mouse (M) +4 000 mg/kg b.w.; racemic permethrin in water
Rabbit (F) +4 000 mg/kg b.w.; racemic permethrin in water
Guinea-pig (M) +4 000 mg/kg b.w.; racemic permethrin in water
Dermal LD50:
Mouse (M, F) +2 500 mg/kg b.w.; racemic permethrin no solvent
Rat (M, F) +2 500 mg/kg b.w.; racemic permethrin no solvent
Rat (M, F) 750 mg/kg b.w.; racemic permethrin in xylene
Rabbit (F) +4 000 mg/kg b.w.; racemic permethrin no solvent
Subcutaneous LD5O:
Mouse (M, F) +10 000 mg/kg b.w.; racemic permethrin in corn oil
Rat (M, F) 6 500 mg/kg b.w.; racemic permethrin in corn oil
Intraperitoneal LD50:
Rat (M, F) +3 500 mg/kg b.w.; racemic permethrin in water
Mouse (M, F) 540 mg/kg b.w.; racemic permethrin no solvent
Inhalation LC50:
Mouse (M, F) +685 mg/m3; racemic permethrin in kerosine
Rat (M, F) +685 mg/m3; racemic permethrin in kerosine
In general pyrethroid poisoning is characterized by hyperactivity
and hypersensitivity (somatosensory). Permethrin is included
among those pyrethroids which produce the T-syndrome in rats,
consisting of hypersensitivity to external stimuli and fine whole
body tremors progressing to gross tremors and prostration.
2.1.5 Toxicity, repeated doses -
Oral: Beagle dogs were given permethrin in gelatin capsules for
three months at dosage levels of 5, 100 or 500 (mg/kg b.w.)/day
in one study and 10, 100 or 5000 (mg/kg b.w.)/day in a second
study. Transient clinical signs of toxicity were observed at 500
and 5000 mg/kg b.w. and liver to body weight ratios were
increased at 5000 mg/kg b.w./day.
Dermal: Rabbits administered up to 1.0 (g/kg b.w.)/day on intact
and abraded skin for 21 days showed no clinical signs of toxicity
other than moderate skin irritation and no other ill-effects. In
a 21 day wear-test, cotton cloth impregnated with permethrin
(0.125or 1.25 mg/cm2) applied to shaved, intact rabbit skin
produced no observed ill-effects.
Inhalation: Sprague Dawley rats subjected to permethrin at 0,
125, 250 or 500 mg/m3 for six hours a day, five days a week for
13 weeks in a metabolism and excretion study exhibited no
observed toxicological effects.
Cumulation of compound: Permethrin does not accumulate in body
tissues due to rapid metabolism and excretion.
Cumulation of effects: No evidence of adverse effects were
presented in the reports of subacute studies.
2.1.6 Dietary studies -
Short-term: Technical permethrin dissolved in corn oil was fed to
mice at dietary levels of 200 to 4000 mg/kg and to an additional
group, 80 mg/kg for two weeks increased to 10 000 mg/kg for the
remainder of the 28-day study; to rats in several studies of
different durations (from 4-26 weeks) and several ranges of
dietary levels up to 3000 mg/kg for 26 weeks, 4000 mg/kg for 13
weeks and 10 000 mg/kg for four weeks; and, to lactating cows at
dietary levels of 0.2 to 50 mg/kg for 28 days. Acetone solutions
of permethrin were given to rats at dietary levels up to 13 000
mg/kg for 90 days and 17 280 mg/kg for 14 days. There were no
observed compound related changes in growth. Mortality was not an
observed effect of permethrin administration except in rats fed
very high dose levels which were usually associated with reduced
food consumption. Corn oil solutions appear to be more toxic
than acetone solutions. In Sprague Dawley rats the observed
minimum lethal level for corn oil solutions was 5000 mg/kg (diet)
compared to 8640 mg/kg (diet) for acetone solutions.
Transient, early clinical signs of toxicity were observed in rats
at high sublethal doses only. Consistently in mice and rats,
liver weight and liver-to-body weight ratios were elevated by
permethrin administration and were accompanied by slight
hypertrophy and fatty changes; these changes were not permanent.
Compound-induced changes in histo-pathology suggestive of
tumorigenicity were not observed. In lactating cows permethrin
residues, originating from the cis isomer primarily, were found
to plateau at low levels in milk and body tissues within a few
days of initial administration. These residues were quickly
eliminated after cessation of exposure.
The observed no-effect level in rats was 2000 mg/kg diet in a 90-
day study, equivalent to 175 (mg/kg b w.)/day and 1500 mg/kg
(diet) in a 26-week study, equivalent to 93 (mg/kg b.w.)/day.
Long-term: At the time of preparation of this data sheet, only
four of several long-term studies were available in published
form. In two mouse chronic studies the dietary levels were 250,
1000 and 2500 mg/kg in one and, 20, 100 and 500 mg/kg in the
other. In the second study, after 2-3 weeks of administration,
the two highest dose levels were increased to 4000 and 5000 mg/kg
respectively, the latter increase was reversed after two weeks
however. In two chronic rat studies, dietary levels of 20, 100
and 500 mg/kg and 500, 1000 and 2500 mg/kg were administered.
There were no consistent compound-related changes in growth or
food consumption in either species. In general, mortality was
not an observed effect of permethrin administration although in
mice, at 4000 mg/kg, the incidence of mortality in the later
stage of the study was increased significantly. Permethrin
caused a dose-dependent increase in liver weights and liver-to-
body weight ratios in both species. In mice, and to a lesser
extent in rats, hepatocellular hypertrophy, pleomorphism and
hepatic degeneration were highest in the treatment groups and
were possibly dose dependent in mice. There was no oncogenic
effect due to permethrin in these studies. The rat chronic study
no effect level was observed to be 100 mg/kg (diet) equivalent
to 5.0 (mg/kg b.w.)/day.
2.1.7 Supplementary studies of toxicity -
Carcinogenicity: Administration of high doses of permethrin to
mice in long-term dietary studies was associated with significant
increases in very frequently occurring benign lung adenomas.
This apparent induction activity was restricted to only one sex
in any given study and to only one species. The lesion was not
seen in comparable rat studies. In mice, the increased incidence
was not associated with increased mortality, decreased latency or
increased malignancy. Furthermore, extensive mutagenicity
testing including point mutation, chromosomal aberration,
dominant lethal, Ames, DNA repair and mammalian cell
transformations (in vivo and in vitro studies) produced no
evidence of permethrin-induced genetic activity. Although
tumorigenic activity has been demonstrated in mice, collectively
these findings do provide any evidence of carcinogenic potential
for permethrin.
Teratogenicity: Permethrin was neither embryotoxic nor
teratogenic in a mouse study at dosage levels of 5-150 mg/kg b.w.
administered from days 7 through 12 of gestation nor in two rat
studies, one at 22.5 to 225 mg/kg b.w. from days 6 through 15 and
another study at 4-83 mg/kg b.w. (in corn oil) from days 6
through 16. It also did not adversely affect weaning efficiency
following normal deliveries in the mouse study nor in a third rat
study at dosage levels of 10-50 mg/kg b.w. administered from day
9 through 14 of gestation. In the latter rat study, the only
observed effect was a slightly increased incidence of
non-ossified sternebrae in the Caesarean delivered pups at
50 mg/kg b.w.
Mutagenicity: See carcinogenicity section above.
Reproduction: In a standard rat three-generation study,
permethrin at dosage levels of 20 and 100 mg/kg (diet) produced
no adverse reproductive effect (including indices of fertility,
gestation, viability and lactation). In a second rat study also,
permethrin at dosage levels of 500, 1000 and 2500 mg/kg (diet)
produced no adverse changes in standard indices of reproductive
success. In the F3 b-litters females displayed transient
clinical signs of acute toxicity, and dose-dependent increased
incidences of hepatic centrilobular hypertrophy and cytoplasmic
eosinophilia were observed in both sekes. (No teratogenic effects
were observed in a third set of litters of the F3 generations at
21 days of gestation.)
Neurotoxicity: In rats, high doses of pemethrin (6.0 g/kg of
diet for 14 days), caused some neuropathy, including minimal
demyelination and myelin ovoids on the sciatic nerve. Clinical
signs of neurotoxicity were observed at doses of 5.0 g/kg diet
and above.
Hens given 1.0 g/kg b.w. doses of permethrin in DMSO (p.o.)
showed no evidence of delayed neuropathy or other adverse effects
during three weeks of post-treatment observation. Changes in EEG
spike and slow wave patterns were observed in rabbits, cats and
guinea-pigs given 100 mg/kg b.w. in a single dose, no EEG changes
were observed at 30 mg/kg b.w.
Primary irritation and sensitization: In rabbits, technical
permethrin produced mild primary skin irritation following 24-
hour application of 0.5 ml to intact and abraded skin and mild
primary eye irritation (conjunctivitis) following ocular
instillation of 0.1 ml without rinsing.
Technical pemethrin did not produce sensitization reactions in
guinea-pigs in a standard Draize test nor acneform dermatitis in
rabbits following 30 daily applications of 0.1 ml to the ears.
It also did not cause dermal photochemical reactions in rabbits
under test conditions.
Special pharmacological effects: In rabbits, 4 mg/kg b.w.
produced hypotension, reduced respiration and an increased heart
rate with no attendant changes in ECG wave pattern. In mice,
dosage levels up to 2000 mg/kg b.w. did not change hexobarbital
induced sleeping time.
2.1.8 Modifications of toxicity - Esterase and oxidase enzyme systems
are important in the detoxification process, inhibitors of these
enzymes will increase the toxicity to permethrin in both mammals
and target organisms.
2.2 TOXICOLOGY - MAN
2.2.1 Absorption route - Permethrin may be readily absorbed from the
gastrointestinal tract; minimally through the intact skin,
especially in non-polar solvents; and by inhalation of dust and
fine spray mist.
2.2.2 Dangerous doses - No information available.
2.2.3 Observations of occupationally exposed workers - In Sweden 33% of
workers polled reported skin and eye irritation following
occupational exposure.
2.2.4 Observations on exposure of the general public - No information
available.
2.2.5 Observations of volunteers - In WHO trials in Nigeria, following
indoor use at doses of 0.5 g/m3, volunteers to exposure made no
complaint about adverse effects nor were any observed.
2.2.6 Reported mishaps - No information available.
2.3 TOXICITY TO NONMAMMALIAN SPECIES
2.3.1 Fish - Permethrin is highly toxic to fish, however the risk is of
short duration due to rapid loss from water by adsorption and
degradation. There have been no reports of problems of fish
toxicity during commercial use (including aerial application).
LC50 (96 h): Technical material
Rainbow trout 0.1-0.5 µg/l
Channel catfish 1.10 µg/l
Large-mouth bass (fingerlings) 8.50 µg/l
Mosquito fish 15.0 µg/l
Salmon 12.0 µg/l
LC50 (24 h):
Rainbow trout 25.0 µg/l (cis)
14.0 µg/l (trans)
18.0 µg/l (technical grade)
LD50 (I.P.):
Rainbow trout 22.0 mg/kg b.w. (cis)
7.0 mg/kg b.w. (trans)
14.0 mg/kg b.w. (technical grade)
2.3.2 Birds - Permethrin is of very low toxicity to birds. Hens
treated with coarse spray mist (3.77-11.94 mg/bird) showed no
adverse effects and no significant accumulation in body tissues
or eggs.
Oral LD50 acute: Technical material
Starlings +32 000 mg/kg b.w.
Mallard duck +11 275 mg/kg b.w.
Oral LD50 subacute:
Pheasants +23 000 mg/kg b.w.
Japanese quail +23 000 mg/kg b.w.
Starlings +23 000 mg/kg b.w.
2.3.3 Beneficial insects - In laboratory studies permethrin is found to
be toxic to bees; however, hazard in the field is limited by
repellancy, low rates of application and lack of toxic effect
once the spray has dried.
2.3.4 Others - Permethrin is toxic to some groups of aquatic
invertebrates, amphibian larval forms, insects and crustaceans.
However, due to the short persistence of permethrin, most
populations soon recover.
3. FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF
COMPOUND
3.1 RECOMMENDED RESTRICTIONS ON AVAIIABILITY - (For definition of
categories see introduction)
All current formulations: Category 5
3.2 TRANSPORTATION AND STORAGE
Formulations in category 5 - Should be transported and stored in
clearly labelled, leakproof containers out of reach of children,
away from food and drink. Avoid contact with metals other than
aluminium and tin.
3.3 HANDLING
Formulations in Category 5 - No facilities other than those
needed for the handling of any chemical are required.
3.4 DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS
All formulations - Containers may be decontaminated (for
method see paragraph 4.3 of Part 4). Decontaminated
containers should not be used for food and drink.
Containers that are not decontaminated should be burned or
should be crushed and buried below topsoil. Care must be
taken to avoid subsequent contamination of water sources.
3.5 SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS
Formulations in Category 5 - Warning of workers to minimize
contact is essential. Persons under medication with
neuroactive drugs should avoid contact.
3.6 ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT
All formulations - Pilots and loaders should have special
training in application methods and recognition of early
warning symptoms of poisoning and, they must wear a suitable
respirator. Flagmen should wear overalls and a broad brimmed
hat and be well away from the dropping zone.
3.7 LABELLING
Formulations in Category 5 - Minimum cautionary statement -
"CAUTION" - This formulation contains permethrin, it may be
poisonous if swallowed. Keep the material out of reach of
children and well away from foodstuffs, animal feed and food
containers.
3.8 RESIDUES IN FOOD
Maximum residue limits for permethrin have been recommended
by the joint FAO/WHO Meeting on Pesticide Residues.
4. PREVENTION OF POISONING IN MAN AND EMERGENCY AID
4.1 PRECAUTIONS IN USE
4.1.1 General - Permethrin is a synthetic pyrethroid and a neurotoxic
agent of low toxicity to mammals. It may be readily absorbed
from the gastrointestinal tract; by inhalation of dust and spray
mist; and, minimally through the intact skin. The health hazard
is considerably diminished by the low concentrations of the
active ingredient in all formulations.
4.1.2 Manufacture and formulation - T.L.V. - No information. Closed
systems and forced ventilation may be required to reduce, as much
as possible, the exposure of workers to the chemical.
4.1.3 Mixers and applicators - When opening a container and when
mixing, protective impermeable boots, clean overalls, impermeable
gloves, eye protection and a respirator should be worn. Mixing,
if not mechanical, should always be carried out with a paddle of
appropriate length. Avoid contact with mouth and eyes. Before
eating, drinking or smoking, hands and other exposed skin should
be thoroughly washed with alkaline soap.
4.1.4 Other associated workers (including flagmen in aerial operations)
- Persons exposed to permethrin and associated with its
application should observe the precautions described above in
4.1.3.
4.1.5 Other populations likely to be affected - With good agricultural
practice, subject to 4.2 below, other populations are not likely
to be exposed to hazardous amounts of permethrin.
4.2 ENTRY OF PERSONS INTO TREATED AREAS - Though permethrin is
relatively persistent, low application rates ensure low
residue levels. Unprotected persons may enter treated areas
almost immediately after spraying without being exposed to
hazardous amounts of permethrin.
4.3 SAFE DISPOSAL OF CONTAINERS AND SPILIAGES - Residues in
containers should be emptied in a diluted form into a deep
pit taking care to avoid ground waters. The empty container
may be decontaminated by rinsing two or three times with
water and detergent and scrubbing the sides. The hands
should be protected during this work. Decontaminated
containers should not be used for food and drink.
4.4 EMERGENCY AID
4.4.1 Early symptoms of poisoning - These may include nausea and
vomiting; shortness of breath and laboured breathing; fine or
coarse tremors, hypersensitivity to external stimuli and general
weakness, and prostration. A burning and itching sensation often
follow contact.
4.4.2 Treatment before person is seen by a physician, if these symptoms
appear following exposure- The person should stop work
immediately, remove contaminated clothing and clean the affected
skin area. First, soak-up any liquid remaining on the skin with
readily disposable material (e.g., talcum powder or absorbant
cloth or paper), wash the affected area with warm water and
alkaline soap. For eye contamination, wash with copious amounts
of 4% sodium bicarbonate or water. Avoid exposing affected skin
or eyes to bright light. If the material was swallowed and signs
of toxicity are severe, induce vomiting if the person is
conscious and aspiration of vomit can be avoided. In the event of
collapse, apply artificial respiration. Keep in mind that if
mouth to mouth respiration is used, vomit may contain toxic
amounts of permethrin. Keep the person calm and comfortable and,
obtain medical help as soon as possible.
5. FOR MEDICAL AND LABORATORY PERSONNEL
5.1 MEDICAL DIAGNOSIS AND TREATMENT OF POISONING
5.1.1 General information - Permethrin is a synthetic pyrethroid
pesticide of low toxicity to mammals. It is readily absorbed
from the gastrointestinal tract; by inhalation of dust and spray
mist; and, through the intact skin to a limited extent. The
hydrolysis and oxidation products of metabolism are rapidly
excreted in the urine and faeces. Permethrin is a neurotoxic
agent most probably acting on the central nervous system to cause
repetitive nerve activity.
5.1.2 Signs and symptoms - Little information is available on the acute
toxic effects of permethrin in humans. Based upon animal
studies, high doses may cause repetitive activity in sensory and
motor nerves. Early signs of poisoning may include nausea and
vomiting; dyspnoea and hyperpnoea; fine or coarse tremors,
hypersensitivity to stimuli and a feeling of general weakness and
prostration. A burning and itching sensation often follow
contact.
5.1.3 Laboratory - There are no established, practical methods for
determining permethrin in body fluids. Urinary levels of 3-
phenoxybenzyl degradation products may be a useful index of
exposure. In addition, electrophysiological monitoring of
sensory nerve potentials and, central nervous and cardiac
activities (EEG and ECG) may be useful in diagnosis and in
assessment of therapy.
5.1.4 Treatment - There are no specific antidotes, treatment must be
symptomatic. Keep the patient warm and calm. In cases of severe
intoxication, therapy should include a sedative and
anticonvulsant (e.g. barbiturates, diazepam, paraldehyde, etc.).
The use of antispasmodic drugs is of limited value, mephenesin
and atropine have been found to effectively alleviate the
symptoms of pyrethroid poisoning in laboratory animals. If a
large quantity of permethrin has been swallowed, unless the
patient is unconscious or vomiting, gastric lavage should be
perfomed using a 5% sodium bicarbonate solution, follow with
powdered activated charcoal. For skin contact, soak up any
liquid remaining on skin with readily disposable absorbent
material, then wash the affected area with warm water and
alkaline soap. If skin irritation occurs treat with a soothing
skin cream and avoid exposure to direct light. For eye
contamination, wash the eye with 4% sodium bicarbonate or any
other non-irritating, alkaline aqueous solution.
5.1.5 Prognosis - There have been no reports of overt symptoms
resulting from poisoning of man by permethrin; the prognosis
therefore is not known. However, by analogy with laboratory
animals it may be assumed that if the acute toxic effect is
survived the chances of complete recovery are good.
5.1.6 References to previously reported cases - No information.
5.2 SURVEILLANCE TESTS - None.
5.3 LABORATORY METHODS - References only are given,
5.3.1 Detection and assay of compound and residues -
Chapman, R. A. & Harris, C. R. (1978) Journal of Chromatography,
166(2), 513-516
Chiba, M. (1978) J. Environ. Sci. Health, B13(3), 261-268
Fujie, G. H. & Fullmar, D. H. (1978) J. Agric. Food Chem.,
26(2), 395-398
Horiba, M., Akira, K. & Murano., A. (1977) Agric. Biol. Chem.,
41(3), 581-586
Kikta, E. J. & Shierling, J. P. (1978) Journal of Chromatography,
150, 229-232
Lam, S. & Grushka, E. (1978) Journal of Chromatography, 154,
318-320
Oshler, D. D. (1979) J. Assoc. Off. Anal. Chem., 62(6),
1309-1311
Papadopoulou-Mourikidou, E., Iwata, Y. & Gunther, F. A. (1980)
J. Agric. Food Chem., 28(6), 1043-1049
Siegel, M. W., Hildebrand, B. E. & Hall, D. R. (1980) Intern.
J. Environs Anal. Chem., 8, 107-126
5.3.2 Other tests in case of poisoning - No information.