(Ailttd Stttm wig, of PwiddM ind ToKie SubMitos
Envlronnrniul Protection Offiet of P««Wd» ProBram (T8-766C)
Washington, DC 20460
xe/EPA Pesticide
Fact Sheet
Name of Chemical: DISUlrara
Reason for Issuance:
Date Issued:
Fact Sheet Numb*?'
DESCRIPTION OF CHEMICAL
Generic Name: 0,0-diethyl S-[2-(ethylthio)ethyl] phospho-
rodithioate
Common Name: Disulfoton
Trade Name: Di-Syston
EPA Shaughnessy Code: 032501
Chemical Abstracts Service (CAS) Number: 298-04-4
Year of Initial Registration: 1958
Pesticide Type: Insecticide/Acaricide
Chemical Family: Organophosphate
U.S. and Foreign Producers: Mobay Chemical Corp.
USE PATTERNS AND FORMULATIONS
Application Sites: Grain crops, nut crops, cole crops,
root crops, pome, strawberry and
pineapple fruits, forage, field and
vegetable crops, sugarcane, seed crops,
forest plantings, ornamentals, and potted
plants (including houseplants)
Types of Formulations: Emulsifiable Concentrates, granulars,
pelleted/tableted, and ready to use
liquids
Types of Methods of Application: Soil incorporation of
granulars, ground and
aerial spray and granular
broadcast applications
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Disulfoton 2
fact sheet
Application Rates: Range fran 0.25 lbs. a.i./A to 8 lbs.
a.i./A for bro ast applications and
.25 oz ai.i./1000 ft. r to 10 oz.
a.i./1000 foot row for band trea rent;
also individual potted plant soil
treatment uses at various rates depending
on plant and pot size.
Usual Carriers: Synthetic clays, various solvents, fertilizers
3. SCI 4cE FIN I S
Summary Scienoe Statement
Disulfoton is very highly toxic to all ma!Inalian systems by
all routes of exposure and is assigned to xicity Category
t, on the basis of ecute toxicity requiring the most stringent
labeling precautions and use restrictions. It is not
considered to be orcogenic, mutagenic, or teratogenic based
upon existing data. B ver, additional studies in a second
species are being requested to fully assess orcogenic and
teratogenic potential. ditional iaitagenicity studies are
also being required. Raprod tion data is lecking and is
required.
tX e to the high ecute toxicity and cbolinesterase inhibition
of disulfoton the Pgercy is imposing a 24- ur reentry
restriction for crop uses until appropriate reentry studies
and dennal absorption data are subnitted and evaluated and a
decision is reeched whether a different time interval is
more appropriate.
Data are insufficient to assess the environn ntal fate of
disulfoton. The Agercy is requesting necessary data to make
this asses nt and also to specifically assess whether or not
disulfoton will leech into ground ter. Considering the high
ecute toxicity of disulfotcn spray drift data are being required
to measure human and non-target organi n exposure resulting fran
spray applications and dennal and thhalation exposure data are
being required to measure rker exposure in outdoor applications.
Disulfoton is very highly toxic to fish, maT als, highly toxic
to birds, and moderately toxic to boney bees. Full field
monitoring studies are required for the terrestrial uses to
assess the exposure potential. Based on these results and
on the results of the outstanding enviroui ntai. fate data,
chronic studies for both aquatic and terrestrial species may
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Disulfoto 3
fact sheet
be required as .wall as full field mc*iitoring studies for the
aquatic uses. Use precautions and restriction are being
licpoeed in the interim to red ce potential hazards.
A nunber of terrestrial and aquatic endangered species have
been identified as at risk fran the use of a minber of
ch nicals, including disulfoton on certain crops. This
issue is currently being idressed as part of a cluster
approech. Interim labeling to protect these species may
be necessary if the cluster analysis is not ca çleted by
1986.
A full tolerance reassessriertt cannot be canpieted. The
previous ADI was established using a rat chronic feeding
study which was found to be un ceptable. The present
Prov .sional ADI was based on a dog chroni c feeding study. The
percent of the PADI utilized is 169%. A second rat
chronic feeding study is required, as ll as an ina.1
mataboli n data to quantify and qualify disulfoton
oxidation metabolites in meat, milk, poultry and eggs
and residue data on nu rous cicpv yjitjeg . The Agency is
requiring that when the tolerance reasses ient is m ji ,
after receipt of the requested data, all tolerances are
to be calculated and expressed in te of disultoton
sulforte, the major metabolite, rather than as ton
(which is F w the Agency previously expressed tolerances
for disulfoton).
Ch nical Char teristics
Physical State: Liquid
Color: Pale yell
Odor: Unkr n
Boiling Point: 62° C at 0.01 niw’Hg
vapor Pressure: 1.8 X millibars at 20° C
Flash Point: >180° F(IOC)
Toxicoloqy Charecteristics
Pcute Oral: 1.9 — 6.2 mg/kg, Toxicity Category I
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Disulfo ton 4
fact sheet
ute Dar’n 1: 3.6 — 15.9 mg/kg. TOxicity Category I
Primary Daz7naJ. Irritation: NA since chemicals toxicity
uld preclude testing for this requir nt
Pcute Inhalation: One study, which did not meet Agency
standards, indicated toxicity at 0.2 mg/i, which uld
place it in TOxicity Category t. -
Neurotoxicity: One study was subnitted which did not meet
Agency standards. The study did not indicate delayed
neurotoxic effects.
Orrogenicity: T studies have been evaluated; one was
acceptable and did not suggest oncogenic potential.
Teratogenicity: T studies re evaluated; one was
acceptable and the other did not fully meet the Agency
standards. The ch nical is not teratogenic at 0.3 mg/kg/
day.
prodtet.ion — 2 generation: Data gap
Metaboliem: The available studies suggest that disu.1foton
is rapidly absorbed and may undergo sequential oxidation
steps that enhance anti-cholinesterase properties. retion
4.5 canpiete and rapid via urine. Major metabolites include
the 0—analog of disulfoton, and the sulfoxide and sulfone
derivatives of both disulfoton and its 0-analog. Data to
further deecribe the nature and dynanics of this process are
necessary.
Mutagenicity: Contradictory reports are available on the
niitagenic potential of disulfoton. ? gerry has concluded
that the imatagenic potential is not adequately defined and
further testing is necessary.
Physiological and Biochemical Behavioral Characteristics
Mechanian of Pesticidal Aticn: A plant systemic insecticide
which is active by contact, ingestion, and vapor action.
Disulfoton and its major metabolites are potent cholinesterase
inhibitors primarily attacking acetyicholinesterase. Poisoning
and death results fran e cessive stiimilation of both the
parasympathetic and central nervous syst , and the consequent
myoneural junction effect as a result of acetyicholinesterase
acc unulat ion.
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Disulfoton
fact sheet 5
S ’inptans of Poisoning: headahe, dizziness, extreme weakness,
ataxja, tiny pupils, twitching, tr r, nausea, slow heartbeat,
pulnxxiary edema, and e essive sweating. Continual daily
absorption at inte diate doses may cause influenza—like
illness char terized by weakness, anorexia, and malaise.
Metaboli n and Persisterce in Plants and Animals :
The metaboli n of disulfoton in plants is adequately understood.
The major plant metabolite appears to be disui.foton sulfone.
Consequently the Agercy believes that the tolerarces for
disulfoton residues should be expressed as disulfoton sulfone.
The metaboli n in animals is not well understood. More data
are required to quantify and qualify animal metar olites, and
to quantify plant inetabolites.
Erivirorunenta.l Char teristics
Available data are insufficient to assess the envirorunental
tate of disulfoton. ta gaps exist for virtually all required
studies. In order to charsoterize the potential of the c ical
to contaninate groundwater adsorption and le hing stt ies are
being requested by the Agercy.
Droplet Size Spectr testing and Drift Field Evaluation studies
are being requested in order to dete nine the m nitude of
exposure to non—target organians.
Ecological Char teristics
Avian Oral:
Mallard d ck — 6.54 uq/kg
Bobwhite iail — 12—31 n Jkg
Avian dietary:
Mallard dtck — 510—692 ppn
Bobwhite quail — 541—715 ppn
ring—necked easant — 634 ppn
Freshwater fish:
coidwater fish (rain ” trout) — 3.0 ppn
wauT ater fish (bluegill sunfish) — 0.039 p
Pcute Freshwater Invertebrates: (All studies listed were
not cord cted cording
to Agency standards)
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Disulfoton
fact sheet 6
Acute Estuarjne and Marine Organisms: Data gaps
Precautionary language is being required to mitigate
hazards to birds, fish, and aquatic organisms. Additional
labeling to protect identified endangered species may be
required at a later date. Because of the lack of environ-
mental fate and field monitoring data to quantify exposure
of disulfoton to these organisms, the Agency can not
quantify the hazard potential. Additional chronic toxicity
studies may be required depending on the results of the
environmental, fate and field monitoring data.
Tolerance Assessment
The Agency is unable to complete a tolerance reassessment
because of certain residue chemistry and toxicology data
gaps.
Tolerances:
Con odity Parts Per Million
alfalfa (fresh) 5.0
alfalfa (hay) 12.0
asparagus 0.1
barley (fodder, green) 5.0
barley (grain) 0.75
barley (straw) 5.0
beans (dry) 0.75
beans (lima) 0.75
beans (snap) 0.75
beans (vines) 5.0
beets, sugar (roots) 0.5
beets, sugar (tops) 2.0
broccoli 0.75
brussels sprouts 0.75
cabbage 0.75
caulifower 0.75
clover (fresh) 5.0
clover (hay) 12.0
coffee beans 0.3
corn, field (fodder) 5.0
corn, field (forage) 5.0
corn, grain 0.3
corn, pop 0.3
corn, pop (fodder) 5.0
corn, pop (forage) 5.0
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• Disulfo ton
fact sheet
7
Tolerances (COn’t):
Cou!nodity Parts Per Million
corn, sweet (fodder) 5.0
corn, sweet (forage) 5.0
corn, sweet, grain
(kernels plus cob with
husks removed) 0.3
cottonseed 0.75
hops 0.5
lettuce 0.75
oats (fodder, green) 5.0
oats (grain) 0.75
oats (straw) 5.0
peanuts 0.75
peanuts (hay) 5.0
peanuts (hull) 0.3
peas 0.75
peas (vines) 5.0
pecans 0.75
peppers 0.1
pineapples (forage) 5.0
potatoes 0.75
rice 0.75
rice (straw) 5.0
sorghum (fodder) 5.0
sorghum (forage) 5.0
sorghum (grain) 0.75
soybeans 0.].
soybeans (forage) 0.25
soybeans (hay) 0.25
spinach 0.75
sugarcane 0.3
tomatoes 0.75
wheat (fodder, green) 5.0
wheat (grain) 0.3
wheat (straw) 5.0
Based on established tolerances the theoretical maximum
residue contribution (TRMC) for disulfoton residue in the
human diet is calculated to be 0.2544 mg/day. The
provisional acceptable daily intake (PADI) of disulfotort
is 0.0025 mg/kg/day. The maximum perinissable intake (MPI)
for a 60 kg person is 0.15 mg/day. The percent of the ADI
utilized is 169%. However a reassessment of the current
tolerances based on actual constituents of the plant
residues (xnetabolites) is necessary as well as toxicity
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Disulfoton
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8
data on the most toxic metabolite. Conformity of U.S.
tolerances with Canada and Codex Alimentaruis tolerances
is withheld pending receipt arta- evaluation ot appropriate
data referred to above.
U.S. tolerances for most raw agricultural commodities are
not supported by current residue data. More data are
required.
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
The Agency has determined that it should continue to allow
the registration of disulfoton. Adequate studies are
available to assess the acute toxicological effects of di—
sulfoton to humans. one of the criteria for unreasonable
adverse effects listed in section 162.11(a) of Title 40
of the U.S. Code of Federal Regulations have been met or
exceeded. However, because of certain gaps in the data
base a full risk assessment of disulfoton cannot be
completed.
Also, a full tolerance reassessment cannot be completed
because of certain residue chemistry and toxicology data
gaps.
The Agency is concerned about whether or not the potential
total human exposure to disulfoton and its metabolites,
both from direct and indirect human contact and the ex-
ceeded ADI, poses any unacceptable hazards. To resolve
this concern, additional residue, metabolism and exposure
data are required, and until it is resolved no new uses
will be granted.
All end—use products formulated at greater than 2% are
classified for Restricted Use, pending receipt and evaluation
of appropriate acute toxicity data. Acute toxicity data
on products 2% and less are being required in order to
determine the appropriateness of a Restricted Use classification.
These steps are being taken due to the extreme toxicity of
disulfoton and the lack of product specific acute toxicity
data.
A federal 24—hour reentry interval is established for treated
crop areas until reentry and dermal absorption data are sub-
mitted, as required, and the Agency decides on the most
appropriate time interval.
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Disulfo ton
fact sheet
9
Available data are insufficient to fully assess the env iron—
mental fate of disulfoton. The Agency is requesting data to
determine if disulfoton will contaminate groundwater.
Toxicity data available for disu].foton indicates that it is
highly toxic to aquatic, terrestrial and avian species. Data
to assess the extent of the potential exposure is currently
lacking and is required to complete the hazard assessment.
5 • SUMMARY OF MAJOR DATA GAPS
Additional residue data on various raw agricultural
and processed commodities are being required. Also
additional chronic toxicity, oncogenicity, and
rnutagenicity data are needed to better define the
long term effects of this chemical. Plant and
animal metabolism, exposure, spray drift, reentry
and subchronic toxicity data are required to better
qualify and quantify human exposure to residues
of disulfoton and its metabolites, both from dietary
and non—dietary sources.
Other requirements
Acute Inhalation
Acute oral, dermal and inhalation studies on formulating
intermediates and end—use products
Acute delayed neurotoxicity
Dermal absorption study
Product Integrity study
Hydrolysis study
Photodegradation studies
Soil and Water Metabolism studies
Mobility studies
Volatility studies
Dissipation studies
Accumulation studies
Large Scale Field Monitoring studies
Acute freshwater invertebrates testing
Acute estuaring and marine organisms testing
Honey bee toxicity of residues on foliage study
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fact sheet
6. COMPLIANCE DATES FOR REVISED LABELING
—For addition of RESTRICTED USE classification to product
formulations containing greater than 2% dlsulfoton. All
such products released for shipment after September 1,
1985 must bear RESTRICTED USE labeling. All such products
in the channels of trade after September 1, 1986 must
be labeled for RESTRICTED USE.
—For intrastate products the Agency Is requiring submission
of applications for full registration of all intrastate
products containing disulfoton by December 31, 1985 .
Holders of such intrastate products who request withdrawal
or who fail to respond to the notification, may not distri-
bute or sell the intrastate product after December 31,
1985 . Products already in the channels of trade as ot
that date may continue to be distributed and sold by dealers
and retailers until June 30, 1986 . Any product found in
the channels of trade after June 30, 1986 will be considered
to be in violation of FIFP.A sec. 12(a)(1)(A).
CONTACT PERSON AT EPA
George T. LaRocca
Product Manager (15)
Insecticide—Rodenticide Branch
Registration Division (TS—767C)
Office of Pesticide Programs
Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
Office location and telephone number:
Room 204, Crystal Mall *2
1921 Jefferson Davis Highway
Arlington, VA 22202
(703) 557—2400
DISCLAIMER: The information presented in this Chemical Information
Fact Sheet is for informational purposes only and may not be used
to fulfill data requirements for pesticide registration and
reregistration.
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