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in 1996. EXTOXNET no longer updates this information, but it may be useful
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names include AC 8911, Agrimet, Geomet, Granutox, Phorate
10G, Rampart, Terrathion, Thimenox, Thimet, Timet, Vegfru, and
Phorate is a highly toxic compound in EPA toxicity class I.
Labels for products containing it must bear the Signal Words
DANGER - POISON. It is a Restricted Use Pesticide (RUP). RUPs may
be purchased and used only by certified applicators.
Phorate is an organophosphorus insecticide and acaricide used to
control sucking and chewing insects, leafhoppers, leafminers,
mites, some nematodes, and rootworms [1,2]. Phorate is used in
pine forests and on root and field crops, including corn, cotton,
coffee, some ornamental and herbaceous plants, and bulbs. It is
available in granular and emulsifiable concentrate formulations.
Formulation: It is
available in granular and emusifiable concentrate formulations.
- Acute toxicity: Phorate is highly toxic
via the oral route with reported oral LD50 values of 1.1
to 3.7 mg/kg in rats [2,13], and 2.25 to 6.59 mg/kg in
mice [2,87]. It is highly toxic via the dermal route as
well, with reported dermal LD50 values of 2.5 to 6.2
mg/kg in rats [2,13], and 5.2 mg/kg in rabbits [2,87].
Guinea pigs reportedly have a dermal LD50 of 20 to 30
mg/kg during a 24-hour exposure [13,87]. The acute 1-hour
inhalation LC50 for rats is reported as 0.06 mg/L .
Symptoms of acute exposure to phorate are similar to
those caused by exposure to other organophosphate
pesticides, except that they may occur at lower doses.
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. Toxicity appears to vary with
age, with the young being more susceptible . Several
poisoning cases involved workers from 16 to 18 years old,
wearing inadequate protection while applying phorate to
crops, or working around machines used to apply phorate
[2,8]. Studies indicate that direct eye exposure may
cause blurring, tearing, and ocular pain .
- Chronic toxicity: Repeated low-level
exposures may result in cholinesterase inhibition and the
associated neurological and neuromuscular effects . A
survey of workers exposed to phorate revealed toxic
effects in 60% of the males tested (after a 2-week
exposure). Symptoms included a lowering of the heart
rate. Effects on cholinesterase in the blood of the
workers were also noted in this study [2,8]. In a study
on dogs, moderate to high doses of phorate 6 days each
week for 13 to 15 weeks lowered cholinesterase activity,
but produced no tissue damage .
- Reproductive effects: Long-term studies
of mice fed high doses of 98.7% pure phorate showed no
effects on fertility, gestation, or viability .
Maternal and embryo toxicity occurred at dietary doses of
0.5 mg/kg/day fed to rats . Available data suggest
that phorate is unlikely to cause reproductive effects.
- Teratogenic effects: No birth defects
were found in two studies on the rat [87,88]. Available
data suggest that phorate does not cause birth defects.
- Mutagenic effects: Studies of phorate in
both bacterial systems or in mice indicate that it is
- Carcinogenic effects: Studies in both
rats and mice produced no evidence of carcinogenicity
- Organ toxicity: Phorate's main target
organ, as determined by animal testing and human use
experience, is the nervous system.
- Fate in humans and animals: Phorate is
readily absorbed by the skin and the gastrointestinal
tract. The major breakdown products of phorate in mammals
are more toxic and have greater anticholinesterase
activity than phorate . Phorate may have a long
residence time in mammalian systems; for example, rats
given a high oral dose excreted less than 40% in 6 days.
The liver, kidney, lung, brain, and glandular tissue held
the remaining residues .
- Effects on birds: Phorate is very highly
toxic to highly toxic to birds. The reported acute oral
LD50 values are 12.8 mg/kg in chukar, 7.5 mg/kg in
starlings, 0.6 to 2.5 mg/kg in mallards, 7 to 21 mg/kg in
northern bobwhite quail, 1 mg/kg in red-winged
blackbirds, and 7 mg/kg in ring-neck pheasants . The
5- to 8-day dietary LC50 values are reported as 370 to
580 ppm in Japanese quail, mallard, northern bobwhite
quail, and ring-neck pheasant .
- Effects on aquatic organisms: Phorate is
very highly toxic to fish. Reported 96-hour LC50 values
range from 2 to 13 ug/L in cutthroat trout, bluegill
sunfish and largemouth bass. Other 96-hour LC50 values
are 110 ug/L in northern pike and 280 ug/L in channel
catfish . Reported 96-hour LC50 values for the
compound in freshwater invertebrates such as stoneflies
and scuds are 4 ug/L, also indicating very high toxicity.
Other LC50 values are 0.006 ug/L for amphipods and 0.11
to 1.9 ug/L in other freshwater invertebrates . The
acute oral LD50 of phorate is 85 mg/kg in bullfrogs .
- Effects on other organisms: Phorate is
toxic to bees, with a reported topical application LD50
of 10 ug per bee .
- Breakdown in soil and groundwater:
Phorate is of moderate persistence in the soil
environment, with reported field half-lives of 2 to 173
days. A representative value may be approximately 60 days
. Actual residence times may be influenced by soil
clay and organic matter content, rainfall, and soil pH
. Soil treatments often leave more residues in plants
than foliar treatments, because the compound persists in
the soil and is readily taken up by plant roots [13,8].
Phorate binds moderately well to most soils and is
slightly soluble in water . It should therefore not
be highly mobile in most soils, and should mainly be
transported with runoff via sediment and water. Phorate
has minimal potential to leach through the soil and
contaminate groundwater. This is most likely where soils
are sandy and aquifers are shallow. Field studies
indicate that leaching is very low in soils high in clay
and organic matter content, and lower in sandy soils .
- Breakdown in water: The half-life of
phorate in acidic water solutions is between a few days
and a few weeks, depending on temperature; the half-life
in alkaline (basic) water may be much shorter [8,88].
Phorate is degraded by waterborne microorganisms and
hydrolysis [8,88]. As it breaks down in water, nontoxic,
water-soluble products are formed.
- Breakdown in vegetation: Phorate itself
is not persistent in plants, but plants metabolize
phorate to very potent anticholinesterase agents such as
the sulfoxide and sulfone derivatives of the compound
. This activity will usually peak several days
following application before decreasing . Phorate and
its soil metabolites are absorbed from the soil by plant
roots and are translocated to above-ground portions of
the plant. Following treatment with a 10% granular
formulation at 1 pound a.i./acre, phorate residues
persisted at very low levels for 28 days in the kernels,
cobs, or husks. After 83 days, there were no detectable
residues of phorate or breakdown products .
- Appearance: Technical phorate is a clear
liquid at room temperature .
- Chemical Name: O,O-diethyl
S-ethylthiomethyl phosphorodithioate 
- CAS Number: 298-02-2
- Molecular Weight: 260.38
- Water Solubility: 50 mg/L @ 25 C 
- Solubility in Other Solvents: v.s. in
xylene, carbon tetrachloride, dioxane, methyl cellosolve,
dibutylphthalate vegetable oils, ethanol, ether, and
aliphatic hydrocarbons 
- Melting Point: Less than -15 C 
- Vapor Pressure: 110 mPa @ 20 C 
- Partition Coefficient: 3.9248 
- Adsorption Coefficient: 1000 (estimated)
- ADI: 0.0002 mg/kg/day 
- MCL: Not Available
- RfD: Not Available
- PEL: Not Available
- HA: Not Available
- TLV: 0.05 mg/m3 (8-hour) (skin) 
American Cyanamid Co.
One Cyanamid Plaza
Wayne, NJ 07470-8426
- Phone: 201-831-2000
- Emergency: 201-835-3100
References for the information in this PIP can be found in
Reference List Number 5
information in this profile does not in any way replace or
supersede the information on the pesticide product labeling or
other regulatory requirements. Please refer to the pesticide