WORLD HEALTH ORGANIZATION FOOD AND AGRICULTURE
ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE ORGANISATION POUR L'ALIMENTATION
ET L'AGRICULTURE
VBC/DS/83.48
ORIGINAL: ENGLISH
DATA SHEETS ON PESTICIDES No. 48
PHENTHOATE
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.
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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.
CLASSIFICATION:
Primary use: Insecticide
Secondary use: Acaricide/Scalicide/Thripicide
Chemical group: Organophosphorus compound
1. GENERAL INFORMATION
1.1 COMMON NAME:
Phenthoate (ISO, BSI, exception; JMAF-PAP)
1.1.1 Identity:
IUPAC S-alpha-ethoxycarbonylbenzyl O,O-dimethyl phosphorodithioate
CAS No. 1 Acetic acid, mercaptophenyl-ethyl ester, S-ester with
O,O-dimethyl phosphorodithioate
CAS Reg. No. 2597-03-07
Molecular formula C12H17O4PS2
Molecular weight 320.3
1.1.2 Synonyms:
Bay 33051, Bayer 18510, CidemulR, CidialR,
dimephenthioate,dimephenthoate, dimethenthoate, ElsanR, ENT 23438,
ENT 27386, ErucinR, ErusanR, fenthoate, L-561, OMS 1075, PAPR,
PapthionR, PhendalR, RogdialR, S-2940, TanoneR, TH 346-1,
TsidialR.
1.2 SYNOPSIS
Phenthoate is a broad spectrum, non-cumulative, organophosphorus
pesticide; a cholinesterase inhibitor with contact and stomach
action; moderately toxic to mammals with no residual activity.
Toxicity is increased after metabolism to the oxygen analogue.
Phenthoate is phytotoxic to some plants.
1.3 SELECTED PROPERTIES
1.3.1 Physical characteristics
The pure substance is a colourless crystalline solid; the technical
product is a reddish-yellow, oily liquid. Both have an aromatic
odour. The melting point is 17-18°C; the density (d420) is
1.226; the refraction index (nD20) is 1.5550; the flash point
(cleveland) is 165-170°C (technical product). Neither the pure
substance nor the technical product is corrosive.
1.3.2 Solubility
water (pure compound) 11 mg/l, 24°C
water (technical product) 200 mg/l, 20°C
N-hexane (technical product) 120 g/l, 20°C
1,2-diethoxyethane (technical product) 200 g/l, 20°C
petroleum ether (technical product) 170 g/l, 20°C
light petroleum (technical product) 100 g/l, 20°C
1.3.3 Stability
It is stable in acid or neutral solutions; in alkali solutions
hydrolysis occurs, at pH 8.0 the half-life is 12 days. It is
thermally unstable; at room temperatures the shelf-life is several
months; at 50°C it is degraded in 110 hours. Solar energy and
aerobic conditions promote volatization and loss from exposed
surfaces. Humidity probably does not directly affect decomposition,
on moist grain over 80% of applied material remains after one year
of storage. Decomposition of soil-applied phenthoate is due to
microbial action with CO2 as the end product.
1.3.4 Vapour pressure
5.33 x 10-6 kPa (4 x 10-5 mmHg) at 40°C.
1.4 AGRICULTURE, HORTICULTURE AND FORESTRY
1.4.1 Common formulations
Emulsifiable concentrates (500-850 g tech./kg); oil solutions (50 g
tech. in 800 g mineral oil); wettable powder (400 g/kg); dust
(30 g/kg); granules (20 g/kg); ULV spray (1 kg/kg).
1.4.2 Pests mainly controlled
Lepidoptera, jassids, aphids and soft scales; mosquito larvae and
adults; blowflies and various strains of houseflies; and ked.
1.4.3 Use pattern
It is used to protect cotton, rice, fruit and vegetable crops, and
ornamental plants. It is used on animals to protect against external
parasites; on and around agricultural structures to control nuisance
and disease vector insects.
1.4.4 Unintended effects
Phytotoxic to some grapes, figs, and chinese cabbage at upper range
of concentration. Discolouration of apples has also been reported.
1.5 PUBLIC HEALTH PROGRAMMES
1.5.1 Common formulations
Emulsifiable concentrates (500-850 g/kg); ULV sprays (1 kg/kg).
1.5.2 Pests mainly controlled
Mosquitos (larvae and adults), houseflies; experimental application
on clothing against human body lice has proved effective.
1.5.3 Use pattern
As recommended by manufacturer.
1.6 HOUSEHOLD USE
No recommended uses.
2. TOXICOLOGY AND RISKS
2.1 TOXICOLOGY - MAMMALS
2.1.1 Absorption route
Absorbed from the gastrointestinal tract; by inhalation; and through
the intact skin.
2.1.2 Mode of action
Cholinesterase inhibition after metabolism. Orally administered
phenthoate is readily converted to phenthoate-oxon, which is the
active form, by liver microsomal enzymes.
2.1.3 Excretion products
A study of the 24-hour cumulative distribution of 32P_ and
14C-phenthoate in the white mouse following a single oral dose
shows that 85-94% of the radioactivity is excreted in the urine,
5-13% in the faeces. Unchanged phenthoate accounts for less than 3%
of total excreted radioactivity and was found in faeces only; no
phenthoate-oxon was detected in either faeces or urine, though
significant levels of its non-toxic metabolites were. The selective
toxicity of phenthoate to insects is attributed to the accumulation
of the oxon form.
2.1.4 Toxicity single dose
Oral: LD50 rat 400 mg/kga (240-400 mg/kg)
mouse 350-400 mg/kg
guinea-pig 377 mg/kg
rabbit 210 mg/kg
hare 72 mg/kg
dog 500 mg/kg
Dermal: LD50 rat > 4000 mg/kg (2000-6750 mg/kg)
aThe WHO accepted value for the rat acute oral LD50, 400 mg/kg,
is used here; the lower range values probably reflect the effect of
toxic impurities found in earlier technical preparation (see section
2.1.8).
2.1.5 Toxicity repeated doses
Oral: No information.
Dermal: No information.
Inhalation: No information.
Cumulation: No information.
2.1.6 Dietary studies
Short-term: No information.
Long-term: In an 88-week rat study the highest non-toxic dose was
established to be 0.5 (mg/kg)/day.
2.1.7 Supplementary studies of toxicity
Carcinogenicity: No information.
Teratosenicity: No information.
Reproduction: No information.
Neurotoxicity: No information.
Mutagenicity: Phenthoate has been shown to be non-mutagenic in two
microbial studies involving several strains of Salmonella
typhimurium and Escherichia coli.
2.1.8 Modifications of toxicity
In mammals potentiation of toxicity occurs with several impurities
found in early preparations of the technical product. These
impurities affect homeotherm toxicity but in heterotherms they have
no potentiation effect. The impurities include:
(MeO)2P(S)CH(C6H5) COOH coded APH
(MeO)2 P (S) (SMe) coded TES
(MeO)2P(O) (SMe) coded OTE
(MeO)2P(O)SCH(C6H5)COOC2H5 coded OPH
(MeS)2P(O)(OME) coded ITE
(MeO)(MeS)P(O)SCH(C6H5)COOC2H5 coded IPH
2.2 TOXICOLOGY - MAN
2.2.1 Absorption route
Absorbed from the gastrointestinal tract; by inhalation; and through
the intact skin.
2.2.2 Dangerous doses
Single: No information.
Repeated: No information.
2.2.3 Observations of occupationally exposed workers
Spraymen in a WHO supervised spray programme showed no ill-effects
over an extended period of spraying. Whole blood cholinesterase
levels were 90% of normal after three days of spraying (tintometric
method).
2.2.4 Observations on exposure of the general population
The population in villages undergoing WHO supervised spraying showed
no signs or symptoms for a 15-day observation period. No inhibition
of whole blood cholinesterase occurred (tintometric method).
2.2.5 Observations of volunteers
Young adult male military recruits wearing garments with sleeves
treated with 1% phenthoate for six weeks, 34-48 hours/week, showed
no noticeable ill-effects.
2.2.6 Reported mishaps
No information.
2.3 TOXICITY TO NON-MAMMALIAN SPECIES
2.3.1 Fish
Toxic. Phenthoate has been implicated in at least three large-scale
accidental fish kills in fresh water containing measurable levels of
phenthoate (0.001-0.002 mg/l). Goby, grey mullet and rainbow trout
body concentrations were 0.03-0.09 mg/kg.
LC100 (96 hours) - goldfish 4.5 mg/l
minnows 3.4 mg/l
mosquito-fish 0.3 mg/l
guppies 2-3.0 mg/l
2.3.2 Birds
Toxic. Oral acute LD50 - pheasants 218 mg/kg
quail 300 mg/kg
2.3.3 Other species
Toxic to honey-bees - not recommended for spraying in vicinity of
bee colony nectar gathering areas. Phenthoate possesses no repellent
properties.
Acute LD50 honey-bee 0.12 mg/bee
Acute LD90 honey-bee 0.40 mg/bee
Toxic to snakes
Toxic to nuisance insects, e.g., midges (Chironomidae)
LC50 midge larvae 0.0019-0.0053 mg/l
LC90 midge larvae 0.0054-0.0150 mg/l
3. FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF
COMPOUND
3.1 RECOMMENDED RESTRICTIONS ON AVAILABILITY
(For definitions of categories see Introduction to data sheets)
Liquids over 20%: category 3. Other liquids and solids over 8%:
category 4. All other solids: category 5.
3.2 TRANSPORTATION AND STORAGE
Formulations in categories 3 and 4 - Should be transported in
clearly labelled, rigid and leakproof containers, away from
containers of food and drink. Storage should be under lock and key
and secure from access by unauthorized persons and children.
Formulations in category 5 - Should be transported and stored in
clearly marked leakproof containers, out of reach of children and
away from food and drink.
3.3 HANDLING
Formulations in categories 3 and 4 - Protective clothing (see
section 4) should be used by all handling the compound. Adequate
washing facilities should be available at all times during handling
and should be close to the site of handling. Eating, drinking and
smoking should be prohibited during and after handling before
washing of hands and face.
Formulations in category 5 - The same facilities required as those
needed for the handling of any chemical.
3.4 DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS
All formulations - Containers may be decontaminated (for method
see section 4.3). Decontaminated containers should not be used for
food and drink. Containers that are not decontaminated should be
burned or 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 categories 3 and 4 - Pre-employment medical
examinations of workers is desirable. Workers suffering from active
hepatic or renal disease should be excluded from contact.
Pre-employment and periodic cholinesterase test for workers
desirable, especially for those handling concentrates. Special
account should be taken of the workers' mental ability to comprehend
and follow instructions. Training of workers in techniques to avoid
contact is essential.
Formulations in category 5 - Warning of workers to minimize
contact is essential.
3.6 ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT
All formulations - Pilot and loaders should have special training
in application methods and early warning symptoms of poisoning, and
they must wear a suitable respirator. Flagmen should wear overalls,
an impermeable brimmed hat, and be located well away from the
dropping zone.
3.7 LABELLING
Formulations in categories 3 and 4 - Minimum cautionary statement
- Phenthoate is an organophosphorus compound that inhibits
cholinesterase. It is poisonous if swallowed. It may be absorbed
through the skin. Avoid skin contact; wear hand protection, clean
protective clothing and a respirator when handling the material.
Wash thoroughly with soap and water after using. Keep the material
out of reach of children and well away from foodstuffs, animal feed
and their containers. If poisoning occurs, call a physician.
Atropine and pralidoxime are specific antidotes and artificial
respiration may be needed.
Formulations in category 5 - Minimum cautionary statement - This
formulation contains phenthoate which is a toxic substance. Keep the
material out of reach of children and well away from foodstuffs,
animal feeds and their containers.
3.8 RESIDUES IN FOOD
Maximum residue limits have been recommended for phenthoate by the
Joint FAO/WHO Meeting on Pesticide Residues. These are subject to
change at annual reviews.
4. PREVENTION OF POISONING IN MAN AND EMERGENCY AID
4.1 PRECAUTIONS IN USE
4.1.1 General
Phenthoate is an organophosphorus pesticide of moderate toxicity. It
is readily absorbed through the intact skin, from the
gastrointestinal tract and by inhalation. Repeated exposure may have
a cumulative effect on cholinesterase levels.
4.1.2 Manufacture and formulation TLV
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, protective impermeable
boots, clean overalls, gloves and respirator should be worn. Mixing,
if not mechanical, should always be carried out with a paddle of
appropriate length. When spraying tall crops or during aerial
application, a face mask should be worn, as well as an impermeable
hat, clothing, boots and gloves. The applicator should avoid working
in spray mist and avoid contact with the mouth. Particular care is
needed when equipment is being washed after use. All protective
clothing should be washed immediately after use, including the
insides of gloves. Splashes must 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 phenthoate and associated with its application
should wear protective clothing and observe the precautions
described above in section 4.1.3 under "mixers and applicators".
4.1.5 Other populations likely to be affected
With good application practice, subject to section 4.2 below, other
persons should not be exposed to hazardous amounts of phenthoate.
4.2 ENTRY OF PERSONS INTO TREATED AREA
Unprotected persons should be kept out of tall crops for four days
and out of other crops for 24 hours.
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 phenthoate 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 may include excessive sweating,
headache, weakness, giddiness, nausea, vomiting, hypersalivation,
stomach pains, blurred vision, slurred speech and muscle twitching.
Later there may be convulsions and coma.
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 wash the affected skin with soap and water, if
available, and flush the area with large quantities of water. If
swallowed, and if the person is conscious, vomiting should be
induced. 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 phenthoate.
5. FOR MEDICAL AND LABORATORY PERSONNEL
5.1 MEDICAL DIAGNOSIS AND TREATMENT IN CASES OF POISONING
5.1.1 General information
Phenthoate is an organophosphorus pesticide of moderate mammalian
toxicity which is active against a variety of agricultural and
public health pests. It is readily absorbed from the
gastrointestinal tract; through the intact skin; and by inhalation.
It is converted in vivo to the oxygen analogue phenthoate-oxon
which inhibits cholinesterase. It does not accumulate in body
tissues.
5.1.2 Symptoms and signs
Initial symptoms of poisoning may include excessive sweating,
headache, weakness, giddiness, nausea, hypersalivation, 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 of activity of blood
cholinesterases. Urinary levels of organic phosphorus containing
metabolites may also be used as a measure of exposure. Neither
method is specific for phenthoate.
5.1.4 Treatment
If the pesticide has been ingested, unless the patient is vomiting,
rapid gastric lavage should be performed using 5% sodium bicarbonate
if available. For skin contact, the skin should be washed with soap
and water. If the compound has entered the eyes, they should be
washed with large quantities of isotonic saline or water.
Persons without signs of respiratory inefficiency but with manifest
peripheral symptoms should be treated with 2-4 mg of atropine
sulfate by intravenous injection and 1000 mg 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.
Diazepam may be given to control convulsions. 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 at the same time as 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 CNS stimulants of all kinds. Pralidoxime and
toxogonin are not regarded as effective antidotes in phenthoate
poisoning.
5.1.5 Prognosis
If the acute toxic effect is survived and adequate artificial
respiration has been given if needed, the chances of complete
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 of previously reported cases
Phenthoate has been implicated in a number of cases of pesticide
poisoning, see WHO, VBC/TOX/77.20.
5.2 SURVEILLANCE TESTS
Test Normal Action Symptomatic
levela levela levela
Plasma cholinesterase 100% 50% Variable
Whole blood or
erythrocyte cholinesterase 100% 70% Usually 40%
aExpressed at percentage of pre-exposure activity.
5.3 LABORATORY METHODS
5.3.1 Detection and assay of compounds
Thin-layer chromatography and gas-liquid chromatography methods have
been used to analyse phenthoate in technical products and in its
formulations. Analysis of residues in plant and animal tissues
gas chromatography and flame photometry methods. See Bazzi, B.
(1976) Anal. Methods Pestic. Plant Growth Regul., 8, 159
5.3.2 Other tests in case of poisoning
Levels of cholinesterase in the blood, particularly plasma, provide
the most useful diagnosis of poisoning. Michel, N. O. (1949)
J. Lab. Clin. Med., 34, 1564-1568. Ellman, G. L. et al. (1961)
Biochem. Pharmacol., 7, 88-95.
Measurement of urine metabolites may also be determined in order to
give an indication of exposure for methods. See section 5.3.1,
Detection and assay.
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