WORLD HEALTH ORGANIZATION FOOD AND AGRICULTURE
ORGANISATION MONDIALE DE LA SANTE ORGANISATION POUR L'ALIMENTATION
DATA SHEETS ON PESTICIDES No. 44
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.
Primary use: Insecticide and nematicide
Secondary use: None
Chemical group: Organophosphorus compound
Date issued: March 1980
1. GENERAL INFORMATION
1.1 COMMON NAME:
O,O-diethyl O-4-(methylsulfinyl)phenyl phosphorothioate
An organophosphorus insecticide and nematicide of high mammalian
toxicity: it may be absorbed through the skin, by inhalation and
from the gastrointestinal tract. It is active upon metabolism.
1.3 SELECTED PROPERTIES
1.3.1 Physical characteristics
An oily liquid of a yellowish colour, b.p. 138 to 141°C at 1.3 Pa.
Slightly soluble in water (1.54 g/l at 25°C) and soluble in most
Stable under normal conditions of storage and use. Half life of 120
hours at 81°C and ph 2.5-6.0.
1.3.4 Vapour pressure (volatility)
low: < 10-6 mbar at 20°C.
1.4 AGRICULTURE, HORTICULTURE AND FORESTRY
1.4.1 Common formulations
Spray concentrate, 6 lbs a.i./gal (600 g/l); granules 50, 100, and
1.4.2 Susceptible pests
Nematodes and soil insects.
1.4.3 Use pattern
Fensulfothion is a systemic organophosphorus nematicide and
insecticide, which is used against soil nematodes (free living, root
knot and cyst forming nematodes) and a broad spectrum of soil borne
insects in field crops, vegetables and fruit. It is also used
against nematodes in turf grasses, flowers and ornamental plants.
For most cultures the material is applied before planting or sowing
or at planting; for others, fensulfothion is applied in the soil in
1.4.4 Unintended effects
1.5 PUBLIC HEALTH PROGRAMME
Not used in public health programmes.
1.6 HOUSEHOLD USE
None, due to toxicity.
2. TOXICOLOGY AND RISKS
2.1 TOXICOLOGY - MAMMALS
2.1.1 Absorption route
Rapidly absorbed by the gastrointestinal tract and by inhalation.
Dermal absorption is somewhat slower although dermal toxicity is
2.1.2 Mode of action
Cholinesterase inhibition after conversion to the oxygen analogue
2.1.3 Excretion products
In mammals, fensulfothion is metabolized largely through oxidative
and hydrolyric pathways. It is excreted, primarily in the urine, as
ethyl and diethyl esters of thiophosphoric acid, p-methyl
sulphinylphenol and p-methylsulfonylphenol.
2.1.4 Toxicity; single dose
Oral: LD50 Rat (M): 3.96-10.5 mg/kg
LD50 Rat (F): 1.8-2.3 mg/kg
Dermal: LD50 Rat (M): 14-30 mg/kg
LD50 Rat (F): 3.5-13 mg/kg
Inhalation: LC50 (M) rats 113 mg/m3 of air, 1 hour exposure
LC50 (M) rats 29.5 mg/m3 of air, 4 hour exposure
2.1.5 Toxicity, repeated doses
The highest daily intraperitoneal dose of fensulfothion that can be
tolerated by rats for a period of 60 days without occurrence of
mortality is 0.25 mg/kg bw.
Oral: See dietary studies below (2.1.6).
Cumulation of compound: Fensulfothion is not cumulative in body
Cumulation of effects: Repeated exposure to sub-lethal amounts may
reduce cholinesterase activity to hazard levels.
2.1.6 Dietary studies.
Short-term: Groups of female rats were fed fensulfothion for eight
weeks at dosage level of 0, 0.5, 1 and 2 mg/kg diet. Erythrocyte
cholinesterase inhibition was observed at 2 mg/kg while plasma and
brain levels were unaffected. No cholinesterase inhibition was
observed at lower dose levels. Mortality, growth, haematology and
clinical chemistry parameters were normal.
Groups of dogs were fed fensulfothion in the diet at levels of 0, 1,
2, 5 and 10 mg/kg diet for 12 weeks. Inhibition of cholinesterase
was observed in serum and erythrocyte at 2 mg/kg and above. At 5 and
10 mg/kg cholinergic effects and weight loss were observed.
Long-term: Groups of rats were fed fensulfothion in the diet for
17 months at dietary levels of 0, 1, 5 and 20 mg/kg diet. Mortality
of males was increased at 5 and 20 mg/kg. Growth of males and
females was slightly impaired at 20 mg/kg. Cholinesterase inhibition
was found in serum (19%), erythrocytes (21%), and brain (24%) in
females fed 1 mg/kg and above in males at 5 mg/kg and above. No
effects were observed on gross or histological examination of organs
Groups of dogs (2 males and 2 females/group) were fed fensulfothion
in the diet at levels of 0, 1, 2 and 5 mg/kg diet for two years.
Severe weight loss and reduced food consumption accompanied by
cholinergic signs were evident in the early weeks of the study at
5 mg/kg. After the second month, food consumption increased and lost
body weight was regained. Slight cholinergic signs were also
observed at 2 mg/kg at the beginning of the study. Reduction of
serum and erythrocyte cholinesterase was evident at 5 mg/kg
throughout the study. Slight reduction was observed at 2 mg/kg with
no effects noted at 1 mg/kg. No death occurred during the feeding
and haematology and gross and histopathologic examination of tissues
and organs were normal.
2.1.7 Supplementary studies of toxicity
Carcinogenicity: No information.
Reproduction studies and teratogenicity: A three generation
reproduction study conducted on mice, showed that levels of
fensulfothion fed at 20 and 5 mg/kg diet, although toxic to mice,
did not affect reproduction. Tests on pregnant New Zealand albino
rabbits showed that fensulfothion at dosage levels of 0.05 and
0.1 (mg/kg)/day, did not affect pregnancy or foetal mortality; there
was no evidence of abnormal foetal development at 0.5 (mg/kg)/day.
Mutagenicity: A dominant lethal study conducted on mice did not
indicate any mutation effect.
Delayed neurotoxicity: Fensulfothion caused no delayed neurotoxic
effects in hens in either acute toxicity tests or in subchronic
feeding experiments using high dose levels.
2.1.8 Modification of toxicity
No potentiation was observed when fensulfothion was administered in
combination with 17 other anticholinesterase pesticides.
2.2 TOXICOLOGY - MAN
2.2.2 Dangerous doses
Single: Not known.
Repeated: Not known.
2.2.3 Observations of occupationally exposed workers
Studies were performed to evaluate the toxicity of a 30 g/kg
granular formulation of fensulfothion for potential hazards to
persons using it in rice fields, and to those working in treated
plantations. No significant inhibition of cholinesterase activity
was noted either in persons who worked in a crop treated with with
the granules at 40 kg/ha or in those who applied fensulfothion
granules by hand.
2.2.4 Observations on exposure of the general population
2.2.5 Observations of volunteers
A 50 g/kg granular formulation of fenitrothion was applied,
air-tight, for two periods of two hours daily to the forearm of
three persons on five consecutive days. During the exposure periods,
no person suffered any ill effect or inhibition of cholinesterase
2.2.6 Reported mishaps
2.3 TOXICITY TO NON MAMMALIAN SPECIES
Bluegill TLm 0.12 mg/l (96 hours)
Rainbow trout TLm 8.6 mg/l (96 hours)
Carp TLm 5.7 mg/l (48 hours)
Mallards LD50 0.749 mg/kg
Starling LD50 0.56 mg/kg
House sparrow LD50 0.32 mg/kg
Redwinged blackbird LD50 0.32 mg/kg
Coupon grackle LD50 0.42 mg/kg
2.3.3 Other species
3. FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF
3.1 RECOMMENDED RESTRICTIONS ON AVAILABILITY
(for definition of categories, see introduction)
Liquid formulations above 15% category 21 all others category 3
Solid formulations 10% or above category 31 all others category 4
3.2 TRANSPORTATION AND STORAGE
All formulations - Should be transported or 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 categories 3 and 4 - Protective clothing should be
used by those handling the compound. Adequate 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 handling and before washing after handling.
Formulations in category 5 - No facilities other than those needed
for handling of any chemical may be required.
3.4 DISPOSAL AND/OR DECONTAMINATION OF CONTAINER:
Containers may be decontaminated (see para. 4.3). Decontaminated
containers should not be used for food and drink. If not
decontaminated, containers 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
All formulations - Pre-employment medical examination of workers
desirable. Workers suffering from active hepatic or renal disease
should be excluded from contact. Pre-employment and periodic
cholinesterase tests for workers essential for those handling
concentrates and desirable for applicators. Special account should
be taken of the workers' mental ability to comprehend and follow
instructions. Training of workers in techniques to 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 symptoms of
poisoning, and must wear a suitable respirator. Flagmen, if used,
should wear overalls and be located well away from the dropping
All formulations - Minimum cautionary statement: "Fensulfothion is
an organophosphorus compound which inhibits cholinesterase. It is
poisonous if swallowed. It may be absorbed through the skin or
inhaled as dusts or mists. Avoid skin contact; wear protective
gloves, 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".
3.8 RESIDUES IN FOOD:
Maximum residue limits have been recommended for fensulfothion by
the Joint FAO/WHO Meeting on Pesticide Residues. These are subject
to change when reviewed.
4. PREVENTION OF POISONING IN MAN AND EMERGENCY AID
4.1 PRECAUTIONS IN USE
Fensulfothion is an organophosphorus pesticide of high toxicity. It
penetrates the intact skin and is also absorbed by inhalation of
dust and spray mists and from the gastrointestinal tract.
Concentrated formulations should be handled by trained personnel
wearing protective clothing.
4.1.2 Manufacture and formulation
T.L.V.: no information. Formulation should not be attempted without
advice from the manufacturer. Closed system and forced ventilation
may be required to reduce as much as possible the exposure of
workers to the chemical. Protective equipment for the skin and
respiratory protection is usually necessary.
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 or during aerial applications, a
face mask should be worn, as well as an impermeable hat, 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
Persons exposed to fensulfothion and associated with its application
should wear protective clothing and observe the precautions
described above in 4.1.3 under "mixers and applicators".
4.1.5 Other populations likely to be affected
With good agricultural and manufacturing practice subject to 4.2
below, other populations should not be exposed to hazardous amounts
4.2 ENTRY OF PERSONS INTO TREATED AREAS:
Unprotected persons should be kept out of treated areas for at least
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 contamination of ground waters. 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 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 and drink.
Spillage of fensulfothion 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 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 clothing and wash
the affected skin with soap and water if available, and flush the
area with large quantities of water. If swallowed, vomiting should
be induced, if the person is conscious. In the event of collapse,
artifical respiration should be given, bearing in mind that if
mouth-to-mouth resuscitation is used, vomit may contain toxic
amounts of fensulfothion.
5. FOR MEDICAL AND LABORATORY PERSONNEL
5.1 MEDICAL DIAGNOSIS AND TREATMENT IN CASES OF POISONING
5.1.1 General information
Fensulfothion is an organophosphorus pesticide of high toxicity,
which is easily absorbed through the intact skin as well as by
inhalation and from the gastrointestinal tract. It acts by
inhibiting acetylcholinesterase. Continued exposure to low amounts
may reduce blood cholinesterase activity 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 advance
symptoms of poisoning may be convulsions, coma, loss of reflexes and
loss of sphincter control.
The most important laboratory finding is reduction in activity of
blood cholinesterases. Urinary levels of organic phosphorus
containing metabolites may also be able to be used as a measure for
exposure. Neither method is specific for fensulfothion.
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. An adult with manifest peripheral symptoms should be treated
with 2-4 atropine sulfate, if necessary repeated every 15 minutes up
to 100 mg within 24 hours, and with 1-2 g of pralidoxime chloride or
250 mg of toxogonin by slow intravenous injection. Diazepam may be
given for the control of 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, other tranquillizers and central stimulants of all
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 Reference of previous reported cases
5.2 SURVEILLANCE TESTS
Test Normal level* Action level* Symptomatic level*
Plasma cholinesterase 100% 50% variable
Erythrocyte cholinesterase 100% 70% usually < 40%
(* Expressed as percentage of pre-exposure activity.)
Urinary levels of either extractable organic phosphorus may also be
used to determine the degree of exposure.
5.3 LABORATORY METHODS
5.3.1 Detection and assay of compound
References are given only
Gas chromatographic methods for analysis of fensulfothion and
metabolites are the methods of choice for residue analysis of
various crops, animal tissues and milk. GLC methods utilizing a KGL
thermionic detector proved to be particularly suitable for
regulatory purposes. See: Katague & Olson, 1969, Olson, 1970 and
1971. GLC methods have been developed for the determination of
individual metabolites (Williams et al., 1971; Bowman & Hill, 1971).
Gas chromatographic methods for determination of fensulfothion and
metabolites in soil have been developed (Olson, 1968; Katague,
5.3.2 Other tests in cases of poisoning
Levels of cholinesterase in blood provide the most useful diagnosis
of poisoning. See: Michel, N. O. (1949), J. Lab. Clin. Med., 34,
1564-1568. Ellman, G. L., Courtney, K. D., Andreas, V. jr &
Featherstone, R. M., (1961) Biochem. Pharmacol., 2, 88-95.
Urinary levels of diethyl phosphate and phosphorothioate can also be
used to determine exposure: method of Shafik & Enos (1969) as
modified by Shafik et al. (1970).
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