||Chemicals / Complex Chemical Agents/
||Chemical name: O,O-dimethyl
O-4-methylthio-m-tolyl phosphorothiaote (W180.Feb02.WNV2)
- Formerly called DMTP.
- Baycid; Baytex; Entex; Lebayeid; Queletox; Spotten; Talodex; Tiguvon; Lebaycid;
O,O-dimethyl-O-[4-(methylthio)-m-tolyl] phosphorothioate; Lebaycid(R); O,O-dimethyl
O-(4-methylmercapto-3-methylphenyl) thionophosphate; O,O-dimethyl
O-(3-methyl-4-methylthiophenyl) thiophosphate; O,O-dimethyl
O-(4-methylthio-3-methylphenyl) thiophosphate; Phosphorothioic acid O,O-dimethyl
O-[3-methyl-4-(methylthio)phenyl]ester; phosphorothioic acid O,O-dimethyl
O-(4-methylthio)-m-tolyl ester; b 29493; bay 29493; bayer 9007; bayer 29493; bayer s-1752;
m-cresol, 4-(methylthio)-, O-ester with O,O-dimethyl phosphorothioate; O,O-dimethyl
O-4-(methylmercapto)-3-methylphenyl phosphorothioate; O,O-dimethyl
O-3-methyl-4-methylthiophenyl phosphorothioate; DMTP; MPP; OMS 2; S 1752; spotton;
Mosquitocide 700; Rid-a-Bird; BX-1; BX-2; Cresol, 4-(methylthio)-, O-ester with
O,O-dimethyl phosphorothioate; Dimethyl (3-methyl-4-(methylthio)phenyl) phosphorothionate;
Dimethyl methylthiotolyl phosphorothioate; Dimethyl
O-(3-methyl-4-(methylthio)phenyl) thiophosphate; Dimethyl O-(4-(methylthio)-m-tolyl)
phosphorothioate; Mercaptofos; Thiophos; 4-Methylmercapto-3-methylphenyl dimethyl
O-[3-methyl-4-(methylthio)phenyl] phosphorothioate. (W325.May01.WNV1)
- Finest (AGRO-SAN Chemicals Industry and Trade Inc.); Fenchem (Chemet Chemicals Ltd.);
Prestig (Hektas Ticaret T.A.S.); Korfen (Koruma Tarim A.S.); Libersan (Kuang Hwa Chemical
is available in dust, emulsifiable concentrate, granular, liquid concentrate, spray
and wettable powder formulations. (W180.Feb02.WNV2,
- Pure: colorless oily liquid.
- Technical grade: yellow or brown oily liquid with a weak garlic odour.
- Melting point: 7.5°C.
- Boiling point: 87°C
at 0.01 mm Hg. (W324.Oct01.WNV1);
87°C at 1.4 Pa (W325.May01.WNV1)
- Density: 1.25 at 20°C. (W324.Oct01.WNV1,
pressure: 0.37 mPa at 20°C. (W325.May01.WNV1)
- Solubility in water: 0.0055 g/100 ml. (W324.Oct01.WNV1)
solubilities: Very readily soluble in dichloromethane, toluene. Readily soluble in
2-propanol. Soluble in n -hexane. (W325.May01.WNV1)
||Fenthion is an organophosphate
compound. These compounds act as an inhibitors of cholinesterase enzymes, which are
involved in normal transmission of nerve impulses within the nervous system. (B36.39.w39)
- Fenthion is a contact and stomach organophosphate
insecticide used against many sucking, biting pests,
especially fruit flies, stem borers, mosquitoes, and Eurygaster cereal bugs, also
insects in fruit, grapes, olives, vegetables, cotton, tea, sugarcane, rice, etc. (W180.Feb02.WNV2,
In mosquitoes, fenthion is toxic to both
the adult and immature forms (larvae). (W180.Feb02.WNV2)
- Once used extensively in the U.S. for controlling
intestinal worms, fenthion no longer has FDA approval due to poisoning deaths. (W180.Feb02.WNV2)
- While it is effective as an insecticide, it is
also moderately toxic to mammals, and highly toxic to birds.
- Based on its high toxicity to birds, fenthion is
used in various parts of the world for weaver bird control. Pest control operators have
used it to control pigeons around public buildings, as well. For bird control, use is made
of fenthion's contact action and its ready absorption through the skin. It is applied as a
paste to roosting areas when utilized for such purposes. (W180.Feb02.WNV2)
||Fenthion is a moderately toxic compound in EPA
toxicity class II. (W180.Feb02.WNV2,
It is classified by the U.S. Environmental
Protection Agency (EPA) as a Restricted Use Pesticide (RUP) due to the special handling
warranted by its toxicity. All bird control products, as well as non-domestic,
non-granular formulations of 70% and greater are RUPs. RUPs may be purchased and used only
by trained certified applicators. Fenthion may not be used on food crops in the USA.
Labels for products containing fenthion must bear the Signal Word "WARNING". (W180.Feb02.WNV2)
- Acute toxicity:
- Moderately toxic via the oral route, with reported
values of 180 to 298 mg/kg in rats (Laboratory rat (Rattus
norvegicus - Brown rat)), 150 mg/kg in
cuniculus - European rabbit (Domestic rabbit)), and 88 to 145 mg/kg in mice (Mus
domesticus - Laboratory mouse).
- Moderately toxic via the dermal route as well,
with reported dermal LD50
values of 330 to 1000 mg/kg in rats, and 500 mg/kg in mice.
- Slightly toxic via inhalation with a reported
1-hour airborne LC50
for fenthion in rats of 2.4 to 3.0 mg/L.
- Acute effects of fenthion are similar to those
caused by other organophosphates, but may take somewhat longer to develop.
- Fenthion is of sufficiently low toxicity it has
been investigated as an agent against insect parasites in animals (e.g., dogs
familiaris - Domestic dog)).
- Symptoms of acute exposure to organophosphate or cholinesterase-inhibiting
compounds may include the following: numbness, tingling sensations, incoordination,
headache, dizziness, tremor, nausea, abdominal cramps, sweating, blurred vision,
difficulty breathing or respiratory depression, and slow heartbeat. Very high doses may
result in unconsciousness, incontinence, and convulsions or fatality.
- Chronic toxicity:
- In rats, 12.5 mg/kg/day caused weight loss and 85%
inhibition of normal brain cholinesterase activity within 4 weeks.
- Much less severe, but still detectable decreases
were noticeable at doses of 2.5 mg/kg/day.
- Repeated or prolonged exposure to organophosphates
may result in the same effects as acute exposure, including the delayed symptoms.
- There was no evidence of weight loss or decreased
food consumption in dogs that were given dietary doses of 1.25 mg/kg/day for 1 year.
- In Nigerian sprayers, those not wearing protective
clothing while spraying showed decreased whole-blood cholinesterase activity.
- Veterinary clinic workers who did not use skin
protection when applying a 20% topical application to dogs experienced symptoms ranging
from tingling and numbness of the hands and feet to generalized weakness and shooting
- Other possible effects are similar to those caused
by the other organophosphates.
- Reproductive effects:
- Single injections of 40 or 80 mg/kg of fenthion
into the abdominal cavities of pregnant female mice caused poisoning in the developing
fetuses, particularly when administered on days 10 to 12 of gestation.
- Fetuses were injured primarily by dosages that
caused toxicity in the maternal mouse.
- No influence was seen on reproduction in other
three-generation studies of mice.
- These data indicate that reproductive effects are
unlikely in humans.
- Teratogenic effects:
- Some reduction in fetal weight occurred, but no
defects were found in mice that were given intraperitoneal doses of up to 80 mg/kg of
fenthion in single-day or 3-day periods during the period of gestation in which organs are
- No teratogenic effects were seen in five
generations of mice that drank water containing 60 mg/L fenthion.
- Other tests on mice and rats did not show
teratogenic effects from fenthion.
- These data indicate that fenthion is not
- Mutagenic effects:
- Tests on mice did not show mutagenic effects from fenthion.
- Available data are insufficient to draw a
conclusion regarding the mutagenicity of the compound.
- Carcinogenic effects:
- One carcinogenicity test on fenthion indicated
that this insecticide may be a carcinogen in male mice. However, no carcinogenic effects
were observed in other 2-year feeding studies of rats and mice.
- Available data are insufficient to draw
conclusions regarding the carcinogenicity of fenthion.
- Organ toxicity:
- Animal tests and human use experience have
identified that target organs affected by fenthion exposure include the central nervous
system, peripheral nervous system, and the heart. (W180.Feb02.WNV2)
- Fate in humans and animals:
- In animals, fenthion is quickly absorbed into the
bloodstream through the digestive tract, lungs, and skin, and is systemically
- Fenthion is eliminated through the urine and the
- A single dose of the insecticide has prolonged
action, suggesting that much of it is stored in body fat and later released for
- Fenthion and its metabolites were found in the fat
of steers slaughtered 3 days after dermal application of
- When cows (Bos
taurus - Domestic cattle) were given a
dermal application of 9 mg of fenthion per kilogram, 45 to 55% of the dose was excreted in
the urine, 2.0 to 2.5% in the feces, and 1.5 to 2.0% was recovered in the milk.
- Breakdown in soil and groundwater:
Fenthion has moderate persistence in soil, with an average field half-life of 34 days
under most conditions. In soil, residues of fenthion may persist for approximately 4 to 6
- It adsorbs fairly strongly to soil particles, and
so is not likely to move (or leach) through the soil. (W180.Feb02.WNV2)
- Breakdown in water: In one study
of its persistence in water, 50% of applied fenthion remained in river water 2 weeks
later, while 10% remained after 4 weeks. (W180.Feb02.WNV2)
- It is more rapidly degraded under alkaline
- Breakdown in vegetation: Fenthion
is phytotoxic (or harmful to plants) to American linden, Hawthorn and sugar maple trees,
and to certain rose varieties. It is not considered phytotoxic when used at recommended
rates, although injury has occurred in certain varieties of apples and cotton.
- Plant foliage should not be sprayed when
temperatures exceed 90° F.
- Only about 10% of applied fenthion remained on
rice plants after 6 hours. Almost half of the activity was found in the rice bran, 6.5%
was in the husk, and 14.7% was in polished rice.
- Water soluble metabolites were found 14 days after
fenthion application to rice plants.
on Non-target Species
- Effects on birds (Aves
- Birds (Class)):
- Fenthion is very highly to highly toxic to birds:
values for various species range from less than 4 mg/kg in bobwhite quail to 26 mg/kg
in ducks. Birds which showed acute LD50
values within this interval were California quail, Japanese quail, Canada geese (Branta
canadensis - Canada goose), finches,
vulgaris - Common starling), sparrows,
platyrhynchos - Mallard), mourning doves
macroura - Mourning dove), and chukar
- Acute symptoms of fenthion poisoning in birds
include tearing of the eyes, foamy salivation, lack of movement, tremors, congestion of
the windpipe, lack of coordination in walking, and an abnormally rapid rate of breathing
or difficult breathing.
- Chickens (Gallus gallus domesticus
- Domestic chicken (Phasianidae
- Grouse, Turkeys, Pheasants, Partridges, etc. (Family))) developed leg weakness when they were fed 25 mg/kg doses
of fenthion. The acute oral LD50
in poultry is 15 to 30 mg/kg.
- The approximate dietary LC50
values (over an unspecified number of days) for fenthion are: Japanese quail, 130 ppm;
colchicus - Common pheasant), 200 ppm;
bobwhite quail 30 ppm,
and mallard, 230 ppm.
- After administration of 0.5 mg/kg/day for 30 days,
the eggs laid by surviving mallards had markedly reduced fertility.
- Effects on aquatic organisms:
- Fenthion is moderately toxic to fish with reported
values of 9.3 mg/L in rainbow trout, 1.33 mg/L in brown trout, 1.32 mg/L in coho
salmon, 1.16 mg/L in carp, 1.54 mg/L in largemouth bass, 1.38 mg/L in bluegill, 1.65 mg/L
in yellow perch, 2.40 mg/L in fathead minnow, and 3.40 mg/L in goldfish.
- Brown bullheads were not affected by the insecticide
when it was applied to a California refuge at 0.01 pounds per acre.
- Fenthion may be very highly toxic to some
freshwater aquatic invertebrates.
- Effects on other organisms:
- Fenthion is toxic to bees. (W180.Feb02.WNV2)
(USA Contacts for Managing WNV Disease)
||Debra Bourne (V.w5)
||Suzanne I. Boardman (V.w6);
Becki Lawson (V.w26)