Fenitrothion is a contact insecticide and selective acaricide of low
ovicidal properties. It belongs to the organophosphate family of insecticides.
It is considered a cholinesterase inhibitor. It may also be used as
a fly, mosquito, and cockroach residual contact spray for farms and
public health programs. Fenitrothion is also effective against household
insects and all of the nuisance insects listed by the World Health Organization.
Its effectiveness as a vector control agent for malaria is confirmed
by the World Health Organization. Fenitrothion is non-systemic, and
non-persistent. Fenitrothion was introduced in 1959 by both Sumitomo
Chemical Company and Bayer Leverkusen and later by American Cyanamid
Company. Fenitrothion is far less toxic than parathion with a range
of insecticidal activity that is very similar and is similar enough
in structure to be produced in the same factories. The difference in
precursor chemicals might make it somewhat more expensive, but it is
heavily used in other countries, including Japan, where parathion has
been banned. Fenitrothion comes in dust, emulsifiable concentrate, flowable,
fogging concentrate, granules, ULV, oil-based
liquid spray, and wettable powder formulations. It is available as a
95% concentrate, 50% emulsifiable concentrate, 40% and 50% wettable
powder and 2%, 2.5%, 3% and 5% dusts. It is compatible with other neutral
O,O-dimethyl O-4-nitro-m-tolyl phosphorothioate
The acute toxicity of fenitrothion to mammals is considered to be low.
The acute oral LD50 for rats ranges between 250-800 mg/kg; 715-870 mg/kg
for mice; and 500 mg/kg for guinea pigs. The acute dermal LD50 for rats
is >890 mg/kg and >3,000 mg/kg for mice. The acute inhalation
LC50 in rats was reported to be 5.0 mg/l. The oral acute toxicity for
cats was 142 mg/kg. Chronic symptoms in humans include: general malaise,
fatigue, headache, loss of memory and ability to concentrate, anorexia,
nausea, thirst, loss of weight, cramps, muscular weakness and tremors.
Effects on Birds:
Negative results were observed in studies on delayed
neurotoxicity in hens. The oral LD50 for chickens is reported as 28
mg/kg. Fenitrothion was found to be highly toxic to upland gamebirds
and slightly toxic to waterfowl (acute oral toxicity value to quail
and mallards was determined to be 23.6 mg/kg and 1,190 mg/kg, respectively).
The LC50 for pheasants was 450 to 500 ppm in diets of 2-week-old birds
when fed fenitrothion-treated feed for 5 days, followed by untreated
feed for 3 days.
Effects on Aquatic Organisms:
The time for achieving the highest
levels of uptake and the extent of retention of organophosphate residues
by fish was directly related to the extent of persistence of a compound
in water. Fenitrothion (4.9 mg/kg) persisted longer than 4 weeks in
fish. Fenitrothion is considered somewhat toxic to fish. The 96-hour
LC50 was 1.7 ppm for brook trout; moderately toxic to both warmwater
and coldwater fish. The chronic toxicity of fenitrothion to fish is
considered low. The 48-hour LC50 values for carp ranged between 2.0
mg/l and 4.1 mg/l. In a study on the acute toxicity of fenitrothion
to rainbow trout, embryos were found to be the least sensitive, the
sacfry stage was intermediate, and fingerlings and adults were the most
sensitive. The toxicity of fenitrothion to rainbow trout increased with
increasing temperature. The sublethal effects of fenitrothion exposure
on fish include:
Morpho Anatomical Changes:
Swelling of the abdomen of fathead minnows occured. Young Atlantic
salmon exposed to 1 mg/l swam with distended fins.
There was a pronounced decline in various agonistic behaviors (chasing,
vacating, nipping, etc.) within 2 hours of exposure to several concentrations
Acetylcholinesterase activity was inhibited 13% to 25% after various
sublethal concentrations of fenitrothion. Cholinesterase activity
in the erythrocytes, gills, heart, and serum of rainbow trout was
reduced within 1 hour after exposure to fenitrothion.
Effect on Growth:
Orally administrated fenitrothion had no effect on the growth
of rainbow trout. The compound is considered very toxic to crustaceans
and aquatic insects and has a medium toxicity to aquatic worms. A
freshwater invertebrate toxicity (48-hour or 96-hour EC50) reported
fenitrothion to be very highly toxic to aquatic invertebrates (3 ppb
for Gammarus fasciatus ).
Effects on Other Animals
(Nontarget species): There is
sufficient information to characterize fenitrothion as highly toxic
to honeybees (acute toxicity value = 0.383 micrograms/bee) when bees
are exposed to direct treatment or to dried residues on foliage. Fenitrothion
is considered toxic to spider mites with long residual action.
of Chemical in Soil and Groundwater: Preliminary
data indicates fenitrothion degrades fairly rapidly in soil with a half-life
of less than one week in non-sterile muck, sandy loam soils. The compound
is intermediately mobile in a variety of soils ranging from sandy loam
of Chemical in Vegetation: Damage to cabbage
and fruit is possible only if the application dose is exceeded. Fenitrothion
has been know to be phytotoxic to cotton, Brassica crops, and certain
fruit crops when high rates were applied. Certain apple varieties may
be russeted. In a study conducted by FAO/WHO, about 50% of 32P-labelled
fenitrothion sprayed on rice plants penetrated into the tissues in 24
hours. At the end of this period only 10% was left, indicating rapid
of Chemical in Air:
An experiment was carried out in a vacant dormitory building
in order to establish the airborne residue of concentrations of seven
pesticides used for cockroach control. Airborne concentrations of fenitrothion
on the day of application were 3 micrograms/cubic meter. All were below
0.7 micrograms/cubic meter by the third day after application. The airborne
concentrations correlated well with the vapor pressures of the various
- Appearance: Pure material forms
a yellowish brown liquid with an unpleasant odor (2, 125)
- Chemical Name: O,O-dimethyl O-4-nitro-m-tolyl
phosphorothioate (IUPAC), O,O-dimethyl O-(3-methyl-4-nitrophenyl)
phosphorothioate (CA), O,O-dimethyl O-(3-methyl-4-nitrophenyl) thiophosphate.
- CAS Number: 122-14-5.
- Molecular Weight: 277.25.
- Water Solubility: In water at 20
degrees C, 30 mg/l; at 30 degrees C, 14 mg/l water; nearly insoluble
in water; insoluble in water.
- Solubility in Other Solvents: Readily
soluble in common organic solvents, e.g. acetone, alcohol, benzene
and chlorinated hydrocarbons. dichloromethane, 2-propanol, toluene.
Hardly soluble in n-hexane. Soluble in ethers, methanol, xylene, ketones,
esters, and aromatic hydrocarbons. Low solubility in alaphatic hydrocarbons.
At 20 -25 degrees C, > 1 kg/kg dichloromethane, methanol and xylene,
42 g/kg haxane, 0.1 - 1.0 kg/kg propan-2-ol. It is hydrolyzed by alkali;
at 30 degrees C, 50% loss occurs in 4.5 hours in 10M sodium hydroxide.
- Melting Point: 0.3 degrees C.
- Vapor Pressure: 7 x 10 to the minus
5 mbar at 20 degrees C (13);18 mPa at 20 degrees C.
- Partition Coefficient: 2380.
- Adsorption Coefficient: Not Available.
- Stability: Fenitrothion is completely
stable for two years if stored at temperatures between 20 and 25 degrees
C. Storage temperature should not exceed 40 degrees C. It is unstable
in alkaline media. The thermal stability of this compound is low,
and when it is heated above 100 degrees C it undergoes Pishchemuka
isomerization and may decompose explosively. It must be stored in
enameled, aluminum or glass containers. Iron promotes decomposition
- Specific gravity: 1.3227; 1.32-1.34;
1.3084 at 20 degrees C.
- Boiling point: 109 degrees C at
0.13 mbar; 164 degrees C at 1.3 mbar (13). 140-145 degrees C/0.1 mmHg.
244 degrees F (118 degrees C) at 0.05 mmHg (113). 118 degrees C at
- Flashpoint: 166 degrees C (closed
- Volatility: 0.09 mg/m3.
When spraying anything
which resembles Terrazzo tiling always do a test spray before committing
yourself. Fenitrothion has a tendency to stain this type of tile yellow,
this reaction is not reversible.
Sources include: Oregon
University and World Health Organisation
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