Unit ad States Oft ice o< Pesticides and 'toxic Substances
Environmental Protection Office of Pesticide Program! (TS-766C)
Agency Washington. DC 2O460
4>EPA Pesticide
Fact Sheet
Name Of Chemical: Oxydemeton-Methyl
Reason for Issuance:
Registration Standard/Initiation
Date Issued: lo/87 of Special Review
Fact Sheet Number: ^44
1. Description of Chemical
Chemical name: S-L2-(Ethylsulfinyl)ethyl]
O,O-dimethyl phosphorothioate
Common name: Oxydemeton-methyl
Other Chemical Names: Demetcn-o-methy 1; s-2-ethylsulphinylethyl-
o,o-dimethyl phosphorothioate; metilmerkapto-
Tbsoksiol; o,o-dimethyl-&-L2- (ethylsulf inyl)
ethyljphosphorothioate; demeston-s-methyl-
sulfoxid;
Trade Names: R2170; Metasystemox; Metasystox-R; and Bay 21097
OPP Shaughnessy No.: 058702
Chemical Abstracts Service (CAS) No.: 3O1-12-2
Year of Initial Registration: 1961
Pesticide Type: Insecticide, Acaricide.
Chemical Family: Organophosphate
U.S. and Foreign Producers: Mobay Chemical Corp., U.S.A.; Bayer AG,
West Germany.
2. Use Patterns and Formulations
Application sites: terrestrial food crops (vegetable, field tree fruit,
and nut crops), terrestrial nonfood crops (ornamentals
and forest trees), greenhouse nonfood crops (research
crops not for consumption), domestic indoor and
outdoor, and forestry (trunk injection only).
Types of Formulation: Oxydemeton-methyl is formulated in combination
with trichlorfon, methoxychlor, carbaryi, dinocap,
dicofol, or folpet. Single ai formulations
consist of 0.48 to 4.O Ib/gal EC, 2%, 2.45%,
and 13.5% BC and 50% P/T.
-------
—2—
Types/Metthds of Application: applied by broadcast spray using ground
equipnent or aircraft 4 soil injection,
tree trunk injection.
3. Science Findings
Suninary Science Stat nent :
0xyd neton—nethyl is an organo t os 1iate cc1T ound. It is classified as
Toxicity ( tegory I due to its dennal toxicity, Toxicity Category II due
to its inhalation and oral toxicity., Toxicity C tegory IV based on
primary dermal irritation potential, and Toxicity ( tegory III because
of its ability to cause primary eye irritation. A 1—year dog feeding
study conducted with the 50% concentrate of the technical material,
instead of the technical grade, at dietary concentrations of 0,
0.0125, 0.125 and 1.25 mg/kg/day, sho ied inhibition of RBC and brain
c1 linesterase at the mid-dose. A n stuiy with the technical
grade is required. Subnitted oncogenicity data are inadequate to
allow an asses nent of the oncogenic potential of oxdemeton—nethyl.
Based on available data, the ency has determined that oxyienetoçi-methyl
has the potential to induce reproductive effects in hunans, and that
that effect is of concern because of the potential exposure to applicators,
mixers, and loaders o use products containing oxydaneton—niethyl.
and to field orkers who may enter treated fields. Additional data
are required to fully assess this concern. Additional toxicology
and residue chemistry data are required for a reasses iient of the
tolerances of oxydaneton-nEthyl and its chDlinesterase-inhibiting
metabolites. Avian acute oral stulies indicate toxicity ranges fran
rrcderately toxic (mallards) to highly toxic (rock dove). Eight-day
dietary stu3 .ies also shoe a wide range of toxicity fran practically
non-toxic (mallards) to highly toxic (bobwhite quail). Available
data indicate oxydeneton-methyl is very highly toxic to daphnids,
iuderately toxic to isopods. highly toxic to amphipods, moderately
to highly toxic to coidwater fish, slightly to mierately toxic to
warm iater fish, and ncderately toxic to estuarine crustaceans.
Additional data are required for the Agency to ccziplete its asses&nent
of potential risks to avian and aquatic species.
Chemical Characteristics :
Physical/chemical properties of pure oxydemeton-methyl, and of the
53.1% FIa and 90% unregistered T:
Color: Colorless (P), yello .i—bro&n (T), Ye1lo. i to amber (Fl)
Physical state: liquid (P. Fl)
Odor: Odorless (P), ‘I ’pical sulfur-containing (T)
Melting Point: <10° C (p) 1 <100 C (T)
Bailing Point: 106° C at 0.013 mbar (P)
Specific Gravity: 1.289 at 200 C (P), 1.03 at 200 C (Fl)
Solubility: 10-100 g/l0O ml of xylene, cyclcthexanone , 2-propaixl.
and methylene chloride at 20° C (P). Miscible in water
at 200 C (P).
a Fl = 53.1% Forn ilation Intermediate; T = unregistered 90% Technical;
P = Pure Active Ingredient;
-------
—3—
Vapor Pressure: 3.8 x 10 ithar at 200 C (P)
Dissociation Ctnstant: N/A
0ctanol/ ter Partition ()efficient: 0.18 (P)
pH: N/A
Toxicology Characteristics
Acute oral: Toxicity ( tegory II
— Supplaiientary data indicates 50—80 mg/kg ui the rat
Acute dermal: Toxicity C tegory I
— 112 and 152 mg/kg in fenale and male rats, respectively
Acute inhalation: Toxicity C tegory II
— 0.51 rr,/L and 1.5 ing/L in mice and rats,
respectively
Primary dermal irritation: Toxicity ( tegory IV
— No irritation ct,served in raI±it
Primary eye irritation: Toxicity Category III
Reversible mild irritation of conjunctivae
in the rat2Dit
Acute delayed neurotoxicity: Data gap
Subchronic oral (rcxlent): Data insufficient to assess subchronic
toxicity
Chronic feeding: Data gap
Ckicogenicity: Data gap, rat and n se
Metabolisn: Data gap
Teratogenicity: Rat - Maternal NOEL = 1.5 mg/kg/day
Maternal LEL = 4.5 mg/kg/day
Develcçznental Toxicity NOEL = 1.5 mg/kg/day
Maternal thE NOEL = 0.5 mg/kg/day (lo iest
dose tested)
Ralbit - Maternal NOEL = 0.2 mg/kg/day
Maternal thE LEL = 0.8 mg/kg/day
Developiiental Toxicity LEL = 0.05 mg/kg/day
(1o ’iest dose tested)
Maternal thE NOEL = 0.2 mg/kg/day
Reproductive Effects: Rat - Reproductive NOEL = 1 ppn
Reproductive LEL = 10 p xn (decreased viability
index and pup body weight, histopat 1ogical
charges in epididymis)
Systeuic NOEL = 1 ppn (decreased testes weight)
Mutagenicity: Data insufficient to assess nutagenic potential
-------
-4-
Physiological and Biod ical Characteristics:
Metalo1i and persistence in plants and animals
The metabolisi of ox deneton-methyl in plants is not adequately
understood. Because of the structural similarity bet en disulfotori,
deneton, and oxyleneton-nethyl it is possible that certain metabolites
of oxydeneton-nethyi will be u ion to those of disulfoton and/or
d reton. } ever, in the absence o adequate data delineating the
nature of residues of oxyd neton—znethyl in plant.s, no cat arisons with
deneton or disulfoton plant metaboli n can be made at this time.
Presently, oxyd neton-inethyl and its chDlinesterase-inhibitiflg metabo-
lites are the residues of concern in plants. The tolerance definition
may be revised to specifically include the metabolites which constitut ę
residues of concern upon receipt of the requested data. The metaboli&n
of oxyl neton—nethyl in runinants and poultry is not adequately
understood. The only available in vi runinant metaboli n st .rIy did
not indicate what percentages of the total radioactivity in tissues
and milk were present in the extracts of these salTples. Additional
metaboli9n studies in plants and animals are required.
Environrrental Characteristics :
The envirorrnental fate of oxydeneton-methyl cannot be fully assessed.
With the exception of a hylrolysis study, available data reviewed by
the Agency are not sufficient to fulfill the envirormental fate data
requir nents. Available data are not adequate to fully assess leaching
potential (e.g., field dissipation). OxydBneton-methyl and its
degradation products are soluble in water. Under aer ic conditions,
as indicated bj preliminary studies, oxyd neton-rTethyl breaks do.. n in
soils of different textures to dimethyl phosphate, 2—sulfonic diethyl
sulfoxide, 2 sulfonic diethyl sulfone, and oxydaneton—rrethyl sulforie.
The Agency cannot conclusively determine the potential for ground
water contamination at this time.
Ecological Characteristics:
Avian Species
The avian acute oral studies with 50% ai oxyd neton-methyl indicate
that the acute toxicity ranges fran moderately toxic to highly toxic,
depending on the species of bird tested. The acute toxicity values
range fran 14 mg/kg (rock dove) to 47.6 mg/kg (California quail) for the
highly toxic range and fran 53.9 mg/kg (mallard) to 120 mg/kg (thuka)
for the moderately toxic range. Likewise, 8-day dietary studies
den nstrate that there is a wide range of toxicity fran practically
rcntoxic (>5000 ppn for mallards) to highly toxic (434 p zn for bob ihite
quail). P ditional data are not required.
-------
—5—
acceptable avian reproduction stt ies are available. t ta are
required to support uses of oxydat eton—methyl on crcçs with multiple
applications such as cotton, alfalfa, grapes and str ar beets.
Avian terrestrial field stu ies are ixt required. A carparison of
the acute toxicity values with estimated pesticide residues on food
itai s indicate that birds will zxt be exposed to lethal cxx centrations
of oxydeneton-methyl in the field at application rates up to 0.75 lb
ai/A (the highest rate currently registered).
Aquatic OrganisitB
The acute toxicity tests with freshwater invertebrates irxlicate that
oxydet ton-rnethyl is very highly toxic to daphnids (3.3 ppb), n derately
toxic to iso 1 x,ds (1400 p b), and rrcderately to highly toxic to amphipc s
(190 to 1000 ppb). Fk iever, r ne of the available stulies satisfies
the requiranent for an acute toxicity stuiy for freshwater invertebrates
since older specimens were used in the tests. A new st .z y is required.
The acute fish sttx3ies indicate that oxydeneton-methyl is moderately
to highly toxic to coldwater fish and slightly to n derately toxic
to waruwater fish. The 96-hour acute toxicity values ranged fran
0.73 ppn to 6.4 pp for rainlx i trout and fran 1.22 ppn to 31.5 ppn
for several species of warim ter fish. Mditional data are rct
required.
Evaluation of tests on a 25% ai oxydeneton—inethyl concentrate
product, indicates this f&rmulation is n x1erate1y toxic to estuarine
crustaceans. The 96- ur acute toxicity value for pink shrimp ( Penaeus
duorarum ) was 1.2 (0.9-1.8) ppn, and the 96—1 ur acute toxicity
value for fiddler crab was 8.6 (6.6—11) ppn.r sed on currently
registered , oxyd eton-methyl is rxt expected to enter estuarine
envirorments in significant concentrations. 1 dditional acute
toxicity testing on estuarine organis is r t required.
Nontarget Insects
Studies indicate that oxydeitetan-methyl is moderately to highly
toxic to ney bees exposed to direct application. ever, toxicity
of foliar residues appears to be slxrt lived. Thxicity to 1 ney
bee larvae is highly variable depending upon larval developnent at
the time of exposure. It is unlikely that these r ntarget insects
ould be affected by application of oxydeiteton-methyl made in
accordance with label directions.
Tolerance Reassessment
¶Iblerances have been established for residues of oxydeiteton-methyl
expressed in terms of cathiried residues of oxydeneton-methyl and its
c1 linesterase-inhibiting metabolites on various raw agricultural
ccxnmDdities (40 CFR 180.330).
A feed additive tolerance of 2.0 ppn is established for the canbined
residues of oxydeneton-methyl and its c linesterase inhibiting
-------
-6-
metabolites in the milled fractions of sor ii (except flour) for
animal feed en present therein as a result of application to gra4ng
sorghtrn (21 CFR 561.234).
Because of the extensive residue ch nistry and toxicology data gaps,
the 1 gency canr t ccxrplete all tolerance reasses neritS.
4. Required Labeling and Regulatory Position SunTnary
Oxyderreton-nethyl is being placed into Special Reviei : The Ngency is
initiating a eqial Review on all uses of pesticide products containing
ox areton-rtethyl, based on concerns regarding reproductive effects. The
Pig ency has determined that oxyd neton-methyl has the potential to induce
reproductive effects in hui ans, and that that effect is of concern
because of the potential exposures of applicators, mixers and loaders
who use products containing oxy tieton-methyl, and to field rkers
entering treated fields.
The follo4ng precautionary measures are being required for all products
containing oxy eneton-methy1 either as a single active ingredient or in
ccxnbination with other active ingredients, pending receipt and
evaluation of a&litional data k ith will allc i the Pigency to fully
assess the potential of oxydei eton-ztethyl to induce adverse effects.
Use Classification : All products containing oxy neton-nethyl are
classified for Restricted Use under this Standard, on the basis of
the potential for reproductive effects.
Protective Clothing/Equipment and Closed SysteTis : The use of maxiJTuTt
full body protective ciothing/equipnent by mixer ! loader s/applicators,
and by field rkers entering treated fields prior to the end
of the 48 hour reentry interval is required.
Reentry Interval : The 48-hour reentry interval established
under 40 CFR 170 for all agricultural uses of oxydeTleton-methyl
ich may involve hand labor tasks will continue to be required.
In acilition, the use of maxijnun protective clothing and equipTient
is required if treated fields are entered prior to the end of
the reentry interval. Reentry data are being required to reassess
the adequacy of the 48 hour reentry interval.
Flaggers : The use of huTlan flaggers during aerial application is
prohibited. unless they are in totally enclosed vehicles.
Tolerances : No new tolerances and food uses will be granted until
the Pigency has received data sufficient to evaluate the dietary
exposure to oxyeneton-methyl.
-------
—7—
5. Suimary of Major Data Gaps
Toxicology: Date Due *
Acute Oral 9 ?tnths
Deririal Sensitization (Guinea pig) 9 Months
Acute Delayed Neuzotoxicity (H is) 12 M ths
& bchronic Oral — Rat 15 Months
— Nan-r o dent 18 Months
(Not required if chronic data are acceptable)
Subchronic Derma 1 (21 - [ ny; Retbit) 12 Months
Sibchronic Neurotoxicity 15 Months
(Required - if acute delayed neurotoxicity
is positive)
thronic ‘I xicity (Rat, dog) 50 Months
oncogenicity (Rat, Mouse) 50 t ths
Mutagenicity Tests (Q ra scnial and [ ) 12 Months
Metaboli n (General) 24 t4 ths
Male ort Term Exposure study 10/31/88
Male Reproductive Systen l’bxicity Study 12/31/87**
vironn nta1 Fate/Exposure
P toiegradation
In ter 9 Months
In soil 4 Months
In air (corxuiditonal)
Mutabolism - Lab
Aerobic Soil 27 Months
Anaerobic Soil 7/14/88
Mobil ity
Leaching and Msorption/De sorption 12 Months
Laboratory Volatility 12 Months
Field Volatility (conditional)
Terrestrial Field Dissipation
Field Dissipation — Soil 27 Months
Long-term Field Dissipation (conditional)
Confined 1 tational Orop 07/14/89
Field Rtational op (conditional)
ray Drift Studies
t)roplet Size Spectrun 27 Months
Drift Field Evaluation 27 Months
Reentry
Foliar Dissipation 27 Months
Soil Dissipation 27 Months
Dermal Exposure (conditional)
Inhalation Exposure (conditional)
* Due date is based on date of receipt of Standard by the registrant, unless
otherwise indicated.
** Study required by the June, 1987 Data ( l1—in and is to be suthtitted by
either Decenber 31, 1987 (if an ongoing study being conducted by t’tbay for
the C 1ifornia Dept. of Food and Agric. is used) or ( tober 31, 1988 (if a
new study is undertaken).
-------
—8-
Ecological Effects Date Due*
Avian Reproduction 04/14/88
aquatic Invertebrate ute ¶Ibxicity 9 Mc nths
Fish E rly Life Stage ar
& uatic Invertebrate Life Cycle 15 tbnths
1 quatic 0rgarii n Accunulation 27 t bnths
Residue Ch istry/Product Ch nistxy
Product th nistry 6 - 12 tbnths
Plant azx 1 nisnal Metabolism 10/14/87
Storage Stability 24 t’bnths
Magnitirie of Residue St z1tes 4/14/88
6. Contact Person at EPA
William H. Miller, (R’i-16)
Insecticide-Rodenticide Branch (TS—767)
401 M Street SiJ.
shington, I 20460.
Tel. 1 b. (703) 557—2600
DISCLAIMER: The information presented in this ch nical Information Fact
Sheet is for informational purp ses only and nay t be used to fulfill
data r uirenents for pesticide registration and reregistration.
------- |