WORLD HEALTH ORGANIZATION FOOD AND AGRICULTURE ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE ORGANISATION POUR L'ALIMENTATION
ET L'AGRICULTURE
VBC/DS/82.49
ORIGINAL: ENGLISH
DATA SHEETS ON PESTICIDES No. 49
PIRIMIPHOS-METHYL
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.
R 185
CLASSIFICATION:
Primary use: Insecticide
Secondary use: Acaricide
Chemical group: Organophosphorus Compound
Date issued: January 1983
1. GENERAL INFORMATION
1.1 COMMON NAME:
Pirimiphos-methyl (BSI, ISO, ANSI)
1.1.1 Identity:
IUPAC 0,2-diethylamino-6-methylpirimidin-4-yl O,O-
dimethyl phosphorothioate
CAS No. 1 phosphorothioic acid, O-(2-(diethylamino)-6-
methyl-4-pyridinyl) O,O-diethyl ester
Cas Reg. No. 29232-93-7
Mol. Formula C11H20N303PS
Mol. Wt. 305.3
1.1.2 Synonyms:
ActellicR; ActellifogR; BlexR; PP511 (discontinued name);
SilosanR; SybolR; OMS 1424.
1.2 SYNOPSIS:
Pirimiphos-methyl is a broad spectrum, non-cumulative
organophosphorus pesticide; a cholinesterase inhibitor with fast
acting fumigant, contact, and stomach action; and slightly toxic to
mammals. Pirimiphos-methyl has translaminar action when sprayed on
plants; short persistence on growing plants; and, long persistence
on inert surfaces, including stored grain.
It is fairly rapidly degraded in the environment.
1.3 SELECTED PROPERTIES
1.3.1 Physical characteristics
The pure substance is a straw-coloured liquid. It has no
characteristic odour; a M.P. of 15-18°C - it freezes to a white
solid at 15°C; a density (d30) of 1.157; and, a refractive index
(nD25) of 1.527. The U.V. spectrum is a strong absorption band
at 248 nm and a weaker band at 300 nm. Weakly alkaline, it is
slightly corrosive to tinplate and mild steel but not corrosive to
brass, copper, stainless steel, nylon, polyethylene or aluminium.
1.3.2 Solubility
5.0 mg/l water at 30°C; miscible with, or very soluble in most
organic solvents.
1.3.3 Stability
Stable for up to six months at normal room temperature, readily
hydrolysed by concentrated acids and alkalis; decomposes in
sunlight, low biological persistence on foliar surfaces and in plant
tissues but excellent persistence on inert surfaces and on stored
crops.
1.3.4 Vapour pressure
1.47 x 10-5 kPa (1.1 x 10-4 mm Hg) at 30°C.
1.4 AGRICULTURE, HORTICULTURE AND FORESTRY
1.4.1 Common formulations
E.c. (250 and 500 g a.i./1), U.L.V. concentrate (500 g a.i./1),
encapsulated formulation (200 g a.i./1), dusts (10 and 20 g
a.i./kg), w.p. (250 and 400 g a.i./kg), a fog (100 g a.i./1), an
aerosol (20 g a.i./1 with pyrethroids), a solvent free formulation
(900 g a.i./kg) and a smoke generator formulation.
1.4.2 Susceptible pests
Pirimiphos-methyl is active against a wide variety of pests
including ants, aphids, beetles, caterpillars, cockroaches, fleas,
flies (including houseflies, Drosophila, and biting flies), mites,
mosquitos, moths, thrips, whiteflies and scales.
1.4.3 Use pattern
Pirimiphos-methyl is used as a general insecticide; in pre-
harvest clean up of fruits and vegetables; and on horticultural
plants. It is not recommended for use on celery. Pre-harvest
withholding intervals of three to seven days are recommended
following spray application, no such intervals are necessary
following the use of fogs or smokes. Pirimiphos-methyl is also used
for eradication of a wide range of stored product pests for long
duration protection and, to control nuisance and disease vector
insects.
1.4.4 Unintended effects
None reported.
1.5 PUBLIC HEALTH USE
1.5.1 Common formulations
E.c. (250 and 500 g a.i./1), U.L.V. concentrate (500 g a.i./1),
encapsulated formulation (200 g a.i./1), dusts (10 and 20 g
a.i./kg), w.p. (250 and 400 g a.i./kg), a fog (100 g a.i./1), an
aerosol (20 g a.i./1 with pyrethroids), a solvent-free formulation
(900 g a.i./kg) and a smoke generator formulation.
1.5.2 Susceptible pests
Ants, beetles, bed-bugs, cockroaches, fleas, flies, lice,
mites, mosquitos, and others as in 1.4.2.
1.5.3 Use pattern
Pirimiphos-methyl is used as a residual insecticide in malaria
control programmes, applied indoors on walls and ceilings at 1 or 2
g a.i./m2, usually as a 2.5-5% suspension at three-monthly
intervals. It is also used as a U.L.V. spray and in thermal fogs to
control mosquitos vectoring viral infections and, as a mosquito
larvicide. It is extensively used as a residual spray in fly control
programmes and as a 2% dust in rodent burrows to control DDT
resistant fleas. It should not be used directly on humans or on
processed foods.
1.5.4 Unintended effects
None reported.
1.6 HOUSEHOLD USE
1.6.1 Common formulations
It is available in emulsifiable concentrates (80 g a.i./1),
dusts and aerosols (with pyrethroids) for home and garden use.
1.6.2 Susceptible pests
Ants, beetles, bed-bugs, cockroaches, fleas, flies, lice,
mites, mosquitos, wasps, and many nuisance insects and other
arthropods.
1.6.3 Use pattern
As recommended by manufacturer; do not use on processed food.
Do not harvest food crops until at least seven days after the last
spray application.
1.6.4 Unintended effects
None reported.
2. TOXICOLOGY AND RISKS
2.1 TOXICOLOGY - MAMMALS
2.1.1 Absorption route
Pirimiphos-methyl may be absorbed from the gastrointestinal
tract; through the intact skin; and less commonly, by inhalation of
fogs, smokes or spray mists.
2.1.2 Mode of action
Cholinesterase inhibition by pirimiphos-methyl. The degradation
products desethyl pirimiphos-methyl and pirimiphos-methyloxon are
also active but of transient stability and have not figured
significantly in mammalian studies.
2.1.3 Excretion products
Detoxification of pirimiphos-methyl by metabolism and excretion
is very rapid in mammals. In 14C-labelled pirimiphos-methyl dosed
rats, over 70% of the radioactivity was excreted within 24 hours and
100% within five to six days, 85% in urine and 15% in faeces. Twelve
metabolites, none with cholinesterase inhibiting activity, were
detected in the urine of treated rats and dogs. Metabolism,
quantitatively similar in both species, proceeds primarily by
cleavage of the P-O bond. The oxon product appears to be an
important active intermediary which is rapidly detoxified in
homeotherms.
2.1.4 Toxicity, single dose
Oral: LD50 Rat (M) 1450 mg/kg b.w.
Rat (F) 1840-2260 mg/kg b.w.
Rabbit (M) 1154-2300 mg/kg b.w.
Mouse (M) 1030-1360 mg/kg b.w.
Guinea-pig (F) 1000-2000 mg/kg b.w.
Dog (M) > 1500 mg kg b.w.
Cat (F) 575-1150 mg kg b.w.
In acute oral toxicity studies on rats the onset of toxicity
signs was delayed 12-14 hours after dosing and persisted for 10-12
days.
Dermal: LD50 Rat (F) > 4500 mg/kg b.w.
I.P.: LD50 Rat (M) 800 mg/kg b.w.
Most susceptible species: No appreciable species variability
among the mammals tested; the hen (LD50 79-80 mg/kg) is the most
susceptible.
2.1.5 Toxicity, repeated doses
Oral: Groups of male and female rats were dosed for two
weeks, five days a week. At 200 mg/kg only mild signs were observed,
toxicity was delayed and reversible. There were no mortalities; body
weights and haemoglobin were reduced; reticulocytosis and spleenic
haematopoesis were observed. At 400 mg/kg severe signs of poisoning
appeared after the second dose; the severity of toxicity increased
with each successive dose; the cumulative mortality was nine of 10
rats from day 4 for males and three of 10 from day 6 for females.
Inhalation: Male and female rats exposed to a nominal vapour
concentration of 3.5 ppm for three weeks showed no signs of toxicity
during the study period, no change in blood cholinesterase levels
and no gross or histopathologic effects.
Dermal: In rabbits, a daily application of 1000 mg/kg b.w. of
pirimiphos-methyl for two weeks produced mild, reversible signs of
poisoning and the onset of poisoning was delayed for several days.
In a later 21-day study, the insecticide was applied to intact or
abraded skin of male and female rabbits in occluded applications of
0, 4, 40 or 400 mg/kg b.w. No treatment related adverse clinical
signs, gross or histopathologic changes were observed. At the
highest dose, on abraded skin, food consumption and plasma
cholinesterase levels were depressed in both sexes; body weights
were reduced in the females only. It was concluded that 40 mg/kg
b.w. is a clear "no-effect" level for rabbits.
Cumulation of compound: There was no evidence of accumulation
of pirimiphos-methyl, or its metabolites in liver, kidney or adipose
tissue of rats following four successive 7.5 mg/kg b.w. per oral
daily doses of the 14C-labelled insecticide. In similar studies on
domesticated animals there was no evidence of residue accumulation
in either body tissues or animal produce.
Cumulation of effects: Repeated exposure of rats to high
doses of pirimiphos-methyl produced cumulative inhibitory effects on
cholinesterase activity.
2.1.6 Dietary studies
Short-term: Pirimiphos-methyl was fed to four groups of rats
(male and female) for 90 days at levels of 0, 8, 80 and 360 mg/kg
diet. There were no mortalities in any of the dose groups. No
effects were observed in the 8 mg/kg diet group. In the groups fed
80 and 360 mg/kg significant signs of toxicity were observed; plasma
and brain cholinesterase were inhibited; and, in females, there was
a significant reduction in weight gain. In the group fed 360 mg/kg
diet, the same effects were observed as in the 80 mg/kg group, but
they were more severe and more rapid in onset; and, erythrocyte
cholinesterase was inhibited. With the exception of brain
cholinesterase activity the above effects were rapidly reversed upon
cessation of treatment.
Pirimiphos-methyl was given groups of dogs, both male and
female, for 90 days at dose levels of O, 2, 10 or 25 mg/kg b.w.
There were no mortalities. Females in the 10 and 25 mg/kg groups and
males in the 25 mg/kg group showed reduced weight gains which were
easily reversed on cessation of treatment. At all dose levels there
was a mild and reversible depression of plasma cholinesterase
activity. At 10 and 25 mg/kg erythrocyte cholinesterase depression
was marked and recovery was slow. Bile duct proliferation was
observed in four out of 16 high dose dogs, three of those had
received the 25 mg/kg dose. In a repeat study at 25 mg/kg, minimal
bile duct proliferation was seen in two of the 10 animals but it was
not observed in two dogs whose dose had been progressively raised to
50 mg/kg b.w. from the eighth week onwards.
Long-term: Pirimiphos-methyl was fed to groups of female and
male mice for 80 weeks at concentrations of 0, 5, 250 or 500 mg/kg
of diet. Animal deaths and rumour incidence were comparable between
controls and treatment groups. At 250 and 500 mg/kg, plasma and
erythrocyte cholinesterase was inhibited. The mouse "no-effect"
level was determined from the 5.0 mg/kg diet to be equivalent to 0.5
(mg/kg b.w.)/day.
Pirimiphos-methyl was fed to groups of male and female rats for
two years at concentrations of 0, 10, 50 or 300 mg/kg of diet. A few
animals from each test group were kept on normal diet for an
additional four to eight weeks, for recovery observations. With one
exception, in males at 300 mg/kg between weeks 54 and 72, there was
no treatment related increase in cumulative mortalities within the
test groups. No adverse effects were seen apart from cholinesterase
inhibition. Marked plasma cholinesterase depression and some
erythrocyte and brain cholinesterase inhibition were observed at 300
mg/kg. At 50 mg/kg, only female plasma cholinesterase activity was
depressed. In all cases these enzyme activities returned to normal
within four weeks after cessation of dosing. On the 10 mg/kg diet,
no ill-effects were observed and therefore this dose was selected
for the "no-effect" level for rats, equivalent to 0, 5 (mg/kg
b.w.)/day.
In a two-year study of dogs, pirimiphos-methyl was given per
oral in doses of 0, 0.5, 2 or 10 (mg/kg b.w.)/day. Mild signs of
toxicity were seen in all the high dose animals. There was no
increase in gross or histopathologic incidences in any of the
treatment groups. Erythrocyte and plasma cholinesterase activities
were depressed in the 2 and 10 mg/kg groups, brain cholinesterase
was inhibited at the 10 mg/kg level only. Cholinesterase activity
was normal at the lower dose level, 0.5 (mg/kg b.w.)/day was
selected as the "no-effect" level for dogs.
2.1.7 Supplementary studies of toxicity
Carcinogenicity: No evidence of carcinogenic activity was
observed in the several diet studies described in section 2.1.6. In
addition, no evidence supportive of a carcinogenic potential for
pirimiphos-methyl was found in several mammalian mutagenicity
studies.
Teratogenicity: No evidence of teratogenicity was observed in
studies of pregnant rats and rabbits fed pirimiphos-methyl in their
diets at concentration levels of 10 and 20 mg/kg and 1 and 16 mg/kg
respectively, for the duration of gestation. In both studies the
litter size was increased and the foetus weights were decreased by
the treatment. Pirimiphos-methyl has been shown to be teratogenic in
chick-egg injection studies only, inducing micromelia and abnormal
feathering after dosing on the fourth day of incubation. However, no
teratogenic effects were observed in a dietary study in laying-hens
at dose levels of 4' to 40 mg/kg of diet.
Reproduction: Pirimiphos-methyl was fed continuously to rats
in two three-generation studies, in one the dose levels were 5, 10
and 100 mg/kg (diet) and in the other were 20 and 200 mg/kg (diet).
No treatment related embryotoxic effects were observed in either
study. The pesticide had no adverse effect on reproduction
performance at dose levels up to 100 mg/kg (diet), at 200 mg/kg
(diet) the pregnancy rate was slightly depressed. (See also the
section on teratogenicity above.)
Mutagenicity: Pirimiphos-methyl showed no mutagenic potential
in several mammalian studies including two three-generation studies,
a micronucleus test in young female ICR mice, or in a mouse dominant
lethal study. It was found to be mutagenically active in a plate
assay of six out of seven S. typhimurium strains but in none of
the E. coli strains used in microbial screening tests.
Irritation and sensitization: There were no signs, of
sensitization nor primary irritation in a 24-hour occluded patch
test in which a 50% pirimiphos-methyl solution in olive oil was
applied to the dorsal skin of guinea-pigs and in another study in
which the undiluted compound was applied to the dorsal skin of rats.
Neurotoxicity: Two groups of five hens were given single oral
doses of pirimiphosmethyl at 50 and 60 mg/kg. One hen died in the
first dose group and three in the latter, at 21 days the dead
animals were replaced, all the hens in each group were redosed and
protected with atropine and pralidoxime. The hens were observed for
an additional 21 days, no neurotoxicity was found in the treatment
groups that could be attributed to pirimiphos-methyl.
In another study, 10 birds received 0, 0.5, 1.0, 2.5, 5.0 or 10
mg/kg b.w. by direct intubation daily for 90 days. There were no
clinical or histopathological findings associated with
neurotoxicity.
2.2 TOXICOLOGY - MAN
2.2.1 Absorption
It may be absorbed from the gastrointestinal tract; through the
intact skin; and, by inhalation of fogs, smokes or spray mist when
used in confined spaces.
2.2.2 Dangerous doses
Single: Not known.
Repeated: Not known.
2.2.3 Observations of occupationally exposed workers
A total of 35 trained personnel participated in two separate
WHO-supervised public health spray programmes, none showed any ill-
effects attributable to pesticide poisoning. At the termination of
one programme three of the 12 spraymen showed plasma cholinesterase
activities which were 70-75% of the mean of two pre-exposure values.
2.2.4 Observations on exposure of the general public
The inhabitants of two locations involved in the above-
mentioned pirimiphos-methyl spray programmes did not show or
complain of any ill-effects attributable to pesticide poisoning; no
observations of cholinesterase activity were reported.
2.2.5 Observations on volunteers
Liver function and blood test results were within the normal
limits in two groups of volunteers given 0.25 (mg/kg)/day, five
males for 28 days and three males and four females for 56 days. From
these results, 0.25 (mg/kg)/day was accepted as the "no observed
effect" level. The acceptable daily intake (ADI) was established at
0.01 mg/kg; the ADI represents the sum of the oxygen analogue,
n-desmethyl pirimiphos-methyl and the parent compound in total
expressed as pirimiphos-methyl.
2.2.6 Reported mishaps
There are no reports of human poisoning attributed to
pirimiphos-methyl.
2.3 TOXICITY TO NON-MAMMALIAN SPECIES
2.3.1 Fish
LC50, static tests: Carp (24-hour) 1.6 mg/l
Carp (48-hour) 1.4 mg/l
Rainbow trout (48-hour) 0.25 mg/l
LC50, flow through tests: Rainbow trout (24-hour) 0.78 mg/l
Rainbow trout (48-hour) 0.53 mg/l
Fathead minnow (24-hour) 5.60 mg/l
Fathead minnow (48-hour) 4.10 mg/l
The threat to fish is greatly reduced by the strong tendency of
pirimiphos-methyl to decompose in aqueous solutions and, to undergo
photo-oxidation.
2.3.2 Birds
Oral: LD50 Chickens 79-80 mg/kg
Japanese quail 140 mg/kg
Green finches 200-400 mg/kg
I.P.: LD50 Japanese quail 140 mg/kg
Diet: LC50 Mallard ducklings 630 mgkg
Bobwhite quail chicks 207 mg/kg
In two diet studies, chickens were fed pirimiphos-methyl in
doses ranging from 4 to 40 ppm, there was no lasting adverse effect
on hens, chicks; or, egg production, quality, or hatchability.
The relatively high toxicity of pirimiphos-methyl to birds
appears to be related to a deficiency of esterases that hydrolyze
pirimiphos-methyloxon. In 14 species of birds representing six avian
orders the rate of hydrolysis of the oxon by in vitro plasma
A-esterase ranged from a non-detectable-level to 71 (nmoles/min.)/ml
plasma, at best it was less than 10% of the lowest recorded
mammalian rate.
2.3.3 Other species
No information.
3. FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION
OF COMPOUND
3.1 RECOMMENDED RESTRICTIONS ON AVAILABILITY
(For definitions of categories, see introduction).
Liquid and solid formulations above 10 and 30% respectively:
category 4.
Other formulations: category 5.
3.2 TRANSPORT AND STORAGE
Formulations in category 4 - Should be transported and stored
in clearly labelled, rigid and leakproof containers, under lock and
key, secure from access by unauthorized persons and children. No
food or drink should be transported or stored in the same
compartment.
Formulations in category 5 - Should be transported and stored
in clearly labelled leak-proof containers out of reach of children,
away from food and drink.
3.3 HANDLING
Formulations in category 4 - Protective clothing (see 4.1.3-
4.1.4) should be used by all persons handling the compound. Adequate
facilities should be available at all times during the handling and
should be close to the site of handling. Eating, drinking and
smoking should be prohibited during handling and before washing of
hands and face.
Formulations in category 5 - No facilities other than those
needed for handling of any chemical are required.
3.4 DISPOSAL AND/OR DECONTAMINATION OF CONTAINER
Containers may be decontaminated. Decontaminated containers
should not be used for food or drink. If not decontaminated, empty
containers should be burned or crushed and buried below topsoil.
Care must be taken to avoid subsequent contamination of water
resources.
3.5SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS
Formulations in category 4 - Pre-employment medical
examination of workers is desirable. Workers suffering from active
hepatic or renal disease should be excluded from contact. Special
account should be taken of workers' mental ability to comprehend and
follow instructions. Training of workers in techniques to avoid
contact is essential.
Formulations in category 5 - No pre-employment medical
examination for workers is necessary. Warning to workers to minimize
contact is essential.
3.6 ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT
All formulation - Pilots and loaders should have special
training in application methods and in recognition of early symptoms
of poisoning. Loaders must wear overalls, rubber gloves and goggles.
Flagmen should wear overalls and an impermeable brimmed hat; and
should be located well away from the dropping zone.
3.7 LABELLING
Formulations in category 4 - Minimum cautionary statement -
Pirimiphos-methyl is an organophosphorus compound. It is of low
toxicity and should not be used by people under medical advice not
to work with such compounds. Avoid all mouth contact, skin contact
or inhalation of spray, dust, fog or smoke. Wash splashes from skin
and eyes immediately wash hands before eating or smoking after
handling the pesticide and, wash oneself and change clothing
immediately after work.
When handling concentrates wear protective gloves, a face
shield, and clean protective clothing. When using foggers or when
fumigating indoors, wear protective gloves, rubber boots, a rubber
coat, sou'wester and a respirator and do not re-enter treated spaces
until they have been thoroughly ventilated.
Remove or cover all food and animal feedstuffs prior to
application and do not apply to food preparation surfaces or
utensils.
Store pesticide in the original container, tightly closed and
in a safe place away from children. Wash out empty containers
thoroughly and dispose of safely. Do not contaminate ponds,
waterways, ditches or ground waters with either the chemical
directly or the used container.
Do not harvest the indicated food crops for human consumption
before the specified interval has elapsed between last application
and harvest. Avoid application when bees are active.
If poisoning occurs take the patient to the hospital
immediately. Atropine and pralidoxime are specific antidotes. No
sedatives should be given. Oxygen and artificial respiration may be
necessary.
Formulations in category 5 - Minimum cautionary statement -
This formulation contains pirimiphos-methyl, a cholinesterase
inhibitor. Avoid all mouth and skin contact, or inhalation of spray
mist, dust, fog or smoke. Wash hands after use. Store in the
original container in a safe place away from children and pets. Wash
out empty container thoroughly and dispose of safely. In addition,
for aerosol preparations, keep away from heat (including sun) and do
not puncture or incinerate even when empty. Do not apply directly on
to food, food utensils or food preparation surfaces. Do not harvest
food crops until at least seven days after the last application.
3.8 RESIDUES IN FOOD
Maximum residue limits for pirimiphos-methyl have been
recommended by the WHO/FAO Meeting on Pesticide Residues.
4. PREVENTION OF POISONING IN MAN AND EMERGENCY AID
4.1 PRECAUTIONS IN USE
4.1.1 General
Pirimiphos-methyl is an organophosphorus pesticide of low
mammalian toxicity which inhibits cholinesterase activity.
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 the container and when mixing, care should be
taken to avoid contact with the mouth and eyes. If necessary, a
facial visor and gloves should be worn. Mixing, if not mechanical,
should always be carried out with a paddle of appropriate length.
Splashes should be washed immediately from the skin or eyes with
large quantities of water. Before eating, drinking or smoking, hands
and exposed skin should be washed. If contaminated, clothing should
be washed at the end of a working day.
4.1.4 Other associated workers (including flagmen in aerial
operations)
Persons exposed to pirimiphos-methyl and associated with its
application should wear clean overalls and observe the precautions
described above in 4.1.3 under "Mixers and applicators".
4.1.5 Other populations likely to be affected
With correct use in agriculture, public health and in the home,
the general population should not be exposed to hazardous amounts of
pirimiphos-methyl. Harvesting intervals should be observed, as shown
on the label they range from three to seven days depending upon the
crop.
4.2 ENTRY OF PERSONS INTO TREATED AREAS
Unprotected persons may enter a treated area immediately after
spraying, however, they should not enter premises recently treated
by sprays, fogs or smokes before those premises have been thoroughly
ventilated.
4.3 DECONTAMINATION OF SPILLAGE AND CONTAINERS
Residues in containers should be emptied in diluted form into a
deep pit taking care to avoid contamination of groundwaters. The
empty containers may be decontaminated by rinsing two or three times
with water and scrubbing the sides. An additional rinse should be
carried out with a 5% sodium hydroxide solution which should remain
in the container overnight. Impermeable gauntlets should be worn
during the work and a soakage pit should be provided for the
rinsings. Decontaminated containers should not be used for food or
drink. Spillage of pirimiphos-methyl and its formulations should be
removed by washing with 5% sodium hydroxide solution and then
rinsing with large quantities of water.
4.4 EMERGENCY AID
4.4.1 Early symptoms of poisoning
These may include excessive sweating, headache, weakness,
giddiness, nausea, vomiting, stomach pains, blurred vision, slurred
speech and muscle twitching. Later there may be convulsions, coma,
loss of reflexes and loss of sphincter control.
4.4.2 Treatment before person is seen by physician, if these
symptoms appear following exposure
The person should stop work immediately, remove contaminated
clothing and wash contaminated skin with soap and water, if
available, and flush with large quantities of water. Vomiting should
not be induced unless it is reasonably certain that a potentially
lethal dose has been swallowed and, provided that the person is
conscious - inhalation of the solvent must be avoided. In the event
of collapse artificial respiration should be given bearing in mind
that if mouth to mouth respiration is used, vomit may contain toxic
amounts of pirimiphos-methyl.
5. FOR MEDICAL AND LABORATORY PERSONNEL
5.1 MEDICAL DIAGNOSIS AND TREATMENT IN CASE OF POISONING
5.1.1 General information
Pirimiphos-methyl is an organophosphorus pesticide of low
mammalian toxicity which may be absorbed from the gastrointestinal
tract; through the intact skin; and by inhalation when fog and smoke
generators are used or when spraying in a confined space. It acts by
inhibiting acetycholinesterase. Continuous exposure to low amounts
may inhibit blood cholinesterase to hazard levels.
5.1.2 Symptoms and signs
Initial symptoms of poisoning may include excessive sweating,
headache, weakness, giddiness, nausea, vomiting, stomach pains,
blurred vision, slurred speech and muscle twitching. More advanced
symptoms of poisoning may be convulsions, coma, loss of reflexes and
loss of sphincter control.
5.1.3 Laboratory
The most important finding is reduction in activity of blood
cholinesterases. Urinary levels of organic phosphorus containing
metabolites could also be used as a measure of exposure. Neither
method is specific for pirimiphos-methyl.
5.1.4 Treatment
If a potentially lethal dose has been ingested, unless the
patient is vomiting, rapid gastric lavage should be performed. For
skin contact, the skin should be washed with soap and water. If the
compound has entered the eyes, they should be washed with isotonic
saline. Persons without signs of respiratory inefficiency but with
manifest peripheral symptoms should be treated with 2-4 mg of
atropine sulfate and 1000-2000 mg of pralidoxime chloride or 250 mg
of toxogonin (adult dose) by slow intravenous injection. More
atropine may be given as needed. Persons with severe intoxication
and with respiratory difficulties, convulsions and unconsciousness
should immediately be given atropine and a reactivator. In such
severe cases 4-6 mg of atropine sulfate should be given initially,
followed by repeated doses of 2 mg at five to 10 minute intervals.
The patient's condition including respiration, blood pressure, pulse
frequency, salivation and convulsions should be carefully observed
as a guide to further administration of atropine. If the patient is
cyanotic, oxygen should be given at the same time as atropine
sulfate. The airways should be kept free and artificial respiration
may be required, preferably by mechanical means. If necessary,
intubation should be perforated. Contraindications are morphine,
barbiturates, phenothiazine, tranquillizers and central stimulants
of all kinds.
5.1.5 Prognosis
If the acute toxic effect is survived and adequate artificial
respiration has been given, if needed, the chances of recovery are
good. However, in very severe cases particularly if artificial
respiration has been inadequate, prolonged anoxia may give rise to
permanent brain damage.
5.1.6 References to previously reported cases
None.
5.2 SURVEILLANCE TESTS
Test Normal Action Symptomatic
level* level* level*
Plasma cholinesterase 100% 50% variable
Whole blood or erythrocyte
cholinesterase 100% 70%
* Expressed as percentage of pre-exposure activity.
Urinary levels of ether-extractable phosphorus compounds may
also be used to determine the degree of exposure.
5.3 LABORATORY METHODS
References only are given,
5.3.1 Detection and assay of compound
Yuen, S. A. (1976) Analyst (London), 101, 533
Bullock, D. J. W. (1976) Analytical methods in pesticides and
plant growth regulators, Vol. VIII, Chapter 9, 185
Kirasnykh, A. A. (1978) Kimiya V Sel'Skom Khozaistve, 16, 36
5.3.2 Other tests in cases of poisoning
The level of cholinesterase in the blood, particularly the
plasma, provides the most useful diagnosis of poisoning, see:
Ellman, G. L. et al. (1961) Biochem. Pharmacol., 7, 88. Michel, N.
O. (1949) J. Lab. Clin. Med., 34, 1564.
Plasma and urine levels of methanol extractable pirimiphos-
methyl and pirimiphos-methyl metabolites may also be useful in
diagnosis of poisoning, see: Brealey, C. J. & Lawrence, D. K. (1979)
Journal of Chromatography, 168, 461.
Note: This data sheet was drafted in the Bureau of Chemical
Standards, Environmental Health Directorate, Health and
Welfare, Canada, and subsequently underwent medical,
scientific, and industrial review.