WORLD HEALTH ORGANIZATION FOOD AND AGRICULTURE
ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE ORGANISATION POUR L'ALIMENTATION
ET L'AGRICULTURE
VBC/DS/75.8 (Rev.1)
ORIGINAL: ENGLISH
DATA SHEETS ON PESTICIDES No. 8 Rev.1
TEMEPHOS
CLASSIFICATION:
Primary use: Insecticide
Secondary uses: None
Chemical group: Organophosphorus compound
Data sheet No. 8, Rev.1 (8/78)
Date issued: March 1975
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: Temephos. This name is under consideration by ISO
but has not yet been adopted.
1.1.1 Identity: 0,0,0',0'-tetramethyl 0,0'-thiodi-p-
phenylenephosphorothioate
1.1.2 Synonyms: OMS 786
"Abate"
difenphos (This was originally considered by ISO as a
Common Name but was replaced by "temephos".)
Local synonyms:
1.2 SYNOPSIS - An organophosphorus insecticide of slight toxicity
which is used largely as a mosquito larvicide. It is non-
systemic and has some residual activity. It is active upon
metabolism.
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 not constitute formal publication.
It should not be reviewed, abstracted or quoted without the
agreement of the Food and Agriculture Organization of the
United Nations or of the World Health Organization.
Ce document ne constitue pas une publication. Il ne doit faire l'objet
d'aucun compte rendu ou résumé ni d'aucune citation sans l'autorisation
de l'Organisation des Nations Unies pour l'Alimentation et
l'Agriculture ou de l'Organisation Mondiale de la Santé.
R 983
1.3 SELECTED PROPERTIES
1.3.1 Physical characteristics - When pure a white crystalline solid,
m.p. 30-30.5°C: the technical product is a brown viscous liquid.
1.3.2 Solubility - Practically insoluble in water at 20°C (less than
1 ppm). Soluble in acetone, acetonitrile, ether and most
aromatic and chlorinated hydrocarbons. Insoluble in hexane.
1.3.3 Stability - Moderately stable to hydrolysis in contact with
aqueous alkali; no observed hydrolysis at pH 8 at room
temperature for several weeks or at pH 11 at 40°C for several
hours.
1.3.4 Vapour pressure - 7.17 x 10-8 mmHg at 25°C.
1.4 AGRICULTURE, HORTICULTURE AND FORESTRY
1.4.1 Common formulations - Wettable powder 50%; emulsifiable
concentrates 20%, 50%; granules 1%.
1.4.2 Susceptible pests - Main use is against mosquitos. Also
effective against Lygus bugs, biting and chiromid midges, gnats,
cutworms, thrips, moth and sand-flies, blackflies and body lice.
1.4.3 Use pattern - Used as mosquito larvicide on ponds, marshes,
swamps and neighbouring ground at 0.1-0.5 kg/ha. Also used for
mosquito control on premises. Used experimentally on cotton,
alfalfa, citrus and other crops for control of cutworms, thrips
on citrus and Lygus bugs. Sometimes mixed with other insecticides
for broader spectrum control. Used for mosquito control in
potable water.
1.4.4 Unintended effects - Young shrimp in treated tidal waters may be
injured. Not phytotoxic and of low toxicity to most non-target
species.
1.5 PUBLIC HEALTH PROGRAMMES - Used at a level of 1 ppm in drinking-
water to control Aedes aegypti larvae. Also used to control the
larvae of black flies (Simulidae) vectors of onchocerciasis.
Used as a formulated powder for the control of body lice
(Pediculus humanus humanus).
1.6 HOUSEHOLD USE - Not used.
2. TOXICOLOGY AND RISKS
2.1 TOXICOLOGY - MAMMALS
2.1.1 Absorption route - Absorbed by all portals, but dermal absorption
is of little significance because absorption by this route is
slow and the toxicity of the compound is inherently low.
2.1.2 Mode of action - Cholinesterase inhibition.
2.1.3 Excretion products - Unchanged temephos constitutes the principal
compound excreted in the faeces along with smaller amounts of the
sulfoxide and phenolic hydrolysis products. In the urine traces
of temephos are found, but the major urinary excretion products
are sulfate ester conjugates of phenolic hydrolysis products.
2.1.4 Toxicity, single dose
Oral: LD50 rat (M): 8600 mg/kg
LD50 rat (F): 1300 mg/kg
Dermal: LD50 rat (M): > 4000 mg/kg
LD50 rat (F): > 4000 mg/kg
LD50 rabbit: 1300-1400 mg/kg
Mont susceptible species - Not known. Reported to show marked
differences in different species.
2.1.5 Toxicity, repeated doses
Oral: Rats, rabbits and guinea-pigs were found to tolerate daily
oral administration of 10 mg/kg of temephos without observable
clinical effect. White rats were fed temephos at doses of 0, 1,
10, 100 mg/kg/day for 44 days. Cholinesterase values remained
normal for the rats receiving 1 mg/kg/day throughout the
experiment. The rats receiving 10 mg/kg/day showed 31%
inhibition of erythrocyte cholinesterase after 14 days and 47%
inhibition after 44 days. The animals never showed symptoms of
organic phosphorous poisoning. The rats given 100 mg/kg/day
developed typical symptoms of organic phosphorus poisoning after
three doses when their erythrocyte cholinesterase was inhibited
by 64%. Gradual recovery from symptoms occurred while dosing
progressed, even though the erythrocyte cholinesterase continued
to fall to 87% inhibition after 11 days of dosing. Some of the
rats were allowed to recover for 32 days without receiving
temephos and erythrocyte cholinesterase returned to a level of
27% inhibition at the end of this period.
Rabbits were administered temephos at doses of 0.1, 1, and 10
mg/kg/day, for 35 days. No significant inhibition of
cholinesterase occurred in the groups receiving 0.1 or 1
mg/kg/day throughout the experiment. After seven days of dosage,
the rabbits on 10 mg/kg/day had developed 26% inhibition of
erythrocyte cholinesterase, and inhibition of erythrocyte
increased to 47% at the end of 35 days of dosage. None of the
animals developed symptoms of organic phosphorus poisoning.
Male guinea-pigs given a daily dose of 100 mg/kg temephos for
five days showed no signs of organic phosphorus poisoning.
Inhalation: No information.
Dermal: Groups of 10 male and 10 female young albino rats
received dosages of 12 mg/kg/day or 60 mg/kg/day of temephos,
applied as an aqueous emulsion, five days per week for three
weeks. One half of the animals within each group had the skin
abraded at the site of the application.
There were no deaths during the test period and the overall
behaviour and appearance of all animals was good. No gross
lesions or tissue changes were referable to the treatments. In
male rats receiving 60 mg/temephos/kg on intact skin, mean food
intake was less than that of their controls. Intact and abraded
skin males receiving 60 mg/temephos/kg had lower mean weight gain
than their control.
Five-day repeated applications to intact rabbit skin show that
0.4 ml (178 mg a.i.)/kg/day for five consecutive days, did not
cause death. Diarrhoea occurred in 7/10 treated animals but not
in the controls. Cholinesterase activity was reduced in treated
animals.
Cumulation of compound: No information. Can be expected to be
stored to some extent in body tissues as indicated by the
excretion of metabolites in the urine.
Cumulation of effect: In spite of its low toxicity continued
ingestion of temephos can be expected to reduce cholinesterase
activity to hazardous levels.
2.1.6 Dietary studies
Short-term: In a 90-day feeding study with rats, 350 ppm (17.5
mg/kg/day) in the diet was without observable clinical effect and
6 ppm (0.3 mg/kg/day) did not affect cholinesterase activity.
Dogs fed a diet containing 500 ppm (25 mg/kg/day) of temephos
showed signs of cholinesterase inhibition while 18 ppm (0.9
mg/kg/day) did not affect the appearance of the dogs or inhibit
cholinesterase activity. Dogs fed 3 to 4 mg/kg/day over a 129-day
test period tolerated the treatment.
Long-term: Study in progress.
2.1.7 Supplementary studies of toxicity
Reproduction: When rats were fed large enough doses to inhibit
cholinesterase and cause some symptoms of toxicity (500 ppm in
the diet - 25 mg/kg/day) they still reproduced normally. Their
young were viable and there was no increase in congenital
defects. Reproduction studies with rats receiving 125 ppm of
temephos in their diet (10 mg/kg/day) through three generations
did not produce lesions in the parents or lesions or anomalies in
the offspring which could be attributed to the compound.
2.1.8 Modifications of toxicity: There is neither significant
antagonism nor potentiation of acute toxicity between temephos
and 23 other cholinesterase inhibiting pesticides when they were
administered in equitoxic proportions.
2.2 TOXICOLOGY - MAN
2.2.1 Dangerous doses
Single: Not known.
Repeated: Not known - >> 256 mg/man/day for five days.
2.2.2 Observations of occupationally exposed workers - No information:
no ill effects have been observed in spraymen.
2.2.3 Observations on exposure of the general population - No clinical
symptoms attributable to temephos were observed among members of
a village in which water storage containers were treated monthly
with 1% temephos granules over a 19-month period. (Monthly
treatment in this fashion should maintain a level of 0.5 ppm
temephos in the water.)
2.2.4 Observations of volunteers - Human subjects tolerated levels of
256 mg/man/day for five days or 64 mg/man/day for 28 days without
developing clinical symptoms attributable to temephos. No
inhibition of plasma or erythrocyte cholinesterase was found.
2.2.5 Reported mishaps - No information. Poisoning in humans by
temephos has not been reported.
2.3 TOXICITY TO NON-MAMMALIAN SPECIES - The entries in these sections
are intended to draw attention to special risks and to give
warnings of any needs for special protection.
2.3.1 Fish - Generally low toxicity to fish but some species are
susceptible: the LC50 (24 hours' exposure) for rainbow trout is
8 ppm. Possibility of injury to young shrimps when used in tidal
waters.
2.3.2 Birds - Toxicity to birds varies both between and within species.
Pheasants, pigeons and sparrows are among the more susceptible
species. Not likely to be hazardous under normal conditions of
use.
2.3.3 Other species - Low toxicity to bees.
3. FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF
COMPOUND
3.1 RECOMMENDED RESTRICTIONS ON AVAILABILITY
(for definition of categories see introduction)
All formulations Category 5
3.2 TRANSPORTATION AND STORAGE
All formulations - Should be transported or stored in clearly
labelled leak-proof containers out of reach of children, away
from food or drink.
3.3 HANDLING
All formulations - Adequate washing facilities should be
provided at all times during handling and should be close to the
site of the handling. Eating, drinking and smoking should be
prohibited during handling and before washing after handling.
3.4 DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS
All formulations - Containers may be decontaminated (for method
see paragraph 4.3 in 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
All formulations - Pre-employment medical examination and
periodic cholinesterase test for workers desirable. Workers
suffering from active hepatic or renal disease should be excluded
from contact. Warning of workers to avoid contact essential.
3.6 ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT -
No special regulations recommended.
3.7 LABELLING
All formulations - Minimum cautionary statement: Temephos is an
organophosphorus compound which inhibits cholinesterase. It is
of low toxicity but may be poisonous if swallowed. Keep the
material out of reach of children and well away from foodstuffs,
animal feed and their containers. If poisoning occurs call a
physician. Atrophine and pralidoxime are specific antidotes and
artificial respiration may be needed.
3.8 RESIDUES IN FOOD - Maximum residue levels have not yet 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 - Temephos is an organophosphorus insecticide of low
toxicity. It can be absorbed by mouth, by inhalation of the dust
and to some extent through the intact skin, although the dermal
route is of little significance because absorption by it is slow
and the toxicity of the compound is inherently low. In liquid
formulations the vehicle (solvent) may be more toxic than the
insecticide.
4.1.2 Manufacture and formulation
T.L.V.: 15 mg/m3 (ACGIH); USSR. Although volatility is low,
vapour and dust should be controlled. Protective equipment for
skin and respiratory protection may be desirable.
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 other exposed skin should be washed.
4.1.4 Other associated workers (including flagmen in aerial operations)
- Persons exposed to temephos and associated with its application
should observe the precautions described above in 4.1.3 under
"mixers and applicators".
4.1.5 Other populations likely to be affected - Populations using
drinking-water containing up to 0.5 ppm of temephos to control
mosquito larvae will not be exposed to hazardous amounts of
temephos.
4.2 ENTRY OF PERSON INTO TREATED AREAS - Persons may enter treated
areas immediately after spraying without being exposed to
hazardous amounts of temephos.
4.3 DECONTAMINATION OF SPILLAGE AND CONTAINERS - 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
scrubbing the sides. An additional rinse should be carried out
with 5% sodium hydroxide solution which should remain in the
container overnight. Impermeable gauntlets should be worn during
this work and a soakage pit should be provided for the rinsings.
Decontaminated containers should not be used for food and drink.
Spillage of temephos 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 - Early symptoms of poisoning
following the ingestion of temephos may include excessive
sweating, headache, weakness, giddiness, nausea, vomiting,
stomach pains, blurred vision, slurred speech, and muscle
twitching. if a massive dose has been swallowed there may be
convulsions, coma, loss of reflexes and loss of sphincter
control. Symptoms of poisoning are very unlikely to occur
following dermal contact.
4.4.2 Treatment before person is seen by a physician, if these symptoms
appear following exposure - If swallowed, vomiting should be
induced if the person is conscious. In the event of a collapse,
artificial respiration should be given.
5. FOR MEDICAL AND LABORATORY PERSONNEL
5.1 MEDICAL DIAGNOSIS AND TREATMENT OF CASES OF POISONING
5.1.1 General information - An organophosphorus insecticide of low
toxicity which can be absorbed by the mouth and by inhalation.
Absorption may occur slowly through the dermal route but this
route is of little significance since the toxicity of the
compound is inherently low. It is a weak inhibitor of acetyl
cholinesterase. It is metabolized and excreted in the urine and
faeces. Poisoning in man has not been reported. In liquid
formulations the vehicle may be more toxic than the insecticide.
5.1.2 Symptoms and signs - Based upon studies and upon symptoms of
poisoning from other organophosphorus pesticides, initial
symptoms of poisoning may include excessive sweating, headache,
weakness, giddiness, nausea, vomiting, stomach pains, blurred
vision, slurred speech and muscle twitching. In the event of
ingestion of an excessive dose 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 ether-extractable
organic phosphorus have been used as a measure of exposure.
5.1.4 Treatment - If pesticide has been ingested, unless the patient is
vomiting, rapid gastric lavage should be performed using 5%
sodium bicarbonate, if available. In spite of the low dermal
toxicity after skin contact, it is advisable to wash the skin
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 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 5-10 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, artificial respiration should be given first, then
atropine sulfate.
The airways should be kept free and artificial respiration should
be applied, if required, preferably by mechanical means. If
necessary intubation should be performed.
Contraindications are morphine, barbiturates, phenothiazine
tranquillizers and central stimulants of all kinds.
5.1.5 Prognosis - As there have been no reports of poisoning of man
with temephos the prognosis is not known. By analogy with other
mildly toxic organophosphorus compounds it may be assumed that if
the acute toxic effect is survived the chances of complete
recovery are good. In very severe cases following the ingestion
of a massive dose of temephos it is possible that without
adequate artificial respiration prolonged hypoxia could give rise
to permanent brain damage.
5.1.6 References of previously reported cases - None.
5.2 SURVEILLANCE TESTS
Test Normal Action Symptomatic
level level level
Plasma cholinesterase 100%* 50% variable
Erythrocyte cholinesterase 100% 70% usually < 40%
Urinary levels of ether-extractable organic phosphorus have also
been used to determine degrees of exposure.
----------
* Percentage of pre-exposure activity by any test.
5.3 LABORATORY METHODS
References are given only,
5.3.1 Detection and assay of compound - To determine levels of temephos
in potable water, see Dale & Miles (1969). A flame photometric
gas-chromatographic method for determining temephos in mosquito
larvae and suspensions is also reported (Bowman et ai., 1968).
5.3.2 Other tests in cases of poisoning
Levels of cholinesterase in blood provide the most useful
diagnosis of poisoning. See: Michel, N. 0. (1949) J. Lab. Clin.
Med., 34, 1564-1568; Ellman, G. L., Courtney, K. D., Andreas,
V. jr & Featherstone, R. M. (1961) Biochem. Pharmacol., 7,
88-95
Urinary levels of ether-extractable organic phosphorus (Mattson &
Sledak, 1960) or dimethyl phosphate and phosphorothionate (Shafik
& Enos, 1969) can also be used to determine exposure.
REFERENCES
Bowman, N. C., Ford, H. R., Lofgren, C. S. & Weidhaas, D. E. (1968)
Residues of Abate: Analysis in Mosquito Larvae and Larvicide
Suspensions by Flame Photometric Gas Chromatography, J. Econ.
Entomol., 61, 1586
Dale, W. E. & Miles, J. W. (1969) Gas Chromatographic Determination of
Abate using Flame Photometric and Electron-Capture Detectors, J.
Agric. Fd Chem., 17, 60
Mattson, A. M. & Sledak, V. A. (1960) Ether-extractable urinary
phosphates in man and rats derived from malathion and similar
compounds, J. Agric. Fd Chem., 8, 107
Shafik, M. T. & Enos, H. F. (1969) Determination of Metabolic and
Hydrolytic Products of Organophosphorus Pesticide Chemicals in
Human Blood and Urine, J. Agric. Fd Chem., 17, 118