United States Office of Pesticides and Toxic Substances
Environmental Protection Office of Pesticide Programs (TS-766C)
Agency Washington, DC 20460
Pesticide
Fact Sheet
Name of Chemical: PHORATE
Reason for Issuance: COMPLIANCE DATE RESTRICTED USE
Date Issued: __ T ......
FEB. 1, 1985
Fact Sheet Number: 34.1
1. Description of chemical
Generic name: 0,0-diethyl S-[(ethylthio)methyl]phosphorodithioate
Common name: Phorate
Trade name: Thimet, Rampart
EPA Shaughnessy Code: 057201
Chemical Abstracts Service (CAS) Number: 298-02-2
Year of Initial Registration: 1959
Pesticide Type: Insecticide-nematicide
Chemical Family: Organophosphate
U.S. and foreign producers: American Cyanamid Co. (U.S.)
Use patterns and formulations
Application Sites: Non-domestic terrestrial and aquatic food/feed
crops; and greenhouse commercial nursery stock (both outdoor and
greenhouse).
Type of Formulations: Granular, emulsifiable concentrate
Application Rates (Ibs. active ingredient): Ornamentals - 8-20 Ibs./A
(10% granular product); Agricultural food/feed crops - 1-3 Ibs./A
(10-20% granular product) except sugarcane which is 4 Ibs./A and
potato which is 3.6 Ibs./A. The emulsifiable concentrates are applied
at 1 Ib./A (6 Ib/gal. emulsifiable concentrate) for Bermudagrass;
and at 2-2.18 lb./150 Ib. seed (8-8.7 Ib./gal. emulsifiable concentrate)
for treatment of cottonseed.
3. Science findings
Summary science statement:
Phorate has a very high acute toxicity to humans, fish and wildlife.
Pertinent data are lacking, however, and the Agency cannot conduct a
full risk assessment until the data required in this Standard are
submitted and evaluated.
Certain oxidation products of phorate are more toxic than phorate
itself. The oxidation products were previously toxicologically
discounted in the establishment of the tolerances for phorate.
The Agency does not, however, have the data needed to determine the
level at which the identified metabolites are present in the residues
occurring in or on the raw agricultural commodities resulting from the
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Phorat e
fact sheet
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current registered uses of phorate. Also, the n tabo1i n of phorate
in animals is not adequately understood. equate n taboli n studies
utilizing rtzninants are needed to determine the distribution and
characterization of residues in tissues and milk • In addition, the
toxicological studies needed to establish the acceptable daily intake
levels of the identified n tabolites are also lacking. t perxIing on
results of the residue studies required to be suth itted under the
Standard, the dietary risk may be greater than it earlier appeared
to be, although it may also be the s ne as before.
Ch nical Characteristics :
Physical State: Liquid
Cblor: Clear
Cxior: Skunk—like
Boiling Point: 118—120°C at 0.8 nun Hg
Melting Point: N/A
Fl nmability: 160°C (tagliabue open cup)
S3lubility in ter: 50 ppn
There are no unusual handling characteristics.
1 xicology Characteristics :
— ute Oral rat L 0 ; 3.7 mg/kg (male); and 1.4 mg/kg (f le);
lbxicity Category I.
— Pcute Dermal rat rJ 0 ; 9 • 3 mg/kg (male); and 3,9 mg/kg (f nale);
1 xicity Category I.
— ?cute Inhalation rat LC ; 60 mg/rn 3 (male); and 11 mg/rn 3 (f 1e);
Ibxicity Category I.
— The major routes of exposure in order of toxicological significance:
inhalation, dermal.
— Chronic toxicology results: equate studies include subchronic
feeding in the rat, oncogerlicity studies in the rat and the nuuse,
three generation reproduction, and teratology study in the rat.
The available nutagenic studies include tests in vitro microbial
and maninalian cells, and in vivo daninant lethal • No adverse
effects re found in any of these studies.
Physiological and Bioch nica1 Behavioral Characteristics :
F liar absorption: N/A
Translocation: Available mataboli9n studies indicate that phorate
and its soil netabolites are absorbed fran the soil by plant roots
and translocated to above-ground portion of the plant.
Mechani n of pesticidal action: As as organophosphate, phorate
exerts its toxic action by inhibiting certain important enz es of
the nervous syst n, chol inesterase (ChE).
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Phorate
fact sheet
Metabolisn and persistence in plants and animals: The matabo1i n in
plants is adequately understood. Phorate is tnetabolized in plants
by rapid oxidation to the sulfoxide (sane oxidation to the 0-analog
may also occur), foll d nore slowly by oxidation to the sulfone
and/or the 0-analog sulfoxide; phorate sulfone and phorate 0-analog
sulfoxide are then further oxidized to the 0-analog sulfone.
Available studies indicate that hydrolysis of the oxidized matabo-
lites eventually occurs to yield non—toxic water—soluble products.
A field study of corn treated at 1 lb. a.i./A with 10% granular
fornulat ion indicate that phorate residues re nondetectable
((0.002 ppn) after 14 days while residues of the sulfoxide and
sulfone persisted to 28 days. After 83 days, there ware no detect-
able residues occuring in the kernels, coos or husks.
The mataboli n of phorate in animals is not presently understood
due to lack of sufficient data.
Environmental Characteristics :
Phorate has sane potential to leach throt h soil and contaminate ground
water, particularly where soils are sandy and aquifers are shallow.
Simulation of the leaching potential of horate using the Pesticide
1 ot Zone t’ del (a canputer nodel which predicts nov nent throu3h the
root zone and the unsaturated soil zone based on ch nical and soil
properties) predicts sane nobility in sandy soils but none in loam
soils under typical phorate use conditions. Because ot lack of
sufficient data regarding the envirorinental behavior of phorate, the
ency is unable to caipletely evaluate the leaching potential.
Additional studies are being requested on an accelerated basis; these
studies include hydrolysis, netabolign, and nobility studies and, in
particular, a field dissipation study which is to be carried out in a
potato-growing area of tong Island, New York.
Ecological Characteristics :
— Avian Oral Lt 0 = 0.62 iw jflcg (mallard) and 7.12 n fkg (pheasant).
— Avian Dietary LC 5 j = 24 to 77 p m (upland garnebirds) arid 712 p n
(waterfowl).
— Fish LC5o = 6 to 13 ppb (coldwater fish) and 2 to 280 ppb (warmwater
fish).
— uatic Invertebrate tC 50 = 4 ppb.
Based on these studies, phorate is very highly toxic to avian species,
freshwater fish and aquatic invertebrates. garding endangered
species, there is a potential risk to the Aleutian Canada goose,
Attwater’s greater prairie chicken and the Kern primrose sphinx
noth.
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Pho rat a
fact sheet 4
tlerance Asses ntS :
Refer to attached table for the list of current tolerances established
for phorate. Available data are not sufficient to conduct a tolerance
asses flt.
4. Sunmary of Regulatory Position and Rationale
Use classification: All emulsifiable concentrate (EC) phorate fornD.1—
lations containing 65% and greater and all granular forrm.ilations of
phorate for use on rice have been previously classified restricted
use pesticides pursuant to 40 CFR 162.31. All, granular fortinilations
containing 5% phorate and greater have been classified as restricted
use pesticides under this Registration Standard. In addition, all
granular formulations containing less than 5% phorate are considered
restricted use pesticides pending receipt and evaluation of data
required to be su nitted under this Standard. All products subject
to the restricted use requirement which are released for shi nt
after September 1, 1985 imist be labeled for restricted use. All
products subject to the restricted use requirement which are in
channsls of trade after September 1, 1986 nLlst be labeled for
restricted use.
Though there are no EC fot ulations containing less than 65% phorate
currently registered, such fornijiations uld be considered restricted
use pesticides.
Use, formm.zlat ion or geographical restrictions: Products containing
phorate are not to be used or stored in or around the hc!ne. Geograph-
ical restrictions of varying degrees currently exist on sate or all
of the uses on rn ida grass, corn, lettuce, rice, sorghum, su arcane,
tanato, wheat, and lilies. d—use products may be granular or
liquid fornuilations.
unique warning stat nts required on labels: Phorate manufacturing—use
products (MP) require the use of protective clothing and respirator.
End—use products require the restricted use statement and use of
protective clothing. The phorate products for greenhouse use require
the use of a respirator. A restriction against reentering treated
fields before 24 hours after application is also required.
b ne uses or tolerances for phorate will be considered until the
human and environmental concerns raised in this DDcullent are sat is—
factorily resolved.
5. Sum iaty of Major 1 ta Gaps
Toxicology: Acute delayed neurotoxicity; 6-ncnth feeding studies (on
the identified oxidation metabolites); chronic feeding study (non—
rodent); a teratology study in a second species (other than the
rat)*; rmitagerticity studies and product integrity studies and a
general metaboli3!t study.
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Phorat a
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A rabbit teratology study has recently been sutinitted and is
currently under review by the Agency.
E virom ental Safety: Avian reproduction; fish life cycle ( freshwater);
full field studies including population n nitoring (avian, m malian
and aquatic species); and secondary poisoning studies for one rnazatial
and one avian species.
Envirorit ntal Fate: Hydrolysis; photodegradation (water, soil, air);
metabolisn (aerobic soil and aquatic, anaerobic soil or aquatic);
leaching; volatility; dissipation; accunulation (rotational crop,
irrigated crop , fish; and aquatic organi ); and re—entry studies
(detmal and inhalation exposure; and soil and foliar dissipation).
i sidue ( emistry: Plant xi tabolisn (the quantification of the oxi-
dation products of pt rate ntained in the residue in or on raw
agricultural ccm dities, including neat, milk, poultry and eggs,
for which tolerances have been established as a result of the maxinun
registered use of phorate); livestock n taboli3n; and additional
residue data (for each established tolerance except Berrm.idagrass and
milk).
All data are to be su idtted by July, 1987.
6. Contact person at EPA :
Willi n H. Miller, (PM—16)
Insecticide— denticide Branch (TS—767)
401 Fl Street, SW.
shington, DC 20460.
Tel. No. (703) 557—2600
DISCLAIMER: The information presented in this C nical Info tnation Fact
Sheet is for info xnational purposes only and may not be used to fulfill data
requir ients for pesticide registration and reregistration.
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